RFC3584
Network Working Group R. Frye Request for Comments: 3584 Vibrant Solutions BCP: 74 D. Levi Obsoletes: 2576 Nortel Networks Category: Best Current Practice S. Routhier
Wind River Systems, Inc.
B. Wijnen
Lucent Technologies
August 2003
Coexistence between Version 1, Version 2, and Version 3
of the Internet-standard Network Management Framework
Status of this Memo
This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The purpose of this document is to describe coexistence between version 3 of the Internet-standard Network Management Framework, (SNMPv3), version 2 of the Internet-standard Network Management Framework (SNMPv2), and the original Internet-standard Network Management Framework (SNMPv1). This document also describes how to convert MIB modules from SMIv1 format to SMIv2 format. This document obsoletes RFC 2576.
Table Of Contents
3.1. Translating SNMPv1 Notification Parameters to
3.2. Translating SNMPv2 Notification Parameters to
4.2.2.2.1. Mapping noSuchObject
4.2.2.2.2. Mapping endOfMibView. . . 18
4.2.2.3. Processing An SNMPv1 GetReques . . . 18
4.2.2.4. Processing An SNMPv1 GetNextRequest. 19
4.2.2.5. Processing An SNMPv1 SetRequest. . . 20
4.3.1. Upstream Version Greater Than Downstream
4.3.2. Upstream Version Less Than Downstream Version. 23
5.2. The SNMPv1 MP Model and SNMPv1 Community-based
Contents
- 1 Overview
- 2 SMI and Management Information Mappings
- 3 Translating Notification Parameters
- 4 Approaches to Coexistence in a Multi-lingual Network
- 5 Message Processing Models and Security Models
- 6 Intellectual Property Statement
- 7 Acknowledgments
- 8 Security Considerations
- 9 References
Overview
The purpose of this document is to describe coexistence between version 3 of the Internet-standard Network Management Framework, termed the SNMP version 3 framework (SNMPv3), version 2 of the Internet-standard Network Management Framework, termed the SNMP version 2 framework (SNMPv2), and the original Internet-standard Network Management Framework (SNMPv1).
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 RFC 2119 RFC2119.
There are four general aspects of coexistence described in this document. Each of these is described in a separate section:
- Conversion of MIB documents between SMIv1 and SMIv2 formats is
documented in section 2.
- Mapping of notification parameters is documented in section 3.
- Approaches to coexistence between entities which support the
various versions of SNMP in a multi-lingual network is documented in section 4. This section addresses the processing of protocol operations in multi-lingual implementations, as well as behaviour of proxy implementations.
- The SNMPv1 Message Processing Model and Community-Based Security
Model, which provides mechanisms for adapting SNMPv1 into the View-Based Access Control Model (VACM) [20], is documented in section 5 (this section also addresses the SNMPv2c Message Processing Model and Community-Based Security Model).
SNMPv1
SNMPv1 is defined by these documents:
- STD 15, RFC 1157 RFC1157 which defines the Simple Network
Management Protocol (SNMPv1), the protocol used for network access to managed objects.
- STD 16, RFC 1155 RFC1155 which defines the Structure of
Management Information (SMIv1), the mechanisms used for describing and naming objects for the purpose of management.
- STD 16, RFC 1212 RFC1212 which defines a more concise
description mechanism, which is wholly consistent with the SMIv1.
- RFC 1215 RFC1215 which defines a convention for defining Traps
for use with the SMIv1.
Note that throughout this document, the term 'SMIv1' is used. This term generally refers to the information presented in RFC 1155, RFC 1212, and RFC 1215.
SNMPv2
SNMPv2 is defined by these documents:
- STD 58, RFC 2578 which defines Version 2 of the Structure of
Management Information (SMIv2) RFC2578.
- STD 58, RFC 2579 which defines common MIB "Textual Conventions"
RFC2579.
- STD 58, RFC 2580 which defines Conformance Statements and
requirements for defining agent and manager capabilities RFC2580.
- STD 62, RFC 3416 which defines the Protocol Operations used in
processing RFC3416.
- STD 62, RFC 3417 which defines the Transport Mappings used "on the
wire" RFC3417.
- STD 62, RFC 3418 which defines the basic Management Information
Base for monitoring and controlling some basic common functions of SNMP entities RFC3418.
Note that SMIv2 as used throughout this document refers to the first three documents listed above (RFCs 2578, 2579, and 2580).
The following document augments the definition of SNMPv2:
- RFC 1901 RFC1901 is an Experimental definition for using SNMPv2
PDUs within a community-based message wrapper. This is referred to throughout this document as SNMPv2c.
SNMPv3
SNMPv3 is defined by these documents:
- STD 62, RFC 3411 which defines an Architecture for Describing SNMP
Management Frameworks RFC3411.
- STD 62, RFC 3412 which defines Message Processing and Dispatching
RFC3412.
- STD 62, RFC 3413 which defines various SNMP Applications
RFC3413.
- STD 62, RFC 3414 which defines the User-based Security Model
(USM), providing for both Authenticated and Private (encrypted) SNMP messages RFC3414.
- STD 62, RFC 3415 which defines the View-based Access Control Model
(VACM), providing the ability to limit access to different MIB objects on a per-user basis RFC3415.
SNMPv3 also uses the SNMPv2 definitions of RFCs 3416 through 3418 and the SMIv2 definitions of 2578 through 2580 described above. Note that text throughout this document that refers to SNMPv2 PDU types and protocol operations applies to both SNMPv2c and SNMPv3.
SMI and Management Information Mappings
The SMIv2 approach towards describing collections of managed objects is nearly a proper superset of the approach defined in the SMIv1. For example, both approaches use an adapted subset of ASN.1 [ASN1] as the basis for a formal descriptive notation. Indeed, one might note that the SMIv2 approach largely codifies the existing practice for defining MIB modules, based on extensive experience with the SMIv1.
The following sections consider the three areas: MIB modules, compliance statements, and capabilities statements.
MIB Modules
MIB modules defined using the SMIv1 may continue to be used with protocol versions which use SNMPv2 PDUs. However, for SMIv1 MIB modules to conform to the SMIv2, the following changes SHALL be made:
Object Definitions
In general, conversion of a MIB module does not require the deprecation of the objects contained therein. If the definition of an object is truly inadequate for its intended purpose, the object SHALL be deprecated or obsoleted, otherwise deprecation is not required.
(1) The IMPORTS statement MUST reference SNMPv2-SMI, instead of
RFC1155-SMI and RFC-1212.
(2) The MODULE-IDENTITY macro MUST be invoked immediately after any
IMPORTs statement.
(3) For any object with a SYNTAX clause value of Counter, the object
MUST have the value of its SYNTAX clause changed to Counter32.
(4) For any object with a SYNTAX clause value of Gauge, the object
MUST have the value of its SYNTAX clause changed to Gauge32, or
Unsigned32 where appropriate.
(5) For all objects, the ACCESS clause MUST be replaced by a MAX-
ACCESS clause. The value of the MAX-ACCESS clause SHALL be the
same as that of the ACCESS clause unless some other value makes
"protocol sense" as the maximal level of access for the object.
In particular, object types for which instances can be
explicitly created by a protocol set operation, SHALL have a
MAX-ACCESS clause of "read-create". If the value of the ACCESS
clause is "write-only", then the value of the MAX-ACCESS clause
MUST be "read-write", and the DESCRIPTION clause SHALL note that
reading this object will result in implementation-specific
results. Note that in SMIv1, the ACCESS clause specifies the
minimal required access, while in SMIv2, the MAX-ACCESS clause
specifies the maximum allowed access. This should be considered
when converting an ACCESS clause to a MAX-ACCESS clause.
(6) For all objects, if the value of the STATUS clause is
"mandatory" or "optional", the value MUST be replaced with
"current", "deprecated", or "obsolete" depending on the current
usage of such objects.
(7) For any object not containing a DESCRIPTION clause, the object
MUST have a DESCRIPTION clause defined.
(8) For any object corresponding to a conceptual row which does not
have an INDEX clause, the object MUST have either an INDEX
clause or an AUGMENTS clause defined.
(9) If any INDEX clause contains a reference to an object with a
syntax of NetworkAddress, then a new object MUST be created and
placed in this INDEX clause immediately preceding the object
whose syntax is NetworkAddress. This new object MUST have a
syntax of INTEGER, it MUST be not-accessible, and its value MUST
always be 1. The effect of this, and the preceding bullet, is
to allow one to convert a MIB module in SMIv1 format to one in
SMIv2 format, and then use it with the SNMPv1 protocol with no
impact to existing SNMPv1 agents and managers.
(10) For any object with a SYNTAX of NetworkAddress, the SYNTAX MUST
be changed to IpAddress. Note that the use of NetworkAddress in
new MIB documents is strongly discouraged (in fact, new MIB
documents should be written using SMIv2, which does not define
NetworkAddress).
(11) For any object containing a DEFVAL clause with an OBJECT
IDENTIFIER value which is expressed as a collection of sub-
identifiers, the value MUST be changed to reference a single
ASN.1 identifier. This may require defining a series of new
administrative assignments (OBJECT IDENTIFIERS) in order to
define the single ASN.1 identifier.
(12) One or more OBJECT-GROUPS MUST be defined, and related objects
MUST be collected into appropriate groups. Note that SMIv2
requires all OBJECT-TYPEs to be a member of at least one
OBJECT-GROUP.
(13) For any non-columnar object that is instanced as if it were
immediately subordinate to a conceptual row, the value of the
STATUS clause of that object MUST be changed to "obsolete".
(14) For any conceptual row object that is not immediately
subordinate to a conceptual table, the value of the STATUS
clause of that object (and all subordinate objects) MUST be
changed to "obsolete".
