Difference between revisions of "RFC3411"

Revision as of 11:28, 24 September 2020

Network Working Group D. Harrington Request for Comments: 3411 Enterasys Networks STD: 62 R. Presuhn Obsoletes: 2571 BMC Software, Inc. Category: Standards Track B. Wijnen

                                                 Lucent Technologies
                                                       December 2002

                 An Architecture for Describing
Simple Network Management Protocol (SNMP) Management Frameworks

Status of this Memo

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Abstract

This document describes an architecture for describing Simple Network Management Protocol (SNMP) Management Frameworks. The architecture is designed to be modular to allow the evolution of the SNMP protocol standards over time. The major portions of the architecture are an SNMP engine containing a Message Processing Subsystem, a Security Subsystem and an Access Control Subsystem, and possibly multiple SNMP applications which provide specific functional processing of management data. This document obsoletes RFC 2571.

Table of Contents

1. Introduction ................................................ 4 1.1. Overview .................................................. 4 1.2. SNMP ...................................................... 5 1.3. Goals of this Architecture ................................ 6 1.4. Security Requirements of this Architecture ................ 6 1.5. Design Decisions .......................................... 8 2. Documentation Overview ...................................... 10 2.1. Document Roadmap .......................................... 11 2.2. Applicability Statement ................................... 11

2.3. Coexistence and Transition ................................ 11 2.4. Transport Mappings ........................................ 12 2.5. Message Processing ........................................ 12 2.6. Security .................................................. 12 2.7. Access Control ............................................ 13 2.8. Protocol Operations ....................................... 13 2.9. Applications .............................................. 14 2.10. Structure of Management Information ...................... 15 2.11. Textual Conventions ...................................... 15 2.12. Conformance Statements ................................... 15 2.13. Management Information Base Modules ...................... 15 2.13.1. SNMP Instrumentation MIBs .............................. 15 2.14. SNMP Framework Documents ................................. 15 3. Elements of the Architecture ................................ 16 3.1. The Naming of Entities .................................... 17 3.1.1. SNMP engine ............................................. 18 3.1.1.1. snmpEngineID .......................................... 18 3.1.1.2. Dispatcher ............................................ 18 3.1.1.3. Message Processing Subsystem .......................... 19 3.1.1.3.1. Message Processing Model ............................ 19 3.1.1.4. Security Subsystem .................................... 20 3.1.1.4.1. Security Model ...................................... 20 3.1.1.4.2. Security Protocol ................................... 20 3.1.2. Access Control Subsystem ................................ 21 3.1.2.1. Access Control Model .................................. 21 3.1.3. Applications ............................................ 21 3.1.3.1. SNMP Manager .......................................... 22 3.1.3.2. SNMP Agent ............................................ 23 3.2. The Naming of Identities .................................. 25 3.2.1. Principal ............................................... 25 3.2.2. securityName ............................................ 25 3.2.3. Model-dependent security ID ............................. 26 3.3. The Naming of Management Information ...................... 26 3.3.1. An SNMP Context ......................................... 28 3.3.2. contextEngineID ......................................... 28 3.3.3. contextName ............................................. 29 3.3.4. scopedPDU ............................................... 29 3.4. Other Constructs .......................................... 29 3.4.1. maxSizeResponseScopedPDU ................................ 29 3.4.2. Local Configuration Datastore ........................... 29 3.4.3. securityLevel ........................................... 29 4. Abstract Service Interfaces ................................. 30 4.1. Dispatcher Primitives ..................................... 30 4.1.1. Generate Outgoing Request or Notification ............... 31 4.1.2. Process Incoming Request or Notification PDU ............ 31 4.1.3. Generate Outgoing Response .............................. 32 4.1.4. Process Incoming Response PDU ........................... 32 4.1.5. Registering Responsibility for Handling SNMP PDUs ....... 32

4.2. Message Processing Subsystem Primitives ................... 33 4.2.1. Prepare Outgoing SNMP Request or Notification Message ... 33 4.2.2. Prepare an Outgoing SNMP Response Message ............... 34 4.2.3. Prepare Data Elements from an Incoming SNMP Message ..... 35 4.3. Access Control Subsystem Primitives ....................... 35 4.4. Security Subsystem Primitives ............................. 36 4.4.1. Generate a Request or Notification Message .............. 36 4.4.2. Process Incoming Message ................................ 36 4.4.3. Generate a Response Message ............................. 37 4.5. Common Primitives ......................................... 37 4.5.1. Release State Reference Information ..................... 37 4.6. Scenario Diagrams ......................................... 38 4.6.1. Command Generator or Notification Originator ............ 38 4.6.2. Scenario Diagram for a Command Responder Application .... 39 5. Managed Object Definitions for SNMP Management Frameworks ... 40 6. IANA Considerations ......................................... 51 6.1. Security Models ........................................... 51 6.2. Message Processing Models ................................. 51 6.3. SnmpEngineID Formats ...................................... 52 7. Intellectual Property ....................................... 52 8. Acknowledgements ............................................ 52 9. Security Considerations ..................................... 54 10. References ................................................. 54 10.1. Normative References ..................................... 54 10.2. Informative References ................................... 56 A. Guidelines for Model Designers .............................. 57 A.1. Security Model Design Requirements ........................ 57 A.1.1. Threats ................................................. 57 A.1.2. Security Processing ..................................... 58 A.1.3. Validate the security-stamp in a received message ....... 59 A.1.4. Security MIBs ........................................... 59 A.1.5. Cached Security Data .................................... 59 A.2. Message Processing Model Design Requirements .............. 60 A.2.1. Receiving an SNMP Message from the Network .............. 60 A.2.2. Sending an SNMP Message to the Network .................. 60 A.3. Application Design Requirements ........................... 61 A.3.1. Applications that Initiate Messages ..................... 61 A.3.2. Applications that Receive Responses ..................... 62 A.3.3. Applications that Receive Asynchronous Messages ......... 62 A.3.4. Applications that Send Responses ........................ 62 A.4. Access Control Model Design Requirements .................. 63 Editors' Addresses ............................................. 63 Full Copyright Statement ....................................... 64

Introduction

Overview

This document defines a vocabulary for describing SNMP Management Frameworks, and an architecture for describing the major portions of SNMP Management Frameworks.

This document does not provide a general introduction to SNMP. Other documents and books can provide a much better introduction to SNMP. Nor does this document provide a history of SNMP. That also can be found in books and other documents.

Section 1 describes the purpose, goals, and design decisions of this architecture.

Section 2 describes various types of documents which define (elements of) SNMP Frameworks, and how they fit into this architecture. It also provides a minimal road map to the documents which have previously defined SNMP frameworks.

Section 3 details the vocabulary of this architecture and its pieces. This section is important for understanding the remaining sections, and for understanding documents which are written to fit within this architecture.

Section 4 describes the primitives used for the abstract service interfaces between the various subsystems, models and applications within this architecture.

Section 5 defines a collection of managed objects used to instrument SNMP entities within this architecture.

Sections 6, 7, 8, 9, 10 and 11 are administrative in nature.

Appendix A contains guidelines for designers of Models which are expected to fit within this architecture.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

SNMP

An SNMP management system contains:

  -  several (potentially many) nodes, each with an SNMP entity
     containing command responder and notification originator
     applications, which have access to management instrumentation
     (traditionally called agents);

  -  at least one SNMP entity containing command generator and/or
     notification receiver applications (traditionally called a
     manager) and,

  -  a management protocol, used to convey management information
     between the SNMP entities.

SNMP entities executing command generator and notification receiver applications monitor and control managed elements. Managed elements are devices such as hosts, routers, terminal servers, etc., which are monitored and controlled via access to their management information.

It is the purpose of this document to define an architecture which can evolve to realize effective management in a variety of configurations and environments. The architecture has been designed to meet the needs of implementations of:

  -  minimal SNMP entities with command responder and/or
     notification originator applications (traditionally called SNMP
     agents),

  -  SNMP entities with proxy forwarder applications (traditionally
     called SNMP proxy agents),

  -  command line driven SNMP entities with command generator and/or
     notification receiver applications (traditionally called SNMP
     command line managers),

  -  SNMP entities with  command generator and/or notification
     receiver, plus command responder and/or notification originator
     applications (traditionally called SNMP mid-level managers or
     dual-role entities),

  -  SNMP entities with command generator and/or notification
     receiver and possibly other types of applications for managing
     a potentially very large number of managed nodes (traditionally
     called (network) management stations).

Goals of this Architecture

This architecture was driven by the following goals:

  -  Use existing materials as much as possible.  It is heavily
     based on previous work, informally known as SNMPv2u and
     SNMPv2*, based in turn on SNMPv2p.

  -  Address the need for secure SET support, which is considered
     the most important deficiency in SNMPv1 and SNMPv2c.

  -  Make it possible to move portions of the architecture forward
     in the standards track, even if consensus has not been reached
     on all pieces.

  -  Define an architecture that allows for longevity of the SNMP
     Frameworks that have been and will be defined.

  -  Keep SNMP as simple as possible.

  -  Make it relatively inexpensive to deploy a minimal conforming
     implementation.

  -  Make it possible to upgrade portions of SNMP as new approaches
     become available, without disrupting an entire SNMP framework.

  -  Make it possible to support features required in large
     networks, but make the expense of supporting a feature directly
     related to the support of the feature.

Security Requirements of this Architecture

Several of the classical threats to network protocols are applicable to the management problem and therefore would be applicable to any Security Model used in an SNMP Management Framework. Other threats are not applicable to the management problem. This section discusses principal threats, secondary threats, and threats which are of lesser importance.

The principal threats against which any Security Model used within this architecture SHOULD provide protection are:

  Modification of Information
     The modification threat is the danger that some unauthorized
     entity may alter in-transit SNMP messages generated on behalf
     of an authorized principal in such a way as to effect
     unauthorized management operations, including falsifying the
     value of an object.

  Masquerade
     The masquerade threat is the danger that management operations
     not authorized for some principal may be attempted by assuming
     the identity of another principal that has the appropriate
     authorizations.

Secondary threats against which any Security Model used within this architecture SHOULD provide protection are:

  Message Stream Modification
     The SNMP protocol is typically based upon a connectionless
     transport service which may operate over any subnetwork
     service.  The re-ordering, delay or replay of messages can and
     does occur through the natural operation of many such
     subnetwork services.  The message stream modification threat is
     the danger that messages may be maliciously re-ordered, delayed
     or replayed to an extent which is greater than can occur
     through the natural operation of a subnetwork service, in order
     to effect unauthorized management operations.

  Disclosure
     The disclosure threat is the danger of eavesdropping on the
     exchanges between SNMP engines.  Protecting against this threat
     may be required as a matter of local policy.

There are at least two threats against which a Security Model within this architecture need not protect, since they are deemed to be of lesser importance in this context:

  Denial of Service
     A Security Model need not attempt to address the broad range of
     attacks by which service on behalf of authorized users is
     denied.  Indeed, such denial-of-service attacks are in many
     cases indistinguishable from the type of network failures with
     which any viable management protocol must cope as a matter of
     course.

  Traffic Analysis
     A Security Model need not attempt to address traffic analysis
     attacks.  Many traffic patterns are predictable - entities may
     be managed on a regular basis by a relatively small number of
     management stations - and therefore there is no significant
     advantage afforded by protecting against traffic analysis.

Design Decisions

Various design decisions were made in support of the goals of the architecture and the security requirements:

  - Architecture
     An architecture should be defined which identifies the
     conceptual boundaries between the documents.  Subsystems should
     be defined which describe the abstract services provided by
     specific portions of an SNMP framework.  Abstract service
     interfaces, as described by service primitives, define the
     abstract boundaries between documents, and the abstract
     services that are provided by the conceptual subsystems of an
     SNMP framework.

  - Self-contained Documents
     Elements of procedure plus the MIB objects which are needed for
     processing for a specific portion of an SNMP framework should
     be defined in the same document, and as much as possible,
     should not be referenced in other documents.  This allows
     pieces to be designed and documented as independent and self-
     contained parts, which is consistent with the general SNMP MIB
     module approach.  As portions of SNMP change over time, the
     documents describing other portions of SNMP are not directly
     impacted.  This modularity allows, for example, Security
     Models, authentication and privacy mechanisms, and message
     formats to be upgraded and supplemented as the need arises.
     The self-contained documents can move along the standards track
     on different time-lines.

     This modularity of specification is not meant to be interpreted
     as imposing any specific requirements on implementation.

  - Threats
     The Security Models in the Security Subsystem SHOULD protect
     against the principal and secondary threats: modification of
     information, masquerade, message stream modification and
     disclosure.  They do not need to protect against denial of
     service and traffic analysis.

  - Remote Configuration
     The Security and Access Control Subsystems add a whole new set
     of SNMP configuration parameters.  The Security Subsystem also
     requires frequent changes of secrets at the various SNMP
     entities.  To make this deployable in a large operational
     environment, these SNMP parameters must be remotely
     configurable.

  - Controlled Complexity
     It is recognized that producers of simple managed devices want
     to keep the resources used by SNMP to a minimum.  At the same
     time, there is a need for more complex configurations which can
     spend more resources for SNMP and thus provide more
     functionality.  The design tries to keep the competing
     requirements of these two environments in balance and allows
     the more complex environments to logically extend the simple
     environment.

Documentation Overview

The following figure shows the set of documents that fit within the SNMP Architecture.

Each of these documents may be replaced or supplemented. This Architecture document specifically describes how new documents fit into the set of documents in the area of Message and PDU handling.

Document Roadmap

One or more documents may be written to describe how sets of documents taken together form specific Frameworks. The configuration of document sets might change over time, so the "road map" should be maintained in a document separate from the standards documents themselves.

An example of such a roadmap is "Introduction and Applicability Statements for the Internet-Standard Management Framework" [RFC3410].

Applicability Statement

SNMP is used in networks that vary widely in size and complexity, by organizations that vary widely in their requirements of management. Some models will be designed to address specific problems of management, such as message security.

One or more documents may be written to describe the environments to which certain versions of SNMP or models within SNMP would be appropriately applied, and those to which a given model might be inappropriately applied.

Coexistence and Transition

The purpose of an evolutionary architecture is to permit new models to replace or supplement existing models. The interactions between models could result in incompatibilities, security "holes", and other undesirable effects.

The purpose of Coexistence documents is to detail recognized anomalies and to describe required and recommended behaviors for resolving the interactions between models within the architecture.

Coexistence documents may be prepared separately from model definition documents, to describe and resolve interaction anomalies between a model definition and one or more other model definitions.

Additionally, recommendations for transitions between models may also be described, either in a coexistence document or in a separate document.

One such coexistence document is [RFC2576], "Coexistence between Version 1, Version 2, and Version 3 of the Internet-Standard Network Management Framework".

Transport Mappings

SNMP messages are sent over various transports. It is the purpose of Transport Mapping documents to define how the mapping between SNMP and the transport is done.

Message Processing

A Message Processing Model document defines a message format, which is typically identified by a version field in an SNMP message header. The document may also define a MIB module for use in message processing and for instrumentation of version-specific interactions.

An SNMP engine includes one or more Message Processing Models, and thus may support sending and receiving multiple versions of SNMP messages.

Security

Some environments require secure protocol interactions. Security is normally applied at two different stages:

  -  in the transmission/receipt of messages, and

  -  in the processing of the contents of messages.

For purposes of this document, "security" refers to message-level security; "access control" refers to the security applied to protocol operations.

Authentication, encryption, and timeliness checking are common functions of message level security.

A security document describes a Security Model, the threats against which the model protects, the goals of the Security Model, the protocols which it uses to meet those goals, and it may define a MIB module to describe the data used during processing, and to allow the remote configuration of message-level security parameters, such as keys.

An SNMP engine may support multiple Security Models concurrently.

Access Control

During processing, it may be required to control access to managed objects for operations.

An Access Control Model defines mechanisms to determine whether access to a managed object should be allowed. An Access Control Model may define a MIB module used during processing and to allow the remote configuration of access control policies.

Protocol Operations

SNMP messages encapsulate an SNMP Protocol Data Unit (PDU). SNMP PDUs define the operations performed by the receiving SNMP engine. It is the purpose of a Protocol Operations document to define the operations of the protocol with respect to the processing of the PDUs. Every PDU belongs to one or more of the PDU classes defined below:

  1) Read Class:

     The Read Class contains protocol operations that retrieve
     management information.  For example, [RFC3416] defines the
     following protocol operations for the Read Class: GetRequest-
     PDU, GetNextRequest-PDU, and GetBulkRequest-PDU.

  2) Write Class:

     The Write Class contains protocol operations which attempt to
     modify management information.  For example, [RFC3416] defines
     the following protocol operation for the Write Class:
     SetRequest-PDU.

  3) Response Class:

     The Response Class contains protocol operations which are sent
     in response to a previous request.  For example, [RFC3416]
     defines the following for the Response Class: Response-PDU,
     Report-PDU.

  4) Notification Class:

     The Notification Class contains protocol operations which send
     a notification to a notification receiver application.  For
     example, [RFC3416] defines the following operations for the
     Notification Class: Trapv2-PDU, InformRequest-PDU.

  5) Internal Class:

     The Internal Class contains protocol operations which are
     exchanged internally between SNMP engines.  For example,
     [RFC3416] defines the following operation for the Internal
     Class: Report-PDU.

The preceding five classifications are based on the functional properties of a PDU. It is also useful to classify PDUs based on whether a response is expected:

  6) Confirmed Class:

     The Confirmed Class contains all protocol operations which
     cause the receiving SNMP engine to send back a response.  For
     example, [RFC3416] defines the following operations for the
     Confirmed Class: GetRequest-PDU, GetNextRequest-PDU,
     GetBulkRequest-PDU, SetRequest-PDU, and InformRequest-PDU.

  7) Unconfirmed Class:

     The Unconfirmed Class contains all protocol operations which
     are not acknowledged.  For example, [RFC3416] defines the
     following operations for the Unconfirmed Class: Report-PDU,
     Trapv2-PDU, and GetResponse-PDU.

An application document defines which Protocol Operations are supported by the application.

Applications

An SNMP entity normally includes a number of applications. Applications use the services of an SNMP engine to accomplish specific tasks. They coordinate the processing of management information operations, and may use SNMP messages to communicate with other SNMP entities.

An applications document describes the purpose of an application, the services required of the associated SNMP engine, and the protocol operations and informational model that the application uses to perform management operations.

An application document defines which set of documents are used to specifically define the structure of management information, textual conventions, conformance requirements, and operations supported by the application.

2.10. Structure of Management Information

Management information is viewed as a collection of managed objects, residing in a virtual information store, termed the Management Information Base (MIB). Collections of related objects are defined in MIB modules.

It is the purpose of a Structure of Management Information document to establish the notation for defining objects, modules, and other elements of managed information.

2.11. Textual Conventions

When designing a MIB module, it is often useful to define new types similar to those defined in the SMI, but with more precise semantics, or which have special semantics associated with them. These newly defined types are termed textual conventions, and may be defined in separate documents, or within a MIB module.

2.12. Conformance Statements

It may be useful to define the acceptable lower-bounds of implementation, along with the actual level of implementation achieved. It is the purpose of the Conformance Statements document to define the notation used for these purposes.

2.13. Management Information Base Modules

MIB documents describe collections of managed objects which instrument some aspect of a managed node.

2.13.1. SNMP Instrumentation MIBs

An SNMP MIB document may define a collection of managed objects which instrument the SNMP protocol itself. In addition, MIB modules may be defined within the documents which describe portions of the SNMP architecture, such as the documents for Message processing Models, Security Models, etc. for the purpose of instrumenting those Models, and for the purpose of allowing their remote configuration.

2.14. SNMP Framework Documents

This architecture is designed to allow an orderly evolution of portions of SNMP Frameworks.

Throughout the rest of this document, the term "subsystem" refers to an abstract and incomplete specification of a portion of a Framework, that is further refined by a model specification.

A "model" describes a specific design of a subsystem, defining additional constraints and rules for conformance to the model. A model is sufficiently detailed to make it possible to implement the specification.

An "implementation" is an instantiation of a subsystem, conforming to one or more specific models.

SNMP version 1 (SNMPv1), is the original Internet-Standard Network Management Framework, as described in RFCs 1155, 1157, and 1212.

SNMP version 2 (SNMPv2), is the SNMPv2 Framework as derived from the SNMPv1 Framework. It is described in STD 58, RFCs 2578, 2579, 2580, and STD 62, RFCs 3416, 3417, and 3418. SNMPv2 has no message definition.

The Community-based SNMP version 2 (SNMPv2c), is an experimental SNMP Framework which supplements the SNMPv2 Framework, as described in [RFC1901]. It adds the SNMPv2c message format, which is similar to the SNMPv1 message format.

SNMP version 3 (SNMPv3), is an extensible SNMP Framework which supplements the SNMPv2 Framework, by supporting the following:

  -  a new SNMP message format,

  -  Security for Messages,

  -  Access Control, and

  -  Remote configuration of SNMP parameters.

Other SNMP Frameworks, i.e., other configurations of implemented subsystems, are expected to also be consistent with this architecture.

Elements of the Architecture

This section describes the various elements of the architecture and how they are named. There are three kinds of naming:

  1) the naming of entities,

  2) the naming of identities, and

  3) the naming of management information.

This architecture also defines some names for other constructs that are used in the documentation.

The Naming of Entities

An SNMP entity is an implementation of this architecture. Each such SNMP entity consists of an SNMP engine and one or more associated applications.

The following figure shows details about an SNMP entity and the components within it.

SNMP engine

An SNMP engine provides services for sending and receiving messages, authenticating and encrypting messages, and controlling access to managed objects. There is a one-to-one association between an SNMP engine and the SNMP entity which contains it.

The engine contains:

  1) a Dispatcher,

  2) a Message Processing Subsystem,

  3) a Security Subsystem, and

  4) an Access Control Subsystem.

snmpEngineID

Within an administrative domain, an snmpEngineID is the unique and unambiguous identifier of an SNMP engine. Since there is a one-to- one association between SNMP engines and SNMP entities, it also uniquely and unambiguously identifies the SNMP entity within that administrative domain. Note that it is possible for SNMP entities in different administrative domains to have the same value for snmpEngineID. Federation of administrative domains may necessitate assignment of new values.

Dispatcher

There is only one Dispatcher in an SNMP engine. It allows for concurrent support of multiple versions of SNMP messages in the SNMP engine. It does so by:

  -  sending and receiving SNMP messages to/from the network,

  -  determining the version of an SNMP message and interacting with
     the corresponding Message Processing Model,

  -  providing an abstract interface to SNMP applications for
     delivery of a PDU to an application.

  -  providing an abstract interface for SNMP applications that
     allows them to send a PDU to a remote SNMP entity.

Message Processing Subsystem

The Message Processing Subsystem is responsible for preparing messages for sending, and extracting data from received messages.

The Message Processing Subsystem potentially contains multiple Message Processing Models as shown in the next figure.

One or more Message Processing Models may be present.

3.1.1.3.1. Message Processing Model

Each Message Processing Model defines the format of a particular version of an SNMP message and coordinates the preparation and extraction of each such version-specific message format.

Security Subsystem

The Security Subsystem provides security services such as the authentication and privacy of messages and potentially contains multiple Security Models as shown in the following figure

One or more Security Models may be present.

+------------------------------------------------------------------+ | | | Security Subsystem | | | | +----------------+ +-----------------+ +-------------------+ | | | * | | * | | * | | | | User-Based | | Other | | Other | | | | Security | | Security | | Security | | | | Model | | Model | | Model | | | | | | | | | | | +----------------+ +-----------------+ +-------------------+ | | | +------------------------------------------------------------------+

3.1.1.4.1. Security Model

A Security Model specifies the threats against which it protects, the goals of its services, and the security protocols used to provide security services such as authentication and privacy.

3.1.1.4.2. Security Protocol

A Security Protocol specifies the mechanisms, procedures, and MIB objects used to provide a security service such as authentication or privacy.

Access Control Subsystem

The Access Control Subsystem provides authorization services by means of one or more (*) Access Control Models.

Access Control Model

An Access Control Model defines a particular access decision function in order to support decisions regarding access rights.

Applications

There are several types of applications, including:

  -  command generators, which monitor and manipulate management
     data,

  -  command responders, which provide access to management data,

  -  notification originators, which initiate asynchronous messages,

  -  notification receivers, which process asynchronous messages,

and

  -  proxy forwarders, which forward messages between entities.

These applications make use of the services provided by the SNMP engine.

SNMP Manager

An SNMP entity containing one or more command generator and/or notification receiver applications (along with their associated SNMP engine) has traditionally been called an SNMP manager.

                   (traditional SNMP manager)

+-------------------------------------------------------------------+ | +--------------+ +--------------+ +--------------+ SNMP entity | | | NOTIFICATION | | NOTIFICATION | | COMMAND | | | | ORIGINATOR | | RECEIVER | | GENERATOR | | | | applications | | applications | | applications | | | +--------------+ +--------------+ +--------------+ | | ^ ^ ^ | | | | | | | v v v | | +-------+--------+-----------------+ | | ^ | | | +---------------------+ +----------------+ | | | | Message Processing | | Security | | | Dispatcher v | Subsystem | | Subsystem | | | +-------------------+ | +------------+ | | | | | | PDU Dispatcher | | +->| v1MP * |<--->| +------------+ | | | | | | | +------------+ | | | Other | | | | | | | | +------------+ | | | Security | | | | | | | +->| v2cMP * |<--->| | Model | | | | | Message | | | +------------+ | | +------------+ | | | | Dispatcher <--------->+ | | | | | | | | | +------------+ | | +------------+ | | | | | | +->| v3MP * |<--->| | User-based | | | | | Transport | | | +------------+ | | | Security | | | | | Mapping | | | +------------+ | | | Model | | | | | (e.g., RFC 3417) | | +->| otherMP * |<--->| +------------+ | | | +-------------------+ | +------------+ | | | | | ^ +---------------------+ +----------------+ | | | | | v | +-------------------------------------------------------------------+ +-----+ +-----+ +-------+ | UDP | | IPX | . . . | other | +-----+ +-----+ +-------+

  ^       ^              ^
  |       |              |      * One or more models may be present.
  v       v              v

+------------------------------+ | Network | +------------------------------+

SNMP Agent

An SNMP entity containing one or more command responder and/or notification originator applications (along with their associated SNMP engine) has traditionally been called an SNMP agent.

One or more models may be present.

+------------------------------+ | Network | +------------------------------+

  ^       ^              ^
  |       |              |
  v       v              v

+-----+ +-----+ +-------+ | UDP | | IPX | . . . | other | +-----+ +-----+ +-------+ (traditional SNMP agent) +-------------------------------------------------------------------+ | ^ | | | +---------------------+ +----------------+ | | | | Message Processing | | Security | | | Dispatcher v | Subsystem | | Subsystem | | | +-------------------+ | +------------+ | | | | | | Transport | | +->| v1MP * |<--->| +------------+ | | | | Mapping | | | +------------+ | | | Other | | | | | (e.g., RFC 3417) | | | +------------+ | | | Security | | | | | | | +->| v2cMP * |<--->| | Model | | | | | Message | | | +------------+ | | +------------+ | | | | Dispatcher <--------->| +------------+ | | +------------+ | | | | | | +->| v3MP * |<--->| | User-based | | | | | | | | +------------+ | | | Security | | | | | PDU Dispatcher | | | +------------+ | | | Model | | | | +-------------------+ | +->| otherMP * |<--->| +------------+ | | | ^ | +------------+ | | | | | | +---------------------+ +----------------+ | | v | | +-------+-------------------------+---------------+ | | ^ ^ ^ | | | | | | | v v v | | +-------------+ +---------+ +--------------+ +-------------+ | | | COMMAND | | ACCESS | | NOTIFICATION | | PROXY | | | | RESPONDER |<->| CONTROL |<->| ORIGINATOR | | FORWARDER | | | | application | | | | applications | | application | | | +-------------+ +---------+ +--------------+ +-------------+ | | ^ ^ | | | | | | v v | | +----------------------------------------------+ | | | MIB instrumentation | SNMP entity | +-------------------------------------------------------------------+

The Naming of Identities

+----------------------------|-------------+ | SNMP engine v | | +--------------+ | | | | | | +-----------------| securityName |---+ | | | Security Model | | | | | | +--------------+ | | | | ^ | | | | | | | | | v | | | | +------------------------------+ | | | | | | | | | | | Model | | | | | | Dependent | | | | | | Security ID | | | | | | | | | | | +------------------------------+ | | | | ^ | | | | | | | | +-------------------------|----------+ | | | | | | | +----------------------------|-------------+

                            |
                            v
                         network

Principal

A principal is the "who" on whose behalf services are provided or processing takes place.

A principal can be, among other things, an individual acting in a particular role; a set of individuals, with each acting in a particular role; an application or a set of applications; and combinations thereof.

securityName

A securityName is a human readable string representing a principal. It has a model-independent format, and can be used outside a particular Security Model.

Model-dependent security ID

A model-dependent security ID is the model-specific representation of a securityName within a particular Security Model.

Model-dependent security IDs may or may not be human readable, and have a model-dependent syntax. Examples include community names, and user names.

The transformation of model-dependent security IDs into securityNames and vice versa is the responsibility of the relevant Security Model.

The Naming of Management Information

Management information resides at an SNMP entity where a Command Responder Application has local access to potentially multiple contexts. This application uses a contextEngineID equal to the snmpEngineID of its associated SNMP engine.

+-----------------------------------------------------------------+ | SNMP entity (identified by snmpEngineID, for example: | | '800002b804616263'H (enterpise 696, string "abc") | | | | +------------------------------------------------------------+ | | | SNMP engine (identified by snmpEngineID) | | | | | | | | +-------------+ +------------+ +-----------+ +-----------+ | | | | | | | | | | | | | | | | | Dispatcher | | Message | | Security | | Access | | | | | | | | Processing | | Subsystem | | Control | | | | | | | | Subsystem | | | | Subsystem | | | | | | | | | | | | | | | | | +-------------+ +------------+ +-----------+ +-----------+ | | | | | | | +------------------------------------------------------------+ | | | | +------------------------------------------------------------+ | | | Command Responder Application | | | | (contextEngineID, example: '800002b804616263'H) | | | | | | | | example contextNames: | | | | | | | | "bridge1" "bridge2" "" (default) | | | | --------- --------- ------------ | | | | | | | | | | +------|------------------|-------------------|--------------+ | | | | | | | +------|------------------|-------------------|--------------+ | | | MIB | instrumentation | | | | | | +---v------------+ +---v------------+ +----v-----------+ | | | | | context | | context | | context | | | | | | | | | | | | | | | | +------------+ | | +------------+ | | +------------+ | | | | | | | bridge MIB | | | | bridge MIB | | | | some MIB | | | | | | | +------------+ | | +------------+ | | +------------+ | | | | | | | | | | | | | | | | | | | | +------------+ | | | | | | | | | | | other MIB | | | | | | | | | | | +------------+ | | | | | | | | | | | | | +-----------------------------------------------------------------+

An SNMP Context

An SNMP context, or just "context" for short, is a collection of management information accessible by an SNMP entity. An item of management information may exist in more than one context. An SNMP entity potentially has access to many contexts.

Typically, there are many instances of each managed object type within a management domain. For simplicity, the method for identifying instances specified by the MIB module does not allow each instance to be distinguished amongst the set of all instances within a management domain; rather, it allows each instance to be identified only within some scope or "context", where there are multiple such contexts within the management domain. Often, a context is a physical device, or perhaps, a logical device, although a context can also encompass multiple devices, or a subset of a single device, or even a subset of multiple devices, but a context is always defined as a subset of a single SNMP entity. Thus, in order to identify an individual item of management information within the management domain, its contextName and contextEngineID must be identified in addition to its object type and its instance.

For example, the managed object type ifDescr [RFC2863], is defined as the description of a network interface. To identify the description of device-X's first network interface, four pieces of information are needed: the snmpEngineID of the SNMP entity which provides access to the management information at device-X, the contextName (device-X), the managed object type (ifDescr), and the instance ("1").

