RFC1157

Network Working Group J. Case Request for Comments: 1157 SNMP Research Obsoletes: RFC 1098 M. Fedor

                                      Performance Systems International
                                                         M. Schoffstall
                                      Performance Systems International
                                                               J. Davin
                                    MIT Laboratory for Computer Science
                                                               May 1990

             A Simple Network Management Protocol (SNMP)

                          Table of Contents

  1. Status of this Memo ...................................    2
  2. Introduction ..........................................    2
  3. The SNMP Architecture .................................    5
  3.1 Goals of the Architecture ............................    5
  3.2 Elements of the Architecture .........................    5
  3.2.1 Scope of Management Information ....................    6
  3.2.2 Representation of Management Information ...........    6
  3.2.3 Operations Supported on Management Information .....    7
  3.2.4 Form and Meaning of Protocol Exchanges .............    8
  3.2.5 Definition of Administrative Relationships .........    8
  3.2.6 Form and Meaning of References to Managed Objects ..   12
  3.2.6.1 Resolution of Ambiguous MIB References ...........   12
  3.2.6.2 Resolution of References across MIB Versions......   12
  3.2.6.3 Identification of Object Instances ...............   12
  3.2.6.3.1 ifTable Object Type Names ......................   13
  3.2.6.3.2 atTable Object Type Names ......................   13
  3.2.6.3.3 ipAddrTable Object Type Names ..................   14
  3.2.6.3.4 ipRoutingTable Object Type Names ...............   14
  3.2.6.3.5 tcpConnTable Object Type Names .................   14
  3.2.6.3.6 egpNeighTable Object Type Names ................   15
  4. Protocol Specification ................................   16
  4.1 Elements of Procedure ................................   17
  4.1.1 Common Constructs ..................................   19
  4.1.2 The GetRequest-PDU .................................   20
  4.1.3 The GetNextRequest-PDU .............................   21
  4.1.3.1 Example of Table Traversal .......................   23
  4.1.4 The GetResponse-PDU ................................   24
  4.1.5 The SetRequest-PDU .................................   25
  4.1.6 The Trap-PDU .......................................   27
  4.1.6.1 The coldStart Trap ...............................   28
  4.1.6.2 The warmStart Trap ...............................   28
  4.1.6.3 The linkDown Trap ................................   28
  4.1.6.4 The linkUp Trap ..................................   28

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  4.1.6.5 The authenticationFailure Trap ...................   28
  4.1.6.6 The egpNeighborLoss Trap .........................   28
  4.1.6.7 The enterpriseSpecific Trap ......................   29
  5. Definitions ...........................................   30
  6. Acknowledgements ......................................   33
  7. References ............................................   34
  8. Security Considerations................................   35
  9. Authors' Addresses.....................................   35

1. Status of this Memo

  This RFC is a re-release of RFC 1098, with a changed "Status of this
  Memo" section plus a few minor typographical corrections.  This memo
  defines a simple protocol by which management information for a
  network element may be inspected or altered by logically remote
  users.  In particular, together with its companion memos which
  describe the structure of management information along with the
  management information base, these documents provide a simple,
  workable architecture and system for managing TCP/IP-based internets
  and in particular the Internet.

  The Internet Activities Board recommends that all IP and TCP
  implementations be network manageable.  This implies implementation
  of the Internet MIB (RFC-1156) and at least one of the two
  recommended management protocols SNMP (RFC-1157) or CMOT (RFC-1095).
  It should be noted that, at this time, SNMP is a full Internet
  standard and CMOT is a draft standard.  See also the Host and Gateway
  Requirements RFCs for more specific information on the applicability
  of this standard.

  Please refer to the latest edition of the "IAB Official Protocol
  Standards" RFC for current information on the state and status of
  standard Internet protocols.

  Distribution of this memo is unlimited.

2. Introduction

  As reported in RFC 1052, IAB Recommendations for the Development of
  Internet Network Management Standards [1], a two-prong strategy for
  network management of TCP/IP-based internets was undertaken.  In the
  short-term, the Simple Network Management Protocol (SNMP) was to be
  used to manage nodes in the Internet community.  In the long-term,
  the use of the OSI network management framework was to be examined.
  Two documents were produced to define the management information: RFC
  1065, which defined the Structure of Management Information (SMI)
  [2], and RFC 1066, which defined the Management Information Base
  (MIB) [3].  Both of these documents were designed so as to be

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  compatible with both the SNMP and the OSI network management
  framework.