Other changes are desirable, but not necessary:
(1) Creation and deletion of conceptual rows is inconsistent using
the SMIv1. The SMIv2 corrects this. As such, if the MIB module
undergoes review early in its lifetime, and it contains
conceptual tables which allow creation and deletion of
conceptual rows, then the objects relating to those tables MAY
be deprecated and replaced with objects defined using the new
approach. The approach based on SMIv2 can be found in section 7
of RFC 2578 RFC2578, and the RowStatus and StorageType
TEXTUAL-CONVENTIONs are described in section 2 of RFC 2579
RFC2579.
(2) For any object with an integer-valued SYNTAX clause, in which
the corresponding INTEGER does not have a range restriction
(i.e., the INTEGER has neither a defined set of named-number
enumerations nor an assignment of lower- and upper-bounds on its
value), the object SHOULD have the value of its SYNTAX clause
changed to Integer32, or have an appropriate range specified.
(3) For any object with a string-valued SYNTAX clause, in which the
corresponding OCTET STRING does not have a size restriction
(i.e., the OCTET STRING has no assignment of lower- and upper-
bounds on its length), the bounds for the size of the object
SHOULD be defined.
(4) All textual conventions informally defined in the MIB module
SHOULD be redefined using the TEXTUAL-CONVENTION macro. Such a
change would not necessitate deprecating objects previously
defined using an informal textual convention.
(5) For any object which represents a measurement in some kind of
units, a UNITS clause SHOULD be added to the definition of that
object.
(6) For any conceptual row which is an extension of another
conceptual row, i.e., for which subordinate columnar objects
both exist and are identified via the same semantics as the
other conceptual row, an AUGMENTS clause SHOULD be used in place
of the INDEX clause for the object corresponding to the
conceptual row which is an extension.
Trap and Notification Definitions
If a MIB module is changed to conform to the SMIv2, then each occurrence of the TRAP-TYPE macro MUST be changed to a corresponding invocation of the NOTIFICATION-TYPE macro:
(1) The IMPORTS statement MUST NOT reference RFC-1215 RFC1215, and
MUST reference SNMPv2-SMI instead.
(2) The ENTERPRISE clause MUST be removed.
(3) The VARIABLES clause MUST be renamed to the OBJECTS clause.
(4) A STATUS clause MUST be added, with an appropriate value.
Normally the value should be 'current', although 'deprecated' or
'obsolete' may be used as needed.
(5) The value of an invocation of the NOTIFICATION-TYPE macro is an
OBJECT IDENTIFIER, not an INTEGER, and MUST be changed
accordingly. Specifically, if the value of the ENTERPRISE
clause is not 'snmp' then the value of the invocation SHALL be
the value of the ENTERPRISE clause extended with two sub-
identifiers, the first of which has the value 0, and the second
has the value of the invocation of the TRAP-TYPE. If the value
of the ENTERPRISE clause is 'snmp', then the value of the
invocation of the NOTIFICATION-TYPE macro SHALL be mapped in the
same manner as described in section 3.1 in this document.
(6) A DESCRIPTION clause MUST be added, if not already present.
(7) One or more NOTIFICATION-GROUPs MUST be defined, and related
notifications MUST be collected into those groups. Note that
SMIv2 requires that all NOTIFICATION-TYPEs be a member of at
least one NOTIFICATION-GROUP.
Compliance Statements
For those information modules which are "standards track", a corresponding invocation of the MODULE-COMPLIANCE macro and related OBJECT-GROUP and/or NOTIFICATION-GROUP macros MUST be included within the information module (or in a companion information module), and any commentary text in the information module which relates to compliance SHOULD be removed. Typically this editing can occur when the information module undergoes review.
Note that a MODULE-COMPLIANCE statement is not required for a MIB document that is not on the standards track (for example, an enterprise MIB), though it may be useful in some circumstances to define a MODULE-COMPLIANCE statement for such a MIB document.
Capabilities Statements
RFC 1303 RFC1303 uses the MODULE-CONFORMANCE macro to describe an agent's capabilities with respect to one or more MIB modules.
Converting such a description for use with the SMIv2 requires these changes:
(1) The macro name AGENT-CAPABILITIES MUST be used instead of
MODULE-CONFORMANCE.
(2) The STATUS clause MUST be added, with a value of 'current'.
(3) All occurrences of the CREATION-REQUIRES clause MUST either be
omitted if appropriate, or be changed such that the semantics
are consistent with RFC 2580 RFC2580.
In order to ease coexistence, object groups defined in an SMIv1 compliant MIB module may be referenced by the INCLUDES clause of an invocation of the AGENT-CAPABILITIES macro: upon encountering a reference to an OBJECT IDENTIFIER subtree defined in an SMIv1 MIB module, all leaf objects which are subordinate to the subtree and have a STATUS clause value of mandatory are deemed to be INCLUDEd. (Note that this method is ambiguous when different revisions of an SMIv1 MIB have different sets of mandatory objects under the same subtree; in such cases, the only solution is to rewrite the MIB using the SMIv2 in order to define the object groups unambiguously.)
Translating Notification Parameters
This section describes how parameters used for generating notifications are translated between the format used for SNMPv1 notification protocol operations and the format used for SNMPv2 notification protocol operations. The parameters used to generate a notification are called 'notification parameters'. The format of parameters used for SNMPv1 notification protocol operations is referred to in this document as 'SNMPv1 notification parameters'. The format of parameters used for SNMPv2 notification protocol operations is referred to in this document as 'SNMPv2 notification parameters'.
The situations where notification parameters MUST be translated are:
- When an entity generates a set of notification parameters in a
particular format, and the configuration of the entity indicates that the notification must be sent using an SNMP message version that requires the other format for notification parameters.
- When a proxy receives a notification that was sent using an SNMP
message version that requires one format of notification parameters, and must forward the notification using an SNMP message version that requires the other format of notification parameters.
In addition, it MAY be desirable to translate notification parameters in a notification receiver application in order to present notifications to the end user in a consistent format.
Note that for the purposes of this section, the set of notification parameters is independent of whether the notification is to be sent as a trap or an inform.
SNMPv1 notification parameters consist of:
- An enterprise parameter (OBJECT IDENTIFIER).
- An agent-addr parameter (NetworkAddress).
- A generic-trap parameter (INTEGER).
- A specific-trap parameter (INTEGER).
- A time-stamp parameter (TimeTicks).
- A list of variable-bindings (VarBindList).
SNMPv2 notification parameters consist of:
- A sysUpTime parameter (TimeTicks). This appears in the first
variable-binding in an SNMPv2-Trap-PDU or InformRequest-PDU.
- An snmpTrapOID parameter (OBJECT IDENTIFIER). This appears in the
second variable-binding in an SNMPv2-Trap-PDU or InformRequest- PDU, and is equal to the value portion of that variable-binding (not the name portion, as both the name and value are OBJECT IDENTIFIERs).
- A list of variable-bindings (VarBindList). This refers to all but
the first two variable-bindings in an SNMPv2-Trap-PDU or InformRequest-PDU.
Translating SNMPv1 Notification Parameters to SNMPv2 Notification
Parameters
The following procedure describes how to translate SNMPv1 notification parameters into SNMPv2 notification parameters:
(1) The SNMPv2 sysUpTime parameter SHALL be taken directly from the
SNMPv1 time-stamp parameter.
(2) If the SNMPv1 generic-trap parameter is 'enterpriseSpecific(6)',
the SNMPv2 snmpTrapOID parameter SHALL be the concatenation of
the SNMPv1 enterprise parameter and two additional sub-
identifiers, '0', and the SNMPv1 specific-trap parameter.
(3) If the SNMPv1 generic-trap parameter is not
'enterpriseSpecific(6)', the SNMPv2 snmpTrapOID parameter SHALL
be the corresponding trap as defined in section 2 of RFC 3418
RFC3418:
generic-trap
parameter snmpTrapOID.0
============ =============
0 1.3.6.1.6.3.1.1.5.1 (coldStart)
1 1.3.6.1.6.3.1.1.5.2 (warmStart)
2 1.3.6.1.6.3.1.1.5.3 (linkDown)
3 1.3.6.1.6.3.1.1.5.4 (linkUp)
4 1.3.6.1.6.3.1.1.5.5 (authenticationFailure)
5 1.3.6.1.6.3.1.1.5.6 (egpNeighborLoss)
(4) The SNMPv2 variable-bindings SHALL be the SNMPv1 variable-
bindings. In addition, if the translation is being performed by
a proxy in order to forward a received trap, three additional
variable-bindings will be appended, if these three additional
variable-bindings do not already exist in the SNMPv1 variable-
bindings. The name portion of the first additional variable
binding SHALL contain snmpTrapAddress.0, and the value SHALL
contain the SNMPv1 agent-addr parameter. The name portion of
the second additional variable binding SHALL contain
snmpTrapCommunity.0, and the value SHALL contain the value of
the community-string field from the received SNMPv1 message
which contained the SNMPv1 Trap-PDU. The name portion of the
third additional variable binding SHALL contain
snmpTrapEnterprise.0 RFC3418, and the value SHALL be the
SNMPv1 enterprise parameter.
Translating SNMPv2 Notification Parameters to SNMPv1 Notification
Parameters
The following procedure describes how to translate SNMPv2 notification parameters into SNMPv1 notification parameters:
(1) The SNMPv1 enterprise parameter SHALL be determined as follows:
- If the SNMPv2 snmpTrapOID parameter is one of the standard
traps as defined in RFC 3418 RFC3418, then the SNMPv1
enterprise parameter SHALL be set to the value of the
variable-binding in the SNMPv2 variable-bindings whose name is
snmpTrapEnterprise.0 if that variable-binding exists. If it
does not exist, the SNMPv1 enterprise parameter SHALL be set
to the value 'snmpTraps' as defined in RFC 3418 RFC3418.