Each context has (at least) one unique identification within the management domain. The same item of management information can exist in multiple contexts. An item of management information may have multiple unique identifications. This occurs when an item of management information exists in multiple contexts, and this also occurs when a context has multiple unique identifications.

The combination of a contextEngineID and a contextName unambiguously identifies a context within an administrative domain; note that there may be multiple unique combinations of contextEngineID and contextName that unambiguously identify the same context.

contextEngineID

Within an administrative domain, a contextEngineID uniquely identifies an SNMP entity that may realize an instance of a context with a particular contextName.

contextName

A contextName is used to name a context. Each contextName MUST be unique within an SNMP entity.

scopedPDU

A scopedPDU is a block of data containing a contextEngineID, a contextName, and a PDU.

The PDU is an SNMP Protocol Data Unit containing information named in the context which is unambiguously identified within an administrative domain by the combination of the contextEngineID and the contextName. See, for example, RFC 3416 for more information about SNMP PDUs.

Other Constructs

maxSizeResponseScopedPDU

The maxSizeResponseScopedPDU is the maximum size of a scopedPDU that a PDU's sender would be willing to accept. Note that the size of a scopedPDU does not include the size of the SNMP message header.

Local Configuration Datastore

The subsystems, models, and applications within an SNMP entity may need to retain their own sets of configuration information.

Portions of the configuration information may be accessible as managed objects.

The collection of these sets of information is referred to as an entity's Local Configuration Datastore (LCD).

securityLevel

This architecture recognizes three levels of security:

  -  without authentication and without privacy (noAuthNoPriv)

  -  with authentication but without privacy (authNoPriv)

  -  with authentication and with privacy (authPriv)

These three values are ordered such that noAuthNoPriv is less than authNoPriv and authNoPriv is less than authPriv.

Every message has an associated securityLevel. All Subsystems (Message Processing, Security, Access Control) and applications are REQUIRED to either supply a value of securityLevel or to abide by the supplied value of securityLevel while processing the message and its contents.

Abstract Service Interfaces

Abstract service interfaces have been defined to describe the conceptual interfaces between the various subsystems within an SNMP entity. The abstract service interfaces are intended to help clarify the externally observable behavior of SNMP entities, and are not intended to constrain the structure or organization of implementations in any way. Most specifically, they should not be interpreted as APIs or as requirements statements for APIs.

These abstract service interfaces are defined by a set of primitives that define the services provided and the abstract data elements that are to be passed when the services are invoked. This section lists the primitives that have been defined for the various subsystems.

Dispatcher Primitives

The Dispatcher typically provides services to the SNMP applications via its PDU Dispatcher. This section describes the primitives provided by the PDU Dispatcher.

Generate Outgoing Request or Notification

The PDU Dispatcher provides the following primitive for an application to send an SNMP Request or Notification to another SNMP entity:

statusInformation = -- sendPduHandle if success

                                -- errorIndication if failure
 sendPdu(
 IN   transportDomain           -- transport domain to be used
 IN   transportAddress          -- transport address to be used
 IN   messageProcessingModel    -- typically, SNMP version
 IN   securityModel             -- Security Model to use
 IN   securityName              -- on behalf of this principal
 IN   securityLevel             -- Level of Security requested
 IN   contextEngineID           -- data from/at this entity
 IN   contextName               -- data from/in this context
 IN   pduVersion                -- the version of the PDU
 IN   PDU                       -- SNMP Protocol Data Unit
 IN   expectResponse            -- TRUE or FALSE
      )

Process Incoming Request or Notification PDU

The PDU Dispatcher provides the following primitive to pass an incoming SNMP PDU to an application:

processPdu( -- process Request/Notification PDU

 IN   messageProcessingModel    -- typically, SNMP version
 IN   securityModel             -- Security Model in use
 IN   securityName              -- on behalf of this principal
 IN   securityLevel             -- Level of Security
 IN   contextEngineID           -- data from/at this SNMP entity
 IN   contextName               -- data from/in this context
 IN   pduVersion                -- the version of the PDU
 IN   PDU                       -- SNMP Protocol Data Unit
 IN   maxSizeResponseScopedPDU  -- maximum size of the Response PDU
 IN   stateReference            -- reference to state information
      )                         -- needed when sending a response

Generate Outgoing Response

The PDU Dispatcher provides the following primitive for an application to return an SNMP Response PDU to the PDU Dispatcher:

result = -- SUCCESS or FAILURE returnResponsePdu(

 IN   messageProcessingModel    -- typically, SNMP version
 IN   securityModel             -- Security Model in use
 IN   securityName              -- on behalf of this principal
 IN   securityLevel             -- same as on incoming request
 IN   contextEngineID           -- data from/at this SNMP entity
 IN   contextName               -- data from/in this context
 IN   pduVersion                -- the version of the PDU
 IN   PDU                       -- SNMP Protocol Data Unit
 IN   maxSizeResponseScopedPDU  -- maximum size sender can accept
 IN   stateReference            -- reference to state information
                                -- as presented with the request
 IN   statusInformation         -- success or errorIndication
      )                         -- error counter OID/value if error

Process Incoming Response PDU

The PDU Dispatcher provides the following primitive to pass an incoming SNMP Response PDU to an application:

processResponsePdu( -- process Response PDU

 IN   messageProcessingModel    -- typically, SNMP version
 IN   securityModel             -- Security Model in use
 IN   securityName              -- on behalf of this principal
 IN   securityLevel             -- Level of Security
 IN   contextEngineID           -- data from/at this SNMP entity
 IN   contextName               -- data from/in this context
 IN   pduVersion                -- the version of the PDU
 IN   PDU                       -- SNMP Protocol Data Unit
 IN   statusInformation         -- success or errorIndication
 IN   sendPduHandle             -- handle from sendPdu
      )

Registering Responsibility for Handling SNMP PDUs

Applications can register/unregister responsibility for a specific contextEngineID, for specific pduTypes, with the PDU Dispatcher according to the following primitives. The list of particular pduTypes that an application can register for is determined by the Message Processing Model(s) supported by the SNMP entity that contains the PDU Dispatcher.

statusInformation = -- success or errorIndication

 registerContextEngineID(
 IN   contextEngineID         -- take responsibility for this one
 IN   pduType                 -- the pduType(s) to be registered
      )

unregisterContextEngineID(

 IN   contextEngineID         -- give up responsibility for this one
 IN   pduType                 -- the pduType(s) to be unregistered
      )

Note that realizations of the registerContextEngineID and unregisterContextEngineID abstract service interfaces may provide implementation-specific ways for applications to register/deregister responsibility for all possible values of the contextEngineID or pduType parameters.

Message Processing Subsystem Primitives

The Dispatcher interacts with a Message Processing Model to process a specific version of an SNMP Message. This section describes the primitives provided by the Message Processing Subsystem.

Prepare Outgoing SNMP Request or Notification Message

The Message Processing Subsystem provides this service primitive for preparing an outgoing SNMP Request or Notification Message:

statusInformation = -- success or errorIndication

 prepareOutgoingMessage(
 IN   transportDomain           -- transport domain to be used
 IN   transportAddress          -- transport address to be used
 IN   messageProcessingModel    -- typically, SNMP version
 IN   securityModel             -- Security Model to use
 IN   securityName              -- on behalf of this principal
 IN   securityLevel             -- Level of Security requested
 IN   contextEngineID           -- data from/at this entity
 IN   contextName               -- data from/in this context
 IN   pduVersion                -- the version of the PDU
 IN   PDU                       -- SNMP Protocol Data Unit
 IN   expectResponse            -- TRUE or FALSE
 IN   sendPduHandle             -- the handle for matching
                                -- incoming responses
 OUT  destTransportDomain       -- destination transport domain
 OUT  destTransportAddress      -- destination transport address
 OUT  outgoingMessage           -- the message to send
 OUT  outgoingMessageLength     -- its length
      )

Prepare an Outgoing SNMP Response Message

The Message Processing Subsystem provides this service primitive for preparing an outgoing SNMP Response Message:

result = -- SUCCESS or FAILURE

 prepareResponseMessage(
 IN   messageProcessingModel    -- typically, SNMP version
 IN   securityModel             -- same as on incoming request
 IN   securityName              -- same as on incoming request
 IN   securityLevel             -- same as on incoming request
 IN   contextEngineID           -- data from/at this SNMP entity
 IN   contextName               -- data from/in this context
 IN   pduVersion                -- the version of the PDU
 IN   PDU                       -- SNMP Protocol Data Unit
 IN   maxSizeResponseScopedPDU  -- maximum size able to accept
 IN   stateReference            -- reference to state information
                                -- as presented with the request
 IN   statusInformation         -- success or errorIndication
                                -- error counter OID/value if error
 OUT  destTransportDomain       -- destination transport domain
 OUT  destTransportAddress      -- destination transport address
 OUT  outgoingMessage           -- the message to send
 OUT  outgoingMessageLength     -- its length
      )

Prepare Data Elements from an Incoming SNMP Message

The Message Processing Subsystem provides this service primitive for preparing the abstract data elements from an incoming SNMP message:

result = -- SUCCESS or errorIndication

 prepareDataElements(
 IN   transportDomain           -- origin transport domain
 IN   transportAddress          -- origin transport address
 IN   wholeMsg                  -- as received from the network
 IN   wholeMsgLength            -- as received from the network
 OUT  messageProcessingModel    -- typically, SNMP version
 OUT  securityModel             -- Security Model to use
 OUT  securityName              -- on behalf of this principal
 OUT  securityLevel             -- Level of Security requested
 OUT  contextEngineID           -- data from/at this entity
 OUT  contextName               -- data from/in this context
 OUT  pduVersion                -- the version of the PDU
 OUT  PDU                       -- SNMP Protocol Data Unit
 OUT  pduType                   -- SNMP PDU type
 OUT  sendPduHandle             -- handle for matched request
 OUT  maxSizeResponseScopedPDU  -- maximum size sender can accept
 OUT  statusInformation         -- success or errorIndication
                                -- error counter OID/value if error
 OUT  stateReference            -- reference to state information
                                -- to be used for possible Response
      )

Access Control Subsystem Primitives

Applications are the typical clients of the service(s) of the Access Control Subsystem.

The following primitive is provided by the Access Control Subsystem to check if access is allowed:

statusInformation = -- success or errorIndication

 isAccessAllowed(
 IN   securityModel             -- Security Model in use
 IN   securityName              -- principal who wants to access
 IN   securityLevel             -- Level of Security
 IN   viewType                  -- read, write, or notify view
 IN   contextName               -- context containing variableName
 IN   variableName              -- OID for the managed object
      )

Security Subsystem Primitives

The Message Processing Subsystem is the typical client of the services of the Security Subsystem.

Generate a Request or Notification Message

The Security Subsystem provides the following primitive to generate a Request or Notification message:

statusInformation =

 generateRequestMsg(
 IN   messageProcessingModel    -- typically, SNMP version
 IN   globalData                -- message header, admin data
 IN   maxMessageSize            -- of the sending SNMP entity
 IN   securityModel             -- for the outgoing message
 IN   securityEngineID          -- authoritative SNMP entity
 IN   securityName              -- on behalf of this principal
 IN   securityLevel             -- Level of Security requested
 IN   scopedPDU                 -- message (plaintext) payload
 OUT  securityParameters        -- filled in by Security Module
 OUT  wholeMsg                  -- complete generated message
 OUT  wholeMsgLength            -- length of the generated message
      )

Process Incoming Message

The Security Subsystem provides the following primitive to process an incoming message:

statusInformation = -- errorIndication or success

                                -- error counter OID/value if error
 processIncomingMsg(
 IN   messageProcessingModel    -- typically, SNMP version
 IN   maxMessageSize            -- of the sending SNMP entity
 IN   securityParameters        -- for the received message
 IN   securityModel             -- for the received message
 IN   securityLevel             -- Level of Security
 IN   wholeMsg                  -- as received on the wire
 IN   wholeMsgLength            -- length as received on the wire
 OUT  securityEngineID          -- authoritative SNMP entity
 OUT  securityName              -- identification of the principal
 OUT  scopedPDU,                -- message (plaintext) payload
 OUT  maxSizeResponseScopedPDU  -- maximum size sender can handle
 OUT  securityStateReference    -- reference to security state
      )                         -- information, needed for response

Generate a Response Message

The Security Subsystem provides the following primitive to generate a Response message:

statusInformation =

 generateResponseMsg(
 IN   messageProcessingModel    -- typically, SNMP version
 IN   globalData                -- message header, admin data
 IN   maxMessageSize            -- of the sending SNMP entity
 IN   securityModel             -- for the outgoing message
 IN   securityEngineID          -- authoritative SNMP entity
 IN   securityName              -- on behalf of this principal
 IN   securityLevel             -- for the outgoing message
 IN   scopedPDU                 -- message (plaintext) payload
 IN   securityStateReference    -- reference to security state
                                -- information from original request
 OUT  securityParameters        -- filled in by Security Module
 OUT  wholeMsg                  -- complete generated message
 OUT  wholeMsgLength            -- length of the generated message
      )

Common Primitives

These primitive(s) are provided by multiple Subsystems.

Release State Reference Information

All Subsystems which pass stateReference information also provide a primitive to release the memory that holds the referenced state information:

stateRelease(

 IN   stateReference       -- handle of reference to be released
      )

Scenario Diagrams

Command Generator or Notification Originator

This diagram shows how a Command Generator or Notification Originator application requests that a PDU be sent, and how the response is returned (asynchronously) to that application.

|----------------------->| |

| | generateRequestMsg |

| |-------------------->|

| | |

| |<--------------------|

| | |

|<-----------------------| |

| | |

|------------------+ | |

| Send SNMP | | |

| Request Message | | |

| to Network | | |

| v | |

: : : :

| | | |

| Receive SNMP | | |

| Response Message | | |

| from Network | | |

|<-----------------+ | |

| | |

| prepareDataElements | |

|----------------------->| |

| | processIncomingMsg |

| |-------------------->|

| | |

| |<--------------------|

| | |

|<-----------------------| |

| processResponsePdu | | | |<-------------------| | | | | | |

Scenario Diagram for a Command Responder Application

This diagram shows how a Command Responder or Notification Receiver application registers for handling a pduType, how a PDU is dispatched to the application after an SNMP message is received, and how the Response is (asynchronously) send back to the network.

Command Dispatcher Message Security Responder | Processing Model | | Model | | | | | | registerContextEngineID | | | |------------------------>| | | |<------------------------| | | | | | Receive SNMP | | |

| Message | | |

| from Network | | |

|<-------------+ | |

| | |

|prepareDataElements | |

|------------------->| |

| | processIncomingMsg |

| |------------------->|

| | |

| |<-------------------|

| | |

|<-------------------| |

| processPdu | | | |<------------------------| | | | | | |

: : :

| returnResponsePdu | | | |------------------------>| | |

| prepareResponseMsg | |

|------------------->| |

| |generateResponseMsg |

| |------------------->|

| | |

| |<-------------------|

| | |

|<-------------------| |

| | |

|--------------+ | |

| Send SNMP | | |

| Message | | |

| to Network | | |

| v | |

Managed Object Definitions for SNMP Management Frameworks

SNMP-FRAMEWORK-MIB DEFINITIONS ::= BEGIN

IMPORTS

MODULE-IDENTITY, OBJECT-TYPE,
OBJECT-IDENTITY,
snmpModules                           FROM SNMPv2-SMI
TEXTUAL-CONVENTION                    FROM SNMPv2-TC
MODULE-COMPLIANCE, OBJECT-GROUP       FROM SNMPv2-CONF;

snmpFrameworkMIB MODULE-IDENTITY

LAST-UPDATED "200210140000Z"
ORGANIZATION "SNMPv3 Working Group"
CONTACT-INFO "WG-EMail:   [email protected]
              Subscribe:  [email protected]

              Co-Chair:   Russ Mundy
                          Network Associates Laboratories
              postal:     15204 Omega Drive, Suite 300
                          Rockville, MD 20850-4601
                          USA
              EMail:      [email protected]
              phone:      +1 301-947-7107

              Co-Chair &
              Co-editor:  David Harrington
                          Enterasys Networks
              postal:     35 Industrial Way
                          P. O. Box 5005
                          Rochester, New Hampshire 03866-5005
                          USA
              EMail:      [email protected]
              phone:      +1 603-337-2614

              Co-editor:  Randy Presuhn
                          BMC Software, Inc.
              postal:     2141 North First Street
                          San Jose, California 95131
                          USA
              EMail:      [email protected]
              phone:      +1 408-546-1006

              Co-editor:  Bert Wijnen
                          Lucent Technologies
              postal:     Schagen 33
                          3461 GL Linschoten
                          Netherlands

              EMail:      [email protected]
              phone:      +31 348-680-485
                "
   DESCRIPTION  "The SNMP Management Architecture MIB

                 Copyright (C) The Internet Society (2002). This
                 version of this MIB module is part of RFC 3411;
                 see the RFC itself for full legal notices.
                "

   REVISION     "200210140000Z"         -- 14 October 2002
   DESCRIPTION  "Changes in this revision:
                 - Updated various administrative information.
                 - Corrected some typos.
                 - Corrected typo in description of SnmpEngineID
                   that led to range overlap for 127.
                 - Changed '255a' to '255t' in definition of
                   SnmpAdminString to align with current SMI.
                 - Reworded 'reserved' for value zero in
                   DESCRIPTION of SnmpSecurityModel.
                 - The algorithm for allocating security models
                   should give 256 per enterprise block, rather
                   than 255.
                 - The example engine ID of 'abcd' is not
                   legal. Replaced with '800002b804616263'H based
                   on example enterprise 696, string 'abc'.
                 - Added clarification that engineID should
                   persist across re-initializations.
                 This revision published as RFC 3411.
                "
   REVISION     "199901190000Z"         -- 19 January 1999
   DESCRIPTION  "Updated editors' addresses, fixed typos.
                 Published as RFC 2571.
                "
   REVISION     "199711200000Z"         -- 20 November 1997
   DESCRIPTION  "The initial version, published in RFC 2271.
                "
   ::= { snmpModules 10 }

-- Textual Conventions used in the SNMP Management Architecture ***

SnmpEngineID ::= TEXTUAL-CONVENTION

STATUS       current
DESCRIPTION "An SNMP engine's administratively-unique identifier.
             Objects of this type are for identification, not for
             addressing, even though it is possible that an
             address may have been used in the generation of
             a specific value.

             The value for this object may not be all zeros or
             all 'ff'H or the empty (zero length) string.

             The initial value for this object may be configured
             via an operator console entry or via an algorithmic
             function.  In the latter case, the following
             example algorithm is recommended.

             In cases where there are multiple engines on the
             same system, the use of this algorithm is NOT
             appropriate, as it would result in all of those
             engines ending up with the same ID value.

             1) The very first bit is used to indicate how the
                rest of the data is composed.

                0 - as defined by enterprise using former methods
                    that existed before SNMPv3. See item 2 below.

                1 - as defined by this architecture, see item 3
                    below.

                Note that this allows existing uses of the
                engineID (also known as AgentID [RFC1910]) to
                co-exist with any new uses.

             2) The snmpEngineID has a length of 12 octets.

                The first four octets are set to the binary
                equivalent of the agent's SNMP management
                private enterprise number as assigned by the
                Internet Assigned Numbers Authority (IANA).
                For example, if Acme Networks has been assigned
                { enterprises 696 }, the first four octets would
                be assigned '000002b8'H.

                The remaining eight octets are determined via
                one or more enterprise-specific methods. Such
                methods must be designed so as to maximize the
                possibility that the value of this object will
                be unique in the agent's administrative domain.
                For example, it may be the IP address of the SNMP
                entity, or the MAC address of one of the
                interfaces, with each address suitably padded
                with random octets.  If multiple methods are
                defined, then it is recommended that the first
                octet indicate the method being used and the
                remaining octets be a function of the method.

             3) The length of the octet string varies.

                The first four octets are set to the binary
                equivalent of the agent's SNMP management
                private enterprise number as assigned by the
                Internet Assigned Numbers Authority (IANA).
                For example, if Acme Networks has been assigned
                { enterprises 696 }, the first four octets would
                be assigned '000002b8'H.

                The very first bit is set to 1. For example, the
                above value for Acme Networks now changes to be
                '800002b8'H.

                The fifth octet indicates how the rest (6th and
                following octets) are formatted. The values for
                the fifth octet are:

                  0     - reserved, unused.

                  1     - IPv4 address (4 octets)
                          lowest non-special IP address

                  2     - IPv6 address (16 octets)
                          lowest non-special IP address

                  3     - MAC address (6 octets)
                          lowest IEEE MAC address, canonical
                          order

                  4     - Text, administratively assigned
                          Maximum remaining length 27

                  5     - Octets, administratively assigned
                          Maximum remaining length 27

                  6-127 - reserved, unused

                128-255 - as defined by the enterprise
                          Maximum remaining length 27
            "
SYNTAX       OCTET STRING (SIZE(5..32))

SnmpSecurityModel ::= TEXTUAL-CONVENTION

STATUS       current
DESCRIPTION "An identifier that uniquely identifies a
             Security Model of the Security Subsystem within
             this SNMP Management Architecture.

             The values for securityModel are allocated as
             follows:

             - The zero value does not identify any particular
               security model.

             - Values between 1 and 255, inclusive, are reserved
               for standards-track Security Models and are
               managed by the Internet Assigned Numbers Authority
               (IANA).
             - Values greater than 255 are allocated to
               enterprise-specific Security Models.  An
               enterprise-specific securityModel value is defined
               to be:

               enterpriseID * 256 + security model within
               enterprise

               For example, the fourth Security Model defined by
               the enterprise whose enterpriseID is 1 would be
               259.

             This scheme for allocation of securityModel
             values allows for a maximum of 255 standards-
             based Security Models, and for a maximum of
             256 Security Models per enterprise.

             It is believed that the assignment of new
             securityModel values will be rare in practice
             because the larger the number of simultaneously
             utilized Security Models, the larger the
             chance that interoperability will suffer.
             Consequently, it is believed that such a range
             will be sufficient.  In the unlikely event that
             the standards committee finds this number to be
             insufficient over time, an enterprise number
             can be allocated to obtain an additional 256
             possible values.

             Note that the most significant bit must be zero;
             hence, there are 23 bits allocated for various
             organizations to design and define non-standard

             securityModels.  This limits the ability to
             define new proprietary implementations of Security
             Models to the first 8,388,608 enterprises.

             It is worthwhile to note that, in its encoded
             form, the securityModel value will normally
             require only a single byte since, in practice,
             the leftmost bits will be zero for most messages
             and sign extension is suppressed by the encoding
             rules.

             As of this writing, there are several values
             of securityModel defined for use with SNMP or
             reserved for use with supporting MIB objects.
             They are as follows:

                 0  reserved for 'any'
                 1  reserved for SNMPv1
                 2  reserved for SNMPv2c
                 3  User-Based Security Model (USM)
            "
SYNTAX       INTEGER(0 .. 2147483647)

SnmpMessageProcessingModel ::= TEXTUAL-CONVENTION

STATUS       current
DESCRIPTION "An identifier that uniquely identifies a Message
             Processing Model of the Message Processing
             Subsystem within this SNMP Management Architecture.

             The values for messageProcessingModel are
             allocated as follows:

             - Values between 0 and 255, inclusive, are
               reserved for standards-track Message Processing
               Models and are managed by the Internet Assigned
               Numbers Authority (IANA).

             - Values greater than 255 are allocated to
               enterprise-specific Message Processing Models.
               An enterprise messageProcessingModel value is
               defined to be:

               enterpriseID * 256 +
                    messageProcessingModel within enterprise

               For example, the fourth Message Processing Model
               defined by the enterprise whose enterpriseID

               is 1 would be 259.

             This scheme for allocating messageProcessingModel
             values allows for a maximum of 255 standards-
             based Message Processing Models, and for a
             maximum of 256 Message Processing Models per
             enterprise.

             It is believed that the assignment of new
             messageProcessingModel values will be rare
             in practice because the larger the number of
             simultaneously utilized Message Processing Models,
             the larger the chance that interoperability
             will suffer. It is believed that such a range
             will be sufficient.  In the unlikely event that
             the standards committee finds this number to be
             insufficient over time, an enterprise number
             can be allocated to obtain an additional 256
             possible values.

             Note that the most significant bit must be zero;
             hence, there are 23 bits allocated for various
             organizations to design and define non-standard
             messageProcessingModels.  This limits the ability
             to define new proprietary implementations of
             Message Processing Models to the first 8,388,608
             enterprises.

             It is worthwhile to note that, in its encoded
             form, the messageProcessingModel value will
             normally require only a single byte since, in
             practice, the leftmost bits will be zero for
             most messages and sign extension is suppressed
             by the encoding rules.

             As of this writing, there are several values of
             messageProcessingModel defined for use with SNMP.
             They are as follows:

                 0  reserved for SNMPv1
                 1  reserved for SNMPv2c
                 2  reserved for SNMPv2u and SNMPv2*
                 3  reserved for SNMPv3
            "
SYNTAX       INTEGER(0 .. 2147483647)

SnmpSecurityLevel ::= TEXTUAL-CONVENTION

STATUS       current
DESCRIPTION "A Level of Security at which SNMP messages can be
             sent or with which operations are being processed;
             in particular, one of:

               noAuthNoPriv - without authentication and
                              without privacy,
               authNoPriv   - with authentication but
                              without privacy,
               authPriv     - with authentication and
                              with privacy.

             These three values are ordered such that
             noAuthNoPriv is less than authNoPriv and
             authNoPriv is less than authPriv.
            "
SYNTAX       INTEGER { noAuthNoPriv(1),
                       authNoPriv(2),
                       authPriv(3)
                     }

SnmpAdminString ::= TEXTUAL-CONVENTION

DISPLAY-HINT "255t"
STATUS       current
DESCRIPTION "An octet string containing administrative
             information, preferably in human-readable form.

             To facilitate internationalization, this
             information is represented using the ISO/IEC
             IS 10646-1 character set, encoded as an octet
             string using the UTF-8 transformation format
             described in [RFC2279].

             Since additional code points are added by
             amendments to the 10646 standard from time
             to time, implementations must be prepared to
             encounter any code point from 0x00000000 to
             0x7fffffff.  Byte sequences that do not
             correspond to the valid UTF-8 encoding of a
             code point or are outside this range are
             prohibited.

             The use of control codes should be avoided.

             When it is necessary to represent a newline,
             the control code sequence CR LF should be used.

             The use of leading or trailing white space should
             be avoided.

             For code points not directly supported by user
             interface hardware or software, an alternative
             means of entry and display, such as hexadecimal,
             may be provided.

             For information encoded in 7-bit US-ASCII,
             the UTF-8 encoding is identical to the
             US-ASCII encoding.

             UTF-8 may require multiple bytes to represent a
             single character / code point; thus the length
             of this object in octets may be different from
             the number of characters encoded.  Similarly,
             size constraints refer to the number of encoded
             octets, not the number of characters represented
             by an encoding.

             Note that when this TC is used for an object that
             is used or envisioned to be used as an index, then
             a SIZE restriction MUST be specified so that the
             number of sub-identifiers for any object instance
             does not exceed the limit of 128, as defined by
             [RFC3416].

             Note that the size of an SnmpAdminString object is
             measured in octets, not characters.
            "
SYNTAX       OCTET STRING (SIZE (0..255))

-- Administrative assignments ***************************************

snmpFrameworkAdmin

OBJECT IDENTIFIER ::= { snmpFrameworkMIB 1 }

snmpFrameworkMIBObjects

OBJECT IDENTIFIER ::= { snmpFrameworkMIB 2 }

snmpFrameworkMIBConformance

OBJECT IDENTIFIER ::= { snmpFrameworkMIB 3 }

-- the snmpEngine Group ********************************************

snmpEngine OBJECT IDENTIFIER ::= { snmpFrameworkMIBObjects 1 }

snmpEngineID OBJECT-TYPE

SYNTAX       SnmpEngineID
MAX-ACCESS   read-only
STATUS       current
DESCRIPTION "An SNMP engine's administratively-unique identifier.

             This information SHOULD be stored in non-volatile
             storage so that it remains constant across
             re-initializations of the SNMP engine.
            "
::= { snmpEngine 1 }

snmpEngineBoots OBJECT-TYPE

SYNTAX       INTEGER (1..2147483647)
MAX-ACCESS   read-only
STATUS       current
DESCRIPTION "The number of times that the SNMP engine has
             (re-)initialized itself since snmpEngineID
             was last configured.
            "
::= { snmpEngine 2 }

snmpEngineTime OBJECT-TYPE

SYNTAX       INTEGER (0..2147483647)
UNITS        "seconds"
MAX-ACCESS   read-only
STATUS       current
DESCRIPTION "The number of seconds since the value of
             the snmpEngineBoots object last changed.
             When incrementing this object's value would
             cause it to exceed its maximum,
             snmpEngineBoots is incremented as if a
             re-initialization had occurred, and this
             object's value consequently reverts to zero.
            "
::= { snmpEngine 3 }

snmpEngineMaxMessageSize OBJECT-TYPE

SYNTAX       INTEGER (484..2147483647)
MAX-ACCESS   read-only
STATUS       current
DESCRIPTION "The maximum length in octets of an SNMP message
             which this SNMP engine can send or receive and
             process, determined as the minimum of the maximum
             message size values supported among all of the
             transports available to and supported by the engine.
            "
::= { snmpEngine 4 }

-- Registration Points for Authentication and Privacy Protocols **

snmpAuthProtocols OBJECT-IDENTITY

STATUS        current
DESCRIPTION  "Registration point for standards-track
              authentication protocols used in SNMP Management
              Frameworks.
             "
::= { snmpFrameworkAdmin 1 }

snmpPrivProtocols OBJECT-IDENTITY

STATUS        current
DESCRIPTION  "Registration point for standards-track privacy
              protocols used in SNMP Management Frameworks.
             "
::= { snmpFrameworkAdmin 2 }

-- Conformance information ******************************************

snmpFrameworkMIBCompliances

           OBJECT IDENTIFIER ::= {snmpFrameworkMIBConformance 1}

snmpFrameworkMIBGroups

           OBJECT IDENTIFIER ::= {snmpFrameworkMIBConformance 2}

-- compliance statements

snmpFrameworkMIBCompliance MODULE-COMPLIANCE

STATUS       current
DESCRIPTION "The compliance statement for SNMP engines which
             implement the SNMP Management Framework MIB.
            "
MODULE    -- this module
    MANDATORY-GROUPS { snmpEngineGroup }

::= { snmpFrameworkMIBCompliances 1 }

-- units of conformance

snmpEngineGroup OBJECT-GROUP

OBJECTS {
          snmpEngineID,
          snmpEngineBoots,
          snmpEngineTime,
          snmpEngineMaxMessageSize
        }
STATUS       current
DESCRIPTION "A collection of objects for identifying and
             determining the configuration and current timeliness

             values of an SNMP engine.
            "
::= { snmpFrameworkMIBGroups 1 }

END

IANA Considerations

This document defines three number spaces administered by IANA, one for security models, another for message processing models, and a third for SnmpEngineID formats.

Security Models

The SnmpSecurityModel TEXTUAL-CONVENTION values managed by IANA are in the range from 0 to 255 inclusive, and are reserved for standards-track Security Models. If this range should in the future prove insufficient, an enterprise number can be allocated to obtain an additional 256 possible values.

As of this writing, there are several values of securityModel defined for use with SNMP or reserved for use with supporting MIB objects. They are as follows:

                       0  reserved for 'any'
                       1  reserved for SNMPv1
                       2  reserved for SNMPv2c
                       3  User-Based Security Model (USM)

Message Processing Models

The SnmpMessageProcessingModel TEXTUAL-CONVENTION values managed by IANA are in the range 0 to 255, inclusive. Each value uniquely identifies a standards-track Message Processing Model of the Message Processing Subsystem within the SNMP Management Architecture.

Should this range prove insufficient in the future, an enterprise number may be obtained for the standards committee to get an additional 256 possible values.