  This strategy was quite successful in the short-term: Internet-based
  network management technology was fielded, by both the research and
  commercial communities, within a few months.  As a result of this,
  portions of the Internet community became network manageable in a
  timely fashion.

  As reported in RFC 1109, Report of the Second Ad Hoc Network
  Management Review Group [4], the requirements of the SNMP and the OSI
  network management frameworks were more different than anticipated.
  As such, the requirement for compatibility between the SMI/MIB and
  both frameworks was suspended.  This action permitted the operational
  network management framework, the SNMP, to respond to new operational
  needs in the Internet community by producing documents defining new
  MIB items.

  The IAB has designated the SNMP, SMI, and the initial Internet MIB to
  be full "Standard Protocols" with "Recommended" status.  By this
  action, the IAB recommends that all IP and TCP implementations be
  network manageable and that the implementations that are network
  manageable are expected to adopt and implement the SMI, MIB, and
  SNMP.

  As such, the current network management framework for TCP/IP- based
  internets consists of:  Structure and Identification of Management
  Information for TCP/IP-based Internets, which describes how managed
  objects contained in the MIB are defined as set forth in RFC 1155
  [5]; Management Information Base for Network Management of TCP/IP-
  based Internets, which describes the managed objects contained in the
  MIB as set forth in RFC 1156 [6]; and, the Simple Network Management
  Protocol, which defines the protocol used to manage these objects, as
  set forth in this memo.

  As reported in RFC 1052, IAB Recommendations for the Development of
  Internet Network Management Standards [1], the Internet Activities
  Board has directed the Internet Engineering Task Force (IETF) to
  create two new working groups in the area of network management.  One
  group was charged with the further specification and definition of
  elements to be included in the Management Information Base (MIB).
  The other was charged with defining the modifications to the Simple
  Network Management Protocol (SNMP) to accommodate the short-term
  needs of the network vendor and operations communities, and to align
  with the output of the MIB working group.

  The MIB working group produced two memos, one which defines a
  Structure for Management Information (SMI) [2] for use by the managed

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  objects contained in the MIB.  A second memo [3] defines the list of
  managed objects.

  The output of the SNMP Extensions working group is this memo, which
  incorporates changes to the initial SNMP definition [7] required to
  attain alignment with the output of the MIB working group.  The
  changes should be minimal in order to be consistent with the IAB's
  directive that the working groups be "extremely sensitive to the need
  to keep the SNMP simple."  Although considerable care and debate has
  gone into the changes to the SNMP which are reflected in this memo,
  the resulting protocol is not backwardly-compatible with its
  predecessor, the Simple Gateway Monitoring Protocol (SGMP) [8].
  Although the syntax of the protocol has been altered, the original
  philosophy, design decisions, and architecture remain intact.  In
  order to avoid confusion, new UDP ports have been allocated for use
  by the protocol described in this memo.

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3. The SNMP Architecture

  Implicit in the SNMP architectural model is a collection of network
  management stations and network elements.  Network management
  stations execute management applications which monitor and control
  network elements.  Network elements are devices such as hosts,
  gateways, terminal servers, and the like, which have management
  agents responsible for performing the network management functions
  requested by the network management stations.  The Simple Network
  Management Protocol (SNMP) is used to communicate management
  information between the network management stations and the agents in
  the network elements.

3.1. Goals of the Architecture

  The SNMP explicitly minimizes the number and complexity of management
  functions realized by the management agent itself.  This goal is
  attractive in at least four respects:

     (1)  The development cost for management agent software
          necessary to support the protocol is accordingly reduced.

     (2)  The degree of management function that is remotely
          supported is accordingly increased, thereby admitting
          fullest use of internet resources in the management task.

     (3)  The degree of management function that is remotely
          supported is accordingly increased, thereby imposing the
          fewest possible restrictions on the form and
          sophistication of management tools.

     (4)  Simplified sets of management functions are easily
          understood and used by developers of network management
          tools.

  A second goal of the protocol is that the functional paradigm for
  monitoring and control be sufficiently extensible to accommodate
  additional, possibly unanticipated aspects of network operation and
  management.