- If the SNMPv2 snmpTrapOID parameter is not one of the standard
traps as defined in RFC 3418 RFC3418, then the SNMPv1
enterprise parameter SHALL be determined from the SNMPv2
snmpTrapOID parameter as follows:
- If the next-to-last sub-identifier of the snmpTrapOID value
is zero, then the SNMPv1 enterprise SHALL be the SNMPv2
snmpTrapOID value with the last 2 sub-identifiers removed,
otherwise
- If the next-to-last sub-identifier of the snmpTrapOID value
is non-zero, then the SNMPv1 enterprise SHALL be the SNMPv2
snmpTrapOID value with the last sub-identifier removed.
(2) The SNMPv1 agent-addr parameter SHALL be determined based on the
situation in which the translation occurs.
- If the translation occurs within a notification originator
application, and the notification is to be sent over IP, the
SNMPv1 agent-addr parameter SHALL be set to the IP address of
the SNMP entity in which the notification originator resides.
If the notification is to be sent over some other transport,
the SNMPv1 agent-addr parameter SHALL be set to 0.0.0.0.
- If the translation occurs within a proxy application, the
proxy must attempt to extract the original source of the
notification from the variable-bindings. If the SNMPv2
variable-bindings contains a variable binding whose name is
snmpTrapAddress.0, the agent-addr parameter SHALL be set to
the value of that variable binding. Otherwise, the SNMPv1
agent-addr parameter SHALL be set to 0.0.0.0.
(3) If the SNMPv2 snmpTrapOID parameter is one of the standard traps
as defined in RFC 3418 RFC3418, the SNMPv1 generic-trap parameter SHALL be set as follows:
snmpTrapOID.0 parameter generic-trap
=============================== ============
1.3.6.1.6.3.1.1.5.1 (coldStart) 0
1.3.6.1.6.3.1.1.5.2 (warmStart) 1
1.3.6.1.6.3.1.1.5.3 (linkDown) 2
1.3.6.1.6.3.1.1.5.4 (linkUp) 3
1.3.6.1.6.3.1.1.5.5 (authenticationFailure) 4
1.3.6.1.6.3.1.1.5.6 (egpNeighborLoss) 5
Otherwise, the SNMPv1 generic-trap parameter SHALL be set to 6.
(4) If the SNMPv2 snmpTrapOID parameter is one of the standard traps
as defined in RFC 3418 RFC3418, the SNMPv1 specific-trap parameter SHALL be set to zero. Otherwise, the SNMPv1 specific-trap parameter SHALL be set to the last sub-identifier of the SNMPv2 snmpTrapOID parameter.
(5) The SNMPv1 time-stamp parameter SHALL be taken directly from the
SNMPv2 sysUpTime parameter.
(6) The SNMPv1 variable-bindings SHALL be the SNMPv2 variable-
bindings (and note that the SNMPv2 variable-bindings do not
include the variable-bindings containing sysUpTime.0,
snmpTrapOID.0). Note, however, that if the SNMPv2 variable-
bindings contain any objects whose type is Counter64, the
translation to SNMPv1 notification parameters cannot be
performed. In this case, the notification cannot be encoded in
an SNMPv1 packet (and so the notification cannot be sent using
SNMPv1, see section 4.2.3 and section 4.3).
Approaches to Coexistence in a Multi-lingual Network
There are two basic approaches to coexistence in a multi-lingual network, multi-lingual implementations and proxy implementations. Multi-lingual implementations allow elements in a network to communicate with each other using an SNMP version which both elements support. This allows a multi-lingual implementation to communicate with any mono-lingual implementation, regardless of the SNMP version supported by the mono-lingual implementation.
Proxy implementations provide a mechanism for translating between SNMP versions using a third party network element. This allows network elements which support only a single, but different, SNMP version to communicate with each other. Proxy implementations are also useful for securing communications over an insecure link between two locally secure networks.
SNMPv1 and SNMPv2 Access to MIB Data
Throughout section 4., this document refers to 'SNMPv1 Access to MIB Data' and 'SNMPv2 Access to MIB Data'. These terms refer to the part of an SNMP agent which actually accesses instances of MIB objects, and which actually initiates generation of notifications. Differences between the two types of access to MIB data are:
- Error-status values generated.
- Generation of exception codes.
- Use of the Counter64 data type.
- The format of parameters provided when a notification is
generated.
SNMPv1 access to MIB data may generate SNMPv1 error-status values, will never generate exception codes nor use the Counter64 data type, and will provide SNMPv1 format parameters for generating notifications. Note also that SNMPv1 access to MIB data will actually never generate a readOnly error (a noSuchName error would always occur in the situation where one would expect a readOnly error).
SNMPv2 access to MIB data may generate SNMPv2 error-status values, may generate exception codes, may use the Counter64 data type, and will provide SNMPv2 format parameters for generating notifications. Note that SNMPv2 access to MIB data will never generate readOnly, noSuchName, or badValue errors.
Note that a particular multi-lingual implementation may choose to implement all access to MIB data as SNMPv2 access to MIB data, and perform the translations described herein for SNMPv1-based transactions.
Further, note that there is no mention of 'SNMPv3 access to MIB data' in this document, as SNMPv3 uses SNMPv2 PDU types and protocol operations.
Multi-lingual implementations
This approach requires an entity to support multiple SNMP message versions. Typically this means supporting SNMPv1, SNMPv2c, and SNMPv3 message versions. The behaviour of various types of SNMP applications which support multiple message versions is described in the following sections. This approach allows entities which support multiple SNMP message versions to coexist with and communicate with entities which support only a single SNMP message version.
Command Generator
A command generator must select an appropriate message version when sending requests to another entity. One way to achieve this is to consult a local database to select the appropriate message version.
In addition, a command generator MUST 'downgrade' GetBulk requests to GetNext requests when selecting SNMPv1 as the message version for an
outgoing request. This is done by simply changing the operation type to GetNext, ignoring any non-repeaters and max-repetitions values, and setting error-status and error-index to zero.
Command Responder
A command responder must be able to deal with both SNMPv1 and SNMPv2 access to MIB data. There are three aspects to dealing with this. A command responder must:
- Deal correctly with SNMPv2 access to MIB data that returns a
Counter64 value while processing an SNMPv1 message,
- Deal correctly with SNMPv2 access to MIB data that returns one of
the three exception values while processing an SNMPv1 message, and
- Map SNMPv2 error codes returned from SNMPv2 access to MIB data
into SNMPv1 error codes when processing an SNMPv1 message.
Note that SNMPv1 error codes SHOULD NOT be used without any change when processing SNMPv2c or SNMPv3 messages, except in the case of proxy forwarding. Also, SNMPv1 access to MIB data SHOULD NOT be used when processing SNMPv2c or SNMPv3 messages. In the case of proxy forwarding, for backwards compatibility, SNMPv1 error codes may be used without any change in a forwarded SNMPv2c or SNMPv3 message.
The following sections describe the behaviour of a command responder application which supports multiple SNMP message versions, and which uses SNMPv2 access to MIB data when processing an SNMPv1 message.
Handling Counter64
The SMIv2 RFC2578 defines one new syntax that is incompatible with SMIv1. This syntax is Counter64. All other syntaxes defined by SMIv2 are compatible with SMIv1.
The impact on multi-lingual command responders is that they MUST NOT ever return a variable binding containing a Counter64 value in a response to a request that was received using the SNMPv1 message version.
Multi-lingual command responders SHALL take the approach that object instances whose type is Counter64 are implicitly excluded from view when processing an SNMPv1 message. So:
- On receipt of an SNMPv1 GetRequest-PDU containing a variable
binding whose name field points to an object instance of type Counter64, a GetResponsePDU SHALL be returned, with an error-
status of noSuchName and the error-index set to the variable binding that caused this error.
- On an SNMPv1 GetNextRequest-PDU, any object instance which
contains a syntax of Counter64 SHALL be skipped, and the next accessible object instance that does not have the syntax of Counter64 SHALL be retrieved. If no such object instance exists, then an error-status of noSuchName SHALL be returned, and the error-index SHALL be set to the variable binding that caused this error.
- Any SNMPv1 request which contains a variable binding with a
Counter64 value is ill-formed, so the foregoing rules do not apply. If that error is detected, a response SHALL NOT be returned, since it would contain a copy of the ill-formed variable binding. Instead, the offending PDU SHALL be discarded and the counter snmpInASNParseErrs SHALL be incremented.
Mapping SNMPv2 Exceptions
SNMPv2 provides a feature called exceptions, which allow an SNMPv2 Response PDU to return as much management information as possible, even when an error occurs. However, SNMPv1 does not support exceptions, and so an SNMPv1 Response PDU cannot return any management information, and can only return an error-status and an error-index value.
When an SNMPv1 request is received, a command responder MUST check any variable bindings returned using SNMPv2 access to MIB data for exception values, and convert these exception values into SNMPv1 error codes.
The type of exception that can be returned when accessing MIB data and the action taken depends on the type of SNMP request.
- For a GetRequest, a noSuchObject or noSuchInstance exception may
be returned.
- For a GetNextRequest, an endOfMibView exception may be returned.
- No exceptions will be returned for a SetRequest, and a
GetBulkRequest should only be received in an SNMPv2c or SNMPv3 message, so these request types may be ignored when mapping exceptions.
Note that when a response contains multiple exceptions, it is an implementation choice as to which variable binding the error-index should reference.
4.2.2.2.1. Mapping noSuchObject and noSuchInstance
A noSuchObject or noSuchInstance exception generated by an SNMPv2 access to MIB data indicates that the requested object instance can not be returned. The SNMPv1 error code for this condition is noSuchName, and so the error-status field of the response PDU SHALL be set to noSuchName. Also, the error-index field SHALL be set to the index of the variable binding for which an exception occurred (if there is more than one then it is an implementation decision as to which is used), and the variable binding list from the original request SHALL be returned with the response PDU.