As of this writing, there are several values of messageProcessingModel defined for use with SNMP. They are as follows:

                       0  reserved for SNMPv1
                       1  reserved for SNMPv2c
                       2  reserved for SNMPv2u and SNMPv2*
                       3  reserved for SNMPv3

SnmpEngineID Formats

The SnmpEngineID TEXTUAL-CONVENTION's fifth octet contains a format identifier. The values managed by IANA are in the range 6 to 127, inclusive. Each value uniquely identifies a standards-track SnmpEngineID format.

Intellectual Property

The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in RFC 2028. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat.

The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director.

Acknowledgements

This document is the result of the efforts of the SNMPv3 Working Group. Some special thanks are in order to the following SNMPv3 WG members:

  Harald Tveit Alvestrand (Maxware)
  Dave Battle (SNMP Research, Inc.)
  Alan Beard (Disney Worldwide Services)
  Paul Berrevoets (SWI Systemware/Halcyon Inc.)
  Martin Bjorklund (Ericsson)
  Uri Blumenthal (IBM T.J. Watson Research Center)
  Jeff Case (SNMP Research, Inc.)
  John Curran (BBN)
  Mike Daniele (Compaq Computer Corporation)
  T. Max Devlin (Eltrax Systems)
  John Flick (Hewlett Packard)
  Rob Frye (MCI)
  Wes Hardaker (U.C.Davis, Information Technology - D.C.A.S.)

  David Harrington (Cabletron Systems Inc.)
  Lauren Heintz (BMC Software, Inc.)
  N.C. Hien (IBM T.J. Watson Research Center)
  Michael Kirkham (InterWorking Labs, Inc.)
  Dave Levi (SNMP Research, Inc.)
  Louis A Mamakos (UUNET Technologies Inc.)
  Joe Marzot (Nortel Networks)
  Paul Meyer (Secure Computing Corporation)
  Keith McCloghrie (Cisco Systems)
  Bob Moore (IBM)
  Russ Mundy (TIS Labs at Network Associates)
  Bob Natale (ACE*COMM Corporation)
  Mike O'Dell (UUNET Technologies Inc.)
  Dave Perkins (DeskTalk)
  Peter Polkinghorne (Brunel University)
  Randy Presuhn (BMC Software, Inc.)
  David Reeder (TIS Labs at Network Associates)
  David Reid (SNMP Research, Inc.)
  Aleksey Romanov (Quality Quorum)
  Shawn Routhier (Epilogue)
  Juergen Schoenwaelder (TU Braunschweig)
  Bob Stewart (Cisco Systems)
  Mike Thatcher (Independent Consultant)
  Bert Wijnen (IBM T.J. Watson Research Center)

The document is based on recommendations of the IETF Security and Administrative Framework Evolution for SNMP Advisory Team. Members of that Advisory Team were:

  David Harrington (Cabletron Systems Inc.)
  Jeff Johnson (Cisco Systems)
  David Levi (SNMP Research Inc.)
  John Linn (Openvision)
  Russ Mundy (Trusted Information Systems) chair
  Shawn Routhier (Epilogue)
  Glenn Waters (Nortel)
  Bert Wijnen (IBM T. J. Watson Research Center)

As recommended by the Advisory Team and the SNMPv3 Working Group Charter, the design incorporates as much as practical from previous RFCs and drafts. As a result, special thanks are due to the authors of previous designs known as SNMPv2u and SNMPv2*:

  Jeff Case (SNMP Research, Inc.)
  David Harrington (Cabletron Systems Inc.)
  David Levi (SNMP Research, Inc.)
  Keith McCloghrie (Cisco Systems)
  Brian O'Keefe (Hewlett Packard)

  Marshall T. Rose (Dover Beach Consulting)
  Jon Saperia (BGS Systems Inc.)
  Steve Waldbusser (International Network Services)
  Glenn W. Waters (Bell-Northern Research Ltd.)

Security Considerations

This document describes how an implementation can include a Security Model to protect management messages and an Access Control Model to control access to management information.

The level of security provided is determined by the specific Security Model implementation(s) and the specific Access Control Model implementation(s) used.

Applications have access to data which is not secured. Applications SHOULD take reasonable steps to protect the data from disclosure.

It is the responsibility of the purchaser of an implementation to ensure that:

  1) an implementation complies with the rules defined by this
     architecture,

  2) the Security and Access Control Models utilized satisfy the
     security and access control needs of the organization,

  3) the implementations of the Models and Applications comply with
     the model and application specifications,

  4) and the implementation protects configuration secrets from
     inadvertent disclosure.

This document also contains a MIB definition module. None of the objects defined is writable, and the information they represent is not deemed to be particularly sensitive. However, if they are deemed sensitive in a particular environment, access to them should be restricted through the use of appropriately configured Security and Access Control models.

10. References

10.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate

           Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO

           10646", RFC 2279, January 1998.

[RFC2578] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,

           Rose, M. and S. Waldbusser, "Structure of Management
           Information Version 2 (SMIv2)", STD 58, RFC 2578, April
           1999.

[RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,

           Rose, M. and S. Waldbusser, "Textual Conventions for
           SMIv2", STD 58, RFC 2579, April 1999.

[RFC2580] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,

           Rose, M. and S. Waldbusser, "Conformance Statements for
           SMIv2", STD 58, RFC 2580, April 1999.

[RFC3412] Case, J., Harrington, D., Presuhn, R. and B. Wijnen,

           "Message Processing and Dispatching for the Simple
           Network Management Protocol (SNMP)", STD 62, RFC 3412,
           December 2002.

[RFC3413] Levi, D., Meyer, P. and B. Stewart, "Simple Network

           Management Protocol (SNMP) Applications", STD 62, RFC
           3413, December 2002.

[RFC3414] Blumenthal, U. and B. Wijnen, "User-Based Security Model

           (USM) for Version 3 of the Simple Network Management
           Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.

[RFC3415] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based

           Access Control Model (VACM) for the Simple Network
           Management Protocol (SNMP)", STD 62, RFC 3415, December
           2002.

[RFC3416] Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.

           Waldbusser, "Protocol Operations for the Simple Network
           Management Protocol (SNMP)", STD 62, RFC 3416, December
           2002.

[RFC3417] Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.

           Waldbusser, "Transport Mappings for the Simple Network
           Management Protocol (SNMP)", STD 62, RFC 3417, December
           2002.

[RFC3418] Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.

           Waldbusser, "Management Information Base (MIB) for the
           Simple Network Management Protocol (SNMP)", STD 62, RFC
           3418, December 2002.

10.2. Informative References

[RFC1155] Rose, M. and K. McCloghrie, "Structure and Identification

           of Management Information for TCP/IP-based internets",
           STD 16, RFC 1155, May 1990.

[RFC1157] Case, J., Fedor, M., Schoffstall, M. and J. Davin, "The

           Simple Network Management Protocol", STD 15, RFC 1157,
           May 1990.

[RFC1212] Rose, M. and K. McCloghrie, "Concise MIB Definitions",

           STD 16, RFC 1212, March 1991.

[RFC1901] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,

           "Introduction to Community-based SNMPv2", RFC 1901,
           January 1996.

[RFC1909] McCloghrie, K., Editor, "An Administrative Infrastructure

           for SNMPv2", RFC 1909, February 1996.

[RFC1910] Waters, G., Editor, "User-based Security Model for

           SNMPv2", RFC 1910, February 1996.

[RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in

           the IETF Standards Process", BCP 11, RFC 2028, October
           1996.

[RFC2576] Frye, R., Levi, D., Routhier, S. and B. Wijnen,

           "Coexistence between Version 1, Version 2, and Version 3
           of the Internet-Standard Network Management Framework",
           RFC 2576, March 2000.

[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group

           MIB", RFC 2863, June 2000.

[RFC3410] Case, J., Mundy, R., Partain, D. and B. Stewart,

           "Introduction and Applicability Statements for Internet-
           Standard Management Framework", RFC 3410, December 2002.

Appendix A

A. Guidelines for Model Designers

This appendix describes guidelines for designers of models which are expected to fit into the architecture defined in this document.

SNMPv1 and SNMPv2c are two SNMP frameworks which use communities to provide trivial authentication and access control. SNMPv1 and SNMPv2c Frameworks can coexist with Frameworks designed according to this architecture, and modified versions of SNMPv1 and SNMPv2c Frameworks could be designed to meet the requirements of this architecture, but this document does not provide guidelines for that coexistence.

Within any subsystem model, there should be no reference to any specific model of another subsystem, or to data defined by a specific model of another subsystem.

Transfer of data between the subsystems is deliberately described as a fixed set of abstract data elements and primitive functions which can be overloaded to satisfy the needs of multiple model definitions.

Documents which define models to be used within this architecture SHOULD use the standard primitives between subsystems, possibly defining specific mechanisms for converting the abstract data elements into model-usable formats. This constraint exists to allow subsystem and model documents to be written recognizing common borders of the subsystem and model. Vendors are not constrained to recognize these borders in their implementations.

The architecture defines certain standard services to be provided between subsystems, and the architecture defines abstract service interfaces to request these services.

Each model definition for a subsystem SHOULD support the standard service interfaces, but whether, or how, or how well, it performs the service is dependent on the model definition.

A.1. Security Model Design Requirements

A.1.1. Threats

A document describing a Security Model MUST describe how the model protects against the threats described under "Security Requirements of this Architecture", section 1.4.

A.1.2. Security Processing

Received messages MUST be validated by a Model of the Security Subsystem. Validation includes authentication and privacy processing if needed, but it is explicitly allowed to send messages which do not require authentication or privacy.

A received message contains a specified securityLevel to be used during processing. All messages requiring privacy MUST also require authentication.

A Security Model specifies rules by which authentication and privacy are to be done. A model may define mechanisms to provide additional security features, but the model definition is constrained to using (possibly a subset of) the abstract data elements defined in this document for transferring data between subsystems.

Each Security Model may allow multiple security protocols to be used concurrently within an implementation of the model. Each Security Model defines how to determine which protocol to use, given the securityLevel and the security parameters relevant to the message. Each Security Model, with its associated protocol(s) defines how the sending/receiving entities are identified, and how secrets are configured.

Authentication and Privacy protocols supported by Security Models are uniquely identified using Object Identifiers. IETF standard protocols for authentication or privacy should have an identifier defined within the snmpAuthProtocols or the snmpPrivProtocols subtrees. Enterprise specific protocol identifiers should be defined within the enterprise subtree.

For privacy, the Security Model defines what portion of the message is encrypted.

The persistent data used for security should be SNMP-manageable, but the Security Model defines whether an instantiation of the MIB is a conformance requirement.

Security Models are replaceable within the Security Subsystem. Multiple Security Model implementations may exist concurrently within an SNMP engine. The number of Security Models defined by the SNMP community should remain small to promote interoperability.

A.1.3. Validate the security-stamp in a received message

A Message Processing Model requests that a Security Model:

  -  verifies that the message has not been altered,

  -  authenticates the identification of the principal for whom the
     message was generated.

  -  decrypts the message if it was encrypted.

Additional requirements may be defined by the model, and additional services may be provided by the model, but the model is constrained to use the following primitives for transferring data between subsystems. Implementations are not so constrained.

A Message Processing Model uses the processIncomingMsg primitive as described in section 4.4.2.

A.1.4. Security MIBs

Each Security Model defines the MIB module(s) required for security processing, including any MIB module(s) required for the security protocol(s) supported. The MIB module(s) SHOULD be defined concurrently with the procedures which use the MIB module(s). The MIB module(s) are subject to normal access control rules.

The mapping between the model-dependent security ID and the securityName MUST be able to be determined using SNMP, if the model- dependent MIB is instantiated and if access control policy allows access.

A.1.5. Cached Security Data

For each message received, the Security Model caches the state information such that a Response message can be generated using the same security information, even if the Local Configuration Datastore is altered between the time of the incoming request and the outgoing response.

A Message Processing Model has the responsibility for explicitly releasing the cached data if such data is no longer needed. To enable this, an abstract securityStateReference data element is passed from the Security Model to the Message Processing Model.

The cached security data may be implicitly released via the generation of a response, or explicitly released by using the stateRelease primitive, as described in section 4.5.1.

A.2. Message Processing Model Design Requirements

An SNMP engine contains a Message Processing Subsystem which may contain multiple Message Processing Models.

The Message Processing Model MUST always (conceptually) pass the complete PDU, i.e., it never forwards less than the complete list of varBinds.

A.2.1. Receiving an SNMP Message from the Network

Upon receipt of a message from the network, the Dispatcher in the SNMP engine determines the version of the SNMP message and interacts with the corresponding Message Processing Model to determine the abstract data elements.

A Message Processing Model specifies the SNMP Message format it supports and describes how to determine the values of the abstract data elements (like msgID, msgMaxSize, msgFlags, msgSecurityParameters, securityModel, securityLevel etc). A Message Processing Model interacts with a Security Model to provide security processing for the message using the processIncomingMsg primitive, as described in section 4.4.2.

A.2.2. Sending an SNMP Message to the Network

The Dispatcher in the SNMP engine interacts with a Message Processing Model to prepare an outgoing message. For that it uses the following primitives:

  -  for requests and notifications: prepareOutgoingMessage, as
     described in section 4.2.1.

  -  for response messages: prepareResponseMessage, as described in
     section 4.2.2.

A Message Processing Model, when preparing an Outgoing SNMP Message, interacts with a Security Model to secure the message. For that it uses the following primitives:

  -  for requests and notifications: generateRequestMsg, as
     described in section 4.4.1.

  -  for response messages: generateResponseMsg as described in
     section 4.4.3.

Once the SNMP message is prepared by a Message Processing Model, the Dispatcher sends the message to the desired address using the appropriate transport.

A.3. Application Design Requirements

Within an application, there may be an explicit binding to a specific SNMP message version, i.e., a specific Message Processing Model, and to a specific Access Control Model, but there should be no reference to any data defined by a specific Message Processing Model or Access Control Model.

Within an application, there should be no reference to any specific Security Model, or any data defined by a specific Security Model.

An application determines whether explicit or implicit access control should be applied to the operation, and, if access control is needed, which Access Control Model should be used.

An application has the responsibility to define any MIB module(s) used to provide application-specific services.

Applications interact with the SNMP engine to initiate messages, receive responses, receive asynchronous messages, and send responses.

A.3.1. Applications that Initiate Messages

Applications may request that the SNMP engine send messages containing SNMP commands or notifications using the sendPdu primitive as described in section 4.1.1.

If it is desired that a message be sent to multiple targets, it is the responsibility of the application to provide the iteration.

The SNMP engine assumes necessary access control has been applied to the PDU, and provides no access control services.

The SNMP engine looks at the "expectResponse" parameter, and if a response is expected, then the appropriate information is cached such that a later response can be associated to this message, and can then be returned to the application. A sendPduHandle is returned to the application so it can later correspond the response with this message as well.

A.3.2. Applications that Receive Responses

The SNMP engine matches the incoming response messages to outstanding messages sent by this SNMP engine, and forwards the response to the associated application using the processResponsePdu primitive, as described in section 4.1.4.

A.3.3. Applications that Receive Asynchronous Messages

When an SNMP engine receives a message that is not the response to a request from this SNMP engine, it must determine to which application the message should be given.

An Application that wishes to receive asynchronous messages registers itself with the engine using the primitive registerContextEngineID as described in section 4.1.5.

An Application that wishes to stop receiving asynchronous messages should unregister itself with the SNMP engine using the primitive unregisterContextEngineID as described in section 4.1.5.

Only one registration per combination of PDU type and contextEngineID is permitted at the same time. Duplicate registrations are ignored. An errorIndication will be returned to the application that attempts to duplicate a registration.

All asynchronously received messages containing a registered combination of PDU type and contextEngineID are sent to the application which registered to support that combination.

The engine forwards the PDU to the registered application, using the processPdu primitive, as described in section 4.1.2.

A.3.4. Applications that Send Responses

Request operations require responses. An application sends a response via the returnResponsePdu primitive, as described in section 4.1.3.

The contextEngineID, contextName, securityModel, securityName, securityLevel, and stateReference parameters are from the initial processPdu primitive. The PDU and statusInformation are the results of processing.

A.4. Access Control Model Design Requirements

An Access Control Model determines whether the specified securityName is allowed to perform the requested operation on a specified managed object. The Access Control Model specifies the rules by which access control is determined.

The persistent data used for access control should be manageable using SNMP, but the Access Control Model defines whether an instantiation of the MIB is a conformance requirement.

The Access Control Model must provide the primitive isAccessAllowed.

Editors' Addresses

Bert Wijnen Lucent Technologies Schagen 33 3461 GL Linschoten Netherlands

Phone: +31 348-680-485 EMail: [email protected]

David Harrington Enterasys Networks Post Office Box 5005 35 Industrial Way Rochester, New Hampshire 03866-5005 USA

Phone: +1 603-337-2614 EMail: [email protected]

Randy Presuhn BMC Software, Inc. 2141 North First Street San Jose, California 95131 USA

Phone: +1 408-546-1006 Fax: +1 408-965-0359 EMail: [email protected]