  A third goal is that the architecture be, as much as possible,
  independent of the architecture and mechanisms of particular hosts or
  particular gateways.

3.2. Elements of the Architecture

  The SNMP architecture articulates a solution to the network
  management problem in terms of:

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     (1)  the scope of the management information communicated by
          the protocol,

     (2)  the representation of the management information
          communicated by the protocol,

     (3)  operations on management information supported by the
          protocol,

     (4)  the form and meaning of exchanges among management
          entities,

     (5)  the definition of administrative relationships among
          management entities, and

     (6)  the form and meaning of references to management
          information.

3.2.1. Scope of Management Information

  The scope of the management information communicated by operation of
  the SNMP is exactly that represented by instances of all non-
  aggregate object types either defined in Internet-standard MIB or
  defined elsewhere according to the conventions set forth in
  Internet-standard SMI [5].

  Support for aggregate object types in the MIB is neither required for
  conformance with the SMI nor realized by the SNMP.

3.2.2. Representation of Management Information

  Management information communicated by operation of the SNMP is
  represented according to the subset of the ASN.1 language [9] that is
  specified for the definition of non-aggregate types in the SMI.

  The SGMP adopted the convention of using a well-defined subset of the
  ASN.1 language [9].  The SNMP continues and extends this tradition by
  utilizing a moderately more complex subset of ASN.1 for describing
  managed objects and for describing the protocol data units used for
  managing those objects.  In addition, the desire to ease eventual
  transition to OSI-based network management protocols led to the
  definition in the ASN.1 language of an Internet-standard Structure of
  Management Information (SMI) [5] and Management Information Base
  (MIB) [6].  The use of the ASN.1 language, was, in part, encouraged
  by the successful use of ASN.1 in earlier efforts, in particular, the
  SGMP.  The restrictions on the use of ASN.1 that are part of the SMI
  contribute to the simplicity espoused and validated by experience
  with the SGMP.

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  Also for the sake of simplicity, the SNMP uses only a subset of the
  basic encoding rules of ASN.1 [10].  Namely, all encodings use the
  definite-length form.  Further, whenever permissible, non-constructor
  encodings are used rather than constructor encodings.  This
  restriction applies to all aspects of ASN.1 encoding, both for the
  top-level protocol data units and the data objects they contain.

3.2.3. Operations Supported on Management Information

  The SNMP models all management agent functions as alterations or
  inspections of variables.  Thus, a protocol entity on a logically
  remote host (possibly the network element itself) interacts with the
  management agent resident on the network element in order to retrieve
  (get) or alter (set) variables.  This strategy has at least two
  positive consequences:

     (1)  It has the effect of limiting the number of essential
          management functions realized by the management agent to
          two:  one operation to assign a value to a specified
          configuration or other parameter and another to retrieve
          such a value.

     (2)  A second effect of this decision is to avoid introducing
          into the protocol definition support for imperative
          management commands:  the number of such commands is in
          practice ever-increasing, and the semantics of such
          commands are in general arbitrarily complex.

  The strategy implicit in the SNMP is that the monitoring of network
  state at any significant level of detail is accomplished primarily by
  polling for appropriate information on the part of the monitoring
  center(s).  A limited number of unsolicited messages (traps) guide
  the timing and focus of the polling.  Limiting the number of
  unsolicited messages is consistent with the goal of simplicity and
  minimizing the amount of traffic generated by the network management
  function.

  The exclusion of imperative commands from the set of explicitly
  supported management functions is unlikely to preclude any desirable
  management agent operation.  Currently, most commands are requests
  either to set the value of some parameter or to retrieve such a
  value, and the function of the few imperative commands currently
  supported is easily accommodated in an asynchronous mode by this
  management model.  In this scheme, an imperative command might be
  realized as the setting of a parameter value that subsequently
  triggers the desired action.  For example, rather than implementing a
  "reboot command," this action might be invoked by simply setting a
  parameter indicating the number of seconds until system reboot.

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3.2.4. Form and Meaning of Protocol Exchanges

  The communication of management information among management entities
  is realized in the SNMP through the exchange of protocol messages.
  The form and meaning of those messages is defined below in Section 4.