4.2.2.2.2. Mapping endOfMibView
When an SNMPv2 access to MIB data returns a variable binding containing an endOfMibView exception, it indicates that there are no object instances available which lexicographically follow the object in the request. In an SNMPv1 agent, this condition normally results in a noSuchName error, and so the error-status field of the response PDU SHALL be set to noSuchName. Also, the error-index field SHALL be set to the index of the variable binding for which an exception occurred (if there is more than one then it is an implementation decision as to which is used), and the variable binding list from the original request SHALL be returned with the response PDU.
Processing An SNMPv1 GetRequest
When processing an SNMPv1 GetRequest, the following procedures MUST be followed when using an SNMPv2 access to MIB data.
When such an access to MIB data returns response data using SNMPv2 syntax and error-status values, then:
(1) If the error-status is anything other than noError,
- The error status SHALL be translated to an SNMPv1 error-
status using the table in section 4.4, "Error Status
Mappings".
- The error-index SHALL be set to the position (in the
original request) of the variable binding that caused the
error-status.
- The variable binding list of the response PDU SHALL be made
exactly the same as the variable binding list that was
received in the original request.
(2) If the error-status is noError, the variable bindings SHALL be
checked for any SNMPv2 exception (noSuchObject or
noSuchInstance) or an SNMPv2 syntax that is unknown to SNMPv1
(Counter64). If there are any such variable bindings, one of
those variable bindings SHALL be selected (it is an
implementation choice as to which is selected), and:
- The error-status SHALL be set to noSuchName,
- The error-index SHALL be set to the position (in the
variable binding list of the original request) of the
selected variable binding, and
- The variable binding list of the response PDU SHALL be
exactly the same as the variable binding list that was
received in the original request.
(3) If there are no such variable bindings, then:
- The error-status SHALL be set to noError,
- The error-index SHALL be set to zero, and
- The variable binding list of the response SHALL be composed
from the data as it is returned by the access to MIB data.
Processing An SNMPv1 GetNextRequest
When processing an SNMPv1 GetNextRequest, the following procedures MUST be followed when SNMPv2 access to MIB data is used as part of processing the request. There may be repetitive accesses to MIB data to try to find the first object which lexicographically follows each of the objects in the request. This is implementation specific. These procedures are followed only for data returned when using SNMPv2 access to MIB data. Data returned using SNMPv1 access to MIB data may be treated in the normal manner for an SNMPv1 request.
First, if the access to MIB data returns an error-status of anything other than noError:
(1) The error status SHALL be translated to an SNMPv1 error-status
using the table in section 4.4, "Error Status Mappings".
(2) The error-index SHALL be set to the position (in the original
request) of the variable binding that caused the error-status.
(3) The variable binding list of the response PDU SHALL be exactly
the same as the variable binding list that was received in the
original request.
Otherwise, if the access to MIB data returns an error-status of noError:
(1) Any variable bindings containing an SNMPv2 syntax of Counter64
SHALL be considered to be not in view, and MIB data SHALL be
accessed as many times as is required until either a value other
than Counter64 is returned, or an error or endOfMibView
exception occurs.
(2) If there is any variable binding that contains an SNMPv2
exception endOfMibView (if there is more than one then it is an
implementation decision as to which is chosen):
- The error-status SHALL be set to noSuchName,
- The error-index SHALL be set to the position (in the
variable binding list of the original request) of the
variable binding that returned such an SNMPv2 exception, and
- The variable binding list of the response PDU SHALL be
exactly the same as the variable binding list that was
received in the original request.
(3) If there are no such variable bindings, then:
- The error-status SHALL be set to noError,
- The error-index SHALL be set to zero, and
- The variable binding list of the response SHALL be composed
from the data as it is returned by the access to MIB data.
Processing An SNMPv1 SetRequest
When processing an SNMPv1 SetRequest, the following procedures MUST be followed when using SNMPv2 access to MIB data.
When such MIB access returns response data using SNMPv2 syntax and error-status values, and the error-status is anything other than noError, then:
- The error status SHALL be translated to an SNMPv1 error-status
using the table in section 4.4, "Error Status Mappings".
- The error-index SHALL be set to the position (in the original
request) of the variable binding that caused the error-status.
- The variable binding list of the response PDU SHALL be made
exactly the same as the variable binding list that was received in the original request.
Notification Originator
A notification originator must be able to translate between SNMPv1 notification parameters and SNMPv2 notification parameters in order to send a notification using a particular SNMP message version. If a notification is generated using SNMPv1 notification parameters, and configuration information specifies that notifications be sent using SNMPv2c or SNMPv3, the notification parameters must be translated to SNMPv2 notification parameters. Likewise, if a notification is generated using SNMPv2 notification parameters, and configuration information specifies that notifications be sent using SNMPv1, the notification parameters must be translated to SNMPv1 notification parameters. In this case, if the notification cannot be translated (due to the presence of a Counter64 type), it will not be sent using SNMPv1.
When a notification originator generates a notification, using parameters obtained from the SNMP-TARGET-MIB and SNMP-NOTIFICATION- MIB, if the SNMP version used to generate the notification is SNMPv1, the PDU type used will always be a TrapPDU, regardless of whether the value of snmpNotifyType is trap(1) or inform(2).
Note also that access control and notification filtering are performed in the usual manner for notifications, regardless of the SNMP message version to be used when sending a notification. The parameters for performing access control are found in the usual manner (i.e., from inspecting the SNMP-TARGET-MIB and SNMP- NOTIFICATION-MIB). In particular, when generating an SNMPv1 Trap, in order to perform the access check specified in RFC3413, section 3.3, bullet (3), the notification originator may need to generate a value for snmpTrapOID.0 as described in section 3.1, bullets (2) and (3) of this document. If the SNMPv1 notification parameters being used were previously translated from a set of SNMPv2 notification parameters, this value may already be known, in which case it need not be generated.
Notification Receiver
There are no special requirements of a notification receiver. However, an implementation may find it useful to allow a higher level application to request whether notifications should be delivered to a
higher level application using SNMPv1 notification parameter or SNMPv2 notification parameters. The notification receiver would then translate notification parameters when required in order to present a notification using the desired set of parameters.
Proxy Implementations
A proxy implementation may be used to enable communication between entities which support different SNMP message versions. This is accomplished in a proxy forwarder application by performing translations on PDUs. These translations depend on the PDU type, the SNMP version of the packet containing a received PDU, and the SNMP version to be used to forward a received PDU. The following sections describe these translations. In all cases other than those described below, the proxy SHALL forward a received PDU without change, subject to size constraints as defined in section 5.3 (Community MIB) of this document. Note that in the following sections, the 'Upstream Version' refers to the version used between the command generator or notification receiver and the proxy, and the 'Downstream Version' refers to the version used between the proxy and the command responder or notification originator, regardless of the PDU type or direction.
Upstream Version Greater Than Downstream Version
- If a GetBulkRequest-PDU is received and must be forwarded using
the SNMPv1 message version, the proxy forwarder SHALL act as if the non-repeaters and max-repetitions fields were both set to 0, and SHALL set the tag of the PDU to GetNextRequest-PDU.
- If a GetResponse-PDU is received whose error-status field has a
value of 'tooBig', and the message will be forwarded using the SNMPv2c or SNMPv3 message version, and the original request received by the proxy was not a GetBulkRequest-PDU, the proxy forwarder SHALL remove the contents of the variable-bindings field and ensure that the error-index field is set to 0 before forwarding the response.
- If a GetResponse-PDU is received whose error-status field has a
value of 'tooBig', and the message will be forwarded using the SNMPv2c or SNMPv3 message version, and the original request received by the proxy was a GetBulkRequest-PDU, the proxy forwarder SHALL re-send the forwarded request (which would have been altered to be a GetNextRequest-PDU) with all but the first variable-binding removed. The proxy forwarder SHALL only re-send such a request a single time. If the resulting GetResponse-PDU also contains an error-status field with a value of 'tooBig', then the proxy forwarder SHALL remove the contents of the variable-
bindings field, and change the error-status field to 'noError', and ensure that the error-index field is set to 0 before forwarding the response. Note that if the original request only contained a single variable-binding, the proxy may skip re-sending the request and simply remove the variable-bindings and change the error-status to 'noError'. Further note that, while it might have been possible to fit more variable bindings if the proxy only re- sent the request multiple times, and stripped only a single variable binding from the request at a time, this is deemed too expensive. The approach described here preserves the behaviour of a GetBulkRequest as closely as possible, without incurring the cost of re-sending the request multiple times.
- If a Trap-PDU is received, and will be forwarded using the SNMPv2c
or SNMPv3 message version, the proxy SHALL apply the translation rules described in section 3, and SHALL forward the notification as an SNMPv2-Trap-PDU.
Note that when an SNMPv1 agent generates a message containing a Trap-PDU which is subsequently forwarded by one or more proxy forwarders using SNMP versions other than SNMPv1, the community string and agent-addr fields from the original message generated by the SNMPv1 agent will be preserved through the use of the snmpTrapAddress and snmpTrapCommunity objects.
Upstream Version Less Than Downstream Version
- If a GetResponse-PDU is received in response to a GetRequest-PDU
(previously generated by the proxy) which contains variable- bindings of type Counter64 or which contain an SNMPv2 exception code, and the message would be forwarded using the SNMPv1 message version, the proxy MUST generate an alternate response PDU consisting of the request-id and variable bindings from the original SNMPv1 request, containing a noSuchName error-status value, and containing an error-index value indicating the position of the variable-binding containing the Counter64 type or exception code.
- If a GetResponse-PDU is received in response to a GetNextRequest-
PDU (previously generated by the proxy) which contains variable- bindings that contain an SNMPv2 exception code, and the message would be forwarded using the SNMPv1 message version, the proxy MUST generate an alternate response PDU consisting of the request-id and variable bindings from the original SNMPv1 request, containing a noSuchName error-status value, and containing an error-index value indicating the position of the variable-binding containing the exception code.