Full Copyright Statement

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@@ Line 1: / Line 1: @@
+Network Working Group                                      D. Harrington
+Request for Comments: 3411                            Enterasys Networks
+STD: 62                                                      R. Presuhn
+Obsoletes: 2571                                      BMC Software, Inc.
+Category: Standards Track                                      B. Wijnen
+                                                  Lucent Technologies
+                                                        December 2002
+                  An Architecture for Describing
+ Simple Network Management Protocol (SNMP) Management Frameworks
+Status of this Memo
+This document specifies an Internet standards track protocol for the
+Internet community, and requests discussion and suggestions for
+improvements.  Please refer to the current edition of the "Internet
+Official Protocol Standards" (STD 1) for the standardization state
+and status of this protocol.  Distribution of this memo is unlimited.
+Copyright Notice
+Copyright (C) The Internet Society (2002).  All Rights Reserved.
-Network Working Group                                      D. HarringtonRequest for Comments: 3411                            Enterasys NetworksSTD: 62                                                      R. PresuhnObsoletes: 2571                                      BMC Software, Inc.Category: Standards Track                                      B. Wijnen                                                  Lucent Technologies                                                        December 2002
-                  An Architecture for Describing Simple Network Management Protocol (SNMP) Management Frameworks
-Status of this Memo
-This document specifies an Internet standards track protocol for theInternet community, and requests discussion and suggestions forimprovements.  Please refer to the current edition of the "InternetOfficial Protocol Standards" (STD 1) for the standardization stateand status of this protocol.  Distribution of this memo is unlimited.
-Copyright Notice
-Copyright (C) The Internet Society (2002).  All Rights Reserved.
 Abstract
@@ Line 21: / Line 31: @@
 Subsystem and an Access Control Subsystem, and possibly multiple SNMP
 applications which provide specific functional processing of
-management data.  This document obsoletes [[RFC2571|RFC 2571]].
+management data.  This document obsoletes RFC 2571.
+Table of Contents
+. Introduction ................................................    4
+.1. Overview ..................................................    4
+.2. SNMP ......................................................    5
+.3. Goals of this Architecture ................................    6
+.4. Security Requirements of this Architecture ................    6
+.5. Design Decisions ..........................................    8
+. Documentation Overview ......................................  10
+.1. Document Roadmap ..........................................  11
+.2. Applicability Statement ...................................  11
+.3. Coexistence and Transition ................................  11
+.4. Transport Mappings ........................................  12
+.5. Message Processing ........................................  12
+.6. Security ..................................................  12
+.7. Access Control ............................................  13
+.8. Protocol Operations .......................................  13
+.9. Applications ..............................................  14
+.10. Structure of Management Information ......................  15
+.11. Textual Conventions ......................................  15
+.12. Conformance Statements ...................................  15
+.13. Management Information Base Modules ......................  15
+.13.1. SNMP Instrumentation MIBs ..............................  15
+.14. SNMP Framework Documents .................................  15
+. Elements of the Architecture ................................  16
+.1. The Naming of Entities ....................................  17
+.1.1. SNMP engine .............................................  18
+.1.1.1. snmpEngineID ..........................................  18
+.1.1.2. Dispatcher ............................................  18
+.1.1.3. Message Processing Subsystem ..........................  19
+.1.1.3.1. Message Processing Model ............................  19
+.1.1.4. Security Subsystem ....................................  20
+.1.1.4.1. Security Model ......................................  20
+.1.1.4.2. Security Protocol ...................................  20
+.1.2. Access Control Subsystem ................................  21
+.1.2.1. Access Control Model ..................................  21
+.1.3. Applications ............................................  21
+.1.3.1. SNMP Manager ..........................................  22
+.1.3.2. SNMP Agent ............................................  23
+.2. The Naming of Identities ..................................  25
+.2.1. Principal ...............................................  25
+.2.2. securityName ............................................  25
+.2.3. Model-dependent security ID .............................  26
+.3. The Naming of Management Information ......................  26
+.3.1. An SNMP Context .........................................  28
+.3.2. contextEngineID .........................................  28
+.3.3. contextName .............................................  29
+.3.4. scopedPDU ...............................................  29
+.4. Other Constructs ..........................................  29
+.4.1. maxSizeResponseScopedPDU ................................  29
+.4.2. Local Configuration Datastore ...........................  29
+.4.3. securityLevel ...........................................  29
+. Abstract Service Interfaces .................................  30
+.1. Dispatcher Primitives .....................................  30
+.1.1. Generate Outgoing Request or Notification ...............  31
+.1.2. Process Incoming Request or Notification PDU ............  31
+.1.3. Generate Outgoing Response ..............................  32
+.1.4. Process Incoming Response PDU ...........................  32
+.1.5. Registering Responsibility for Handling SNMP PDUs .......  32
+.2. Message Processing Subsystem Primitives ...................  33
+.2.1. Prepare Outgoing SNMP Request or Notification Message ...  33
+.2.2. Prepare an Outgoing SNMP Response Message ...............  34
+.2.3. Prepare Data Elements from an Incoming SNMP Message .....  35
+.3. Access Control Subsystem Primitives .......................  35
+.4. Security Subsystem Primitives .............................  36
+.4.1. Generate a Request or Notification Message ..............  36
+.4.2. Process Incoming Message ................................  36
+.4.3. Generate a Response Message .............................  37
+.5. Common Primitives .........................................  37
+.5.1. Release State Reference Information .....................  37
+.6. Scenario Diagrams .........................................  38
+.6.1. Command Generator or Notification Originator ............  38
+.6.2. Scenario Diagram for a Command Responder Application ....  39
+. Managed Object Definitions for SNMP Management Frameworks ...  40
+. IANA Considerations .........................................  51
+.1. Security Models ...........................................  51
+.2. Message Processing Models .................................  51
+.3. SnmpEngineID Formats ......................................  52
+. Intellectual Property .......................................  52
+. Acknowledgements ............................................  52
+. Security Considerations .....................................  54
+. References .................................................  54
+.1. Normative References .....................................  54
+.2. Informative References ...................................  56
+A. Guidelines for Model Designers ..............................  57
+A.1. Security Model Design Requirements ........................  57
+A.1.1. Threats .................................................  57
+A.1.2. Security Processing .....................................  58
+A.1.3. Validate the security-stamp in a received message .......  59
+A.1.4. Security MIBs ...........................................  59
+A.1.5. Cached Security Data ....................................  59
+A.2. Message Processing Model Design Requirements ..............  60
+A.2.1. Receiving an SNMP Message from the Network ..............  60
+A.2.2. Sending an SNMP Message to the Network ..................  60
+A.3. Application Design Requirements ...........................  61
+A.3.1. Applications that Initiate Messages .....................  61
+A.3.2. Applications that Receive Responses .....................  62
+A.3.3. Applications that Receive Asynchronous Messages .........  62
+A.3.4. Applications that Send Responses ........................  62
+A.4. Access Control Model Design Requirements ..................  63
+Editors' Addresses .............................................  63
+Full Copyright Statement .......................................  64
 == Introduction ==
@@ Line 64: / Line 179: @@
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].
 === SNMP ===
@@ Line 122: / Line 226: @@
        a potentially very large number of managed nodes (traditionally
        called (network) management stations).
 === Goals of this Architecture ===
@@ Line 177: / Line 275: @@
        unauthorized management operations, including falsifying the
        value of an object.
    Masquerade
@@ Line 226: / Line 320: @@
        advantage afforded by protecting against traffic analysis.
+=== Design Decisions ===
+Various design decisions were made in support of the goals of the
-=== Design Decisions ===
-Various design decisions were made in support of the goals of the
 architecture and the security requirements:
@@ Line 282: / Line 367: @@
        environment, these SNMP parameters must be remotely
        configurable.
    - Controlled Complexity
@@ Line 298: / Line 378: @@
        environment.
+== Documentation Overview ==
+The following figure shows the set of documents that fit within the
+SNMP Architecture.
++------------------------- Document Set ----------------------------+
+|                                                                  |
+| +----------+              +-----------------+  +----------------+ |
+| | Document |              | Applicability  |  | Coexistence    | |
+| | Roadmap  |              | Statement      |  | & Transition  | |
+| +----------+              +-----------------+  +----------------+ |
+|                                                                  |
+| +---------------------------------------------------------------+ |
+| | Message Handling                                              | |
+| | +----------------+  +-----------------+  +-----------------+  | |
+| | | Transport      |  | Message        |  | Security        |  | |
+| | | Mappings      |  | Processing and  |  |                |  | |
+| | |                |  | Dispatcher      |  |                |  | |
+| | +----------------+  +-----------------+  +-----------------+  | |
+| +---------------------------------------------------------------+ |
+|                                                                  |
+| +---------------------------------------------------------------+ |
+| | PDU Handling                                                  | |
+| | +----------------+  +-----------------+  +-----------------+  | |
+| | | Protocol      |  | Applications    |  | Access          |  | |
+| | | Operations    |  |                |  | Control        |  | |
+| | +----------------+  +-----------------+  +-----------------+  | |
+| +---------------------------------------------------------------+ |
+|                                                                  |
+| +---------------------------------------------------------------+ |
+| | Information Model                                            | |
+| | +--------------+  +--------------+    +---------------+      | |
+| | | Structure of |  | Textual      |    | Conformance  |      | |
+| | | Management  |  | Conventions  |    | Statements    |      | |
+| | | Information  |  |              |    |              |      | |
+| | +--------------+  +--------------+    +---------------+      | |
+| +---------------------------------------------------------------+ |
+|                                                                  |
+| +---------------------------------------------------------------+ |
+| | MIB Modules written in various formats, e.g.:                | |
+| | +----------------+ +----------------+                        | |
+| | | SMIv1 (STD 18) | | SMIv2 (STD 58) |                        | |
+| | | format        | | format        |                        | |
+| | +----------------+ +----------------+                        | |
+| +---------------------------------------------------------------+ |
+|                                                                  |
++-------------------------------------------------------------------+
+Each of these documents may be replaced or supplemented.  This
+Architecture document specifically describes how new documents fit
+into the set of documents in the area of Message and PDU handling.
+=== Document Roadmap ===
+One or more documents may be written to describe how sets of
+documents taken together form specific Frameworks.  The configuration
+of document sets might change over time, so the "road map" should be
+maintained in a document separate from the standards documents
+themselves.
+An example of such a roadmap is "Introduction and Applicability
+Statements for the Internet-Standard Management Framework" [RFC3410].
+=== Applicability Statement ===
+SNMP is used in networks that vary widely in size and complexity, by
+organizations that vary widely in their requirements of management.
+Some models will be designed to address specific problems of
+management, such as message security.
+One or more documents may be written to describe the environments to
+which certain versions of SNMP or models within SNMP would be
+appropriately applied, and those to which a given model might be
+inappropriately applied.
+=== Coexistence and Transition ===
+The purpose of an evolutionary architecture is to permit new models
+to replace or supplement existing models.  The interactions between
+models could result in incompatibilities, security "holes", and other
+undesirable effects.
+The purpose of Coexistence documents is to detail recognized
+anomalies and to describe required and recommended behaviors for
+resolving the interactions between models within the architecture.
+Coexistence documents may be prepared separately from model
+definition documents, to describe and resolve interaction anomalies
+between a model definition and one or more other model definitions.
+Additionally, recommendations for transitions between models may also
+be described, either in a coexistence document or in a separate
+document.
+One such coexistence document is [RFC2576], "Coexistence between
+Version 1, Version 2, and Version 3 of the Internet-Standard Network
+Management Framework".
+=== Transport Mappings ===
+SNMP messages are sent over various transports.  It is the purpose of
+Transport Mapping documents to define how the mapping between SNMP
+and the transport is done.
+=== Message Processing ===
+A Message Processing Model document defines a message format, which
+is typically identified by a version field in an SNMP message header.
+The document may also define a MIB module for use in message
+processing and for instrumentation of version-specific interactions.
+An SNMP engine includes one or more Message Processing Models, and
+thus may support sending and receiving multiple versions of SNMP
+messages.
+=== Security ===
+Some environments require secure protocol interactions.  Security is
+normally applied at two different stages:
+  -  in the transmission/receipt of messages, and
+  -  in the processing of the contents of messages.
+For purposes of this document, "security" refers to message-level
+security; "access control" refers to the security applied to protocol
+operations.
+Authentication, encryption, and timeliness checking are common
+functions of message level security.
+A security document describes a Security Model, the threats against
+which the model protects, the goals of the Security Model, the
+protocols which it uses to meet those goals, and it may define a MIB
+module to describe the data used during processing, and to allow the
+remote configuration of message-level security parameters, such as
+keys.
+An SNMP engine may support multiple Security Models concurrently.
+=== Access Control ===
+During processing, it may be required to control access to managed
+objects for operations.
+An Access Control Model defines mechanisms to determine whether
+access to a managed object should be allowed.  An Access Control
+Model may define a MIB module used during processing and to allow the
+remote configuration of access control policies.
+=== Protocol Operations ===
+SNMP messages encapsulate an SNMP Protocol Data Unit (PDU).  SNMP
+PDUs define the operations performed by the receiving SNMP engine.
+It is the purpose of a Protocol Operations document to define the
+operations of the protocol with respect to the processing of the
+PDUs.  Every PDU belongs to one or more of the PDU classes defined
+below:
+) Read Class:
+      The Read Class contains protocol operations that retrieve
+      management information.  For example, [RFC3416] defines the
+      following protocol operations for the Read Class: GetRequest-
+      PDU, GetNextRequest-PDU, and GetBulkRequest-PDU.
+) Write Class:
+      The Write Class contains protocol operations which attempt to
+      modify management information.  For example, [RFC3416] defines
+      the following protocol operation for the Write Class:
+      SetRequest-PDU.
+) Response Class:
+      The Response Class contains protocol operations which are sent
+      in response to a previous request.  For example, [RFC3416]
+      defines the following for the Response Class: Response-PDU,
+      Report-PDU.
+) Notification Class:
+      The Notification Class contains protocol operations which send
+      a notification to a notification receiver application.  For
+      example, [RFC3416] defines the following operations for the
+      Notification Class: Trapv2-PDU, InformRequest-PDU.
+) Internal Class:
+      The Internal Class contains protocol operations which are
+      exchanged internally between SNMP engines.  For example,
+      [RFC3416] defines the following operation for the Internal
+      Class: Report-PDU.
+The preceding five classifications are based on the functional
+properties of a PDU.  It is also useful to classify PDUs based on
+whether a response is expected:
+) Confirmed Class:
+      The Confirmed Class contains all protocol operations which
+      cause the receiving SNMP engine to send back a response.  For
+      example, [RFC3416] defines the following operations for the
+      Confirmed Class: GetRequest-PDU, GetNextRequest-PDU,
+      GetBulkRequest-PDU, SetRequest-PDU, and InformRequest-PDU.
+) Unconfirmed Class:
+      The Unconfirmed Class contains all protocol operations which
+      are not acknowledged.  For example, [RFC3416] defines the
+      following operations for the Unconfirmed Class: Report-PDU,
+      Trapv2-PDU, and GetResponse-PDU.
-== Documentation Overview ==
+An application document defines which Protocol Operations are
+supported by the application.
-The following figure shows the set of documents that fit within the
-SNMP Architecture.
-+------------------------- Document Set ----------------------------+
-|                                                                  |
-| +----------+              +-----------------+  +----------------+ |
-| | Document |              | Applicability  |  | Coexistence    | |
-| | Roadmap  |              | Statement      |  | & Transition  | |
-| +----------+              +-----------------+  +----------------+ |
-|                                                                  |
-| +---------------------------------------------------------------+ |
-| | Message Handling                                              | |
-| | +----------------+  +-----------------+  +-----------------+  | |
-| | | Transport      |  | Message        |  | Security        |  | |
-| | | Mappings      |  | Processing and  |  |                |  | |
-| | |                |  | Dispatcher      |  |                |  | |
-| | +----------------+  +-----------------+  +-----------------+  | |
-| +---------------------------------------------------------------+ |
-|                                                                  |
-| +---------------------------------------------------------------+ |
-| | PDU Handling                                                  | |
-| | +----------------+  +-----------------+  +-----------------+  | |
-| | | Protocol       |  | Applications    |  | Access          |  | |
-| | | Operations     |  |                |  | Control        |  | |
-| | +----------------+  +-----------------+  +-----------------+  | |
-| +---------------------------------------------------------------+ |
-|                                                                  |
-| +---------------------------------------------------------------+ |
-| | Information Model                                            | |
-| | +--------------+  +--------------+    +---------------+      | |
-| | | Structure of |  | Textual      |    | Conformance  |      | |
-| | | Management  |  | Conventions  |    | Statements    |      | |
-| | | Information  |  |              |    |              |      | |
-| | +--------------+  +--------------+    +---------------+      | |
-| +---------------------------------------------------------------+ |
-|                                                                  |
-| +---------------------------------------------------------------+ |
-| | MIB Modules written in various formats, e.g.:                | |
-| | +----------------+ +----------------+                        | |
-| | | SMIv1 (STD 18) | | SMIv2 (STD 58) |                        | |
-| | | format        | | format        |                        | |
-| | +----------------+ +----------------+                        | |
-| +---------------------------------------------------------------+ |
-|                                                                  |
-+-------------------------------------------------------------------+
-Each of these documents may be replaced or supplemented.  This
+=== Applications ===
-Architecture document specifically describes how new documents fit
-into the set of documents in the area of Message and PDU handling.
-=== Document Roadmap ===
+An SNMP entity normally includes a number of applications.
+Applications use the services of an SNMP engine to accomplish
+specific tasks.  They coordinate the processing of management
+information operations, and may use SNMP messages to communicate with
+other SNMP entities.
-One or more documents may be written to describe how sets of
+An applications document describes the purpose of an application, the
-documents taken together form specific Frameworks.  The configuration
+services required of the associated SNMP engine, and the protocol
-of document sets might change over time, so the "road map" should be
+operations and informational model that the application uses to
-maintained in a document separate from the standards documents
+perform management operations.
-themselves.
-An example of such a roadmap is "Introduction and Applicability
+An application document defines which set of documents are used to
-Statements for the Internet-Standard Management Framework" [RFC3410].
+specifically define the structure of management information, textual
+conventions, conformance requirements, and operations supported by
+the application.
-=== Applicability Statement ===
+.10.  Structure of Management Information
-SNMP is used in networks that vary widely in size and complexity, by
+Management information is viewed as a collection of managed objects,
-organizations that vary widely in their requirements of management.
+residing in a virtual information store, termed the Management
-Some models will be designed to address specific problems of
+Information Base (MIB).  Collections of related objects are defined
-management, such as message security.
+in MIB modules.
-One or more documents may be written to describe the environments to
+It is the purpose of a Structure of Management Information document
-which certain versions of SNMP or models within SNMP would be
+to establish the notation for defining objects, modules, and other
-appropriately applied, and those to which a given model might be
+elements of managed information.
-inappropriately applied.
-=== Coexistence and Transition ===
+.11.  Textual Conventions
-The purpose of an evolutionary architecture is to permit new models
+When designing a MIB module, it is often useful to define new types
-to replace or supplement existing models.  The interactions between
+similar to those defined in the SMI, but with more precise semantics,
-models could result in incompatibilities, security "holes", and other
+or which have special semantics associated with them.  These newly
-undesirable effects.
+defined types are termed textual conventions, and may be defined in
+separate documents, or within a MIB module.
-The purpose of Coexistence documents is to detail recognized
+.12.  Conformance Statements
-anomalies and to describe required and recommended behaviors for
-resolving the interactions between models within the architecture.
-Coexistence documents may be prepared separately from model
+It may be useful to define the acceptable lower-bounds of
-definition documents, to describe and resolve interaction anomalies
+implementation, along with the actual level of implementation
-between a model definition and one or more other model definitions.
+achieved.  It is the purpose of the Conformance Statements document
+to define the notation used for these purposes.
-Additionally, recommendations for transitions between models may also
+.13.  Management Information Base Modules
-be described, either in a coexistence document or in a separate
-document.
+MIB documents describe collections of managed objects which
+instrument some aspect of a managed node.
+.13.1.  SNMP Instrumentation MIBs
+An SNMP MIB document may define a collection of managed objects which
+instrument the SNMP protocol itself.  In addition, MIB modules may be
+defined within the documents which describe portions of the SNMP
+architecture, such as the documents for Message processing Models,
+Security Models, etc. for the purpose of instrumenting those Models,
+and for the purpose of allowing their remote configuration.
+.14.  SNMP Framework Documents
+This architecture is designed to allow an orderly evolution of
+portions of SNMP Frameworks.
+Throughout the rest of this document, the term "subsystem" refers to
+an abstract and incomplete specification of a portion of a Framework,
+that is further refined by a model specification.
+A "model" describes a specific design of a subsystem, defining
+additional constraints and rules for conformance to the model.  A
+model is sufficiently detailed to make it possible to implement the
+specification.
-One such coexistence document is [RFC2576], "Coexistence between
+An "implementation" is an instantiation of a subsystem, conforming to
-Version 1, Version 2, and Version 3 of the Internet-Standard Network
+one or more specific models.
-Management Framework".
-=== Transport Mappings ===
+SNMP version 1 (SNMPv1), is the original Internet-Standard Network
+Management Framework, as described in RFCs 1155, 1157, and 1212.
-SNMP messages are sent over various transports.  It is the purpose of
+SNMP version 2 (SNMPv2), is the SNMPv2 Framework as derived from the
-Transport Mapping documents to define how the mapping between SNMP
+SNMPv1 Framework.  It is described in STD 58, RFCs 2578, 2579, 2580,
-and the transport is done.
+and STD 62, RFCs 3416, 3417, and 3418.  SNMPv2 has no message
+definition.
-=== Message Processing ===
+The Community-based SNMP version 2 (SNMPv2c), is an experimental SNMP
+Framework which supplements the SNMPv2 Framework, as described in
-A Message Processing Model document defines a message format, which
+[RFC1901].  It adds the SNMPv2c message format, which is similar to
-is typically identified by a version field in an SNMP message header.
+the SNMPv1 message format.
-The document may also define a MIB module for use in message
-processing and for instrumentation of version-specific interactions.
+SNMP version 3 (SNMPv3), is an extensible SNMP Framework which
+supplements the SNMPv2 Framework, by supporting the following:
-An SNMP engine includes one or more Message Processing Models, and
+  -  a new SNMP message format,
-thus may support sending and receiving multiple versions of SNMP
-messages.
-=== Security ===
+  -  Security for Messages,
-Some environments require secure protocol interactions.  Security is
+  -  Access Control, and
-normally applied at two different stages:
-   -  in the transmission/receipt of messages, and
+   -  Remote configuration of SNMP parameters.
-  -  in the processing of the contents of messages.
+Other SNMP Frameworks, i.e., other configurations of implemented
+subsystems, are expected to also be consistent with this
+architecture.
-For purposes of this document, "security" refers to message-level
+== Elements of the Architecture ==
-security; "access control" refers to the security applied to protocol
-operations.
-Authentication, encryption, and timeliness checking are common
+This section describes the various elements of the architecture and
-functions of message level security.
+how they are named.  There are three kinds of naming:
-A security document describes a Security Model, the threats against
+) the naming of entities,
-which the model protects, the goals of the Security Model, the
-protocols which it uses to meet those goals, and it may define a MIB
-module to describe the data used during processing, and to allow the
-remote configuration of message-level security parameters, such as
-keys.
-An SNMP engine may support multiple Security Models concurrently.
+) the naming of identities, and
+) the naming of management information.
+This architecture also defines some names for other constructs that
+are used in the documentation.
+=== The Naming of Entities ===
+An SNMP entity is an implementation of this architecture.  Each such
+SNMP entity consists of an SNMP engine and one or more associated
+applications.
+The following figure shows details about an SNMP entity and the
+components within it.
++-------------------------------------------------------------------+
+|  SNMP entity                                                      |
+|                                                                  |
+|  +-------------------------------------------------------------+  |
+|  |  SNMP engine (identified by snmpEngineID)                  |  |
+|  |                                                            |  |
+|  |  +------------+ +------------+ +-----------+ +-----------+  |  |
+|  |  |            | |            | |          | |          |  |  |
+|  |  | Dispatcher | | Message    | | Security  | | Access    |  |  |
+|  |  |            | | Processing | | Subsystem | | Control  |  |  |
+|  |  |            | | Subsystem  | |          | | Subsystem |  |  |
+|  |  |            | |            | |          | |          |  |  |
+|  |  +------------+ +------------+ +-----------+ +-----------+  |  |
+|  |                                                            |  |
+|  +-------------------------------------------------------------+  |
+|                                                                  |
+|  +-------------------------------------------------------------+  |
+|  |  Application(s)                                            |  |
+|  |                                                            |  |
+|  |  +-------------+  +--------------+  +--------------+        |  |
+|  |  | Command    |  | Notification |  | Proxy        |        |  |
+|  |  | Generator  |  | Receiver    |  | Forwarder    |        |  |
+|  |  +-------------+  +--------------+  +--------------+        |  |
+|  |                                                            |  |
+|  |  +-------------+  +--------------+  +--------------+        |  |
+|  |  | Command    |  | Notification |  | Other        |        |  |
+|  |  | Responder  |  | Originator  |  |              |        |  |
+|  |  +-------------+  +--------------+  +--------------+        |  |
+|  |                                                            |  |
+|  +-------------------------------------------------------------+  |
+|                                                                  |
++-------------------------------------------------------------------+
+==== SNMP engine ====
-=== Access Control ===
+An SNMP engine provides services for sending and receiving messages,
+authenticating and encrypting messages, and controlling access to
-During processing, it may be required to control access to managed
+managed objects.  There is a one-to-one association between an SNMP
-objects for operations.
+engine and the SNMP entity which contains it.
-An Access Control Model defines mechanisms to determine whether
+The engine contains:
-access to a managed object should be allowed.  An Access Control
-Model may define a MIB module used during processing and to allow the
-remote configuration of access control policies.
-=== Protocol Operations ===
-SNMP messages encapsulate an SNMP Protocol Data Unit (PDU).  SNMP
-PDUs define the operations performed by the receiving SNMP engine.
-It is the purpose of a Protocol Operations document to define the
-operations of the protocol with respect to the processing of the
-PDUs.  Every PDU belongs to one or more of the PDU classes defined
-below:
-) Read Class:
+) a Dispatcher,
-      The Read Class contains protocol operations that retrieve
+) a Message Processing Subsystem,
-      management information.  For example, [RFC3416] defines the
-      following protocol operations for the Read Class: GetRequest-
-      PDU, GetNextRequest-PDU, and GetBulkRequest-PDU.
-) Write Class:
+) a Security Subsystem, and
-      The Write Class contains protocol operations which attempt to
+) an Access Control Subsystem.
-      modify management information.  For example, [RFC3416] defines
-      the following protocol operation for the Write Class:
-      SetRequest-PDU.
-) Response Class:
+===== snmpEngineID =====
-      The Response Class contains protocol operations which are sent
+Within an administrative domain, an snmpEngineID is the unique and
-      in response to a previous request.  For example, [RFC3416]
+unambiguous identifier of an SNMP engine.  Since there is a one-to-
-      defines the following for the Response Class: Response-PDU,
+one association between SNMP engines and SNMP entities, it also
-      Report-PDU.
+uniquely and unambiguously identifies the SNMP entity within that
+administrative domain.  Note that it is possible for SNMP entities in
+different administrative domains to have the same value for
+snmpEngineID.  Federation of administrative domains may necessitate
+assignment of new values.
-) Notification Class:
+===== Dispatcher =====
-      The Notification Class contains protocol operations which send
+There is only one Dispatcher in an SNMP engine.  It allows for
-      a notification to a notification receiver application.  For
+concurrent support of multiple versions of SNMP messages in the SNMP
-      example, [RFC3416] defines the following operations for the
+engine.  It does so by:
-      Notification Class: Trapv2-PDU, InformRequest-PDU.
+  -  sending and receiving SNMP messages to/from the network,
+  -  determining the version of an SNMP message and interacting with
+      the corresponding Message Processing Model,
+  -  providing an abstract interface to SNMP applications for
+      delivery of a PDU to an application.
+  -  providing an abstract interface for SNMP applications that
+      allows them to send a PDU to a remote SNMP entity.
+===== Message Processing Subsystem =====
+The Message Processing Subsystem is responsible for preparing
+messages for sending, and extracting data from received messages.
-) Internal Class:
+The Message Processing Subsystem potentially contains multiple
+Message Processing Models as shown in the next figure.
-      The Internal Class contains protocol operations which are
+* One or more Message Processing Models may be present.
-      exchanged internally between SNMP engines.  For example,
-      [RFC3416] defines the following operation for the Internal
-      Class: Report-PDU.
-The preceding five classifications are based on the functional
++------------------------------------------------------------------+
-properties of a PDU.  It is also useful to classify PDUs based on
+|                                                                  |
-whether a response is expected:
+|  Message Processing Subsystem                                    |
+|                                                                  |
-) Confirmed Class:
+|  +------------+  +------------+  +------------+  +------------+  |
+|  |          * |  |          * |  |          * |  |          * |  |
+|  | SNMPv3    |  | SNMPv1    |  | SNMPv2c   |  | Other      |  |
+|  | Message    |  | Message    |  | Message    |  | Message    |  |
+|  | Processing |  | Processing |  | Processing |  | Processing |  |
+|  | Model      |  | Model      |  | Model      |  | Model      |  |
+|  |            |  |            |  |            |  |            |  |
+|  +------------+  +------------+  +------------+  +------------+  |
+|                                                                  |
++------------------------------------------------------------------+
-      The Confirmed Class contains all protocol operations which
+.1.1.3.1.  Message Processing Model
-      cause the receiving SNMP engine to send back a response.  For
-      example, [RFC3416] defines the following operations for the
-      Confirmed Class: GetRequest-PDU, GetNextRequest-PDU,
-      GetBulkRequest-PDU, SetRequest-PDU, and InformRequest-PDU.
-) Unconfirmed Class:
+Each Message Processing Model defines the format of a particular
+version of an SNMP message and coordinates the preparation and
+extraction of each such version-specific message format.
-      The Unconfirmed Class contains all protocol operations which
+===== Security Subsystem =====
-      are not acknowledged.  For example, [RFC3416] defines the
-      following operations for the Unconfirmed Class: Report-PDU,
-      Trapv2-PDU, and GetResponse-PDU.
-An application document defines which Protocol Operations are
+The Security Subsystem provides security services such as the
-supported by the application.
+authentication and privacy of messages and potentially contains
+multiple Security Models as shown in the following figure
-=== Applications ===
+* One or more Security Models may be present.
-An SNMP entity normally includes a number of applications.
++------------------------------------------------------------------+
-Applications use the services of an SNMP engine to accomplish
+|                                                                  |
-specific tasks.  They coordinate the processing of management
+|  Security Subsystem                                              |
-information operations, and may use SNMP messages to communicate with
+|                                                                  |
-other SNMP entities.
+|  +----------------+  +-----------------+  +-------------------+  |
+|  |              * |  |              * |  |                * |  |
+|  | User-Based    |  | Other          |  | Other            |  |
+|  | Security      |  | Security        |  | Security          |  |
+|  | Model          |  | Model          |  | Model            |  |
+|  |                |  |                |  |                  |  |
+|  +----------------+  +-----------------+  +-------------------+  |
+|                                                                  |
++------------------------------------------------------------------+
-An applications document describes the purpose of an application, the
+.1.1.4.1.  Security Model
-services required of the associated SNMP engine, and the protocol
-operations and informational model that the application uses to
-perform management operations.
-An application document defines which set of documents are used to
-specifically define the structure of management information, textual
-conventions, conformance requirements, and operations supported by
-the application.
+A Security Model specifies the threats against which it protects, the
+goals of its services, and the security protocols used to provide
+security services such as authentication and privacy.
+.1.1.4.2.  Security Protocol
+A Security Protocol specifies the mechanisms, procedures, and MIB
+objects used to provide a security service such as authentication or
+privacy.
+==== Access Control Subsystem ====
+The Access Control Subsystem provides authorization services by means
+of one or more (*) Access Control Models.
++------------------------------------------------------------------+
+|                                                                  |
+|  Access Control Subsystem                                        |
+|                                                                  |
+|  +---------------+  +-----------------+  +------------------+  |
+|  |            * |  |              * |  |                * |  |
+|  | View-Based    |  | Other          |  | Other            |  |
+|  | Access        |  | Access          |  | Access          |  |
+|  | Control      |  | Control        |  | Control          |  |
+|  | Model        |  | Model          |  | Model            |  |
+|  |              |  |                |  |                  |  |
+|  +---------------+  +-----------------+  +------------------+  |
+|                                                                  |
++------------------------------------------------------------------+
-=== Structure of Management Information ===
+===== Access Control Model =====
-Management information is viewed as a collection of managed objects,
+An Access Control Model defines a particular access decision function
-residing in a virtual information store, termed the Management
+in order to support decisions regarding access rights.
-Information Base (MIB).  Collections of related objects are defined
-in MIB modules.
-It is the purpose of a Structure of Management Information document
+==== Applications ====
-to establish the notation for defining objects, modules, and other
-elements of managed information.
-=== Textual Conventions ===
+There are several types of applications, including:
-When designing a MIB module, it is often useful to define new types
+  -  command generators, which monitor and manipulate management
-similar to those defined in the SMI, but with more precise semantics,
+      data,
-or which have special semantics associated with them.  These newly
-defined types are termed textual conventions, and may be defined in
-separate documents, or within a MIB module.
-=== Conformance Statements ===
+  -  command responders, which provide access to management data,
-It may be useful to define the acceptable lower-bounds of
+  -  notification originators, which initiate asynchronous messages,
-implementation, along with the actual level of implementation
-achieved.  It is the purpose of the Conformance Statements document
-to define the notation used for these purposes.
-=== Management Information Base Modules ===
+  -  notification receivers, which process asynchronous messages,
-MIB documents describe collections of managed objects which
+  and
-instrument some aspect of a managed node.
-==== SNMP Instrumentation MIBs ====
+  -  proxy forwarders, which forward messages between entities.
-An SNMP MIB document may define a collection of managed objects which
+These applications make use of the services provided by the SNMP
-instrument the SNMP protocol itself.  In addition, MIB modules may be
+engine.
-defined within the documents which describe portions of the SNMP
-architecture, such as the documents for Message processing Models,
-Security Models, etc. for the purpose of instrumenting those Models,
-and for the purpose of allowing their remote configuration.
-=== SNMP Framework Documents ===
-This architecture is designed to allow an orderly evolution of
-portions of SNMP Frameworks.
-Throughout the rest of this document, the term "subsystem" refers to
-an abstract and incomplete specification of a portion of a Framework,
-that is further refined by a model specification.
+===== SNMP Manager =====
+An SNMP entity containing one or more command generator and/or
+notification receiver applications (along with their associated SNMP
+engine) has traditionally been called an SNMP manager.
+                    (traditional SNMP manager)
++-------------------------------------------------------------------+
+| +--------------+  +--------------+  +--------------+  SNMP entity |
+| | NOTIFICATION |  | NOTIFICATION |  |  COMMAND    |              |
+| |  ORIGINATOR  |  |  RECEIVER  |  |  GENERATOR  |              |
+| | applications |  | applications |  | applications |              |
+| +--------------+  +--------------+  +--------------+              |
+|        ^                ^                ^                      |
+|        |                |                |                      |
+|        v                v                v                      |
+|        +-------+--------+-----------------+                      |
+|                ^                                                |
+|                |    +---------------------+  +----------------+ |
+|                |    | Message Processing  |  | Security      | |
+| Dispatcher      v    | Subsystem          |  | Subsystem      | |
+| +-------------------+ |    +------------+  |  |                | |
+| | PDU Dispatcher    | |  +->| v1MP    * |<--->| +------------+ | |
+| |                  | |  |  +------------+  |  | | Other      | | |
+| |                  | |  |  +------------+  |  | | Security  | | |
+| |                  | |  +->| v2cMP    * |<--->| | Model      | | |
+| | Message          | |  |  +------------+  |  | +------------+ | |
+| | Dispatcher  <--------->+                  |  |                | |
+| |                  | |  |  +------------+  |  | +------------+ | |
+| |                  | |  +->| v3MP    * |<--->| | User-based | | |
+| | Transport        | |  |  +------------+  |  | | Security  | | |
+| | Mapping          | |  |  +------------+  |  | | Model      | | |
+| | (e.g., RFC 3417)  | |  +->| otherMP  * |<--->| +------------+ | |
+| +-------------------+ |    +------------+  |  |                | |
+|          ^            +---------------------+  +----------------+ |
+|          |                                                        |
+|          v                                                        |
++-------------------------------------------------------------------+
++-----+ +-----+      +-------+
+| UDP | | IPX | . . . | other |
++-----+ +-----+      +-------+
+  ^      ^              ^
+  |      |              |      * One or more models may be present.
+  v      v              v
++------------------------------+
+|          Network            |
++------------------------------+
+===== SNMP Agent =====
-A "model" describes a specific design of a subsystem, defining
+An SNMP entity containing one or more command responder and/or
-additional constraints and rules for conformance to the model.  A
+notification originator applications (along with their associated
-model is sufficiently detailed to make it possible to implement the
+SNMP engine) has traditionally been called an SNMP agent.
-specification.
-An "implementation" is an instantiation of a subsystem, conforming to
+* One or more models may be present.
-one or more specific models.
-SNMP version 1 (SNMPv1), is the original Internet-Standard Network
++------------------------------+
-Management Framework, as described in RFCs 1155, 1157, and 1212.
+|          Network           |
++------------------------------+
-SNMP version 2 (SNMPv2), is the SNMPv2 Framework as derived from the
+  ^      ^              ^
-SNMPv1 Framework.  It is described in STD 58, RFCs 2578, 2579, 2580,
+  |      |              |
-and STD 62, RFCs 3416, 3417, and 3418.  SNMPv2 has no message
+  v      v              v
-definition.
++-----+ +-----+      +-------+
+| UDP | | IPX | . . . | other |
-The Community-based SNMP version 2 (SNMPv2c), is an experimental SNMP
++-----+ +-----+      +-------+              (traditional SNMP agent)
-Framework which supplements the SNMPv2 Framework, as described in
++-------------------------------------------------------------------+
-[RFC1901].  It adds the SNMPv2c message format, which is similar to
+|              ^                                                    |
-the SNMPv1 message format.
+|              |        +---------------------+  +----------------+ |
+|              |        | Message Processing  |  | Security      | |
+| Dispatcher  v        | Subsystem          |  | Subsystem      | |
+| +-------------------+ |    +------------+  |  |                | |
+| | Transport        | |  +->| v1MP    * |<--->| +------------+ | |
+| | Mapping          | |  |  +------------+  |  | | Other      | | |
+| | (e.g., RFC 3417)  | |  |  +------------+  |  | | Security  | | |
+| |                  | |  +->| v2cMP    * |<--->| | Model      | | |
+| | Message          | |  |  +------------+  |  | +------------+ | |
+| | Dispatcher  <--------->|  +------------+  |  | +------------+ | |
+| |                  | |  +->| v3MP    * |<--->| | User-based | | |
+| |                  | |  |  +------------+  |  | | Security  | | |
+| | PDU Dispatcher    | |  |  +------------+  |  | | Model      | | |
+| +-------------------+ |  +->| otherMP  * |<--->| +------------+ | |
+|              ^        |    +------------+  |  |                | |
+|              |        +---------------------+  +----------------+ |
+|              v                                                    |
+|      +-------+-------------------------+---------------+          |
+|      ^                                ^              ^          |
+|      |                                |              |          |
+|      v                                v              v          |
+| +-------------+  +---------+  +--------------+  +-------------+ |
+| |  COMMAND  |  | ACCESS  |  | NOTIFICATION |  |    PROXY    | |
+| |  RESPONDER  |<->| CONTROL |<->|  ORIGINATOR  |  |  FORWARDER  | |
+| | application |  |        |  | applications |  | application | |
+| +-------------+  +---------+  +--------------+  +-------------+ |
+|      ^                                ^                          |
+|      |                                |                          |
+|      v                                v                          |
+| +----------------------------------------------+                  |
+| |            MIB instrumentation              |      SNMP entity |
++-------------------------------------------------------------------+
-SNMP version 3 (SNMPv3), is an extensible SNMP Framework which
+=== The Naming of Identities ===
-supplements the SNMPv2 Framework, by supporting the following:
-  -  a new SNMP message format,
+                        principal
+                            ^
+                            |
+                            |
++----------------------------|-------------+
+| SNMP engine                v            |
+|                    +--------------+      |
+|                    |              |      |
+|  +-----------------| securityName |---+  |
+|  | Security Model  |              |  |  |
+|  |                +--------------+  |  |
+|  |                        ^          |  |
+|  |                        |          |  |
+|  |                        v          |  |
+|  |  +------------------------------+  |  |
+|  |  |                              |  |  |
+|  |  | Model                        |  |  |
+|  |  | Dependent                    |  |  |
+|  |  | Security ID                  |  |  |
+|  |  |                              |  |  |
+|  |  +------------------------------+  |  |
+|  |                        ^          |  |
+|  |                        |          |  |
+|  +-------------------------|----------+  |
+|                            |            |
+|                            |            |
++----------------------------|-------------+
+                            |
+                            v
+                          network
-  -  Security for Messages,
+==== Principal ====
-  -  Access Control, and
+A principal is the "who" on whose behalf services are provided or
+processing takes place.
-  -  Remote configuration of SNMP parameters.
+A principal can be, among other things, an individual acting in a
+particular role; a set of individuals, with each acting in a
+particular role; an application or a set of applications; and
+combinations thereof.