  Consistent with the goal of minimizing complexity of the management
  agent, the exchange of SNMP messages requires only an unreliable
  datagram service, and every message is entirely and independently
  represented by a single transport datagram.  While this document
  specifies the exchange of messages via the UDP protocol [11], the
  mechanisms of the SNMP are generally suitable for use with a wide
  variety of transport services.

3.2.5. Definition of Administrative Relationships

  The SNMP architecture admits a variety of administrative
  relationships among entities that participate in the protocol.  The
  entities residing at management stations and network elements which
  communicate with one another using the SNMP are termed SNMP
  application entities.  The peer processes which implement the SNMP,
  and thus support the SNMP application entities, are termed protocol
  entities.

  A pairing of an SNMP agent with some arbitrary set of SNMP
  application entities is called an SNMP community.  Each SNMP
  community is named by a string of octets, that is called the
  community name for said community.

  An SNMP message originated by an SNMP application entity that in fact
  belongs to the SNMP community named by the community component of
  said message is called an authentic SNMP message.  The set of rules
  by which an SNMP message is identified as an authentic SNMP message
  for a particular SNMP community is called an authentication scheme.
  An implementation of a function that identifies authentic SNMP
  messages according to one or more authentication schemes is called an
  authentication service.

  Clearly, effective management of administrative relationships among
  SNMP application entities requires authentication services that (by
  the use of encryption or other techniques) are able to identify
  authentic SNMP messages with a high degree of certainty.  Some SNMP
  implementations may wish to support only a trivial authentication
  service that identifies all SNMP messages as authentic SNMP messages.

  For any network element, a subset of objects in the MIB that pertain
  to that element is called a SNMP MIB view.  Note that the names of
  the object types represented in a SNMP MIB view need not belong to a

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  single sub-tree of the object type name space.

  An element of the set { READ-ONLY, READ-WRITE } is called an SNMP
  access mode.

  A pairing of a SNMP access mode with a SNMP MIB view is called an
  SNMP community profile.  A SNMP community profile represents
  specified access privileges to variables in a specified MIB view. For
  every variable in the MIB view in a given SNMP community profile,
  access to that variable is represented by the profile according to
  the following conventions:

     (1)  if said variable is defined in the MIB with "Access:" of
          "none," it is unavailable as an operand for any operator;

     (2)  if said variable is defined in the MIB with "Access:" of
          "read-write" or "write-only" and the access mode of the
          given profile is READ-WRITE, that variable is available
          as an operand for the get, set, and trap operations;

     (3)  otherwise, the variable is available as an operand for
          the get and trap operations.

     (4)  In those cases where a "write-only" variable is an
          operand used for the get or trap operations, the value
          given for the variable is implementation-specific.

  A pairing of a SNMP community with a SNMP community profile is called
  a SNMP access policy. An access policy represents a specified
  community profile afforded by the SNMP agent of a specified SNMP
  community to other members of that community.  All administrative
  relationships among SNMP application entities are architecturally
  defined in terms of SNMP access policies.

  For every SNMP access policy, if the network element on which the
  SNMP agent for the specified SNMP community resides is not that to
  which the MIB view for the specified profile pertains, then that
  policy is called a SNMP proxy access policy. The SNMP agent
  associated with a proxy access policy is called a SNMP proxy agent.
  While careless definition of proxy access policies can result in
  management loops, prudent definition of proxy policies is useful in
  at least two ways:

     (1)  It permits the monitoring and control of network elements
          which are otherwise not addressable using the management
          protocol and the transport protocol.  That is, a proxy
          agent may provide a protocol conversion function allowing
          a management station to apply a consistent management

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          framework to all network elements, including devices such
          as modems, multiplexors, and other devices which support
          different management frameworks.

     (2)  It potentially shields network elements from elaborate
          access control policies.  For example, a proxy agent may
          implement sophisticated access control whereby diverse
          subsets of variables within the MIB are made accessible
          to different management stations without increasing the
          complexity of the network element.

  By way of example, Figure 1 illustrates the relationship between
  management stations, proxy agents, and management agents.  In this
  example, the proxy agent is envisioned to be a normal Internet
  Network Operations Center (INOC) of some administrative domain which
  has a standard managerial relationship with a set of management
  agents.