- If a GetResponse-PDU is received in response to a GetNextRequest-
PDU (previously generated by the proxy) which contains variable- bindings of type Counter64, the proxy MUST re-send the entire GetNextRequest-PDU, with the following modifications. For any variable bindings in the received GetResponse which contained Counter64 types, the proxy substitutes the object names of these variable bindings for the corresponding object names in the previously-sent GetNextRequest. The proxy MUST repeat this process until no Counter64 objects are returned. Note that an implementation may attempt to optimize this process of skipping Counter64 objects. One approach to such an optimization would be to replace the last sub-identifier of the object names of varbinds containing a Counter64 type with 65535 if that sub-identifier is less than 65535, or with 4294967295 if that sub-identifier is greater than 65535. This approach should skip multiple instances of the same Counter64 object, while maintaining compatibility with some broken agent implementations (which only use 16-bit integers for sub-identifiers).
Deployment Hint: The process of repeated GetNext requests used by a proxy when Counter64 types are returned can be expensive. When deploying a proxy, this can be avoided by configuring the target agents to which the proxy forwards requests in a manner such that any objects of type Counter64 are in fact not-in-view for the principal that the proxy is using when communicating with these agents. However, when using such a configuration, one should be careful to use a different principal for communicating with the target agent when an incoming SNMPv2c or SNMPv3 request is received, to ensure that objects of type Counter64 are properly returned.
- If a GetResponse-PDU is received which contains an SNMPv2 error-
status value of wrongValue, wrongEncoding, wrongType, wrongLength, inconsistentValue, noAccess, notWritable, noCreation, inconsistentName, resourceUnavailable, commitFailed, undoFailed, or authorizationError, and the message would be forwarded using the SNMPv1 message version, the error-status value is modified using the mappings in section 4.4.
- If an SNMPv2-Trap-PDU is received, and will be forwarded using the
SNMPv1 message version, the proxy SHALL apply the translation rules described in section 3, and SHALL forward the notification as a Trap-PDU. Note that if the translation fails due to the existence of a Counter64 data-type in the received SNMPv2-Trap- PDU, the trap cannot be forwarded using SNMPv1.
- If an InformRequest-PDU is received, any configuration information
indicating that it would be forwarded using the SNMPv1 message version SHALL be ignored. An InformRequest-PDU can only be forwarded using the SNMPv2c or SNMPv3 message version. The InformRequest-PDU may still be forwarded if there is other configuration information indicating that it should be forwarded using SNMPv2c or SNMPv3.
Error Status Mappings
The following tables shows the mappings of SNMPv1 error-status values into SNMPv2 error-status values, and the mappings of SNMPv2 error- status values into SNMPv1 error-status values.
SNMPv1 error-status SNMPv2 error-status =================== =================== noError noError tooBig tooBig noSuchName noSuchName badValue badValue genErr genErr
SNMPv2 error-status SNMPv1 error-status =================== =================== noError noError tooBig tooBig genErr genErr wrongValue badValue wrongEncoding badValue wrongType badValue wrongLength badValue inconsistentValue badValue noAccess noSuchName notWritable noSuchName noCreation noSuchName inconsistentName noSuchName resourceUnavailable genErr commitFailed genErr undoFailed genErr authorizationError noSuchName
Whenever the SNMPv2 error-status value of authorizationError is translated to an SNMPv1 error-status value of noSuchName, the value of snmpInBadCommunityUses MUST be incremented.
Message Processing Models and Security Models
In order to adapt SNMPv1 (and SNMPv2c) into the SNMP architecture, the following Message Processing (MP) models are defined in this document:
- The SNMPv1 Message Processing Model
- The SNMPv1 Community-Based Security Model
- The SNMPv2c Message Processing Model
- The SNMPv2c Community-Based Security Model
In most respects, the SNMPv1 Message Processing Model and the SNMPv2c Message Processing Model are identical, and so these are not discussed independently in this document. Differences between the two models are described as required.
Similarly, the SNMPv1 Community-Based Security Model and the SNMPv2c Community-Based Security Model are nearly identical, and so are not discussed independently. Differences between these two models are also described as required.
Mappings
The SNMPv1 (and SNMPv2c) Message Processing Model and Security Model require mappings between parameters used in SNMPv1 (and SNMPv2c) messages, and the version independent parameters used in the SNMP architecture RFC3411. The parameters which MUST be mapped consist of the SNMPv1 (and SNMPv2c) community name, and the SNMP securityName and contextEngineID/contextName pair. A MIB module (the SNMP- COMMUNITY-MIB) is provided in this document in order to perform these mappings. This MIB provides mappings in both directions, that is, a community name may be mapped to a securityName, contextEngineID, and contextName, or the combination of securityName, contextEngineID, and contextName may be mapped to a community name.
The SNMPv1 MP Model and SNMPv1 Community-based Security Model
The SNMPv1 Message Processing Model handles processing of SNMPv1 messages. The processing of messages is handled generally in the same manner as described in RFC 1157 RFC1157, with differences and clarifications as described in the following sections. The SnmpMessageProcessingModel value for SNMPv1 is 0 (the value for SNMPv2c is 1).
Processing An Incoming Request
In RFC 1157 RFC1157, section 4.1, item (3) for an entity which receives a message, states that various parameters are passed to the "desired authentication scheme". The desired authentication scheme in this case is the SNMPv1 Community-Based Security Model, which will be called using the processIncomingMsg ASI. The parameters passed to this ASI are:
- The messageProcessingModel, which will be 0 (or 1 for SNMPv2c).
- The maxMessageSize, which should be the maximum size of a message
that the receiving entity can generate (since there is no such value in the received message).
- The securityParameters, which consist of the community string and
the message's source and destination transport domains and addresses.
- The securityModel, which will be 1 (or 2 for SNMPv2c).
- The securityLevel, which will be noAuthNoPriv.
- The wholeMsg and wholeMsgLength.
The Community-Based Security Model will attempt to select a row in the snmpCommunityTable. This is done by performing a search through the snmpCommunityTable in lexicographic order. The first entry for which the following matching criteria are satisfied will be selected:
- The community string is equal to the snmpCommunityName value.
- If the snmpCommunityTransportTag is an empty string, it is ignored
for the purpose of matching. If the snmpCommunityTransportTag is not an empty string, the transportDomain and transportAddress from which the message was received must match one of the entries in the snmpTargetAddrTable selected by the snmpCommunityTransportTag value. The snmpTargetAddrTMask object is used as described in section 5.3 when checking whether the transportDomain and transportAddress matches a entry in the snmpTargetAddrTable.
If no such entry can be found, an authentication failure occurs as described in RFC 1157 RFC1157, and the snmpInBadCommunityNames counter is incremented.
The parameters returned from the Community-Based Security Model are:
- The securityEngineID, which will always be the local value of
snmpEngineID.0.
- The securityName, which will be the value of
snmpCommunitySecurityName from the selected row in the snmpCommunityTable.
- The scopedPDU. Note that this parameter will actually consist of
three values, the contextSnmpEngineID (which will be the value of snmpCommunityContextEngineID from the selected entry in the snmpCommunityTable), the contextName (which will be the value of snmpCommunityContextName from the selected entry in the snmpCommunityTable), and the PDU. These must be separate values, since the first two do not actually appear in the message.
- The maxSizeResponseScopedPDU, which will be derived using the
minimum of the maxMessageSize above, and the value of snmpTargetAddrMMS of the selected row in the snmpTargetAddrTable. If no such entry was selected, then this value will be derived from the maxMessageSize only.
- The securityStateReference, which MUST contain the community
string from the original request.
The appropriate SNMP application will then be called (depending on the value of the contextEngineID and the request type in the PDU) using the processPdu ASI. The parameters passed to this ASI are:
- The messageProcessingModel, which will be 0 (or 1 for SNMPv2c).
- The securityModel, which will be 1 (or 2 for SNMPv2c).
- The securityName, which was returned from the call to
processIncomingMsg.
- The securityLevel, which is noAuthNoPriv.
- The contextEngineID, which was returned as part of the ScopedPDU
from the call to processIncomingMsg.
- The contextName, which was returned as part of the ScopedPDU from
the call to processIncomingMsg.
- The pduVersion, which should indicate an SNMPv1 version PDU (if
the message version was SNMPv2c, this would be an SNMPv2 version PDU).
- The PDU, which was returned as part of the ScopedPDU from the call
to processIncomingMsg.
- The maxSizeResponseScopedPDU which was returned from the call to
processIncomingMsg.
- The stateReference which was returned from the call to
processIncomingMsg.
The SNMP application should process the request as described previously in this document. Note that access control is applied by an SNMPv3 command responder application as usual. The parameters as passed to the processPdu ASI will be used in calls to the isAccessAllowed ASI.
Generating An Outgoing Response
There is no special processing required for generating an outgoing response. However, the community string used in an outgoing response must be the same as the community string from the original request. The original community string MUST be present in the securityStateReference information of the original request.
Generating An Outgoing Notification
In a multi-lingual SNMP entity, the parameters used for generating notifications will be obtained by examining the SNMP-TARGET-MIB and SNMP-NOTIFICATION-MIB. These parameters will be passed to the SNMPv1 Message Processing Model using the sendPdu ASI. The SNMPv1 Message Processing Model will attempt to locate an appropriate community string in the snmpCommunityTable based on the parameters passed to the sendPdu ASI. This is done by performing a search through the snmpCommunityTable in lexicographic order. The first entry for which the following matching criteria are satisfied will be selected:
- The securityName must be equal to the snmpCommunitySecurityName
value.
- The contextEngineID must be equal to the
snmpCommunityContextEngineID value.
- The contextName must be equal to the snmpCommunityContextName
value.