-Other SNMP Frameworks, i.e., other configurations of implemented
+==== securityName ====
-subsystems, are expected to also be consistent with this
-architecture.
-== Elements of the Architecture ==
+A securityName is a human readable string representing a principal.
+It has a model-independent format, and can be used outside a
+particular Security Model.
-This section describes the various elements of the architecture and
+==== Model-dependent security ID ====
-how they are named.  There are three kinds of naming:
-) the naming of entities,
+A model-dependent security ID is the model-specific representation of
+a securityName within a particular Security Model.
-) the naming of identities, and
+Model-dependent security IDs may or may not be human readable, and
+have a model-dependent syntax.  Examples include community names, and
+user names.
-) the naming of management information.
+The transformation of model-dependent security IDs into securityNames
+and vice versa is the responsibility of the relevant Security Model.
+=== The Naming of Management Information ===
+Management information resides at an SNMP entity where a Command
+Responder Application has local access to potentially multiple
+contexts.  This application uses a contextEngineID equal to the
+snmpEngineID of its associated SNMP engine.
++-----------------------------------------------------------------+
+|  SNMP entity (identified by snmpEngineID, for example:          |
+|  '800002b804616263'H (enterpise 696, string "abc")              |
+|                                                                |
+|  +------------------------------------------------------------+ |
+|  | SNMP engine (identified by snmpEngineID)                  | |
+|  |                                                            | |
+|  | +-------------+ +------------+ +-----------+ +-----------+ | |
+|  | |            | |            | |          | |          | | |
+|  | | Dispatcher  | | Message    | | Security  | | Access    | | |
+|  | |            | | Processing | | Subsystem | | Control  | | |
+|  | |            | | Subsystem  | |          | | Subsystem | | |
+|  | |            | |            | |          | |          | | |
+|  | +-------------+ +------------+ +-----------+ +-----------+ | |
+|  |                                                            | |
+|  +------------------------------------------------------------+ |
+|                                                                |
+|  +------------------------------------------------------------+ |
+|  |  Command Responder Application                            | |
+|  |  (contextEngineID, example: '800002b804616263'H)          | |
+|  |                                                            | |
+|  |  example contextNames:                                    | |
+|  |                                                            | |
+|  |  "bridge1"          "bridge2"            "" (default)      | |
+|  |  ---------          ---------            ------------      | |
+|  |      |                  |                  |              | |
+|  +------|------------------|-------------------|--------------+ |
+|        |                  |                  |                |
+|  +------|------------------|-------------------|--------------+ |
+|  |  MIB | instrumentation  |                  |              | |
+|  |  +---v------------+ +---v------------+ +----v-----------+  | |
+|  |  | context        | | context        | | context        |  | |
+|  |  |                | |                | |                |  | |
+|  |  | +------------+ | | +------------+ | | +------------+ |  | |
+|  |  | | bridge MIB | | | | bridge MIB | | | | some  MIB  | |  | |
+|  |  | +------------+ | | +------------+ | | +------------+ |  | |
+|  |  |                | |                | |                |  | |
+|  |  |                | |                | | +------------+ |  | |
+|  |  |                | |                | | | other MIB  | |  | |
+|  |  |                | |                | | +------------+ |  | |
+|  |  |                | |                | |                |  | |
++-----------------------------------------------------------------+
+==== An SNMP Context ====
+An SNMP context, or just "context" for short, is a collection of
+management information accessible by an SNMP entity.  An item of
+management information may exist in more than one context.  An SNMP
+entity potentially has access to many contexts.
+Typically, there are many instances of each managed object type
+within a management domain.  For simplicity, the method for
+identifying instances specified by the MIB module does not allow each
+instance to be distinguished amongst the set of all instances within
+a management domain; rather, it allows each instance to be identified
+only within some scope or "context", where there are multiple such
+contexts within the management domain.  Often, a context is a
+physical device, or perhaps, a logical device, although a context can
+also encompass multiple devices, or a subset of a single device, or
+even a subset of multiple devices, but a context is always defined as
+a subset of a single SNMP entity.  Thus, in order to identify an
+individual item of management information within the management
+domain, its contextName and contextEngineID must be identified in
+addition to its object type and its instance.
-This architecture also defines some names for other constructs that
+For example, the managed object type ifDescr [RFC2863], is defined as
-are used in the documentation.
+the description of a network interface.  To identify the description
+of device-X's first network interface, four pieces of information are
-=== The Naming of Entities ===
+needed: the snmpEngineID of the SNMP entity which provides access to
+the management information at device-X, the contextName (device-X),
-An SNMP entity is an implementation of this architecture.  Each such
+the managed object type (ifDescr), and the instance ("1").
-SNMP entity consists of an SNMP engine and one or more associated
-applications.
-The following figure shows details about an SNMP entity and the
-components within it.
-+-------------------------------------------------------------------+
-|  SNMP entity                                                     |
-|                                                                  |
-|  +-------------------------------------------------------------+  |
-|  |  SNMP engine (identified by snmpEngineID)                   |  |
-|  |                                                            |  |
-|  |  +------------+ +------------+ +-----------+ +-----------+  |  |
-|  |  |            | |            | |          | |          |  |  |
-|  |  | Dispatcher | | Message    | | Security  | | Access    |  |  |
-|  |  |            | | Processing | | Subsystem | | Control  |  |  |
-|  |  |            | | Subsystem  | |          | | Subsystem |  |  |
-|  |  |            | |            | |          | |          |  |  |
-|  |  +------------+ +------------+ +-----------+ +-----------+  |  |
-|  |                                                            |  |
-|  +-------------------------------------------------------------+  |
-|                                                                  |
-|  +-------------------------------------------------------------+  |
-|  |  Application(s)                                             |  |
-|  |                                                            |  |
-|  |  +-------------+  +--------------+  +--------------+        |  |
-|  |  | Command    |  | Notification |  | Proxy        |        |  |
-|  |  | Generator  |  | Receiver    |  | Forwarder    |        |  |
-|  |  +-------------+  +--------------+  +--------------+        |  |
-|  |                                                            |  |
-|  |  +-------------+  +--------------+  +--------------+        |  |
-|  |  | Command    |  | Notification |  | Other        |        |  |
-|  |  | Responder  |  | Originator  |  |              |        |  |
-|  |  +-------------+  +--------------+  +--------------+        |  |
-|  |                                                            |  |
-|  +-------------------------------------------------------------+  |
-|                                                                  |
-+-------------------------------------------------------------------+
-==== SNMP engine ====
-An SNMP engine provides services for sending and receiving messages,
+Each context has (at least) one unique identification within the
-authenticating and encrypting messages, and controlling access to
+management domain.  The same item of management information can exist
-managed objects.  There is a one-to-one association between an SNMP
+in multiple contexts.  An item of management information may have
-engine and the SNMP entity which contains it.
+multiple unique identifications.  This occurs when an item of
+management information exists in multiple contexts, and this also
+occurs when a context has multiple unique identifications.
-The engine contains:
+The combination of a contextEngineID and a contextName unambiguously
+identifies a context within an administrative domain; note that there
+may be multiple unique combinations of contextEngineID and
+contextName that unambiguously identify the same context.
-) a Dispatcher,
+==== contextEngineID ====
-) a Message Processing Subsystem,
+Within an administrative domain, a contextEngineID uniquely
+identifies an SNMP entity that may realize an instance of a context
+with a particular contextName.
-) a Security Subsystem, and
+==== contextName ====
-) an Access Control Subsystem.
+A contextName is used to name a context.  Each contextName MUST be
+unique within an SNMP entity.
-.1.1.1.  snmpEngineID
+==== scopedPDU ====
-Within an administrative domain, an snmpEngineID is the unique and
+A scopedPDU is a block of data containing a contextEngineID, a
-unambiguous identifier of an SNMP engine.  Since there is a one-to-
+contextName, and a PDU.
-one association between SNMP engines and SNMP entities, it also
-uniquely and unambiguously identifies the SNMP entity within that
-administrative domain.  Note that it is possible for SNMP entities in
-different administrative domains to have the same value for
-snmpEngineID.  Federation of administrative domains may necessitate
-assignment of new values.
-.1.1.2.  Dispatcher
+The PDU is an SNMP Protocol Data Unit containing information named in
+the context which is unambiguously identified within an
+administrative domain by the combination of the contextEngineID and
+the contextName.  See, for example, RFC 3416 for more information
+about SNMP PDUs.
-There is only one Dispatcher in an SNMP engine.  It allows for
+=== Other Constructs ===
-concurrent support of multiple versions of SNMP messages in the SNMP
-engine.  It does so by:
-  -  sending and receiving SNMP messages to/from the network,
+==== maxSizeResponseScopedPDU ====
-  -  determining the version of an SNMP message and interacting with
+The maxSizeResponseScopedPDU is the maximum size of a scopedPDU that
-      the corresponding Message Processing Model,
+a PDU's sender would be willing to accept.  Note that the size of a
+scopedPDU does not include the size of the SNMP message header.
-  -  providing an abstract interface to SNMP applications for
+==== Local Configuration Datastore ====
-      delivery of a PDU to an application.
-  -  providing an abstract interface for SNMP applications that
+The subsystems, models, and applications within an SNMP entity may
-      allows them to send a PDU to a remote SNMP entity.
+need to retain their own sets of configuration information.
+Portions of the configuration information may be accessible as
+managed objects.
+The collection of these sets of information is referred to as an
+entity's Local Configuration Datastore (LCD).
+==== securityLevel ====
+This architecture recognizes three levels of security:
+  -  without authentication and without privacy (noAuthNoPriv)
+  -  with authentication but without privacy (authNoPriv)
+  -  with authentication and with privacy (authPriv)
+These three values are ordered such that noAuthNoPriv is less than
+authNoPriv and authNoPriv is less than authPriv.
-.1.1.3.  Message Processing Subsystem
+Every message has an associated securityLevel.  All Subsystems
+(Message Processing, Security, Access Control) and applications are
+REQUIRED to either supply a value of securityLevel or to abide by the
+supplied value of securityLevel while processing the message and its
+contents.
-The Message Processing Subsystem is responsible for preparing
+== Abstract Service Interfaces ==
-messages for sending, and extracting data from received messages.
-The Message Processing Subsystem potentially contains multiple
+Abstract service interfaces have been defined to describe the
-Message Processing Models as shown in the next figure.
+conceptual interfaces between the various subsystems within an SNMP
+entity.  The abstract service interfaces are intended to help clarify
-* One or more Message Processing Models may be present.
+the externally observable behavior of SNMP entities, and are not
+intended to constrain the structure or organization of
-+------------------------------------------------------------------+
+implementations in any way.  Most specifically, they should not be
-|                                                                  |
+interpreted as APIs or as requirements statements for APIs.
-|  Message Processing Subsystem                                    |
-|                                                                  |
-|  +------------+  +------------+  +------------+  +------------+  |
-|  |          * |  |          * |  |          * |  |          * |  |
-|  | SNMPv3    |  | SNMPv1    |  | SNMPv2c    |  | Other      |  |
-|  | Message    |  | Message    |  | Message    |  | Message    |  |
-|  | Processing |  | Processing |  | Processing |  | Processing |  |
-|  | Model      |  | Model      |  | Model      |  | Model      |  |
-|  |            |  |            |  |            |  |            |  |
-|  +------------+  +------------+  +------------+  +------------+  |
-|                                                                  |
-+------------------------------------------------------------------+
-.1.1.3.1.  Message Processing Model
-Each Message Processing Model defines the format of a particular
-version of an SNMP message and coordinates the preparation and
-extraction of each such version-specific message format.
+These abstract service interfaces are defined by a set of primitives
+that define the services provided and the abstract data elements that
+are to be passed when the services are invoked.  This section lists
+the primitives that have been defined for the various subsystems.
+=== Dispatcher Primitives ===
+The Dispatcher typically provides services to the SNMP applications
+via its PDU Dispatcher.  This section describes the primitives
+provided by the PDU Dispatcher.
+==== Generate Outgoing Request or Notification ====
+The PDU Dispatcher provides the following primitive for an
+application to send an SNMP Request or Notification to another SNMP
+entity:
+statusInformation =              -- sendPduHandle if success
+                                -- errorIndication if failure
+  sendPdu(
+  IN  transportDomain          -- transport domain to be used
+  IN  transportAddress          -- transport address to be used
+  IN  messageProcessingModel    -- typically, SNMP version
+  IN  securityModel            -- Security Model to use
+  IN  securityName              -- on behalf of this principal
+  IN  securityLevel            -- Level of Security requested
+  IN  contextEngineID          -- data from/at this entity
+  IN  contextName              -- data from/in this context
+  IN  pduVersion                -- the version of the PDU
+  IN  PDU                      -- SNMP Protocol Data Unit
+  IN  expectResponse            -- TRUE or FALSE
+      )
+==== Process Incoming Request or Notification PDU ====
+The PDU Dispatcher provides the following primitive to pass an
+incoming SNMP PDU to an application:
+processPdu(                      -- process Request/Notification PDU
+  IN  messageProcessingModel    -- typically, SNMP version
+  IN  securityModel            -- Security Model in use
+  IN  securityName              -- on behalf of this principal
+  IN  securityLevel            -- Level of Security
+  IN  contextEngineID          -- data from/at this SNMP entity
+  IN  contextName              -- data from/in this context
+  IN  pduVersion                -- the version of the PDU
+  IN  PDU                      -- SNMP Protocol Data Unit
+  IN  maxSizeResponseScopedPDU  -- maximum size of the Response PDU
+  IN  stateReference            -- reference to state information
+      )                        -- needed when sending a response
+==== Generate Outgoing Response ====
+The PDU Dispatcher provides the following primitive for an
+application to return an SNMP Response PDU to the PDU Dispatcher:
+result =                        -- SUCCESS or FAILURE
+returnResponsePdu(
+  IN  messageProcessingModel    -- typically, SNMP version
+  IN  securityModel            -- Security Model in use
+  IN  securityName              -- on behalf of this principal
+  IN  securityLevel            -- same as on incoming request
+  IN  contextEngineID          -- data from/at this SNMP entity
+  IN  contextName              -- data from/in this context
+  IN  pduVersion                -- the version of the PDU
+  IN  PDU                      -- SNMP Protocol Data Unit
+  IN  maxSizeResponseScopedPDU  -- maximum size sender can accept
+  IN  stateReference            -- reference to state information
+                                -- as presented with the request
+  IN  statusInformation        -- success or errorIndication
+      )                        -- error counter OID/value if error
+==== Process Incoming Response PDU ====
+The PDU Dispatcher provides the following primitive to pass an
+incoming SNMP Response PDU to an application:
+processResponsePdu(              -- process Response PDU
+  IN  messageProcessingModel    -- typically, SNMP version
+  IN  securityModel            -- Security Model in use
+  IN  securityName              -- on behalf of this principal
+  IN  securityLevel            -- Level of Security
+  IN  contextEngineID          -- data from/at this SNMP entity
+  IN  contextName              -- data from/in this context
+  IN  pduVersion                -- the version of the PDU
+  IN  PDU                      -- SNMP Protocol Data Unit
+  IN  statusInformation        -- success or errorIndication
+  IN  sendPduHandle            -- handle from sendPdu
+      )
+==== Registering Responsibility for Handling SNMP PDUs ====
+Applications can register/unregister responsibility for a specific
+contextEngineID, for specific pduTypes, with the PDU Dispatcher
+according to the following primitives.  The list of particular
+pduTypes that an application can register for is determined by the
+Message Processing Model(s) supported by the SNMP entity that
+contains the PDU Dispatcher.
+statusInformation =            -- success or errorIndication
+  registerContextEngineID(
+  IN  contextEngineID        -- take responsibility for this one
+  IN  pduType                -- the pduType(s) to be registered
+      )
+unregisterContextEngineID(
+  IN  contextEngineID        -- give up responsibility for this one
+  IN  pduType                -- the pduType(s) to be unregistered
+      )
+Note that realizations of the registerContextEngineID and
+unregisterContextEngineID abstract service interfaces may provide
+implementation-specific ways for applications to register/deregister
+responsibility for all possible values of the contextEngineID or
+pduType parameters.
+=== Message Processing Subsystem Primitives ===
+The Dispatcher interacts with a Message Processing Model to process a
+specific version of an SNMP Message.  This section describes the
+primitives provided by the Message Processing Subsystem.
-.1.1.4.  Security Subsystem
+==== Prepare Outgoing SNMP Request or Notification Message ====
-The Security Subsystem provides security services such as the
+The Message Processing Subsystem provides this service primitive for
-authentication and privacy of messages and potentially contains
+preparing an outgoing SNMP Request or Notification Message:
-multiple Security Models as shown in the following figure
-* One or more Security Models may be present.
+statusInformation =              -- success or errorIndication
+  prepareOutgoingMessage(
-+------------------------------------------------------------------+
+  IN  transportDomain          -- transport domain to be used
-|                                                                  |
+  IN  transportAddress          -- transport address to be used
-|  Security Subsystem                                              |
+  IN  messageProcessingModel    -- typically, SNMP version
-|                                                                  |
+  IN  securityModel            -- Security Model to use
-|  +----------------+  +-----------------+  +-------------------+  |
+  IN  securityName              -- on behalf of this principal
-|  |              * |  |              * |  |                * |  |
+  IN  securityLevel            -- Level of Security requested
-|  | User-Based    |  | Other          |  | Other            |  |
+  IN  contextEngineID          -- data from/at this entity
-|  | Security      |  | Security        |  | Security          |  |
+  IN  contextName              -- data from/in this context
-|  | Model          |  | Model           |  | Model            |  |
+  IN  pduVersion                -- the version of the PDU
-|  |                |  |                |  |                  |  |
+  IN  PDU                      -- SNMP Protocol Data Unit
-|  +----------------+  +-----------------+  +-------------------+  |
+  IN  expectResponse            -- TRUE or FALSE
-|                                                                  |
+  IN  sendPduHandle            -- the handle for matching
-+------------------------------------------------------------------+
+                                -- incoming responses
+  OUT  destTransportDomain      -- destination transport domain
+  OUT  destTransportAddress      -- destination transport address
+  OUT  outgoingMessage           -- the message to send
+  OUT  outgoingMessageLength    -- its length
+      )
-.1.1.4.1.  Security Model
+==== Prepare an Outgoing SNMP Response Message ====
-A Security Model specifies the threats against which it protects, the
+The Message Processing Subsystem provides this service primitive for
-goals of its services, and the security protocols used to provide
+preparing an outgoing SNMP Response Message:
-security services such as authentication and privacy.
-.1.1.4.2.  Security Protocol
-A Security Protocol specifies the mechanisms, procedures, and MIB
-objects used to provide a security service such as authentication or
-privacy.
+result =                        -- SUCCESS or FAILURE
+  prepareResponseMessage(
+  IN  messageProcessingModel    -- typically, SNMP version
+  IN  securityModel            -- same as on incoming request
+  IN  securityName              -- same as on incoming request
+  IN  securityLevel            -- same as on incoming request
+  IN  contextEngineID          -- data from/at this SNMP entity
+  IN  contextName              -- data from/in this context
+  IN  pduVersion                -- the version of the PDU
+  IN  PDU                      -- SNMP Protocol Data Unit
+  IN  maxSizeResponseScopedPDU  -- maximum size able to accept
+  IN  stateReference            -- reference to state information
+                                -- as presented with the request
+  IN  statusInformation        -- success or errorIndication
+                                -- error counter OID/value if error
+  OUT  destTransportDomain      -- destination transport domain
+  OUT  destTransportAddress      -- destination transport address
+  OUT  outgoingMessage          -- the message to send
+  OUT  outgoingMessageLength    -- its length
+      )
+==== Prepare Data Elements from an Incoming SNMP Message ====
+The Message Processing Subsystem provides this service primitive for
+preparing the abstract data elements from an incoming SNMP message:
+result =                        -- SUCCESS or errorIndication
+  prepareDataElements(
+  IN  transportDomain          -- origin transport domain
+  IN  transportAddress          -- origin transport address
+  IN  wholeMsg                  -- as received from the network
+  IN  wholeMsgLength            -- as received from the network
+  OUT  messageProcessingModel    -- typically, SNMP version
+  OUT  securityModel            -- Security Model to use
+  OUT  securityName              -- on behalf of this principal
+  OUT  securityLevel            -- Level of Security requested
+  OUT  contextEngineID          -- data from/at this entity
+  OUT  contextName              -- data from/in this context
+  OUT  pduVersion                -- the version of the PDU
+  OUT  PDU                      -- SNMP Protocol Data Unit
+  OUT  pduType                  -- SNMP PDU type
+  OUT  sendPduHandle            -- handle for matched request
+  OUT  maxSizeResponseScopedPDU  -- maximum size sender can accept
+  OUT  statusInformation        -- success or errorIndication
+                                -- error counter OID/value if error
+  OUT  stateReference            -- reference to state information
+                                -- to be used for possible Response
+      )
+=== Access Control Subsystem Primitives ===
+Applications are the typical clients of the service(s) of the Access
+Control Subsystem.
+The following primitive is provided by the Access Control Subsystem
+to check if access is allowed:
+statusInformation =              -- success or errorIndication
+  isAccessAllowed(
+  IN  securityModel            -- Security Model in use
+  IN  securityName              -- principal who wants to access
+  IN  securityLevel            -- Level of Security
+  IN  viewType                  -- read, write, or notify view
+  IN  contextName              -- context containing variableName
+  IN  variableName              -- OID for the managed object
+      )
+=== Security Subsystem Primitives ===
+The Message Processing Subsystem is the typical client of the
+services of the Security Subsystem.
+==== Generate a Request or Notification Message ====
+The Security Subsystem provides the following primitive to generate a
+Request or Notification message:
+statusInformation =
+  generateRequestMsg(
+  IN  messageProcessingModel    -- typically, SNMP version
+  IN  globalData                -- message header, admin data
+  IN  maxMessageSize            -- of the sending SNMP entity
+  IN  securityModel            -- for the outgoing message
+  IN  securityEngineID          -- authoritative SNMP entity
+  IN  securityName              -- on behalf of this principal
+  IN  securityLevel            -- Level of Security requested
+  IN  scopedPDU                -- message (plaintext) payload
+  OUT  securityParameters        -- filled in by Security Module
+  OUT  wholeMsg                  -- complete generated message
+  OUT  wholeMsgLength            -- length of the generated message
+      )
+==== Process Incoming Message ====
+The Security Subsystem provides the following primitive to process an
+incoming message:
+statusInformation =              -- errorIndication or success
+                                -- error counter OID/value if error
+  processIncomingMsg(
+  IN  messageProcessingModel    -- typically, SNMP version
+  IN  maxMessageSize            -- of the sending SNMP entity
+  IN  securityParameters        -- for the received message
+  IN  securityModel            -- for the received message
+  IN  securityLevel            -- Level of Security
+  IN  wholeMsg                  -- as received on the wire
+  IN  wholeMsgLength            -- length as received on the wire
+  OUT  securityEngineID          -- authoritative SNMP entity
+  OUT  securityName              -- identification of the principal
+  OUT  scopedPDU,                -- message (plaintext) payload
+  OUT  maxSizeResponseScopedPDU  -- maximum size sender can handle
+  OUT  securityStateReference    -- reference to security state
+      )                        -- information, needed for response
+==== Generate a Response Message ====
+The Security Subsystem provides the following primitive to generate a
+Response message:
+statusInformation =
+  generateResponseMsg(
+  IN  messageProcessingModel    -- typically, SNMP version
+  IN  globalData                -- message header, admin data
+  IN  maxMessageSize            -- of the sending SNMP entity
+  IN  securityModel            -- for the outgoing message
+  IN  securityEngineID          -- authoritative SNMP entity
+  IN  securityName              -- on behalf of this principal
+  IN  securityLevel            -- for the outgoing message
+  IN  scopedPDU                -- message (plaintext) payload
+  IN  securityStateReference    -- reference to security state
+                                -- information from original request
+  OUT  securityParameters        -- filled in by Security Module
+  OUT  wholeMsg                  -- complete generated message
+  OUT  wholeMsgLength            -- length of the generated message
+      )
-==== Access Control Subsystem ====
+=== Common Primitives ===
-The Access Control Subsystem provides authorization services by means
-of one or more (*) Access Control Models.
-+------------------------------------------------------------------+
-|                                                                  |
-|  Access Control Subsystem                                        |
-|                                                                  |
-|  +---------------+  +-----------------+  +------------------+  |
-|  |            * |  |              * |  |                * |  |
-|  | View-Based    |  | Other          |  | Other            |  |
-|  | Access        |  | Access          |  | Access          |  |
-|  | Control      |  | Control        |  | Control          |  |
-|  | Model        |  | Model          |  | Model            |  |
-|  |              |  |                |  |                  |  |
-|  +---------------+  +-----------------+  +------------------+  |
-|                                                                  |
-+------------------------------------------------------------------+
-.1.2.1.  Access Control Model
-An Access Control Model defines a particular access decision function
-in order to support decisions regarding access rights.
-==== Applications ====
-There are several types of applications, including:
-  -  command generators, which monitor and manipulate management
-      data,
-  -  command responders, which provide access to management data,
-  -  notification originators, which initiate asynchronous messages,
-  -  notification receivers, which process asynchronous messages,
-  and
-  -  proxy forwarders, which forward messages between entities.
-These applications make use of the services provided by the SNMP
-engine.
-.1.3.1.  SNMP Manager
-An SNMP entity containing one or more command generator and/or
-notification receiver applications (along with their associated SNMP
-engine) has traditionally been called an SNMP manager.
-                    (traditional SNMP manager)
-+-------------------------------------------------------------------+
-| +--------------+  +--------------+  +--------------+  SNMP entity |
-| | NOTIFICATION |  | NOTIFICATION |  |  COMMAND    |              |
-| |  ORIGINATOR  |  |  RECEIVER  |  |  GENERATOR  |              |
-| | applications |  | applications |  | applications |              |
-| +--------------+  +--------------+  +--------------+              |
-|        ^                ^                ^                      |
-|        |                |                |                      |
-|        v                v                v                      |
-|        +-------+--------+-----------------+                      |
-|                ^                                                |
-|                |    +---------------------+  +----------------+ |
-|                |    | Message Processing  |  | Security      | |
-| Dispatcher      v    | Subsystem          |  | Subsystem      | |
-| +-------------------+ |    +------------+  |  |                | |
-| | PDU Dispatcher    | |  +->| v1MP    * |<--->| +------------+ | |
-| |                  | |  |  +------------+  |  | | Other      | | |
-| |                  | |  |  +------------+  |  | | Security  | | |
-| |                  | |  +->| v2cMP    * |<--->| | Model      | | |
-| | Message          | |  |  +------------+  |  | +------------+ | |
-| | Dispatcher  <--------->+                  |  |                | |
-| |                  | |  |  +------------+  |  | +------------+ | |
-| |                  | |  +->| v3MP    * |<--->| | User-based | | |
-| | Transport        | |  |  +------------+  |  | | Security  | | |
-| | Mapping          | |  |  +------------+  |  | | Model      | | |
-| | (e.g., [[RFC3417|RFC 3417]])  | |  +->| otherMP  * |<--->| +------------+ | |
-| +-------------------+ |    +------------+  |  |                | |
-|          ^            +---------------------+  +----------------+ |
-|          |                                                        |
-|          v                                                        |
-+-------------------------------------------------------------------+
-+-----+ +-----+      +-------+
-| UDP | | IPX | . . . | other |
-+-----+ +-----+      +-------+
-  ^      ^              ^
-  |      |              |      * One or more models may be present.
-  v      v              v
-+------------------------------+
-|          Network            |
-+------------------------------+
-.1.3.2.  SNMP Agent
-An SNMP entity containing one or more command responder and/or
-notification originator applications (along with their associated
-SNMP engine) has traditionally been called an SNMP agent.
+These primitive(s) are provided by multiple Subsystems.
+==== Release State Reference Information ====
+All Subsystems which pass stateReference information also provide a
+primitive to release the memory that holds the referenced state
+information:
+stateRelease(
+  IN  stateReference      -- handle of reference to be released
+      )
+=== Scenario Diagrams ===
+==== Command Generator or Notification Originator ====
+This diagram shows how a Command Generator or Notification Originator
+application requests that a PDU be sent, and how the response is
+returned (asynchronously) to that application.
+Command          Dispatcher              Message          Security
+Generator            |                    Processing          Model
+|                    |                    Model                    |
+|      sendPdu      |                        |                    |
+|------------------->|                        |                    |
+|                    | prepareOutgoingMessage |                    |
+:                    |----------------------->|                    |
+:                    |                        | generateRequestMsg  |
+:                    |                        |-------------------->|
+:                    |                        |                    |
+:                    |                        |<--------------------|
+:                    |                        |                    |
+:                    |<-----------------------|                    |
+:                    |                        |                    |
+:                    |------------------+    |                    |
+:                    | Send SNMP        |    |                    |
+:                    | Request Message  |    |                    |
+:                    | to Network      |    |                    |
+:                    |                  v    |                    |
+:                    :                  :    :                    :
+:                    :                  :    :                    :
+:                    :                  :    :                    :
+:                    |                  |    |                    |
+:                    | Receive SNMP    |    |                    |
+:                    | Response Message |    |                    |
+:                    | from Network    |    |                    |
+:                    |<-----------------+    |                    |
+:                    |                        |                    |
+:                    |  prepareDataElements  |                    |
+:                    |----------------------->|                    |
+:                    |                        | processIncomingMsg  |
+:                    |                        |-------------------->|
+:                    |                        |                    |
+:                    |                        |<--------------------|
+:                    |                        |                    |
+:                    |<-----------------------|                    |
+| processResponsePdu |                        |                    |
+|<-------------------|                        |                    |
+|                    |                        |                    |
+==== Scenario Diagram for a Command Responder Application ====
+This diagram shows how a Command Responder or Notification Receiver
+application registers for handling a pduType, how a PDU is dispatched
+to the application after an SNMP message is received, and how the
+Response is (asynchronously) send back to the network.
+Command              Dispatcher            Message          Security
+Responder                |                Processing          Model
+|                        |                Model                  |
+|                        |                    |                    |
+| registerContextEngineID |                    |                    |
+|------------------------>|                    |                    |
+|<------------------------|              |    |                    |
+|                        | Receive SNMP |    |                    |
+:                        | Message      |    |                    |
+:                        | from Network |    |                    |
+:                        |<-------------+    |                    |
+:                        |                    |                    |
+:                        |prepareDataElements |                    |
+:                        |------------------->|                    |
+:                        |                    | processIncomingMsg |
+:                        |                    |------------------->|
+:                        |                    |                    |
+:                        |                    |<-------------------|
+:                        |                    |                    |
+:                        |<-------------------|                    |
+|    processPdu          |                    |                    |
+|<------------------------|                    |                    |
+|                        |                    |                    |
+:                        :                    :                    :
+:                        :                    :                    :
+|    returnResponsePdu    |                    |                    |
+|------------------------>|                    |                    |
+:                        | prepareResponseMsg |                    |
+:                        |------------------->|                    |
+:                        |                    |generateResponseMsg |
+:                        |                    |------------------->|
+:                        |                    |                    |
+:                        |                    |<-------------------|
+:                        |                    |                    |
+:                        |<-------------------|                    |
+:                        |                    |                    |
+:                        |--------------+    |                    |
+:                        | Send SNMP    |    |                    |
+:                        | Message      |    |                    |
+:                        | to Network  |    |                    |
+:                        |              v    |                    |
+== Managed Object Definitions for SNMP Management Frameworks ==
+SNMP-FRAMEWORK-MIB DEFINITIONS ::= BEGIN
+IMPORTS
+ MODULE-IDENTITY, OBJECT-TYPE,
+ OBJECT-IDENTITY,
+ snmpModules                          FROM SNMPv2-SMI
+ TEXTUAL-CONVENTION                    FROM SNMPv2-TC
+ MODULE-COMPLIANCE, OBJECT-GROUP      FROM SNMPv2-CONF;
+snmpFrameworkMIB MODULE-IDENTITY
+ LAST-UPDATED "200210140000Z"
+ ORGANIZATION "SNMPv3 Working Group"
+ CONTACT-INFO "WG-EMail:  [email protected]
+              Subscribe:  [email protected]
+              Co-Chair:  Russ Mundy
+                          Network Associates Laboratories
+              postal:    15204 Omega Drive, Suite 300
+                          Rockville, MD 20850-4601
+                          USA
+              EMail:      [email protected]
+              phone:      +1 301-947-7107
+              Co-Chair &
+              Co-editor:  David Harrington
+                          Enterasys Networks
+              postal:    35 Industrial Way
+                          P. O. Box 5005
+                          Rochester, New Hampshire 03866-5005
+                          USA
+              EMail:      [email protected]
+              phone:      +1 603-337-2614
+              Co-editor:  Randy Presuhn
+                          BMC Software, Inc.
+              postal:    2141 North First Street
+                          San Jose, California 95131
+                          USA
+              EMail:      [email protected]
+              phone:      +1 408-546-1006
+              Co-editor:  Bert Wijnen
+                          Lucent Technologies
+              postal:    Schagen 33
+GL Linschoten
+                          Netherlands
+              EMail:      [email protected]
+              phone:      +31 348-680-485
+                "
+    DESCRIPTION  "The SNMP Management Architecture MIB
+                  Copyright (C) The Internet Society (2002). This
+                  version of this MIB module is part of RFC 3411;
+                  see the RFC itself for full legal notices.
+                "
+    REVISION    "200210140000Z"        -- 14 October 2002
+    DESCRIPTION  "Changes in this revision:
+                  - Updated various administrative information.
+                  - Corrected some typos.
+                  - Corrected typo in description of SnmpEngineID
+                    that led to range overlap for 127.
+                  - Changed '255a' to '255t' in definition of
+                    SnmpAdminString to align with current SMI.
+                  - Reworded 'reserved' for value zero in
+                    DESCRIPTION of SnmpSecurityModel.
+                  - The algorithm for allocating security models
+                    should give 256 per enterprise block, rather
+                    than 255.
+                  - The example engine ID of 'abcd' is not
+                    legal. Replaced with '800002b804616263'H based
+                    on example enterprise 696, string 'abc'.
+                  - Added clarification that engineID should
+                    persist across re-initializations.
+                  This revision published as RFC 3411.
+                "
+    REVISION    "199901190000Z"        -- 19 January 1999
+    DESCRIPTION  "Updated editors' addresses, fixed typos.
+                  Published as RFC 2571.
+                "
+    REVISION    "199711200000Z"        -- 20 November 1997
+    DESCRIPTION  "The initial version, published in RFC 2271.
+                "
+    ::= { snmpModules 10 }
+-- Textual Conventions used in the SNMP Management Architecture ***
+SnmpEngineID ::= TEXTUAL-CONVENTION
+ STATUS      current
+ DESCRIPTION "An SNMP engine's administratively-unique identifier.
+              Objects of this type are for identification, not for
+              addressing, even though it is possible that an
+              address may have been used in the generation of
+              a specific value.
+              The value for this object may not be all zeros or
+              all 'ff'H or the empty (zero length) string.
+              The initial value for this object may be configured
+              via an operator console entry or via an algorithmic
+              function.  In the latter case, the following
+              example algorithm is recommended.
+              In cases where there are multiple engines on the
+              same system, the use of this algorithm is NOT
+              appropriate, as it would result in all of those
+              engines ending up with the same ID value.
+) The very first bit is used to indicate how the
+                rest of the data is composed.
+- as defined by enterprise using former methods
+                    that existed before SNMPv3. See item 2 below.
+- as defined by this architecture, see item 3
+                    below.
+                Note that this allows existing uses of the
+                engineID (also known as AgentID [RFC1910]) to
+                co-exist with any new uses.
+) The snmpEngineID has a length of 12 octets.
+                The first four octets are set to the binary
+                equivalent of the agent's SNMP management
+                private enterprise number as assigned by the
+                Internet Assigned Numbers Authority (IANA).
+                For example, if Acme Networks has been assigned
+                { enterprises 696 }, the first four octets would
+                be assigned '000002b8'H.
+                The remaining eight octets are determined via
+                one or more enterprise-specific methods. Such
+                methods must be designed so as to maximize the
+                possibility that the value of this object will
+                be unique in the agent's administrative domain.
+                For example, it may be the IP address of the SNMP
+                entity, or the MAC address of one of the
+                interfaces, with each address suitably padded
+                with random octets.  If multiple methods are
+                defined, then it is recommended that the first
+                octet indicate the method being used and the
+                remaining octets be a function of the method.
+) The length of the octet string varies.
+                The first four octets are set to the binary
+                equivalent of the agent's SNMP management
+                private enterprise number as assigned by the
+                Internet Assigned Numbers Authority (IANA).
+                For example, if Acme Networks has been assigned
+                { enterprises 696 }, the first four octets would
+                be assigned '000002b8'H.
+                The very first bit is set to 1. For example, the
+                above value for Acme Networks now changes to be
+                '800002b8'H.
+                The fifth octet indicates how the rest (6th and
+                following octets) are formatted. The values for
+                the fifth octet are:
+    - reserved, unused.
+    - IPv4 address (4 octets)
+                          lowest non-special IP address
+    - IPv6 address (16 octets)
+                          lowest non-special IP address
+    - MAC address (6 octets)
+                          lowest IEEE MAC address, canonical
+                          order
+    - Text, administratively assigned
+                          Maximum remaining length 27
+    - Octets, administratively assigned
+                          Maximum remaining length 27
+-127 - reserved, unused
+-255 - as defined by the enterprise
+                          Maximum remaining length 27
+            "
+ SYNTAX      OCTET STRING (SIZE(5..32))
+SnmpSecurityModel ::= TEXTUAL-CONVENTION
+ STATUS      current
+ DESCRIPTION "An identifier that uniquely identifies a
+              Security Model of the Security Subsystem within
+              this SNMP Management Architecture.
+              The values for securityModel are allocated as
+              follows:
-* One or more models may be present.
+              - The zero value does not identify any particular
+                security model.
-+------------------------------+
-|          Network            |
-+------------------------------+
-  ^      ^              ^
-  |      |              |
-  v      v              v
-+-----+ +-----+      +-------+
-| UDP | | IPX | . . . | other |
-+-----+ +-----+      +-------+              (traditional SNMP agent)
-+-------------------------------------------------------------------+
-|              ^                                                    |
-|              |        +---------------------+  +----------------+ |
-|              |        | Message Processing  |  | Security      | |
-| Dispatcher  v        | Subsystem          |  | Subsystem      | |
-| +-------------------+ |    +------------+  |  |                | |
-| | Transport        | |  +->| v1MP    * |<--->| +------------+ | |
-| | Mapping          | |  |  +------------+  |  | | Other      | | |
-| | (e.g., [[RFC3417|RFC 3417]])  | |  |  +------------+  |  | | Security  | | |
-| |                  | |  +->| v2cMP    * |<--->| | Model      | | |
-| | Message          | |  |  +------------+  |  | +------------+ | |
-| | Dispatcher  <--------->|  +------------+  |  | +------------+ | |
-| |                  | |  +->| v3MP    * |<--->| | User-based | | |
-| |                  | |  |  +------------+  |  | | Security  | | |
-| | PDU Dispatcher    | |  |  +------------+  |  | | Model      | | |
-| +-------------------+ |  +->| otherMP  * |<--->| +------------+ | |
-|              ^        |    +------------+  |  |                | |
-|              |        +---------------------+  +----------------+ |
-|              v                                                    |
-|      +-------+-------------------------+---------------+          |
-|      ^                                ^              ^          |
-|      |                                |              |          |
-|      v                                v              v          |
-| +-------------+  +---------+  +--------------+  +-------------+ |
-| |  COMMAND  |  | ACCESS  |  | NOTIFICATION |  |    PROXY    | |
-| |  RESPONDER  |<->| CONTROL |<->|  ORIGINATOR  |  |  FORWARDER  | |
-| | application |  |        |  | applications |  | application | |
-| +-------------+  +---------+  +--------------+  +-------------+ |
-|      ^                                ^                          |
-|      |                                |                          |
-|      v                                v                          |
-| +----------------------------------------------+                  |
-| |            MIB instrumentation              |      SNMP entity |
-+-------------------------------------------------------------------+
+              - Values between 1 and 255, inclusive, are reserved
+                for standards-track Security Models and are
+                managed by the Internet Assigned Numbers Authority
+                (IANA).
+              - Values greater than 255 are allocated to
+                enterprise-specific Security Models.  An
+                enterprise-specific securityModel value is defined
+                to be:
+                enterpriseID * 256 + security model within
+                enterprise
+                For example, the fourth Security Model defined by
+                the enterprise whose enterpriseID is 1 would be
+.
+              This scheme for allocation of securityModel
+              values allows for a maximum of 255 standards-
+              based Security Models, and for a maximum of
+Security Models per enterprise.
+              It is believed that the assignment of new
+              securityModel values will be rare in practice
+              because the larger the number of simultaneously
+              utilized Security Models, the larger the
+              chance that interoperability will suffer.
+              Consequently, it is believed that such a range
+              will be sufficient.  In the unlikely event that
+              the standards committee finds this number to be
+              insufficient over time, an enterprise number
+              can be allocated to obtain an additional 256
+              possible values.
+              Note that the most significant bit must be zero;
+              hence, there are 23 bits allocated for various
+              organizations to design and define non-standard
+              securityModels.  This limits the ability to
+              define new proprietary implementations of Security
+              Models to the first 8,388,608 enterprises.
+              It is worthwhile to note that, in its encoded
+              form, the securityModel value will normally
+              require only a single byte since, in practice,
+              the leftmost bits will be zero for most messages
+              and sign extension is suppressed by the encoding
+              rules.