- If the snmpCommunityTransportTag is an empty string, it is ignored
for the purpose of matching. If the snmpCommunityTransportTag is not an empty string, the transportDomain and transportAddress must match one of the entries in the snmpTargetAddrTable selected by the snmpCommunityTransportTag value.
If no such entry can be found, the notification is not sent. Otherwise, the community string used in the outgoing notification will be the value of the snmpCommunityName column of the selected row.
Proxy Forwarding Of Requests
In a proxy forwarding application, when a received request is to be forwarded using the SNMPv1 Message Processing Model, the parameters used for forwarding will be obtained by examining the SNMP-PROXY-MIB and the SNMP-TARGET-MIB. These parameters will be passed to the SNMPv1 Message Processing Model using the sendPdu ASI. The SNMPv1 Message Processing Model will attempt to locate an appropriate community string in the snmpCommunityTable based on the parameters passed to the sendPdu ASI. This is done by performing a search through the snmpCommunityTable in lexicographic order. The first entry for which the following matching criteria are satisfied will be selected:
- The securityName must be equal to the snmpCommunitySecurityName
value.
- The contextEngineID must be equal to the
snmpCommunityContextEngineID value.
- The contextName must be equal to the snmpCommunityContextName
value.
If no such entry can be found, the proxy forwarding application should follow the procedure described in RFC 3413 RFC3413, section 3.5.1.1, item (2). This procedure states that the snmpProxyDrops counter RFC3418 is incremented, and that a Response-PDU is generated by calling the Dispatcher using the returnResponsePdu abstract service interface.
The SNMP Community MIB Module
The SNMP-COMMUNITY-MIB contains objects for mapping between community strings and version-independent SNMP message parameters. In addition, this MIB provides a mechanism for performing source address validation on incoming requests, and for selecting community strings based on target addresses for outgoing notifications. These two
features are accomplished by providing a tag in the snmpCommunityTable which selects sets of entries in the snmpTargetAddrTable RFC3413. In addition, the SNMP-COMMUNITY-MIB augments the snmpTargetAddrTable with a transport address mask value and a maximum message size value. These values are used only where explicitly stated. In cases where the snmpTargetAddrTable is used without mention of these augmenting values, the augmenting values should be ignored.
The mask value, snmpTargetAddrTMask, allows selected entries in the snmpTargetAddrTable to specify multiple addresses (rather than just a single address per entry). This would typically be used to specify a subnet in an snmpTargetAddrTable rather than just a single address. The mask value is used to select which bits of a transport address must match bits of the corresponding instance of snmpTargetAddrTAddress, in order for the transport address to match a particular entry in the snmpTargetAddrTable. The value of an instance of snmpTargetAddrTMask must always be an OCTET STRING whose length is either zero or the same as that of the corresponding instance of snmpTargetAddrTAddress.
Note that the snmpTargetAddrTMask object is only used where explicitly stated. In particular, it is not used when generating notifications (i.e., when generating notifications, entries in the snmpTargetAddrTable only specify individual addresses). If use of the snmpTargetAddrTMask object is not mentioned in text describing matching addresses in the snmpTargetAddrTable, then its value MUST be ignored.
When checking whether a transport address matches an entry in the snmpTargetAddrTable, if the value of snmpTargetAddrTMask is a zero- length OCTET STRING, the mask value is ignored, and the value of snmpTargetAddrTAddress must exactly match a transport address. Otherwise, each bit of each octet in the snmpTargetAddrTMask value corresponds to the same bit of the same octet in the snmpTargetAddrTAddress value. For bits that are set in the snmpTargetAddrTMask value (i.e., bits equal to 1), the corresponding bits in the snmpTargetAddrTAddress value must match the bits in a transport address. If all such bits match, the transport address is matched by that snmpTargetAddrTable entry. Otherwise, the transport address is not matched.
The maximum message size value, snmpTargetAddrMMS, is used to determine the maximum message size acceptable to another SNMP entity when the value cannot be determined from the protocol.
SNMP-COMMUNITY-MIB DEFINITIONS ::= BEGIN
IMPORTS
IpAddress,
MODULE-IDENTITY,
OBJECT-TYPE,
Integer32,
snmpModules
FROM SNMPv2-SMI
RowStatus,
StorageType
FROM SNMPv2-TC
SnmpAdminString,
SnmpEngineID
FROM SNMP-FRAMEWORK-MIB
SnmpTagValue,
snmpTargetAddrEntry
FROM SNMP-TARGET-MIB
MODULE-COMPLIANCE,
OBJECT-GROUP
FROM SNMPv2-CONF;
snmpCommunityMIB MODULE-IDENTITY
LAST-UPDATED "200308060000Z" -- 06 Aug 2003, midnight
ORGANIZATION "SNMPv3 Working Group"
CONTACT-INFO "WG-email: [email protected]
Subscribe: [email protected]
In msg body: subscribe snmpv3
Co-Chair: Russ Mundy
SPARTA, Inc
Postal: 7075 Samuel Morse Drive
Columbia, MD 21045
USA
EMail: [email protected]
Phone: +1 410-872-1515
Co-Chair: 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: Rob Frye
Vibrant Solutions
Postal: 2711 Prosperity Ave
Fairfax, Virginia 22031
USA
E-mail: [email protected]
Phone: +1-703-270-2000
Co-editor: David B. Levi
Nortel Networks
Postal: 3505 Kesterwood Drive
Knoxville, Tennessee 37918
E-mail: [email protected]
Phone: +1 865 686 0432
Co-editor: Shawn A. Routhier
Wind River Systems, Inc.
Postal: 500 Wind River Way
Alameda, CA 94501
E-mail: [email protected]
Phone: +1 510 749 2095
Co-editor: Bert Wijnen
Lucent Technologies
Postal: Schagen 33
3461 GL Linschoten
Netherlands
Email: [email protected]
Phone: +31-348-407-775
"
DESCRIPTION
"This MIB module defines objects to help support
coexistence between SNMPv1, SNMPv2c, and SNMPv3.
Copyright (C) The Internet Society (2003) This
version of this MIB module is part of RFC 3584;
see the RFC itself for full legal notices."
REVISION "200308060000Z" -- 06 Aug 2003
DESCRIPTION
"Updated the LAST-UPDATED, CONTACT-INFO, and REVISION
clauses and added a copyright notice to the
DESCRIPTION clause of the MIB module's
MODULE-IDENTITY invocation.
Updated the description of snmpCommunityTransportTag
to make it consistent with the rest of the document.
Updated the description of `snmpTargetAddrMMS' to
clarify that a value of 0 means that the maximum
message size is unknown.
Changed the name of 'snmpCommunityGroup' to
snmpCommunityTableGroup to avoid a name conflict
with the SNMPv2-MIB.
Updated DESCRIPTION of snmpCommunityName.
Updated DESCRIPTION of snmpTrapCommunity.
Added snmpCommunityMIBFullCompliance.
This version published as RFC 3584."
REVISION "200003060000Z" -- 6 Mar 2000
DESCRIPTION "This version published as RFC 2576."
::= { snmpModules 18 }
-- Administrative assignments ************************************
snmpCommunityMIBObjects
OBJECT IDENTIFIER ::= { snmpCommunityMIB 1 }
snmpCommunityMIBConformance
OBJECT IDENTIFIER ::= { snmpCommunityMIB 2 }
-- -- The snmpCommunityTable contains a database of community -- strings. This table provides mappings between community -- strings, and the parameters required for View-based Access -- Control. --
snmpCommunityTable OBJECT-TYPE
SYNTAX SEQUENCE OF SnmpCommunityEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The table of community strings configured in the SNMP
engine's Local Configuration Datastore (LCD)."
::= { snmpCommunityMIBObjects 1 }
snmpCommunityEntry OBJECT-TYPE
SYNTAX SnmpCommunityEntry MAX-ACCESS not-accessible STATUS current
DESCRIPTION
"Information about a particular community string."
INDEX { IMPLIED snmpCommunityIndex }
::= { snmpCommunityTable 1 }
SnmpCommunityEntry ::= SEQUENCE {
snmpCommunityIndex SnmpAdminString, snmpCommunityName OCTET STRING, snmpCommunitySecurityName SnmpAdminString, snmpCommunityContextEngineID SnmpEngineID, snmpCommunityContextName SnmpAdminString, snmpCommunityTransportTag SnmpTagValue, snmpCommunityStorageType StorageType, snmpCommunityStatus RowStatus
}
snmpCommunityIndex OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(1..32))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The unique index value of a row in this table."
::= { snmpCommunityEntry 1 }
snmpCommunityName OBJECT-TYPE
SYNTAX OCTET STRING
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The community string for which a row in this table
represents a configuration. There is no SIZE constraint
specified for this object because RFC 1157 does not
impose any explicit limitation on the length of community
strings (their size is constrained indirectly by the
SNMP message size)."
::= { snmpCommunityEntry 2 }
snmpCommunitySecurityName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(1..32))
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"A human readable string representing the corresponding
value of snmpCommunityName in a Security Model
independent format."
::= { snmpCommunityEntry 3 }
snmpCommunityContextEngineID OBJECT-TYPE
SYNTAX SnmpEngineID
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The contextEngineID indicating the location of the
context in which management information is accessed
when using the community string specified by the
corresponding instance of snmpCommunityName.
The default value is the snmpEngineID of the entity in
which this object is instantiated."
::= { snmpCommunityEntry 4 }
snmpCommunityContextName OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE(0..32))
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The context in which management information is accessed
when using the community string specified by the
corresponding instance of snmpCommunityName."
DEFVAL { H } -- the empty string
::= { snmpCommunityEntry 5 }
snmpCommunityTransportTag OBJECT-TYPE
SYNTAX SnmpTagValue
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"This object specifies a set of transport endpoints
which are used in two ways:
- to specify the transport endpoints from which an
SNMP entity will accept management requests, and
- to specify the transport endpoints to which a
notification may be sent using the community
string matching the corresponding instance of
snmpCommunityName.