+              As of this writing, there are several values
+              of securityModel defined for use with SNMP or
+              reserved for use with supporting MIB objects.
+              They are as follows:
+  reserved for 'any'
+  reserved for SNMPv1
+  reserved for SNMPv2c
+  User-Based Security Model (USM)
+            "
+ SYNTAX      INTEGER(0 .. 2147483647)
+SnmpMessageProcessingModel ::= TEXTUAL-CONVENTION
+ STATUS      current
+ DESCRIPTION "An identifier that uniquely identifies a Message
+              Processing Model of the Message Processing
+              Subsystem within this SNMP Management Architecture.
-=== The Naming of Identities ===
+              The values for messageProcessingModel are
+              allocated as follows:
-                        principal
+              - Values between 0 and 255, inclusive, are
-                            ^
+                reserved for standards-track Message Processing
-                            |
+                Models and are managed by the Internet Assigned
-                            |
+                 Numbers Authority (IANA).
-+----------------------------|-------------+
-| SNMP engine                v            |
-|                    +--------------+      |
-|                    |              |      |
-|  +-----------------| securityName |---+  |
-|  | Security Model  |              |  |  |
-|  |                 +--------------+  |  |
-|  |                        ^          |  |
-|  |                        |          |  |
-|  |                        v          |  |
-|  |  +------------------------------+  |  |
-|  |  |                              |  |  |
-|  |  | Model                        |  |  |
-|  |  | Dependent                    |  |  |
-|  |  | Security ID                  |  |  |
-|  |  |                              |  |  |
-|  |  +------------------------------+  |  |
-|  |                        ^          |  |
-|  |                        |          |  |
-|  +-------------------------|----------+  |
-|                            |            |
-|                            |            |
-+----------------------------|-------------+
-                            |
-                            v
-                          network
-==== Principal ====
+              - Values greater than 255 are allocated to
+                enterprise-specific Message Processing Models.
+                An enterprise messageProcessingModel value is
+                defined to be:
-A principal is the "who" on whose behalf services are provided or
+                enterpriseID * 256 +
-processing takes place.
+                    messageProcessingModel within enterprise
-A principal can be, among other things, an individual acting in a
+                For example, the fourth Message Processing Model
-particular role; a set of individuals, with each acting in a
+                defined by the enterprise whose enterpriseID
-particular role; an application or a set of applications; and
-combinations thereof.
-==== securityName ====
+                is 1 would be 259.
-A securityName is a human readable string representing a principal.
+              This scheme for allocating messageProcessingModel
-It has a model-independent format, and can be used outside a
+              values allows for a maximum of 255 standards-
-particular Security Model.
+              based Message Processing Models, and for a
+              maximum of 256 Message Processing Models per
+              enterprise.
+              It is believed that the assignment of new
+              messageProcessingModel values will be rare
+              in practice because the larger the number of
+              simultaneously utilized Message Processing Models,
+              the larger the chance that interoperability
+              will suffer. It is believed that such a range
+              will be sufficient.  In the unlikely event that
+              the standards committee finds this number to be
+              insufficient over time, an enterprise number
+              can be allocated to obtain an additional 256
+              possible values.
+              Note that the most significant bit must be zero;
+              hence, there are 23 bits allocated for various
+              organizations to design and define non-standard
+              messageProcessingModels.  This limits the ability
+              to define new proprietary implementations of
+              Message Processing Models to the first 8,388,608
+              enterprises.
+              It is worthwhile to note that, in its encoded
+              form, the messageProcessingModel value will
+              normally require only a single byte since, in
+              practice, the leftmost bits will be zero for
+              most messages and sign extension is suppressed
+              by the encoding rules.
+              As of this writing, there are several values of
+              messageProcessingModel defined for use with SNMP.
+              They are as follows:
-==== Model-dependent security ID ====
+  reserved for SNMPv1
+  reserved for SNMPv2c
+  reserved for SNMPv2u and SNMPv2*
+  reserved for SNMPv3
+            "
+ SYNTAX      INTEGER(0 .. 2147483647)
-A model-dependent security ID is the model-specific representation of
+SnmpSecurityLevel ::= TEXTUAL-CONVENTION
-a securityName within a particular Security Model.
+ STATUS      current
+ DESCRIPTION "A Level of Security at which SNMP messages can be
+              sent or with which operations are being processed;
+              in particular, one of:
-Model-dependent security IDs may or may not be human readable, and
+                noAuthNoPriv - without authentication and
-have a model-dependent syntax.  Examples include community names, and
+                              without privacy,
-user names.
+                authNoPriv  - with authentication but
+                              without privacy,
+                authPriv    - with authentication and
+                              with privacy.
-The transformation of model-dependent security IDs into securityNames
+              These three values are ordered such that
-and vice versa is the responsibility of the relevant Security Model.
+              noAuthNoPriv is less than authNoPriv and
+              authNoPriv is less than authPriv.
-=== The Naming of Management Information ===
+            "
+ SYNTAX      INTEGER { noAuthNoPriv(1),
-Management information resides at an SNMP entity where a Command
+                        authNoPriv(2),
-Responder Application has local access to potentially multiple
+                        authPriv(3)
-contexts.  This application uses a contextEngineID equal to the
+                      }
-snmpEngineID of its associated SNMP engine.
+SnmpAdminString ::= TEXTUAL-CONVENTION
+ DISPLAY-HINT "255t"
+ STATUS      current
+ DESCRIPTION "An octet string containing administrative
+              information, preferably in human-readable form.
+              To facilitate internationalization, this
+              information is represented using the ISO/IEC
+              IS 10646-1 character set, encoded as an octet
+              string using the UTF-8 transformation format
+              described in [RFC2279].
+              Since additional code points are added by
+              amendments to the 10646 standard from time
+              to time, implementations must be prepared to
+              encounter any code point from 0x00000000 to
+x7fffffff.  Byte sequences that do not
+              correspond to the valid UTF-8 encoding of a
+              code point or are outside this range are
+              prohibited.
+              The use of control codes should be avoided.
+              When it is necessary to represent a newline,
+              the control code sequence CR LF should be used.
+              The use of leading or trailing white space should
+              be avoided.
+              For code points not directly supported by user
+              interface hardware or software, an alternative
+              means of entry and display, such as hexadecimal,
+              may be provided.
+              For information encoded in 7-bit US-ASCII,
+              the UTF-8 encoding is identical to the
+              US-ASCII encoding.
+              UTF-8 may require multiple bytes to represent a
+              single character / code point; thus the length
+              of this object in octets may be different from
+              the number of characters encoded.  Similarly,
+              size constraints refer to the number of encoded
+              octets, not the number of characters represented
+              by an encoding.
+              Note that when this TC is used for an object that
+              is used or envisioned to be used as an index, then
+              a SIZE restriction MUST be specified so that the
+              number of sub-identifiers for any object instance
+              does not exceed the limit of 128, as defined by
+              [RFC3416].
+              Note that the size of an SnmpAdminString object is
+              measured in octets, not characters.
+            "
+ SYNTAX      OCTET STRING (SIZE (0..255))
+-- Administrative assignments ***************************************
+snmpFrameworkAdmin
+ OBJECT IDENTIFIER ::= { snmpFrameworkMIB 1 }
+snmpFrameworkMIBObjects
+ OBJECT IDENTIFIER ::= { snmpFrameworkMIB 2 }
+snmpFrameworkMIBConformance
+ OBJECT IDENTIFIER ::= { snmpFrameworkMIB 3 }
+-- the snmpEngine Group ********************************************
+snmpEngine OBJECT IDENTIFIER ::= { snmpFrameworkMIBObjects 1 }
+snmpEngineID    OBJECT-TYPE
+ SYNTAX      SnmpEngineID
+ MAX-ACCESS  read-only
+ STATUS      current
+ DESCRIPTION "An SNMP engine's administratively-unique identifier.
+              This information SHOULD be stored in non-volatile
+              storage so that it remains constant across
+              re-initializations of the SNMP engine.
+            "
+ ::= { snmpEngine 1 }
+snmpEngineBoots  OBJECT-TYPE
+ SYNTAX      INTEGER (1..2147483647)
+ MAX-ACCESS  read-only
+ STATUS      current
+ DESCRIPTION "The number of times that the SNMP engine has
+              (re-)initialized itself since snmpEngineID
+              was last configured.
+            "
+ ::= { snmpEngine 2 }
+snmpEngineTime  OBJECT-TYPE
+ SYNTAX      INTEGER (0..2147483647)
+ UNITS        "seconds"
+ MAX-ACCESS  read-only
+ STATUS      current
+ DESCRIPTION "The number of seconds since the value of
+              the snmpEngineBoots object last changed.
+              When incrementing this object's value would
+              cause it to exceed its maximum,
+              snmpEngineBoots is incremented as if a
+              re-initialization had occurred, and this
+              object's value consequently reverts to zero.
+            "
+ ::= { snmpEngine 3 }
+snmpEngineMaxMessageSize OBJECT-TYPE
+ SYNTAX      INTEGER (484..2147483647)
+ MAX-ACCESS  read-only
+ STATUS      current
+ DESCRIPTION "The maximum length in octets of an SNMP message
+              which this SNMP engine can send or receive and
+              process, determined as the minimum of the maximum
+              message size values supported among all of the
+              transports available to and supported by the engine.
+            "
+ ::= { snmpEngine 4 }
+-- Registration Points for Authentication and Privacy Protocols **
+snmpAuthProtocols OBJECT-IDENTITY
+ STATUS        current
+ DESCRIPTION  "Registration point for standards-track
+              authentication protocols used in SNMP Management
+              Frameworks.
+              "
+ ::= { snmpFrameworkAdmin 1 }
+snmpPrivProtocols OBJECT-IDENTITY
+ STATUS        current
+ DESCRIPTION  "Registration point for standards-track privacy
+              protocols used in SNMP Management Frameworks.
+              "
+ ::= { snmpFrameworkAdmin 2 }
+-- Conformance information ******************************************
+snmpFrameworkMIBCompliances
+            OBJECT IDENTIFIER ::= {snmpFrameworkMIBConformance 1}
+snmpFrameworkMIBGroups
+            OBJECT IDENTIFIER ::= {snmpFrameworkMIBConformance 2}
+-- compliance statements
+snmpFrameworkMIBCompliance MODULE-COMPLIANCE
+ STATUS      current
+ DESCRIPTION "The compliance statement for SNMP engines which
+              implement the SNMP Management Framework MIB.
+            "
+ MODULE    -- this module
+    MANDATORY-GROUPS { snmpEngineGroup }
+ ::= { snmpFrameworkMIBCompliances 1 }
+-- units of conformance
+snmpEngineGroup OBJECT-GROUP
+ OBJECTS {
+          snmpEngineID,
+          snmpEngineBoots,
+          snmpEngineTime,
+          snmpEngineMaxMessageSize
+        }
+ STATUS      current
+ DESCRIPTION "A collection of objects for identifying and
+              determining the configuration and current timeliness
+              values of an SNMP engine.
+            "
+ ::= { snmpFrameworkMIBGroups 1 }
+END
+== IANA Considerations ==
+This document defines three number spaces administered by IANA, one
+for security models, another for message processing models, and a
+third for SnmpEngineID formats.
+=== Security Models ===
-+-----------------------------------------------------------------+
+The SnmpSecurityModel TEXTUAL-CONVENTION values managed by IANA are
-|  SNMP entity (identified by snmpEngineID, for example:          |
+in the range from 0 to 255 inclusive, and are reserved for
-|  '800002b804616263'H (enterpise 696, string "abc")              |
+standards-track Security Models.  If this range should in the future
-|                                                                |
+prove insufficient, an enterprise number can be allocated to obtain
-|  +------------------------------------------------------------+ |
+an additional 256 possible values.
-|  | SNMP engine (identified by snmpEngineID)                  | |
-|  |                                                            | |
+As of this writing, there are several values of securityModel defined
-|  | +-------------+ +------------+ +-----------+ +-----------+ | |
+for use with SNMP or reserved for use with supporting MIB objects.
-|  | |            | |            | |          | |          | | |
+They are as follows:
-|  | | Dispatcher  | | Message    | | Security  | | Access    | | |
-|  | |            | | Processing | | Subsystem | | Control  | | |
+reserved for 'any'
-|  | |            | | Subsystem  | |          | | Subsystem | | |
+reserved for SNMPv1
-|  | |            | |            | |          | |          | | |
+reserved for SNMPv2c
-|  | +-------------+ +------------+ +-----------+ +-----------+ | |
+User-Based Security Model (USM)
-|  |                                                            | |
-|  +------------------------------------------------------------+ |
+=== Message Processing Models ===
-|                                                                |
-|  +------------------------------------------------------------+ |
+The SnmpMessageProcessingModel TEXTUAL-CONVENTION values managed by
-|  |  Command Responder Application                            | |
+IANA are in the range 0 to 255, inclusive.  Each value uniquely
-|  |  (contextEngineID, example: '800002b804616263'H)          | |
+identifies a standards-track Message Processing Model of the Message
-|  |                                                            | |
+Processing Subsystem within the SNMP Management Architecture.
-|  |  example contextNames:                                    | |
-|  |                                                            | |
-|  |  "bridge1"          "bridge2"            "" (default)     | |
-|  |  ---------          ---------            ------------      | |
-|  |      |                  |                  |              | |
-|  +------|------------------|-------------------|--------------+ |
-|        |                  |                  |                |
-|  +------|------------------|-------------------|--------------+ |
-|  |  MIB | instrumentation  |                  |              | |
-|  |  +---v------------+ +---v------------+ +----v-----------+  | |
-|  |  | context        | | context        | | context        |  | |
-|  |  |                | |                | |                |  | |
-|  |  | +------------+ | | +------------+ | | +------------+ |  | |
-|  |  | | bridge MIB | | | | bridge MIB | | | | some  MIB  | |  | |
-|  |  | +------------+ | | +------------+ | | +------------+ |  | |
-|  |  |                | |                | |                |  | |
-|  |  |                | |                | | +------------+ |  | |
-|  |  |                | |                | | | other MIB  | |  | |
-|  |  |                | |                | | +------------+ |  | |
-|  |  |                | |                | |                |  | |
-+-----------------------------------------------------------------+
+Should this range prove insufficient in the future, an enterprise
+number may be obtained for the standards committee to get an
+additional 256 possible values.
+As of this writing, there are several values of
+messageProcessingModel defined for use with SNMP.  They are as
+follows:
+  reserved for SNMPv1
+  reserved for SNMPv2c
+  reserved for SNMPv2u and SNMPv2*
+  reserved for SNMPv3
+=== SnmpEngineID Formats ===
+The SnmpEngineID TEXTUAL-CONVENTION's fifth octet contains a format
+identifier.  The values managed by IANA are in the range 6 to 127,
+inclusive.  Each value uniquely identifies a standards-track
+SnmpEngineID format.
+== Intellectual Property ==
+The IETF takes no position regarding the validity or scope of any
+intellectual property or other rights that might be claimed to
+pertain to the implementation or use of the technology described in
+this document or the extent to which any license under such rights
+might or might not be available; neither does it represent that it
+has made any effort to identify any such rights.  Information on the
+IETF's procedures with respect to rights in standards-track and
+standards-related documentation can be found in RFC 2028.  Copies of
+claims of rights made available for publication and any assurances of
+licenses to be made available, or the result of an attempt made to
+obtain a general license or permission for the use of such
+proprietary rights by implementors or users of this specification can
+be obtained from the IETF Secretariat.
+The IETF invites any interested party to bring to its attention any
+copyrights, patents or patent applications, or other proprietary
+rights which may cover technology that may be required to practice
+this standard.  Please address the information to the IETF Executive
+Director.
+== Acknowledgements ==
+This document is the result of the efforts of the SNMPv3 Working
+Group.  Some special thanks are in order to the following SNMPv3 WG
+members:
-==== An SNMP Context ====
+  Harald Tveit Alvestrand (Maxware)
+  Dave Battle (SNMP Research, Inc.)
-An SNMP context, or just "context" for short, is a collection of
+  Alan Beard (Disney Worldwide Services)
-management information accessible by an SNMP entity.  An item of
+  Paul Berrevoets (SWI Systemware/Halcyon Inc.)
-management information may exist in more than one context.  An SNMP
+  Martin Bjorklund (Ericsson)
-entity potentially has access to many contexts.
+  Uri Blumenthal (IBM T.J. Watson Research Center)
+  Jeff Case (SNMP Research, Inc.)
+  John Curran (BBN)
+  Mike Daniele (Compaq Computer Corporation)
+  T. Max Devlin (Eltrax Systems)
+  John Flick (Hewlett Packard)
+  Rob Frye (MCI)
+  Wes Hardaker (U.C.Davis, Information Technology - D.C.A.S.)
-Typically, there are many instances of each managed object type
+  David Harrington (Cabletron Systems Inc.)
-within a management domain.  For simplicity, the method for
+  Lauren Heintz (BMC Software, Inc.)
-identifying instances specified by the MIB module does not allow each
+  N.C. Hien (IBM T.J. Watson Research Center)
-instance to be distinguished amongst the set of all instances within
+  Michael Kirkham (InterWorking Labs, Inc.)
-a management domain; rather, it allows each instance to be identified
+  Dave Levi (SNMP Research, Inc.)
-only within some scope or "context", where there are multiple such
+  Louis A Mamakos (UUNET Technologies Inc.)
-contexts within the management domain.  Often, a context is a
+  Joe Marzot (Nortel Networks)
-physical device, or perhaps, a logical device, although a context can
+  Paul Meyer (Secure Computing Corporation)
-also encompass multiple devices, or a subset of a single device, or
+  Keith McCloghrie (Cisco Systems)
-even a subset of multiple devices, but a context is always defined as
+  Bob Moore (IBM)
-a subset of a single SNMP entity.  Thus, in order to identify an
+  Russ Mundy (TIS Labs at Network Associates)
-individual item of management information within the management
+  Bob Natale (ACE*COMM Corporation)
-domain, its contextName and contextEngineID must be identified in
+  Mike O'Dell (UUNET Technologies Inc.)
-addition to its object type and its instance.
+  Dave Perkins (DeskTalk)
+  Peter Polkinghorne (Brunel University)
+  Randy Presuhn (BMC Software, Inc.)
+  David Reeder (TIS Labs at Network Associates)
+  David Reid (SNMP Research, Inc.)
+  Aleksey Romanov (Quality Quorum)
+  Shawn Routhier (Epilogue)
+  Juergen Schoenwaelder (TU Braunschweig)
+  Bob Stewart (Cisco Systems)
+  Mike Thatcher (Independent Consultant)
+  Bert Wijnen (IBM T.J. Watson Research Center)
-For example, the managed object type ifDescr [RFC2863], is defined as
+The document is based on recommendations of the IETF Security and
-the description of a network interface.  To identify the description
+Administrative Framework Evolution for SNMP Advisory Team.  Members
-of device-X's first network interface, four pieces of information are
+of that Advisory Team were:
-needed: the snmpEngineID of the SNMP entity which provides access to
-the management information at device-X, the contextName (device-X),
-the managed object type (ifDescr), and the instance ("1").
-Each context has (at least) one unique identification within the
+  David Harrington (Cabletron Systems Inc.)
-management domain.  The same item of management information can exist
+  Jeff Johnson (Cisco Systems)
-in multiple contexts.  An item of management information may have
+  David Levi (SNMP Research Inc.)
-multiple unique identifications.  This occurs when an item of
+  John Linn (Openvision)
-management information exists in multiple contexts, and this also
+  Russ Mundy (Trusted Information Systems) chair
-occurs when a context has multiple unique identifications.
+  Shawn Routhier (Epilogue)
+  Glenn Waters (Nortel)
+  Bert Wijnen (IBM T. J. Watson Research Center)
-The combination of a contextEngineID and a contextName unambiguously
+As recommended by the Advisory Team and the SNMPv3 Working Group
-identifies a context within an administrative domain; note that there
+Charter, the design incorporates as much as practical from previous
-may be multiple unique combinations of contextEngineID and
+RFCs and drafts. As a result, special thanks are due to the authors
-contextName that unambiguously identify the same context.
+of previous designs known as SNMPv2u and SNMPv2*:
-==== contextEngineID ====
+  Jeff Case (SNMP Research, Inc.)
+  David Harrington (Cabletron Systems Inc.)
+  David Levi (SNMP Research, Inc.)
+  Keith McCloghrie (Cisco Systems)
+  Brian O'Keefe (Hewlett Packard)
-Within an administrative domain, a contextEngineID uniquely
+  Marshall T. Rose (Dover Beach Consulting)
-identifies an SNMP entity that may realize an instance of a context
+  Jon Saperia (BGS Systems Inc.)
-with a particular contextName.
+  Steve Waldbusser (International Network Services)
+  Glenn W. Waters (Bell-Northern Research Ltd.)
+== Security Considerations ==
+This document describes how an implementation can include a Security
+Model to protect management messages and an Access Control Model to
+control access to management information.
+The level of security provided is determined by the specific Security
+Model implementation(s) and the specific Access Control Model
+implementation(s) used.
+Applications have access to data which is not secured.  Applications
+SHOULD take reasonable steps to protect the data from disclosure.
+It is the responsibility of the purchaser of an implementation to
+ensure that:
+) an implementation complies with the rules defined by this
+      architecture,
-==== contextName ====
+) the Security and Access Control Models utilized satisfy the
+      security and access control needs of the organization,
+) the implementations of the Models and Applications comply with
+      the model and application specifications,
-A contextName is used to name a context.  Each contextName MUST be
+) and the implementation protects configuration secrets from
-unique within an SNMP entity.
+      inadvertent disclosure.
-==== scopedPDU ====
+This document also contains a MIB definition module.  None of the
+objects defined is writable, and the information they represent is
+not deemed to be particularly sensitive.  However, if they are deemed
+sensitive in a particular environment, access to them should be
+restricted through the use of appropriately configured Security and
+Access Control models.
-A scopedPDU is a block of data containing a contextEngineID, a
+.  References
-contextName, and a PDU.
-The PDU is an SNMP Protocol Data Unit containing information named in
+.1.  Normative References
-the context which is unambiguously identified within an
-administrative domain by the combination of the contextEngineID and
-the contextName.  See, for example, [[RFC3416|RFC 3416]] for more information
-about SNMP PDUs.
-=== Other Constructs ===
+[RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+            Requirement Levels", BCP 14, RFC 2119, March 1997.
-==== maxSizeResponseScopedPDU ====
+[RFC2279]  Yergeau, F., "UTF-8, a transformation format of ISO
+", RFC 2279, January 1998.
-The maxSizeResponseScopedPDU is the maximum size of a scopedPDU that
+[RFC2578]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
-a PDU's sender would be willing to accept.  Note that the size of a
+            Rose, M. and S. Waldbusser, "Structure of Management
-scopedPDU does not include the size of the SNMP message header.
+            Information Version 2 (SMIv2)", STD 58, RFC 2578, April
+.
-==== Local Configuration Datastore ====
+[RFC2579]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
+            Rose, M. and S. Waldbusser, "Textual Conventions for
+            SMIv2", STD 58, RFC 2579, April 1999.
-The subsystems, models, and applications within an SNMP entity may
+[RFC2580]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
-need to retain their own sets of configuration information.
+            Rose, M. and S. Waldbusser, "Conformance Statements for
+            SMIv2", STD 58, RFC 2580, April 1999.
-Portions of the configuration information may be accessible as
+[RFC3412]  Case, J., Harrington, D., Presuhn, R. and B. Wijnen,
-managed objects.
+            "Message Processing and Dispatching for the Simple
+            Network Management Protocol (SNMP)", STD 62, RFC 3412,
+            December 2002.
-The collection of these sets of information is referred to as an
+[RFC3413]  Levi, D., Meyer, P. and B. Stewart, "Simple Network
-entity's Local Configuration Datastore (LCD).
+            Management Protocol (SNMP) Applications", STD 62, RFC
+, December 2002.
-==== securityLevel ====
+[RFC3414]  Blumenthal, U. and B. Wijnen, "User-Based Security Model
+            (USM) for Version 3 of the Simple Network Management
+            Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
-This architecture recognizes three levels of security:
+[RFC3415]  Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based
+            Access Control Model (VACM) for the Simple Network
+            Management Protocol (SNMP)", STD 62, RFC 3415, December
+.
-  -  without authentication and without privacy (noAuthNoPriv)
+[RFC3416]  Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.
+            Waldbusser, "Protocol Operations for the Simple Network
+            Management Protocol (SNMP)", STD 62, RFC 3416, December
+.
-  -  with authentication but without privacy (authNoPriv)
+[RFC3417]  Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.
+            Waldbusser, "Transport Mappings for the Simple Network
+            Management Protocol (SNMP)", STD 62, RFC 3417, December
+.
-  -  with authentication and with privacy (authPriv)
+[RFC3418]  Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.
+            Waldbusser, "Management Information Base (MIB) for the
+            Simple Network Management Protocol (SNMP)", STD 62, RFC
+, December 2002.
+.2.  Informative References
+[RFC1155]  Rose, M. and K. McCloghrie, "Structure and Identification
+            of Management Information for TCP/IP-based internets",
+            STD 16, RFC 1155, May 1990.
+[RFC1157]  Case, J., Fedor, M., Schoffstall, M. and J. Davin, "The
+            Simple Network Management Protocol", STD 15, RFC 1157,
+            May 1990.
+[RFC1212]  Rose, M. and K. McCloghrie, "Concise MIB Definitions",
+            STD 16, RFC 1212, March 1991.
+[RFC1901]  Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
+            "Introduction to Community-based SNMPv2", RFC 1901,
+            January 1996.
+[RFC1909]  McCloghrie, K., Editor, "An Administrative Infrastructure
+            for SNMPv2", RFC 1909, February 1996.
+[RFC1910]  Waters, G., Editor, "User-based Security Model for
+            SNMPv2", RFC 1910, February 1996.
+[RFC2028]  Hovey, R. and S. Bradner, "The Organizations Involved in
+            the IETF Standards Process", BCP 11, RFC 2028, October
+.
-These three values are ordered such that noAuthNoPriv is less than
+[RFC2576]  Frye, R., Levi, D., Routhier, S. and B. Wijnen,
-authNoPriv and authNoPriv is less than authPriv.
+            "Coexistence between Version 1, Version 2, and Version 3
+            of the Internet-Standard Network Management Framework",
+            RFC 2576, March 2000.
-Every message has an associated securityLevel.  All Subsystems
+[RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group
-(Message Processing, Security, Access Control) and applications are
+            MIB", RFC 2863, June 2000.
-REQUIRED to either supply a value of securityLevel or to abide by the
-supplied value of securityLevel while processing the message and its
-contents.
-== Abstract Service Interfaces ==
+[RFC3410]  Case, J., Mundy, R., Partain, D. and B. Stewart,
+            "Introduction and Applicability Statements for Internet-
+            Standard Management Framework", RFC 3410, December 2002.
-Abstract service interfaces have been defined to describe the
+Appendix A
-conceptual interfaces between the various subsystems within an SNMP
-entity.  The abstract service interfaces are intended to help clarify
-the externally observable behavior of SNMP entities, and are not
-intended to constrain the structure or organization of
-implementations in any way.  Most specifically, they should not be
-interpreted as APIs or as requirements statements for APIs.
-These abstract service interfaces are defined by a set of primitives
+A.  Guidelines for Model Designers
-that define the services provided and the abstract data elements that
-are to be passed when the services are invoked.  This section lists
-the primitives that have been defined for the various subsystems.
-=== Dispatcher Primitives ===
+This appendix describes guidelines for designers of models which are
+expected to fit into the architecture defined in this document.
-The Dispatcher typically provides services to the SNMP applications
+SNMPv1 and SNMPv2c are two SNMP frameworks which use communities to
-via its PDU Dispatcher.  This section describes the primitives
+provide trivial authentication and access control.  SNMPv1 and
-provided by the PDU Dispatcher.
+SNMPv2c Frameworks can coexist with Frameworks designed according to
+this architecture, and modified versions of SNMPv1 and SNMPv2c
+Frameworks could be designed to meet the requirements of this
+architecture, but this document does not provide guidelines for that
+coexistence.
+Within any subsystem model, there should be no reference to any
+specific model of another subsystem, or to data defined by a specific
+model of another subsystem.
+Transfer of data between the subsystems is deliberately described as
+a fixed set of abstract data elements and primitive functions which
+can be overloaded to satisfy the needs of multiple model definitions.
+Documents which define models to be used within this architecture
+SHOULD use the standard primitives between subsystems, possibly
+defining specific mechanisms for converting the abstract data
+elements into model-usable formats.  This constraint exists to allow
+subsystem and model documents to be written recognizing common
+borders of the subsystem and model.  Vendors are not constrained to
+recognize these borders in their implementations.
+The architecture defines certain standard services to be provided
+between subsystems, and the architecture defines abstract service
+interfaces to request these services.
+Each model definition for a subsystem SHOULD support the standard
+service interfaces, but whether, or how, or how well, it performs the
+service is dependent on the model definition.
+A.1.  Security Model Design Requirements
+A.1.1.  Threats
+A document describing a Security Model MUST describe how the model
+protects against the threats described under "Security Requirements
+of this Architecture", section 1.4.
+A.1.2.  Security Processing
+Received messages MUST be validated by a Model of the Security
+Subsystem.  Validation includes authentication and privacy processing
+if needed, but it is explicitly allowed to send messages which do not
+require authentication or privacy.
+A received message contains a specified securityLevel to be used
+during processing.  All messages requiring privacy MUST also require
+authentication.
+A Security Model specifies rules by which authentication and privacy
+are to be done.  A model may define mechanisms to provide additional
+security features, but the model definition is constrained to using
+(possibly a subset of) the abstract data elements defined in this
+document for transferring data between subsystems.
+Each Security Model may allow multiple security protocols to be used
+concurrently within an implementation of the model.  Each Security
+Model defines how to determine which protocol to use, given the
+securityLevel and the security parameters relevant to the message.
+Each Security Model, with its associated protocol(s) defines how the
+sending/receiving entities are identified, and how secrets are
+configured.
+Authentication and Privacy protocols supported by Security Models are
+uniquely identified using Object Identifiers.  IETF standard
+protocols for authentication or privacy should have an identifier
+defined within the snmpAuthProtocols or the snmpPrivProtocols
+subtrees.  Enterprise specific protocol identifiers should be defined
+within the enterprise subtree.
+For privacy, the Security Model defines what portion of the message
+is encrypted.
+The persistent data used for security should be SNMP-manageable, but
+the Security Model defines whether an instantiation of the MIB is a
+conformance requirement.
+Security Models are replaceable within the Security Subsystem.
+Multiple Security Model implementations may exist concurrently within
+an SNMP engine.  The number of Security Models defined by the SNMP
+community should remain small to promote interoperability.
+A.1.3.  Validate the security-stamp in a received message
+A Message Processing Model requests that a Security Model:
+  -  verifies that the message has not been altered,
+  -  authenticates the identification of the principal for whom the
+      message was generated.
+  -  decrypts the message if it was encrypted.
+Additional requirements may be defined by the model, and additional
+services may be provided by the model, but the model is constrained
+to use the following primitives for transferring data between
+subsystems.  Implementations are not so constrained.
+A Message Processing Model uses the processIncomingMsg primitive as
+described in section 4.4.2.
-==== Generate Outgoing Request or Notification ====
+A.1.4.  Security MIBs
+Each Security Model defines the MIB module(s) required for security
+processing, including any MIB module(s) required for the security
+protocol(s) supported.  The MIB module(s) SHOULD be defined
+concurrently with the procedures which use the MIB module(s).  The
+MIB module(s) are subject to normal access control rules.
-The PDU Dispatcher provides the following primitive for an
+The mapping between the model-dependent security ID and the
-application to send an SNMP Request or Notification to another SNMP
+securityName MUST be able to be determined using SNMP, if the model-
-entity:
+dependent MIB is instantiated and if access control policy allows
+access.
-statusInformation =              -- sendPduHandle if success
+A.1.5.  Cached Security Data
-                                -- errorIndication if failure
-  sendPdu(
-  IN  transportDomain          -- transport domain to be used
-  IN  transportAddress          -- transport address to be used
-  IN  messageProcessingModel    -- typically, SNMP version
-  IN  securityModel            -- Security Model to use
-  IN  securityName              -- on behalf of this principal
-  IN  securityLevel            -- Level of Security requested
-  IN  contextEngineID          -- data from/at this entity
-  IN  contextName              -- data from/in this context
-  IN  pduVersion                -- the version of the PDU
-  IN  PDU                      -- SNMP Protocol Data Unit
-  IN  expectResponse            -- TRUE or FALSE
-      )
-==== Process Incoming Request or Notification PDU ====
+For each message received, the Security Model caches the state
+information such that a Response message can be generated using the
+same security information, even if the Local Configuration Datastore
+is altered between the time of the incoming request and the outgoing
+response.
-The PDU Dispatcher provides the following primitive to pass an
+A Message Processing Model has the responsibility for explicitly
-incoming SNMP PDU to an application:
+releasing the cached data if such data is no longer needed.  To
+enable this, an abstract securityStateReference data element is
+passed from the Security Model to the Message Processing Model.
-processPdu(                      -- process Request/Notification PDU
+The cached security data may be implicitly released via the
-  IN  messageProcessingModel    -- typically, SNMP version
+generation of a response, or explicitly released by using the
-  IN  securityModel            -- Security Model in use
+stateRelease primitive, as described in section 4.5.1.
-  IN  securityName              -- on behalf of this principal
-  IN  securityLevel            -- Level of Security
-  IN  contextEngineID          -- data from/at this SNMP entity
-  IN  contextName              -- data from/in this context
-  IN  pduVersion                -- the version of the PDU
-  IN  PDU                      -- SNMP Protocol Data Unit
-  IN  maxSizeResponseScopedPDU  -- maximum size of the Response PDU
-  IN  stateReference            -- reference to state information
-      )                        -- needed when sending a response
+A.2.  Message Processing Model Design Requirements
+An SNMP engine contains a Message Processing Subsystem which may
+contain multiple Message Processing Models.
+The Message Processing Model MUST always (conceptually) pass the
+complete PDU, i.e., it never forwards less than the complete list of
+varBinds.
+A.2.1.  Receiving an SNMP Message from the Network
+Upon receipt of a message from the network, the Dispatcher in the
+SNMP engine determines the version of the SNMP message and interacts
+with the corresponding Message Processing Model to determine the
+abstract data elements.
+A Message Processing Model specifies the SNMP Message format it
+supports and describes how to determine the values of the abstract
+data elements (like msgID, msgMaxSize, msgFlags,
+msgSecurityParameters, securityModel, securityLevel etc).  A Message
+Processing Model interacts with a Security Model to provide security
+processing for the message using the processIncomingMsg primitive, as
+described in section 4.4.2.
+A.2.2.  Sending an SNMP Message to the Network
+The Dispatcher in the SNMP engine interacts with a Message Processing
+Model to prepare an outgoing message.  For that it uses the following
+primitives:
+  -  for requests and notifications: prepareOutgoingMessage, as
+      described in section 4.2.1.
+  -  for response messages: prepareResponseMessage, as described in
+      section 4.2.2.
+A Message Processing Model, when preparing an Outgoing SNMP Message,
+interacts with a Security Model to secure the message.  For that it
+uses the following primitives:
+  -  for requests and notifications: generateRequestMsg, as
+      described in section 4.4.1.
+  -  for response messages: generateResponseMsg as described in
+      section 4.4.3.
-==== Generate Outgoing Response ====
+Once the SNMP message is prepared by a Message Processing Model, the
+Dispatcher sends the message to the desired address using the
+appropriate transport.
-The PDU Dispatcher provides the following primitive for an
+A.3.  Application Design Requirements
-application to return an SNMP Response PDU to the PDU Dispatcher:
-result =                        -- SUCCESS or FAILURE
+Within an application, there may be an explicit binding to a specific
-returnResponsePdu(
+SNMP message version, i.e., a specific Message Processing Model, and
-  IN  messageProcessingModel    -- typically, SNMP version
+to a specific Access Control Model, but there should be no reference
-  IN  securityModel            -- Security Model in use
+to any data defined by a specific Message Processing Model or Access
-  IN  securityName              -- on behalf of this principal
+Control Model.
-  IN  securityLevel            -- same as on incoming request
-  IN  contextEngineID          -- data from/at this SNMP entity
-  IN  contextName              -- data from/in this context
-  IN  pduVersion                -- the version of the PDU
-  IN  PDU                      -- SNMP Protocol Data Unit
-  IN  maxSizeResponseScopedPDU  -- maximum size sender can accept
-  IN  stateReference            -- reference to state information
-                                -- as presented with the request
-  IN  statusInformation        -- success or errorIndication
-      )                        -- error counter OID/value if error
-==== Process Incoming Response PDU ====
+Within an application, there should be no reference to any specific
+Security Model, or any data defined by a specific Security Model.
-The PDU Dispatcher provides the following primitive to pass an
+An application determines whether explicit or implicit access control
-incoming SNMP Response PDU to an application:
+should be applied to the operation, and, if access control is needed,
+which Access Control Model should be used.
+An application has the responsibility to define any MIB module(s)
+used to provide application-specific services.
-processResponsePdu(              -- process Response PDU
+Applications interact with the SNMP engine to initiate messages,
-  IN  messageProcessingModel    -- typically, SNMP version
+receive responses, receive asynchronous messages, and send responses.
-  IN  securityModel            -- Security Model in use
-  IN  securityName              -- on behalf of this principal
-  IN  securityLevel            -- Level of Security
-  IN  contextEngineID          -- data from/at this SNMP entity
-  IN  contextName              -- data from/in this context
-  IN  pduVersion                -- the version of the PDU
-  IN  PDU                      -- SNMP Protocol Data Unit
-  IN  statusInformation        -- success or errorIndication
-  IN  sendPduHandle            -- handle from sendPdu
-      )
-==== Registering Responsibility for Handling SNMP PDUs ====
+A.3.1.  Applications that Initiate Messages
-Applications can register/unregister responsibility for a specific
+Applications may request that the SNMP engine send messages
-contextEngineID, for specific pduTypes, with the PDU Dispatcher
+containing SNMP commands or notifications using the sendPdu primitive
-according to the following primitives.  The list of particular
+as described in section 4.1.1.
-pduTypes that an application can register for is determined by the
-Message Processing Model(s) supported by the SNMP entity that
-contains the PDU Dispatcher.
+If it is desired that a message be sent to multiple targets, it is
+the responsibility of the application to provide the iteration.
+The SNMP engine assumes necessary access control has been applied to
+the PDU, and provides no access control services.
+The SNMP engine looks at the "expectResponse" parameter, and if a
+response is expected, then the appropriate information is cached such
+that a later response can be associated to this message, and can then
+be returned to the application.  A sendPduHandle is returned to the
+application so it can later correspond the response with this message
+as well.
+A.3.2.  Applications that Receive Responses
+The SNMP engine matches the incoming response messages to outstanding
+messages sent by this SNMP engine, and forwards the response to the
+associated application using the processResponsePdu primitive, as
+described in section 4.1.4.
-statusInformation =            -- success or errorIndication
+A.3.3.  Applications that Receive Asynchronous Messages
-  registerContextEngineID(
-  IN  contextEngineID        -- take responsibility for this one
-  IN  pduType                -- the pduType(s) to be registered
-      )
-unregisterContextEngineID(
-  IN  contextEngineID        -- give up responsibility for this one
-  IN  pduType                -- the pduType(s) to be unregistered
-      )
-Note that realizations of the registerContextEngineID and
-unregisterContextEngineID abstract service interfaces may provide
-implementation-specific ways for applications to register/deregister
-responsibility for all possible values of the contextEngineID or
-pduType parameters.
-=== Message Processing Subsystem Primitives ===
-The Dispatcher interacts with a Message Processing Model to process a
-specific version of an SNMP Message.  This section describes the
-primitives provided by the Message Processing Subsystem.
-==== Prepare Outgoing SNMP Request or Notification Message ====
-The Message Processing Subsystem provides this service primitive for
-preparing an outgoing SNMP Request or Notification Message:
-statusInformation =              -- success or errorIndication
-  prepareOutgoingMessage(
-  IN  transportDomain          -- transport domain to be used
-  IN  transportAddress          -- transport address to be used
-  IN  messageProcessingModel    -- typically, SNMP version
-  IN  securityModel            -- Security Model to use
-  IN  securityName              -- on behalf of this principal
-  IN  securityLevel            -- Level of Security requested
-  IN  contextEngineID          -- data from/at this entity
-  IN  contextName              -- data from/in this context
-  IN  pduVersion                -- the version of the PDU
-  IN  PDU                      -- SNMP Protocol Data Unit
-  IN  expectResponse            -- TRUE or FALSE
-  IN  sendPduHandle            -- the handle for matching
-                                -- incoming responses
-  OUT  destTransportDomain      -- destination transport domain
-  OUT  destTransportAddress      -- destination transport address
-  OUT  outgoingMessage          -- the message to send
-  OUT  outgoingMessageLength    -- its length
-      )
-==== Prepare an Outgoing SNMP Response Message ====
-The Message Processing Subsystem provides this service primitive for
-preparing an outgoing SNMP Response Message:
-result =                        -- SUCCESS or FAILURE
-  prepareResponseMessage(
-  IN  messageProcessingModel    -- typically, SNMP version
-  IN  securityModel            -- same as on incoming request
-  IN  securityName              -- same as on incoming request
-  IN  securityLevel            -- same as on incoming request
-  IN  contextEngineID          -- data from/at this SNMP entity
-  IN  contextName              -- data from/in this context
-  IN  pduVersion                -- the version of the PDU
-  IN  PDU                      -- SNMP Protocol Data Unit
-  IN  maxSizeResponseScopedPDU  -- maximum size able to accept
-  IN  stateReference            -- reference to state information
-                                -- as presented with the request
-  IN  statusInformation        -- success or errorIndication
-                                -- error counter OID/value if error
-  OUT  destTransportDomain      -- destination transport domain
-  OUT  destTransportAddress      -- destination transport address
-  OUT  outgoingMessage          -- the message to send
-  OUT  outgoingMessageLength    -- its length
-      )
-==== Prepare Data Elements from an Incoming SNMP Message ====
-The Message Processing Subsystem provides this service primitive for
-preparing the abstract data elements from an incoming SNMP message:
-result =                        -- SUCCESS or errorIndication
-  prepareDataElements(
-  IN  transportDomain          -- origin transport domain
-  IN  transportAddress          -- origin transport address
-  IN  wholeMsg                  -- as received from the network
-  IN  wholeMsgLength            -- as received from the network
-  OUT  messageProcessingModel    -- typically, SNMP version
-  OUT  securityModel            -- Security Model to use
-  OUT  securityName              -- on behalf of this principal
-  OUT  securityLevel            -- Level of Security requested
-  OUT  contextEngineID          -- data from/at this entity
-  OUT  contextName              -- data from/in this context
-  OUT  pduVersion                -- the version of the PDU
-  OUT  PDU                      -- SNMP Protocol Data Unit
-  OUT  pduType                  -- SNMP PDU type
-  OUT  sendPduHandle            -- handle for matched request
-  OUT  maxSizeResponseScopedPDU  -- maximum size sender can accept
-  OUT  statusInformation        -- success or errorIndication
-                                -- error counter OID/value if error
-  OUT  stateReference            -- reference to state information
-                                -- to be used for possible Response
-      )
-=== Access Control Subsystem Primitives ===
-Applications are the typical clients of the service(s) of the Access
-Control Subsystem.
-The following primitive is provided by the Access Control Subsystem
-to check if access is allowed:
-statusInformation =              -- success or errorIndication
-  isAccessAllowed(
-  IN  securityModel            -- Security Model in use
-  IN  securityName              -- principal who wants to access
-  IN  securityLevel            -- Level of Security
-  IN  viewType                  -- read, write, or notify view
-  IN  contextName              -- context containing variableName
-  IN  variableName              -- OID for the managed object
-      )
-=== Security Subsystem Primitives ===
-The Message Processing Subsystem is the typical client of the
-services of the Security Subsystem.
-==== Generate a Request or Notification Message ====
-The Security Subsystem provides the following primitive to generate a
-Request or Notification message:
-statusInformation =
-  generateRequestMsg(
-  IN  messageProcessingModel    -- typically, SNMP version
-  IN  globalData                -- message header, admin data
-  IN  maxMessageSize            -- of the sending SNMP entity
-  IN  securityModel            -- for the outgoing message
-  IN  securityEngineID          -- authoritative SNMP entity
-  IN  securityName              -- on behalf of this principal
-  IN  securityLevel            -- Level of Security requested
-  IN  scopedPDU                -- message (plaintext) payload
-  OUT  securityParameters        -- filled in by Security Module
-  OUT  wholeMsg                  -- complete generated message
-  OUT  wholeMsgLength            -- length of the generated message
-      )
-==== Process Incoming Message ====
-The Security Subsystem provides the following primitive to process an
-incoming message:
-statusInformation =              -- errorIndication or success
-                                -- error counter OID/value if error
-  processIncomingMsg(
-  IN  messageProcessingModel    -- typically, SNMP version
-  IN  maxMessageSize            -- of the sending SNMP entity
-  IN  securityParameters        -- for the received message
-  IN  securityModel            -- for the received message
-  IN  securityLevel            -- Level of Security
-  IN  wholeMsg                  -- as received on the wire
-  IN  wholeMsgLength            -- length as received on the wire
-  OUT  securityEngineID          -- authoritative SNMP entity
-  OUT  securityName              -- identification of the principal
-  OUT  scopedPDU,                -- message (plaintext) payload
-  OUT  maxSizeResponseScopedPDU  -- maximum size sender can handle
-  OUT  securityStateReference    -- reference to security state
-      )                        -- information, needed for response
-==== Generate a Response Message ====
-The Security Subsystem provides the following primitive to generate a
-Response message:
-statusInformation =
-  generateResponseMsg(
-  IN  messageProcessingModel    -- typically, SNMP version