In either case, if the value of this object has
zero-length, transport endpoints are not checked when
either authenticating messages containing this community
string, nor when generating notifications.
The transports identified by this object are specified
in the snmpTargetAddrTable. Entries in that table
whose snmpTargetAddrTagList contains this tag value
are identified.
If a management request containing a community string
that matches the corresponding instance of
snmpCommunityName is received on a transport endpoint
other than the transport endpoints identified by this
object the request is deemed unauthentic.
When a notification is to be sent using an entry in
this table, if the destination transport endpoint of
the notification does not match one of the transport
endpoints selected by this object, the notification
is not sent."
DEFVAL { H } -- the empty string
::= { snmpCommunityEntry 6 }
snmpCommunityStorageType OBJECT-TYPE
SYNTAX StorageType
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The storage type for this conceptual row in the
snmpCommunityTable. Conceptual rows having the value
'permanent' need not allow write-access to any
columnar object in the row."
::= { snmpCommunityEntry 7 }
snmpCommunityStatus OBJECT-TYPE
SYNTAX RowStatus
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The status of this conceptual row in the
snmpCommunityTable.
An entry in this table is not qualified for activation
until instances of all corresponding columns have been
initialized, either through default values, or through
Set operations. The snmpCommunityName and
snmpCommunitySecurityName objects must be explicitly set.
There is no restriction on setting columns in this table
when the value of snmpCommunityStatus is active(1)."
::= { snmpCommunityEntry 8 }
-- -- The snmpTargetAddrExtTable --
snmpTargetAddrExtTable OBJECT-TYPE
SYNTAX SEQUENCE OF SnmpTargetAddrExtEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The table of mask and maximum message size (mms) values
associated with the snmpTargetAddrTable.
The snmpTargetAddrExtTable augments the
snmpTargetAddrTable with a transport address mask value
and a maximum message size value. The transport address
mask allows entries in the snmpTargetAddrTable to define
a set of addresses instead of just a single address.
The maximum message size value allows the maximum
message size of another SNMP entity to be configured for
use in SNMPv1 (and SNMPv2c) transactions, where the
message format does not specify a maximum message size."
::= { snmpCommunityMIBObjects 2 }
snmpTargetAddrExtEntry OBJECT-TYPE
SYNTAX SnmpTargetAddrExtEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Information about a particular mask and mms value."
AUGMENTS { snmpTargetAddrEntry }
::= { snmpTargetAddrExtTable 1 }
SnmpTargetAddrExtEntry ::= SEQUENCE {
snmpTargetAddrTMask OCTET STRING, snmpTargetAddrMMS Integer32
}
snmpTargetAddrTMask OBJECT-TYPE
SYNTAX OCTET STRING (SIZE (0..255))
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The mask value associated with an entry in the
snmpTargetAddrTable. The value of this object must
have the same length as the corresponding instance of
snmpTargetAddrTAddress, or must have length 0. An
attempt to set it to any other value will result in
an inconsistentValue error.
The value of this object allows an entry in the
snmpTargetAddrTable to specify multiple addresses.
The mask value is used to select which bits of
a transport address must match bits of the corresponding
instance of snmpTargetAddrTAddress, in order for the
transport address to match a particular entry in the
snmpTargetAddrTable. Bits which are 1 in the mask
value indicate bits in the transport address which
must match bits in the snmpTargetAddrTAddress value.
Bits which are 0 in the mask indicate bits in the
transport address which need not match. If the
length of the mask is 0, the mask should be treated
as if all its bits were 1 and its length were equal
to the length of the corresponding value of
snmpTargetAddrTable.
This object may not be modified while the value of the
corresponding instance of snmpTargetAddrRowStatus is
active(1). An attempt to set this object in this case
will result in an inconsistentValue error."
DEFVAL { H }
::= { snmpTargetAddrExtEntry 1 }
snmpTargetAddrMMS OBJECT-TYPE
SYNTAX Integer32 (0|484..2147483647)
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The maximum message size value associated with an entry
in the snmpTargetAddrTable. Note that a value of 0 means
that the maximum message size is unknown."
DEFVAL { 484 }
::= { snmpTargetAddrExtEntry 2 }
-- -- The snmpTrapAddress and snmpTrapCommunity objects are included -- in notifications that are forwarded by a proxy, which were -- originally received as SNMPv1 Trap messages. --
snmpTrapAddress OBJECT-TYPE
SYNTAX IpAddress
MAX-ACCESS accessible-for-notify
STATUS current
DESCRIPTION
"The value of the agent-addr field of a Trap PDU which
is forwarded by a proxy forwarder application using
an SNMP version other than SNMPv1. The value of this
object SHOULD contain the value of the agent-addr field
from the original Trap PDU as generated by an SNMPv1
agent."
::= { snmpCommunityMIBObjects 3 }
snmpTrapCommunity OBJECT-TYPE
SYNTAX OCTET STRING
MAX-ACCESS accessible-for-notify
STATUS current
DESCRIPTION
"The value of the community string field of an SNMPv1
message containing a Trap PDU which is forwarded by a
a proxy forwarder application using an SNMP version
other than SNMPv1. The value of this object SHOULD
contain the value of the community string field from
the original SNMPv1 message containing a Trap PDU as
generated by an SNMPv1 agent. There is no SIZE
constraint specified for this object because RFC 1157
does not impose any explicit limitation on the length
of community strings (their size is constrained
indirectly by the SNMP message size)."
::= { snmpCommunityMIBObjects 4 }
-- Conformance Information **************************************
snmpCommunityMIBCompliances OBJECT IDENTIFIER
::= { snmpCommunityMIBConformance 1 }
snmpCommunityMIBGroups OBJECT IDENTIFIER
::= { snmpCommunityMIBConformance 2 }
-- Compliance statements
snmpCommunityMIBCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for SNMP engines which
implement the SNMP-COMMUNITY-MIB."
MODULE -- this module
MANDATORY-GROUPS { snmpCommunityTableGroup }
OBJECT snmpCommunityName
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT snmpCommunitySecurityName
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT snmpCommunityContextEngineID
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT snmpCommunityContextName
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT snmpCommunityTransportTag
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT snmpCommunityStorageType
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
OBJECT snmpCommunityStatus
MIN-ACCESS read-only
DESCRIPTION "Write access is not required."
::= { snmpCommunityMIBCompliances 1 }
snmpProxyTrapForwardCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for SNMP engines which
contain a proxy forwarding application which is
capable of forwarding SNMPv1 traps using SNMPv2c
or SNMPv3."
MODULE -- this module
MANDATORY-GROUPS { snmpProxyTrapForwardGroup }
::= { snmpCommunityMIBCompliances 2 }
snmpCommunityMIBFullCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for SNMP engines which
implement the SNMP-COMMUNITY-MIB with full read-create
access."
MODULE -- this module
MANDATORY-GROUPS { snmpCommunityTableGroup }
::= { snmpCommunityMIBCompliances 3 }
snmpCommunityTableGroup OBJECT-GROUP
OBJECTS {
snmpCommunityName,
snmpCommunitySecurityName,
snmpCommunityContextEngineID,
snmpCommunityContextName,
snmpCommunityTransportTag,
snmpCommunityStorageType,
snmpCommunityStatus,
snmpTargetAddrTMask,
snmpTargetAddrMMS
}
STATUS current
DESCRIPTION
"A collection of objects providing for configuration
of community strings for SNMPv1 (and SNMPv2c) usage."
::= { snmpCommunityMIBGroups 1 }
snmpProxyTrapForwardGroup OBJECT-GROUP
OBJECTS {
snmpTrapAddress,
snmpTrapCommunity
}
STATUS current
DESCRIPTION
"Objects which are used by proxy forwarding applications
when translating traps between SNMP versions. These are
used to preserve SNMPv1-specific information when
translating to SNMPv2c or SNMPv3."
::= { snmpCommunityMIBGroups 3 }
END
Intellectual Property Statement
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 BCP-11. 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.
Acknowledgments
This document is the result of the efforts of the SNMPv3 Working Group. The design of the SNMP-COMMUNITY-MIB incorporates work done by the authors of SNMPv2*:
Jeff Case (SNMP Research, Inc.) David Harrington (Enterasys Networks) David Levi (Nortel Networks) Brian O'Keefe (Hewlett Packard) Jon Saperia (IronBridge Networks, Inc.) Steve Waldbusser (International Network Services)
Security Considerations
Although SNMPv1 and SNMPv2 do not provide any security, allowing community names to be mapped into securityName/contextName provides the ability to use view-based access control to limit the access of unsecured SNMPv1 and SNMPv2 operations. In fact, it is important for network administrators to make use of this capability in order to avoid unauthorized access to MIB data that would otherwise be secure.
When a proxy implementation translates messages between SNMPv1 (or SNMPv2c) and SNMPv3, there may be a loss of security. For example, an SNMPv3 message received using authentication and privacy which is subsequently forwarded using SNMPv1 will lose the security benefits of using authentication and privacy (also known as confidentiality). Careful configuration of proxies is required to address such situations. One approach to deal with such situations might be to use an encrypted tunnel.
There are a number of management objects defined in this MIB module with a MAX-ACCESS clause of read-write and/or read-create. Such objects may be considered sensitive or vulnerable in some network environments. The support for SET operations in a non-secure environment without proper protection can have a negative effect on network operations. These are the tables and objects and their sensitivity/vulnerability:
- The snmpCommunityTable allows creation and deletion of community
strings, which is potentially a serious security hole. Access to this table should be greatly restricted, preferably by only allowing write access using SNMPv3 VACM and USM, with authentication and privacy.
- The snmpTargetAddrExtTable contains write-able objects which may
also be considered sensitive, and so access to it should be restricted as well.