-  IN  globalData                -- message header, admin data
-  IN  maxMessageSize            -- of the sending SNMP entity
-  IN  securityModel            -- for the outgoing message
-  IN  securityEngineID          -- authoritative SNMP entity
-  IN  securityName              -- on behalf of this principal
-  IN  securityLevel            -- for the outgoing message
-  IN  scopedPDU                -- message (plaintext) payload
-  IN  securityStateReference    -- reference to security state
-                                -- information from original request
-  OUT  securityParameters        -- filled in by Security Module
-  OUT  wholeMsg                  -- complete generated message
-  OUT  wholeMsgLength            -- length of the generated message
-      )
-=== Common Primitives ===
-These primitive(s) are provided by multiple Subsystems.
-==== Release State Reference Information ====
-All Subsystems which pass stateReference information also provide a
-primitive to release the memory that holds the referenced state
-information:
-stateRelease(
-  IN  stateReference      -- handle of reference to be released
-      )
-=== Scenario Diagrams ===
-==== Command Generator or Notification Originator ====
-This diagram shows how a Command Generator or Notification Originator
-application requests that a PDU be sent, and how the response is
-returned (asynchronously) to that application.
-Command          Dispatcher              Message          Security
-Generator            |                    Processing          Model
-|                    |                    Model                    |
-|      sendPdu      |                        |                    |
-|------------------->|                        |                    |
-|                    | prepareOutgoingMessage |                    |
-:                    |----------------------->|                    |
-:                    |                        | generateRequestMsg  |
-:                    |                        |-------------------->|
-:                    |                        |                    |
-:                    |                        |<--------------------|
-:                    |                        |                    |
-:                    |<-----------------------|                    |
-:                    |                        |                    |
-:                    |------------------+    |                    |
-:                    | Send SNMP        |    |                    |
-:                    | Request Message  |    |                    |
-:                    | to Network      |    |                    |
-:                    |                  v    |                    |
-:                    :                  :    :                    :
-:                    :                  :    :                    :
-:                    :                  :    :                    :
-:                    |                  |    |                    |
-:                    | Receive SNMP    |    |                    |
-:                    | Response Message |    |                    |
-:                    | from Network    |    |                    |
-:                    |<-----------------+    |                    |
-:                    |                        |                    |
-:                    |  prepareDataElements  |                    |
-:                    |----------------------->|                    |
-:                    |                        | processIncomingMsg  |
-:                    |                        |-------------------->|
-:                    |                        |                    |
-:                    |                        |<--------------------|
-:                    |                        |                    |
-:                    |<-----------------------|                    |
-| processResponsePdu |                        |                    |
-|<-------------------|                        |                    |
-|                    |                        |                    |
-==== Scenario Diagram for a Command Responder Application ====
-This diagram shows how a Command Responder or Notification Receiver
-application registers for handling a pduType, how a PDU is dispatched
-to the application after an SNMP message is received, and how the
-Response is (asynchronously) send back to the network.
-Command              Dispatcher            Message          Security
-Responder                |                Processing          Model
-|                        |                Model                  |
-|                        |                    |                    |
-| registerContextEngineID |                    |                    |
-|------------------------>|                    |                    |
-|<------------------------|              |    |                    |
-|                        | Receive SNMP |    |                    |
-:                        | Message      |    |                    |
-:                        | from Network |    |                    |
-:                        |<-------------+    |                    |
-:                        |                    |                    |
-:                        |prepareDataElements |                    |
-:                        |------------------->|                    |
-:                        |                    | processIncomingMsg |
-:                        |                    |------------------->|
-:                        |                    |                    |
-:                        |                    |<-------------------|
-:                        |                    |                    |
-:                        |<-------------------|                    |
-|    processPdu          |                    |                    |
-|<------------------------|                    |                    |
-|                        |                    |                    |
-:                        :                    :                    :
-:                        :                    :                    :
-|    returnResponsePdu    |                    |                    |
-|------------------------>|                    |                    |
-:                        | prepareResponseMsg |                    |
-:                        |------------------->|                    |
-:                        |                    |generateResponseMsg |
-:                        |                    |------------------->|
-:                        |                    |                    |
-:                        |                    |<-------------------|
-:                        |                    |                    |
-:                        |<-------------------|                    |
-:                        |                    |                    |
-:                        |--------------+    |                    |
-:                        | Send SNMP    |    |                    |
-:                        | Message      |    |                    |
-:                        | to Network  |    |                    |
-:                        |              v    |                    |
-== Managed Object Definitions for SNMP Management Frameworks ==
-SNMP-FRAMEWORK-MIB DEFINITIONS ::= BEGIN
-IMPORTS
- MODULE-IDENTITY, OBJECT-TYPE,
- OBJECT-IDENTITY,
- snmpModules                          FROM SNMPv2-SMI
- TEXTUAL-CONVENTION                    FROM SNMPv2-TC
- MODULE-COMPLIANCE, OBJECT-GROUP      FROM SNMPv2-CONF;
-snmpFrameworkMIB MODULE-IDENTITY
- LAST-UPDATED "200210140000Z"
- ORGANIZATION "SNMPv3 Working Group"
- CONTACT-INFO "WG-EMail:  [email protected]
-              Subscribe:  [email protected]
-              Co-Chair:  Russ Mundy
-                          Network Associates Laboratories
-              postal:    15204 Omega Drive, Suite 300
-                          Rockville, MD 20850-4601
-                          USA
-              EMail:      [email protected]
-              phone:      +1 301-947-7107
-              Co-Chair &
-              Co-editor:  David Harrington
-                          Enterasys Networks
-              postal:    35 Industrial Way
-                          P. O. Box 5005
-                          Rochester, New Hampshire 03866-5005
-                          USA
-              EMail:      [email protected]
-              phone:      +1 603-337-2614
-              Co-editor:  Randy Presuhn
-                          BMC Software, Inc.
-              postal:    2141 North First Street
-                          San Jose, California 95131
-                          USA
-              EMail:      [email protected]
-              phone:      +1 408-546-1006
-              Co-editor:  Bert Wijnen
-                          Lucent Technologies
-              postal:    Schagen 33
-GL Linschoten
-                          Netherlands
-              EMail:      [email protected]
-              phone:      +31 348-680-485
-                "
-    DESCRIPTION  "The SNMP Management Architecture MIB
-                  Copyright (C) The Internet Society (2002). This
-                  version of this MIB module is part of [[RFC3411|RFC 3411]];
-                  see the RFC itself for full legal notices.
-                "
-    REVISION    "200210140000Z"        -- 14 October 2002
-    DESCRIPTION  "Changes in this revision:
-                  - Updated various administrative information.
-                  - Corrected some typos.
-                  - Corrected typo in description of SnmpEngineID
-                    that led to range overlap for 127.
-                  - Changed '255a' to '255t' in definition of
-                    SnmpAdminString to align with current SMI.
-                  - Reworded 'reserved' for value zero in
-                    DESCRIPTION of SnmpSecurityModel.
-                  - The algorithm for allocating security models
-                    should give 256 per enterprise block, rather
-                    than 255.
-                  - The example engine ID of 'abcd' is not
-                    legal. Replaced with '800002b804616263'H based
-                    on example enterprise 696, string 'abc'.
-                  - Added clarification that engineID should
-                    persist across re-initializations.
-                  This revision published as [[RFC3411|RFC 3411]].
-                "
-    REVISION    "199901190000Z"        -- 19 January 1999
-    DESCRIPTION  "Updated editors' addresses, fixed typos.
-                  Published as [[RFC2571|RFC 2571]].
-                "
-    REVISION    "199711200000Z"        -- 20 November 1997
-    DESCRIPTION  "The initial version, published in [[RFC2271|RFC 2271]].
-                "
-    ::= { snmpModules 10 }
--- Textual Conventions used in the SNMP Management Architecture ***
-SnmpEngineID ::= TEXTUAL-CONVENTION
- STATUS      current
- DESCRIPTION "An SNMP engine's administratively-unique identifier.
-              Objects of this type are for identification, not for
-              addressing, even though it is possible that an
-              address may have been used in the generation of
-              a specific value.
-              The value for this object may not be all zeros or
-              all 'ff'H or the empty (zero length) string.
-              The initial value for this object may be configured
-              via an operator console entry or via an algorithmic
-              function.  In the latter case, the following
-              example algorithm is recommended.
-              In cases where there are multiple engines on the
-              same system, the use of this algorithm is NOT
-              appropriate, as it would result in all of those
-              engines ending up with the same ID value.
-) The very first bit is used to indicate how the
-                rest of the data is composed.
-- as defined by enterprise using former methods
-                    that existed before SNMPv3. See item 2 below.
-- as defined by this architecture, see item 3
-                    below.
-                Note that this allows existing uses of the
-                engineID (also known as AgentID [RFC1910]) to
-                co-exist with any new uses.
-) The snmpEngineID has a length of 12 octets.
-                The first four octets are set to the binary
-                equivalent of the agent's SNMP management
-                private enterprise number as assigned by the
-                Internet Assigned Numbers Authority (IANA).
-                For example, if Acme Networks has been assigned
-                { enterprises 696 }, the first four octets would
-                be assigned '000002b8'H.
-                The remaining eight octets are determined via
-                one or more enterprise-specific methods. Such
-                methods must be designed so as to maximize the
-                possibility that the value of this object will
-                be unique in the agent's administrative domain.
-                For example, it may be the IP address of the SNMP
-                entity, or the MAC address of one of the
-                interfaces, with each address suitably padded
-                with random octets.  If multiple methods are
-                defined, then it is recommended that the first
-                octet indicate the method being used and the
-                remaining octets be a function of the method.
-) The length of the octet string varies.
-                The first four octets are set to the binary
-                equivalent of the agent's SNMP management
-                private enterprise number as assigned by the
-                Internet Assigned Numbers Authority (IANA).
-                For example, if Acme Networks has been assigned
-                { enterprises 696 }, the first four octets would
-                be assigned '000002b8'H.
-                The very first bit is set to 1. For example, the
-                above value for Acme Networks now changes to be
-                '800002b8'H.
-                The fifth octet indicates how the rest (6th and
-                following octets) are formatted. The values for
-                the fifth octet are:
-    - reserved, unused.
-    - IPv4 address (4 octets)
-                          lowest non-special IP address
-    - IPv6 address (16 octets)
-                          lowest non-special IP address
-    - MAC address (6 octets)
-                          lowest IEEE MAC address, canonical
-                          order
-    - Text, administratively assigned
-                          Maximum remaining length 27
-    - Octets, administratively assigned
-                          Maximum remaining length 27
--127 - reserved, unused
--255 - as defined by the enterprise
-                          Maximum remaining length 27
-            "
- SYNTAX      OCTET STRING (SIZE(5..32))
-SnmpSecurityModel ::= TEXTUAL-CONVENTION
- STATUS      current
- DESCRIPTION "An identifier that uniquely identifies a
-              Security Model of the Security Subsystem within
-              this SNMP Management Architecture.
-              The values for securityModel are allocated as
-              follows:
-              - The zero value does not identify any particular
-                security model.
-              - Values between 1 and 255, inclusive, are reserved
-                for standards-track Security Models and are
-                managed by the Internet Assigned Numbers Authority
-                (IANA).
-              - Values greater than 255 are allocated to
-                enterprise-specific Security Models.  An
-                enterprise-specific securityModel value is defined
-                to be:
-                enterpriseID * 256 + security model within
-                enterprise
-                For example, the fourth Security Model defined by
-                the enterprise whose enterpriseID is 1 would be
-.
-              This scheme for allocation of securityModel
-              values allows for a maximum of 255 standards-
-              based Security Models, and for a maximum of
-Security Models per enterprise.
-              It is believed that the assignment of new
-              securityModel values will be rare in practice
-              because the larger the number of simultaneously
-              utilized Security Models, the larger the
-              chance that interoperability will suffer.
-              Consequently, it is believed that such a range
-              will be sufficient.  In the unlikely event that
-              the standards committee finds this number to be
-              insufficient over time, an enterprise number
-              can be allocated to obtain an additional 256
-              possible values.
-              Note that the most significant bit must be zero;
-              hence, there are 23 bits allocated for various
-              organizations to design and define non-standard
-              securityModels.  This limits the ability to
-              define new proprietary implementations of Security
-              Models to the first 8,388,608 enterprises.
-              It is worthwhile to note that, in its encoded
-              form, the securityModel value will normally
-              require only a single byte since, in practice,
-              the leftmost bits will be zero for most messages
-              and sign extension is suppressed by the encoding
-              rules.
-              As of this writing, there are several values
-              of securityModel defined for use with SNMP or
-              reserved for use with supporting MIB objects.
-              They are as follows:
-  reserved for 'any'
-  reserved for SNMPv1
-  reserved for SNMPv2c
-  User-Based Security Model (USM)
-            "
- SYNTAX      INTEGER(0 .. 2147483647)
-SnmpMessageProcessingModel ::= TEXTUAL-CONVENTION
- STATUS      current
- DESCRIPTION "An identifier that uniquely identifies a Message
-              Processing Model of the Message Processing
-              Subsystem within this SNMP Management Architecture.
-              The values for messageProcessingModel are
-              allocated as follows:
-              - Values between 0 and 255, inclusive, are
-                reserved for standards-track Message Processing
-                Models and are managed by the Internet Assigned
-                Numbers Authority (IANA).
-              - Values greater than 255 are allocated to
-                enterprise-specific Message Processing Models.
-                An enterprise messageProcessingModel value is
-                defined to be:
-                enterpriseID * 256 +
-                    messageProcessingModel within enterprise
-                For example, the fourth Message Processing Model
-                defined by the enterprise whose enterpriseID
-                is 1 would be 259.
-              This scheme for allocating messageProcessingModel
-              values allows for a maximum of 255 standards-
-              based Message Processing Models, and for a
-              maximum of 256 Message Processing Models per
-              enterprise.
-              It is believed that the assignment of new
-              messageProcessingModel values will be rare
-              in practice because the larger the number of
-              simultaneously utilized Message Processing Models,
-              the larger the chance that interoperability
-              will suffer. It is believed that such a range
-              will be sufficient.  In the unlikely event that
-              the standards committee finds this number to be
-              insufficient over time, an enterprise number
-              can be allocated to obtain an additional 256
-              possible values.
-              Note that the most significant bit must be zero;
-              hence, there are 23 bits allocated for various
-              organizations to design and define non-standard
-              messageProcessingModels.  This limits the ability
-              to define new proprietary implementations of
-              Message Processing Models to the first 8,388,608
-              enterprises.
-              It is worthwhile to note that, in its encoded
-              form, the messageProcessingModel value will
-              normally require only a single byte since, in
-              practice, the leftmost bits will be zero for
-              most messages and sign extension is suppressed
-              by the encoding rules.
-              As of this writing, there are several values of
-              messageProcessingModel defined for use with SNMP.
-              They are as follows:
-  reserved for SNMPv1
-  reserved for SNMPv2c
-  reserved for SNMPv2u and SNMPv2*
-  reserved for SNMPv3
-            "
- SYNTAX      INTEGER(0 .. 2147483647)
-SnmpSecurityLevel ::= TEXTUAL-CONVENTION
- STATUS      current
- DESCRIPTION "A Level of Security at which SNMP messages can be
-              sent or with which operations are being processed;
-              in particular, one of:
-                noAuthNoPriv - without authentication and
-                              without privacy,
-                authNoPriv  - with authentication but
-                              without privacy,
-                authPriv    - with authentication and
-                              with privacy.
-              These three values are ordered such that
-              noAuthNoPriv is less than authNoPriv and
-              authNoPriv is less than authPriv.
-            "
- SYNTAX      INTEGER { noAuthNoPriv(1),
-                        authNoPriv(2),
-                        authPriv(3)
-                      }
-SnmpAdminString ::= TEXTUAL-CONVENTION
- DISPLAY-HINT "255t"
- STATUS      current
- DESCRIPTION "An octet string containing administrative
-              information, preferably in human-readable form.
-              To facilitate internationalization, this
-              information is represented using the ISO/IEC
-              IS 10646-1 character set, encoded as an octet
-              string using the UTF-8 transformation format
-              described in [RFC2279].
-              Since additional code points are added by
-              amendments to the 10646 standard from time
-              to time, implementations must be prepared to
-              encounter any code point from 0x00000000 to
-x7fffffff.  Byte sequences that do not
-              correspond to the valid UTF-8 encoding of a
-              code point or are outside this range are
-              prohibited.
-              The use of control codes should be avoided.
-              When it is necessary to represent a newline,
-              the control code sequence CR LF should be used.
-              The use of leading or trailing white space should
-              be avoided.
-              For code points not directly supported by user
-              interface hardware or software, an alternative
-              means of entry and display, such as hexadecimal,
-              may be provided.
-              For information encoded in 7-bit US-ASCII,
-              the UTF-8 encoding is identical to the
-              US-ASCII encoding.
-              UTF-8 may require multiple bytes to represent a
-              single character / code point; thus the length
-              of this object in octets may be different from
-              the number of characters encoded.  Similarly,
-              size constraints refer to the number of encoded
-              octets, not the number of characters represented
-              by an encoding.
-              Note that when this TC is used for an object that
-              is used or envisioned to be used as an index, then
-              a SIZE restriction MUST be specified so that the
-              number of sub-identifiers for any object instance
-              does not exceed the limit of 128, as defined by
-              [RFC3416].
-              Note that the size of an SnmpAdminString object is
-              measured in octets, not characters.
-            "
- SYNTAX      OCTET STRING (SIZE (0..255))
--- Administrative assignments ***************************************
-snmpFrameworkAdmin
- OBJECT IDENTIFIER ::= { snmpFrameworkMIB 1 }
-snmpFrameworkMIBObjects
- OBJECT IDENTIFIER ::= { snmpFrameworkMIB 2 }
-snmpFrameworkMIBConformance
- OBJECT IDENTIFIER ::= { snmpFrameworkMIB 3 }
--- the snmpEngine Group ********************************************
-snmpEngine OBJECT IDENTIFIER ::= { snmpFrameworkMIBObjects 1 }
-snmpEngineID    OBJECT-TYPE
- SYNTAX      SnmpEngineID
- MAX-ACCESS  read-only
- STATUS      current
- DESCRIPTION "An SNMP engine's administratively-unique identifier.
-              This information SHOULD be stored in non-volatile
-              storage so that it remains constant across
-              re-initializations of the SNMP engine.
-            "
- ::= { snmpEngine 1 }
-snmpEngineBoots  OBJECT-TYPE
- SYNTAX      INTEGER (1..2147483647)
- MAX-ACCESS  read-only
- STATUS      current
- DESCRIPTION "The number of times that the SNMP engine has
-              (re-)initialized itself since snmpEngineID
-              was last configured.
-            "
- ::= { snmpEngine 2 }
-snmpEngineTime  OBJECT-TYPE
- SYNTAX      INTEGER (0..2147483647)
- UNITS        "seconds"
- MAX-ACCESS  read-only
- STATUS      current
- DESCRIPTION "The number of seconds since the value of
-              the snmpEngineBoots object last changed.
-              When incrementing this object's value would
-              cause it to exceed its maximum,
-              snmpEngineBoots is incremented as if a
-              re-initialization had occurred, and this
-              object's value consequently reverts to zero.
-            "
- ::= { snmpEngine 3 }
-snmpEngineMaxMessageSize OBJECT-TYPE
- SYNTAX      INTEGER (484..2147483647)
- MAX-ACCESS  read-only
- STATUS      current
- DESCRIPTION "The maximum length in octets of an SNMP message
-              which this SNMP engine can send or receive and
-              process, determined as the minimum of the maximum
-              message size values supported among all of the
-              transports available to and supported by the engine.
-            "
- ::= { snmpEngine 4 }
--- Registration Points for Authentication and Privacy Protocols **
-snmpAuthProtocols OBJECT-IDENTITY
- STATUS        current
- DESCRIPTION  "Registration point for standards-track
-              authentication protocols used in SNMP Management
-              Frameworks.
-              "
- ::= { snmpFrameworkAdmin 1 }
-snmpPrivProtocols OBJECT-IDENTITY
- STATUS        current
- DESCRIPTION  "Registration point for standards-track privacy
-              protocols used in SNMP Management Frameworks.
-              "
- ::= { snmpFrameworkAdmin 2 }
--- Conformance information ******************************************
-snmpFrameworkMIBCompliances
-            OBJECT IDENTIFIER ::= {snmpFrameworkMIBConformance 1}
-snmpFrameworkMIBGroups
-            OBJECT IDENTIFIER ::= {snmpFrameworkMIBConformance 2}
--- compliance statements
-snmpFrameworkMIBCompliance MODULE-COMPLIANCE
- STATUS      current
- DESCRIPTION "The compliance statement for SNMP engines which
-              implement the SNMP Management Framework MIB.
-            "
- MODULE    -- this module
-    MANDATORY-GROUPS { snmpEngineGroup }
- ::= { snmpFrameworkMIBCompliances 1 }
--- units of conformance
-snmpEngineGroup OBJECT-GROUP
- OBJECTS {
-          snmpEngineID,
-          snmpEngineBoots,
-          snmpEngineTime,
-          snmpEngineMaxMessageSize
-        }
- STATUS      current
- DESCRIPTION "A collection of objects for identifying and
-              determining the configuration and current timeliness
-              values of an SNMP engine.
-            "
- ::= { snmpFrameworkMIBGroups 1 }
-END
-== IANA Considerations ==
-This document defines three number spaces administered by IANA, one
-for security models, another for message processing models, and a
-third for SnmpEngineID formats.
-=== Security Models ===
-The SnmpSecurityModel TEXTUAL-CONVENTION values managed by IANA are
-in the range from 0 to 255 inclusive, and are reserved for
-standards-track Security Models.  If this range should in the future
-prove insufficient, an enterprise number can be allocated to obtain
-an additional 256 possible values.
-As of this writing, there are several values of securityModel defined
-for use with SNMP or reserved for use with supporting MIB objects.
-They are as follows:
-  reserved for 'any'
-  reserved for SNMPv1
-  reserved for SNMPv2c
-User-Based Security Model (USM)
-=== Message Processing Models ===
-The SnmpMessageProcessingModel TEXTUAL-CONVENTION values managed by
-IANA are in the range 0 to 255, inclusive.  Each value uniquely
-identifies a standards-track Message Processing Model of the Message
-Processing Subsystem within the SNMP Management Architecture.
-Should this range prove insufficient in the future, an enterprise
-number may be obtained for the standards committee to get an
-additional 256 possible values.
-As of this writing, there are several values of
-messageProcessingModel defined for use with SNMP.  They are as
-follows:
-  reserved for SNMPv1
-  reserved for SNMPv2c
-  reserved for SNMPv2u and SNMPv2*
-reserved for SNMPv3
-=== SnmpEngineID Formats ===
-The SnmpEngineID TEXTUAL-CONVENTION's fifth octet contains a format
-identifier.  The values managed by IANA are in the range 6 to 127,
-inclusive.  Each value uniquely identifies a standards-track
-SnmpEngineID format.
-== Intellectual Property ==
-The IETF takes no position regarding the validity or scope of any
-intellectual property or other rights that might be claimed to
-pertain to the implementation or use of the technology described in
-this document or the extent to which any license under such rights
-might or might not be available; neither does it represent that it
-has made any effort to identify any such rights.  Information on the
-IETF's procedures with respect to rights in standards-track and
-standards-related documentation can be found in [[RFC2028|RFC 2028]].  Copies of
-claims of rights made available for publication and any assurances of
-licenses to be made available, or the result of an attempt made to
-obtain a general license or permission for the use of such
-proprietary rights by implementors or users of this specification can
-be obtained from the IETF Secretariat.
-The IETF invites any interested party to bring to its attention any
-copyrights, patents or patent applications, or other proprietary
-rights which may cover technology that may be required to practice
-this standard.  Please address the information to the IETF Executive
-Director.
-== Acknowledgements ==
-This document is the result of the efforts of the SNMPv3 Working
-Group.  Some special thanks are in order to the following SNMPv3 WG
-members:
-  Harald Tveit Alvestrand (Maxware)
-  Dave Battle (SNMP Research, Inc.)
-  Alan Beard (Disney Worldwide Services)
-  Paul Berrevoets (SWI Systemware/Halcyon Inc.)
-  Martin Bjorklund (Ericsson)
-  Uri Blumenthal (IBM T.J. Watson Research Center)
-  Jeff Case (SNMP Research, Inc.)
-  John Curran (BBN)
-  Mike Daniele (Compaq Computer Corporation)
-  T. Max Devlin (Eltrax Systems)
-  John Flick (Hewlett Packard)
-  Rob Frye (MCI)
-  Wes Hardaker (U.C.Davis, Information Technology - D.C.A.S.)
-  David Harrington (Cabletron Systems Inc.)
-  Lauren Heintz (BMC Software, Inc.)
-  N.C. Hien (IBM T.J. Watson Research Center)
-  Michael Kirkham (InterWorking Labs, Inc.)
-  Dave Levi (SNMP Research, Inc.)
-  Louis A Mamakos (UUNET Technologies Inc.)
-  Joe Marzot (Nortel Networks)
-  Paul Meyer (Secure Computing Corporation)
-  Keith McCloghrie (Cisco Systems)
-  Bob Moore (IBM)
-  Russ Mundy (TIS Labs at Network Associates)
-  Bob Natale (ACE*COMM Corporation)
-  Mike O'Dell (UUNET Technologies Inc.)
-  Dave Perkins (DeskTalk)
-  Peter Polkinghorne (Brunel University)
-  Randy Presuhn (BMC Software, Inc.)
-  David Reeder (TIS Labs at Network Associates)
-  David Reid (SNMP Research, Inc.)
-  Aleksey Romanov (Quality Quorum)
-  Shawn Routhier (Epilogue)
-  Juergen Schoenwaelder (TU Braunschweig)
-  Bob Stewart (Cisco Systems)
-  Mike Thatcher (Independent Consultant)
-  Bert Wijnen (IBM T.J. Watson Research Center)
-The document is based on recommendations of the IETF Security and
-Administrative Framework Evolution for SNMP Advisory Team.  Members
-of that Advisory Team were:
-  David Harrington (Cabletron Systems Inc.)
-  Jeff Johnson (Cisco Systems)
-  David Levi (SNMP Research Inc.)
-  John Linn (Openvision)
-  Russ Mundy (Trusted Information Systems) chair
-  Shawn Routhier (Epilogue)
-  Glenn Waters (Nortel)
-  Bert Wijnen (IBM T. J. Watson Research Center)
-As recommended by the Advisory Team and the SNMPv3 Working Group
-Charter, the design incorporates as much as practical from previous
-RFCs and drafts. As a result, special thanks are due to the authors
-of previous designs known as SNMPv2u and SNMPv2*:
-  Jeff Case (SNMP Research, Inc.)
-  David Harrington (Cabletron Systems Inc.)
-  David Levi (SNMP Research, Inc.)
-  Keith McCloghrie (Cisco Systems)
-  Brian O'Keefe (Hewlett Packard)
-  Marshall T. Rose (Dover Beach Consulting)
-  Jon Saperia (BGS Systems Inc.)
-  Steve Waldbusser (International Network Services)
-  Glenn W. Waters (Bell-Northern Research Ltd.)
-== Security Considerations ==
-This document describes how an implementation can include a Security
-Model to protect management messages and an Access Control Model to
-control access to management information.
-The level of security provided is determined by the specific Security
-Model implementation(s) and the specific Access Control Model
-implementation(s) used.
-Applications have access to data which is not secured.  Applications
-SHOULD take reasonable steps to protect the data from disclosure.
-It is the responsibility of the purchaser of an implementation to
-ensure that:
-) an implementation complies with the rules defined by this
-      architecture,
-) the Security and Access Control Models utilized satisfy the
-      security and access control needs of the organization,
-) the implementations of the Models and Applications comply with
-      the model and application specifications,
-) and the implementation protects configuration secrets from
-      inadvertent disclosure.
-This document also contains a MIB definition module.  None of the
-objects defined is writable, and the information they represent is
-not deemed to be particularly sensitive.  However, if they are deemed
-sensitive in a particular environment, access to them should be
-restricted through the use of appropriately configured Security and
-Access Control models.
-== References ==
-=== Normative References ===
-[RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate            Requirement Levels", [[BCP14|BCP 14]], [[RFC2119|RFC 2119]], March 1997.
-[RFC2279]  Yergeau, F., "UTF-8, a transformation format of ISO            10646", [[RFC2279|RFC 2279]], January 1998.
-[RFC2578]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,            Rose, M. and S. Waldbusser, "Structure of Management            Information Version 2 (SMIv2)", STD 58, [[RFC2578|RFC 2578]], April            1999.
-[RFC2579]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,            Rose, M. and S. Waldbusser, "Textual Conventions for            SMIv2", STD 58, [[RFC2579|RFC 2579]], April 1999.
-[RFC2580]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,            Rose, M. and S. Waldbusser, "Conformance Statements for            SMIv2", STD 58, [[RFC2580|RFC 2580]], April 1999.
-[RFC3412]  Case, J., Harrington, D., Presuhn, R. and B. Wijnen,            "Message Processing and Dispatching for the Simple            Network Management Protocol (SNMP)", STD 62, [[RFC3412|RFC 3412]],            December 2002.
-[RFC3413]  Levi, D., Meyer, P. and B. Stewart, "Simple Network            Management Protocol (SNMP) Applications", STD 62, RFC            3413, December 2002.
-[RFC3414]  Blumenthal, U. and B. Wijnen, "User-Based Security Model            (USM) for Version 3 of the Simple Network Management            Protocol (SNMPv3)", STD 62, [[RFC3414|RFC 3414]], December 2002.
-[RFC3415]  Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based            Access Control Model (VACM) for the Simple Network            Management Protocol (SNMP)", STD 62, [[RFC3415|RFC 3415]], December            2002.
-[RFC3416]  Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.            Waldbusser, "Protocol Operations for the Simple Network            Management Protocol (SNMP)", STD 62, [[RFC3416|RFC 3416]], December            2002.
-[RFC3417]  Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.            Waldbusser, "Transport Mappings for the Simple Network            Management Protocol (SNMP)", STD 62, [[RFC3417|RFC 3417]], December            2002.
-[RFC3418]  Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.            Waldbusser, "Management Information Base (MIB) for the            Simple Network Management Protocol (SNMP)", STD 62, RFC            3418, December 2002.
-=== Informative References ===
-[RFC1155]  Rose, M. and K. McCloghrie, "Structure and Identification            of Management Information for TCP/IP-based internets",            STD 16, [[RFC1155|RFC 1155]], May 1990.
-[RFC1157]  Case, J., Fedor, M., Schoffstall, M. and J. Davin, "The            Simple Network Management Protocol", STD 15, [[RFC1157|RFC 1157]],            May 1990.
-[RFC1212]  Rose, M. and K. McCloghrie, "Concise MIB Definitions",            STD 16, [[RFC1212|RFC 1212]], March 1991.
-[RFC1901]  Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,            "Introduction to Community-based SNMPv2", [[RFC1901|RFC 1901]],            January 1996.
-[RFC1909]  McCloghrie, K., Editor, "An Administrative Infrastructure            for SNMPv2", [[RFC1909|RFC 1909]], February 1996.
-[RFC1910]  Waters, G., Editor, "User-based Security Model for            SNMPv2", [[RFC1910|RFC 1910]], February 1996.
-[RFC2028]  Hovey, R. and S. Bradner, "The Organizations Involved in            the IETF Standards Process", [[BCP11|BCP 11]], [[RFC2028|RFC 2028]], October            1996.
-[RFC2576]  Frye, R., Levi, D., Routhier, S. and B. Wijnen,            "Coexistence between Version 1, Version 2, and Version 3            of the Internet-Standard Network Management Framework",            [[RFC2576|RFC 2576]], March 2000.
-[RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group            MIB", [[RFC2863|RFC 2863]], June 2000.
-[RFC3410]  Case, J., Mundy, R., Partain, D. and B. Stewart,            "Introduction and Applicability Statements for Internet-            Standard Management Framework", [[RFC3410|RFC 3410]], December 2002.
-Appendix A
-A.  Guidelines for Model Designers
-This appendix describes guidelines for designers of models which areexpected to fit into the architecture defined in this document.
-SNMPv1 and SNMPv2c are two SNMP frameworks which use communities toprovide trivial authentication and access control.  SNMPv1 andSNMPv2c Frameworks can coexist with Frameworks designed according tothis architecture, and modified versions of SNMPv1 and SNMPv2cFrameworks could be designed to meet the requirements of thisarchitecture, but this document does not provide guidelines for thatcoexistence.
-Within any subsystem model, there should be no reference to anyspecific model of another subsystem, or to data defined by a specificmodel of another subsystem.
-Transfer of data between the subsystems is deliberately described asa fixed set of abstract data elements and primitive functions whichcan be overloaded to satisfy the needs of multiple model definitions.
-Documents which define models to be used within this architectureSHOULD use the standard primitives between subsystems, possiblydefining specific mechanisms for converting the abstract dataelements into model-usable formats.  This constraint exists to allowsubsystem and model documents to be written recognizing commonborders of the subsystem and model.  Vendors are not constrained torecognize these borders in their implementations.
-The architecture defines certain standard services to be providedbetween subsystems, and the architecture defines abstract serviceinterfaces to request these services.
-Each model definition for a subsystem SHOULD support the standardservice interfaces, but whether, or how, or how well, it performs theservice is dependent on the model definition.
-A.1.  Security Model Design Requirements
-A.1.1.  Threats
-A document describing a Security Model MUST describe how the modelprotects against the threats described under "Security Requirementsof this Architecture", section 1.4.
+When an SNMP engine receives a message that is not the response to a
+request from this SNMP engine, it must determine to which application
+the message should be given.
+An Application that wishes to receive asynchronous messages registers
+itself with the engine using the primitive registerContextEngineID as
+described in section 4.1.5.
-A.1.2.  Security Processing
+An Application that wishes to stop receiving asynchronous messages
-Received messages MUST be validated by a Model of the SecuritySubsystem.  Validation includes authentication and privacy processingif needed, but it is explicitly allowed to send messages which do notrequire authentication or privacy.
+should unregister itself with the SNMP engine using the primitive
-A received message contains a specified securityLevel to be usedduring processing.  All messages requiring privacy MUST also requireauthentication.
+unregisterContextEngineID as described in section 4.1.5.
-A Security Model specifies rules by which authentication and privacyare to be done.  A model may define mechanisms to provide additionalsecurity features, but the model definition is constrained to using(possibly a subset of) the abstract data elements defined in thisdocument for transferring data between subsystems.
-Each Security Model may allow multiple security protocols to be usedconcurrently within an implementation of the model.  Each SecurityModel defines how to determine which protocol to use, given thesecurityLevel and the security parameters relevant to the message.Each Security Model, with its associated protocol(s) defines how thesending/receiving entities are identified, and how secrets areconfigured.
-Authentication and Privacy protocols supported by Security Models areuniquely identified using Object Identifiers.  IETF standardprotocols for authentication or privacy should have an identifierdefined within the snmpAuthProtocols or the snmpPrivProtocolssubtrees.  Enterprise specific protocol identifiers should be definedwithin the enterprise subtree.
-For privacy, the Security Model defines what portion of the messageis encrypted.
-The persistent data used for security should be SNMP-manageable, butthe Security Model defines whether an instantiation of the MIB is aconformance requirement.
-Security Models are replaceable within the Security Subsystem.Multiple Security Model implementations may exist concurrently withinan SNMP engine.  The number of Security Models defined by the SNMPcommunity should remain small to promote interoperability.
+Only one registration per combination of PDU type and contextEngineID
+is permitted at the same time.  Duplicate registrations are ignored.
+An errorIndication will be returned to the application that attempts
+to duplicate a registration.
+All asynchronously received messages containing a registered
+combination of PDU type and contextEngineID are sent to the
+application which registered to support that combination.
+The engine forwards the PDU to the registered application, using the
+processPdu primitive, as described in section 4.1.2.
+A.3.4.  Applications that Send Responses
+Request operations require responses.  An application sends a
+response via the returnResponsePdu primitive, as described in section
+.1.3.
+The contextEngineID, contextName, securityModel, securityName,
+securityLevel, and stateReference parameters are from the initial
+processPdu primitive.  The PDU and statusInformation are the results
+of processing.
+A.4.  Access Control Model Design Requirements
+An Access Control Model determines whether the specified securityName
+is allowed to perform the requested operation on a specified managed
+object.  The Access Control Model specifies the rules by which access
+control is determined.
-A.1.3.  Validate the security-stamp in a received message
+The persistent data used for access control should be manageable
-A Message Processing Model requests that a Security Model:
+using SNMP, but the Access Control Model defines whether an
-  -  verifies that the message has not been altered,
+instantiation of the MIB is a conformance requirement.
-  -  authenticates the identification of the principal for whom the      message was generated.
-  -  decrypts the message if it was encrypted.
-Additional requirements may be defined by the model, and additionalservices may be provided by the model, but the model is constrainedto use the following primitives for transferring data betweensubsystems.  Implementations are not so constrained.
-A Message Processing Model uses the processIncomingMsg primitive asdescribed in section 4.4.2.
-A.1.4.  Security MIBs
-Each Security Model defines the MIB module(s) required for securityprocessing, including any MIB module(s) required for the securityprotocol(s) supported.  The MIB module(s) SHOULD be definedconcurrently with the procedures which use the MIB module(s).  TheMIB module(s) are subject to normal access control rules.
-The mapping between the model-dependent security ID and thesecurityName MUST be able to be determined using SNMP, if the model-dependent MIB is instantiated and if access control policy allowsaccess.
-A.1.5.  Cached Security Data
-For each message received, the Security Model caches the stateinformation such that a Response message can be generated using thesame security information, even if the Local Configuration Datastoreis altered between the time of the incoming request and the outgoingresponse.
-A Message Processing Model has the responsibility for explicitlyreleasing the cached data if such data is no longer needed.  Toenable this, an abstract securityStateReference data element ispassed from the Security Model to the Message Processing Model.
-The cached security data may be implicitly released via thegeneration of a response, or explicitly released by using thestateRelease primitive, as described in section 4.5.1.
+The Access Control Model must provide the primitive isAccessAllowed.
-A.2.  Message Processing Model Design Requirements
-An SNMP engine contains a Message Processing Subsystem which maycontain multiple Message Processing Models.
-The Message Processing Model MUST always (conceptually) pass thecomplete PDU, i.e., it never forwards less than the complete list ofvarBinds.
-A.2.1.  Receiving an SNMP Message from the Network
-Upon receipt of a message from the network, the Dispatcher in theSNMP engine determines the version of the SNMP message and interactswith the corresponding Message Processing Model to determine theabstract data elements.
-A Message Processing Model specifies the SNMP Message format itsupports and describes how to determine the values of the abstractdata elements (like msgID, msgMaxSize, msgFlags,msgSecurityParameters, securityModel, securityLevel etc).  A MessageProcessing Model interacts with a Security Model to provide securityprocessing for the message using the processIncomingMsg primitive, asdescribed in section 4.4.2.
-A.2.2.  Sending an SNMP Message to the Network
-The Dispatcher in the SNMP engine interacts with a Message ProcessingModel to prepare an outgoing message.  For that it uses the followingprimitives:
-  -  for requests and notifications: prepareOutgoingMessage, as      described in section 4.2.1.
-  -  for response messages: prepareResponseMessage, as described in      section 4.2.2.
-A Message Processing Model, when preparing an Outgoing SNMP Message,interacts with a Security Model to secure the message.  For that ituses the following primitives:
-  -  for requests and notifications: generateRequestMsg, as      described in section 4.4.1.
-  -  for response messages: generateResponseMsg as described in      section 4.4.3.
-Once the SNMP message is prepared by a Message Processing Model, theDispatcher sends the message to the desired address using theappropriate transport.
-A.3.  Application Design Requirements
-Within an application, there may be an explicit binding to a specificSNMP message version, i.e., a specific Message Processing Model, andto a specific Access Control Model, but there should be no referenceto any data defined by a specific Message Processing Model or AccessControl Model.
-Within an application, there should be no reference to any specificSecurity Model, or any data defined by a specific Security Model.
-An application determines whether explicit or implicit access controlshould be applied to the operation, and, if access control is needed,which Access Control Model should be used.
-An application has the responsibility to define any MIB module(s)used to provide application-specific services.
-Applications interact with the SNMP engine to initiate messages,receive responses, receive asynchronous messages, and send responses.
-A.3.1.  Applications that Initiate Messages
-Applications may request that the SNMP engine send messagescontaining SNMP commands or notifications using the sendPdu primitiveas described in section 4.1.1.
-If it is desired that a message be sent to multiple targets, it isthe responsibility of the application to provide the iteration.
-The SNMP engine assumes necessary access control has been applied tothe PDU, and provides no access control services.
-The SNMP engine looks at the "expectResponse" parameter, and if aresponse is expected, then the appropriate information is cached suchthat a later response can be associated to this message, and can thenbe returned to the application.  A sendPduHandle is returned to theapplication so it can later correspond the response with this messageas well.
-A.3.2.  Applications that Receive Responses
-The SNMP engine matches the incoming response messages to outstandingmessages sent by this SNMP engine, and forwards the response to theassociated application using the processResponsePdu primitive, asdescribed in section 4.1.4.
-A.3.3.  Applications that Receive Asynchronous Messages
-When an SNMP engine receives a message that is not the response to arequest from this SNMP engine, it must determine to which applicationthe message should be given.
-An Application that wishes to receive asynchronous messages registersitself with the engine using the primitive registerContextEngineID asdescribed in section 4.1.5.
-An Application that wishes to stop receiving asynchronous messagesshould unregister itself with the SNMP engine using the primitiveunregisterContextEngineID as described in section 4.1.5.
-Only one registration per combination of PDU type and contextEngineIDis permitted at the same time.  Duplicate registrations are ignored.An errorIndication will be returned to the application that attemptsto duplicate a registration.
-All asynchronously received messages containing a registeredcombination of PDU type and contextEngineID are sent to theapplication which registered to support that combination.
-The engine forwards the PDU to the registered application, using theprocessPdu primitive, as described in section 4.1.2.
-A.3.4.  Applications that Send Responses
-Request operations require responses.  An application sends aresponse via the returnResponsePdu primitive, as described in section4.1.3.
-The contextEngineID, contextName, securityModel, securityName,securityLevel, and stateReference parameters are from the initialprocessPdu primitive.  The PDU and statusInformation are the resultsof processing.
-A.4.  Access Control Model Design Requirements
-An Access Control Model determines whether the specified securityNameis allowed to perform the requested operation on a specified managedobject.  The Access Control Model specifies the rules by which accesscontrol is determined.
-The persistent data used for access control should be manageableusing SNMP, but the Access Control Model defines whether aninstantiation of the MIB is a conformance requirement.
-The Access Control Model must provide the primitive isAccessAllowed.
 Editors' Addresses
-Bert WijnenLucent TechnologiesSchagen 333461 GL LinschotenNetherlands
-Phone: +31 348-680-485EMail: [email protected]
-David HarringtonEnterasys NetworksPost Office Box 500535 Industrial WayRochester, New Hampshire 03866-5005USA
-Phone: +1 603-337-2614EMail: [email protected]
-Randy PresuhnBMC Software, Inc.2141 North First StreetSan Jose, California 95131USA
-Phone: +1 408-546-1006Fax: +1 408-965-0359EMail: [email protected]
+Bert Wijnen
+Lucent Technologies
+Schagen 33
+GL Linschoten
+Netherlands
+Phone: +31 348-680-485
+EMail: [email protected]
+David Harrington
+Enterasys Networks
+Post Office Box 5005
+Industrial Way
+Rochester, New Hampshire 03866-5005
+USA
+Phone: +1 603-337-2614
+EMail: [email protected]
+Randy Presuhn
+BMC Software, Inc.
+North First Street
+San Jose, California 95131
+USA
+Phone: +1 408-546-1006
+Fax: +1 408-965-0359
+EMail: [email protected]
 Full Copyright Statement
@@ Line 2,933: / Line 2,786: @@
 Funding for the RFC Editor function is currently provided by the
 Internet Society.
-[[Category:Standards Track]]