Some of the readable objects in this MIB module (i.e., objects with a MAX-ACCESS other than not-accessible) may be considered sensitive or vulnerable in some network environments. It is thus important to control even GET and/or NOTIFY access to these objects and possibly to even encrypt the values of these objects when sending them over the network via SNMP. These are the tables and objects and their sensitivity/vulnerability:
- The snmpCommunityTable has the potential to expose community
strings which provide access to more information than that which is available using the usual 'public' community string. For this reason, a security administrator may wish to limit accessibility to objects in the snmpCommunityTable, and in particular, to make it inaccessible when using the 'public' community string.
SNMP versions prior to SNMPv3 did not include adequate security. Even if the network itself is secure (for example by using IPSec), even then, there is no control as to who on the secure network is allowed to access and GET/SET (read/change/create/delete) the objects in this MIB module.
It is RECOMMENDED that implementers consider the security features as provided by the SNMPv3 framework (see RFC3410, section 8), including full support for the SNMPv3 cryptographic mechanisms (for authentication and privacy).
Further, deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED. Instead, it is RECOMMENDED to deploy SNMPv3 and to enable cryptographic security. It is then a customer/operator responsibility to ensure that the SNMP entity giving access to an instance of this MIB module is properly configured to give access to the objects only to those principals (users) that have legitimate rights to indeed GET or SET (change/create/delete) them.
References
Normative 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 C. Davin,
"Simple Network Management Protocol (SNMP)", STD 15, RFC 1157, May 1990.
RFC1212 Rose, M. and K. McCloghrie, Eds., "Concise MIB
Definitions", STD 16, RFC 1212, March 1991.
RFC1215 Rose, M., "A Convention for Defining Traps for use with
the SNMP", RFC 1215, March 1991.
RFC1303 McCloghrie, K. and M. Rose, "A Convention for Describing
SNMP-based Agents", RFC 1303, February 1992.
RFC1901 Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
"Introduction to Community-based SNMPv2", RFC 1901, January 1996.
RFC2119 Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
RFC2578 McCloghrie, K., Perkins, D. and J. Schoenwaelder,
"Structure of Management Information Version 2 (SMIv2)",
RFC 2578, STD 58, April 1999.
RFC2579 McCloghrie, K., Perkins, D. and J. Schoenwaelder,
"Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999.
RFC2580 McCloghrie, K., Perkins, D. and J. Schoenwaelder,
"Conformance Statements for SMIv2", STD 58, RFC 2580, April 1999.
RFC3411 Harrington, D., Presuhn, R. and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
December 2002.
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, "The User-Based Security
Model (USM) for Version 3 of the Simple Network
Management Protocol (SNMP)", 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., Ed., "Version 2 of the Protocol Operations
for the Simple Network Management Protocol (SNMPv2)", STD
62, RFC 3416, December 2002.
RFC3417 Presuhn, R., Ed., "Transport Mappings for Version 2 of
the Simple Network Management Protocol (SNMPv2)", STD 62, RFC 3417, December 2002.
RFC3418 Presuhn, R., Ed., "Management Information Base (MIB) for
Version 2 of the Simple Network Management Protocol
(SNMP)", STD 62, RFC 3418, December 2002.
[ASN1] Information processing systems - Open Systems
Interconnection - Specification of Abstract Syntax
Notation One (ASN.1), International Organization for
Standardization. International Standard 8824, (December,
1987).
Informative References
RFC1908 Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
"Coexistence between Version 1 and Version 2 of the
Internet-standard Network Management Framework", RFC
1908, January 1996.
RFC2089 Levi, D. and B. Wijnen, "Mapping SNMPv2 onto SNMPv1
within a bilingual SNMP agent", RFC 2089, January 1997.
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.
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. Change Log
A.1. Changes From RFC 2576
Section numbers below refer to the old section numbers from RFC 2576. Some section numbers have changed since RFC 2576.
- Added text to abstract about conversion of MIBs from SMIv1 to
SMIv2.
- Added note at end of section 1.3 that all discussion of SNMPv2 PDU
types and protocol operations applies to both SNMPv2c and SNMPv3.
- Added text at end of section 1.4 to clarify that there is no such
thing as 'SNMPv3 access to MIB data', as SNMPv3 just uses SNMPv2 PDU types and protocol operations.
- Moved section 1.4 to the beginning of section 4.
- Changed "MUST" to "SHOULD" in item (3) of the first list in
Section 2.1.1 to since unconstrained INTEGER is not actually illegal in SMIv2.
- Changed "SHOULD" to "MUST" in item (13) of the first list in
Section 2.1.1 to clarify that collecting related objects into groups is required when translating a MIB module from SMIv1 to SMIv2.
- Re-organized bullets in section 2.1.1 to improve clarity.
- Changed "SHOULD" to "MUST" in items (1) and (2) of Section 2.3
since those updates are indeed required when translating a capabilities statement from the language defined by RFC 1303 into SMIv2.
- In the second bullet of the last part of Section 3 listing the
SNMPv2 notification parameters, clarified that the snmpTrapOID parameter refers to the value portion (not the name portion) of the second variable-binding, and changed the wording in the text under bullet (1) of Section 3.2 from "the snmpTrapOID" to "the snmpTrapOID value" to emphasize this point.
- In bullet (6) of Section 3.2 emphasized that the SNMPv2 variable-
bindings do not include sysUpTime.0 an snmpTrapOID.0.
- In Section 4.2 clarified that the 'Upstream Version' refers to the
version used between the command generator or notification receiver and the proxy, and the 'Downstream Version' refers to the
version used between the proxy and the command responder or notification originator. RFC 2576 neglected to mention the notification receiver and notification originator.
- In Section 4.1.2 added text noting that SNMPv1 access to MIB data
SHOULD NOT be used when processing SNMPv2c or SNMPv3 messages and re-worded final paragraph to note that the sub-sections that follow are concerned solely with command responders that use SNMPv2 access to MIB data while processing an SNMPv1 request.
- Re-worded first bullet, section 4.2.1, to make it more readable.
- In Section 4.2.1 clarified that the error-index field must be set
to zero in a translated GetResponse-PDU with an error-status of 'tooBig' and made explicit the rationale for retrying a GetBulkRequest-PDU only once.
- Added text to the Deployment Hint in Section 4.2.2 to clarify that
different principals should be used for SNMPv1 requests and SNMPv2/v3c requests if for SNMPv1 requests a principal for which Counter64 objects are not-in-view is used.
- In Section 5.2.1 clarified that the securityName value and the
scopedPDU's contextSnmpEngineID and contextName values come from the selected entry in the snmpCommunityTable. Also clarified how maxSizeResponseScopedPDU is determined and that securityStateReference must contain the community string of the original request.
- Added Section 5.2.4 on Proxy Forwarding Of Requests.
- In Section 5.3 clarified that snmpTargetAddrTMask is to be ignored
whenever its use is not explicitly called for.
- Updated the LAST-UPDATED, CONTACT-INFO, and REVISION clauses and
added a copyright notice to the DESCRIPTION clause of the MIB module's MODULE-IDENTITY invocation.
- Added text to DESCRIPTION of snmpCommunityName and
snmpTrapCommunity to clarify why the object has no size restriction.
- Updated the description of snmpCommunityTransportTag to make it
consistent with the rest of the document.
- Updated the description of 'snmpTargetAddrMMS' to clarify that a
value of 0 means that the maximum message size is unknown.
- Changed the name of 'snmpCommunityGroup' to
'snmpCommunityTableGroup' in order to resolve a name conflict with the SNMPv2-MIB.
- Added compliance statement to SNMP-COMMUNITY-MIB for full read-
create compliance.
- Divided references into Normative References and Informative
Reference and updated them to point to current documents.
- Inserted current year into all copyright notices.
- Corrected various typographical and grammatical errors.
A.2. Changes Between RFC 1908 and RFC 2576
- Editorial changes to comply with current RFC requirements.
- Added/updated copyright statements.
- Added Intellectual Property section.
- Replaced old introduction with complete new introduction/overview.
- Added content for the Security Considerations Section.
- Updated References to current documents.
- Updated text to use current SNMP terminology.
- Added coexistence for/with SNMPv3.
- Added description for SNMPv1 and SNMPv2c Message Processing Models
and SNMPv1 and SNMPv2c Community-based Security Models.
- Added snmpCommunityMIB so that SNMPv1 and SNMPv2 community strings
can be mapped into the SNMP Version Independent parameters which can then be used for access control using the standard SNMPv3 View-based Access Control Model and the snmpVacmMIB.
- Added two MIB objects such that when an SNMPv1 notification (trap)
must be converted into an SNMPv2 notification we add those two objects in order to preserve information about the address and community of the originating SNMPv1 agent.
- Included (and extended) from RFC 2089 the SNMPv2 to SNMPv1 mapping
within a multi-lingual SNMP Engine.
- Use keywords from RFC 2119 to describe requirements for
compliance.
- Changed/added some rules for converting a MIB module from SMIv1 to
SMIv2.
- Extended and improved the description of Proxy Forwarder behaviour
when multiple SNMP versions are involved.
Editors' Addresses
Rob Frye Vibrant Solutions 2711 Prosperity Ave Fairfax, Virginia 22031 U.S.A.
Phone: +1 703 270 2000 EMail: [email protected]
David B. Levi Nortel Networks 3505 Kesterwood Drive Knoxville, TN 37918 U.S.A.
Phone: +1 865 686 0432 EMail: [email protected]
Shawn A. Routhier Wind River Systems, Inc. 500 Wind River Way Alameda, CA 94501 U.S.A.
Phone: + 1 510 749 2095 EMail: [email protected]
Bert Wijnen Lucent Technologies Schagen 33 3461 GL Linschoten Netherlands
Phone: +31 348 407 775 EMail: [email protected]
Full Copyright Statement
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Acknowledgement
Funding for the RFC Editor function is currently provided by the Internet Society.