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Difference between revisions of "RFC3411"

Revision as of 11:28, 24 September 2020

Contents

Introduction

Overview

SNMP

Goals of this Architecture

Security Requirements of this Architecture

Design Decisions

Documentation Overview

Document Roadmap

Applicability Statement

Coexistence and Transition

Transport Mappings

Message Processing

Security

Access Control

Protocol Operations

Applications

Elements of the Architecture

The Naming of Entities

SNMP engine

snmpEngineID

Dispatcher

Message Processing Subsystem

Security Subsystem

Access Control Subsystem

Access Control Model

Applications

SNMP Manager

SNMP Agent

The Naming of Identities

Principal

securityName

Model-dependent security ID

The Naming of Management Information

An SNMP Context

contextEngineID

contextName

scopedPDU

Other Constructs

maxSizeResponseScopedPDU

Local Configuration Datastore

securityLevel

Abstract Service Interfaces

Dispatcher Primitives

Generate Outgoing Request or Notification

Process Incoming Request or Notification PDU

Generate Outgoing Response

Process Incoming Response PDU

Registering Responsibility for Handling SNMP PDUs

Message Processing Subsystem Primitives

Prepare Outgoing SNMP Request or Notification Message

Prepare an Outgoing SNMP Response Message

Prepare Data Elements from an Incoming SNMP Message

Access Control Subsystem Primitives

Security Subsystem Primitives

Generate a Request or Notification Message

Process Incoming Message

Generate a Response Message

Common Primitives

Release State Reference Information

Scenario Diagrams

Command Generator or Notification Originator

Scenario Diagram for a Command Responder Application

Managed Object Definitions for SNMP Management Frameworks

IANA Considerations

Security Models

Message Processing Models

SnmpEngineID Formats

Intellectual Property

Acknowledgements

Security Considerations

Navigation

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