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  +------------------+       +----------------+      +----------------+
  |  Region #1 INOC  |       |Region #2 INOC  |      |PC in Region #3 |
  |                  |       |                |      |                |
  |Domain=Region #1  |       |Domain=Region #2|      |Domain=Region #3|
  |CPU=super-mini-1  |       |CPU=super-mini-1|      |CPU=Clone-1     |
  |PCommunity=pub    |       |PCommunity=pub  |      |PCommunity=slate|
  |                  |       |                |      |                |
  +------------------+       +----------------+      +----------------+
         /|\                      /|\                     /|\
          |                        |                       |
          |                        |                       |
          |                       \|/                      |
          |               +-----------------+              |
          +-------------->| Region #3 INOC  |<-------------+
                          |                 |
                          |Domain=Region #3 |
                          |CPU=super-mini-2 |
                          |PCommunity=pub,  |
                          |         slate   |
                          |DCommunity=secret|
          +-------------->|                 |<-------------+
          |               +-----------------+              |
          |                       /|\                      |
          |                        |                       |
          |                        |                       |
         \|/                      \|/                     \|/
  +-----------------+     +-----------------+       +-----------------+
  |Domain=Region#3  |     |Domain=Region#3  |       |Domain=Region#3  |
  |CPU=router-1     |     |CPU=mainframe-1  |       |CPU=modem-1      |
  |DCommunity=secret|     |DCommunity=secret|       |DCommunity=secret|
  +-----------------+     +-----------------+       +-----------------+

  Domain:  the administrative domain of the element
  PCommunity:  the name of a community utilizing a proxy agent
  DCommunity:  the name of a direct community

                                Figure 1
                Example Network Management Configuration

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3.2.6. Form and Meaning of References to Managed Objects

  The SMI requires that the definition of a conformant management
  protocol address:

     (1)  the resolution of ambiguous MIB references,

     (2)  the resolution of MIB references in the presence multiple
          MIB versions, and

     (3)  the identification of particular instances of object
          types defined in the MIB.

3.2.6.1. Resolution of Ambiguous MIB References

  Because the scope of any SNMP operation is conceptually confined to
  objects relevant to a single network element, and because all SNMP
  references to MIB objects are (implicitly or explicitly) by unique
  variable names, there is no possibility that any SNMP reference to
  any object type defined in the MIB could resolve to multiple
  instances of that type.

3.2.6.2. Resolution of References across MIB Versions

  The object instance referred to by any SNMP operation is exactly that
  specified as part of the operation request or (in the case of a get-
  next operation) its immediate successor in the MIB as a whole.  In
  particular, a reference to an object as part of some version of the
  Internet-standard MIB does not resolve to any object that is not part
  of said version of the Internet-standard MIB, except in the case that
  the requested operation is get-next and the specified object name is
  lexicographically last among the names of all objects presented as
  part of said version of the Internet-Standard MIB.

3.2.6.3. Identification of Object Instances

  The names for all object types in the MIB are defined explicitly
  either in the Internet-standard MIB or in other documents which
  conform to the naming conventions of the SMI.  The SMI requires that
  conformant management protocols define mechanisms for identifying
  individual instances of those object types for a particular network
  element.

  Each instance of any object type defined in the MIB is identified in
  SNMP operations by a unique name called its "variable name." In
  general, the name of an SNMP variable is an OBJECT IDENTIFIER of the
  form x.y, where x is the name of a non-aggregate object type defined
  in the MIB and y is an OBJECT IDENTIFIER fragment that, in a way

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  specific to the named object type, identifies the desired instance.

  This naming strategy admits the fullest exploitation of the semantics
  of the GetNextRequest-PDU (see Section 4), because it assigns names
  for related variables so as to be contiguous in the lexicographical
  ordering of all variable names known in the MIB.

  The type-specific naming of object instances is defined below for a
  number of classes of object types.  Instances of an object type to
  which none of the following naming conventions are applicable are
  named by OBJECT IDENTIFIERs of the form x.0, where x is the name of
  said object type in the MIB definition.

  For example, suppose one wanted to identify an instance of the
  variable sysDescr The object class for sysDescr is:

            iso org dod internet mgmt mib system sysDescr
             1   3   6     1      2    1    1       1

  Hence, the object type, x, would be 1.3.6.1.2.1.1.1 to which is
  appended an instance sub-identifier of 0.  That is, 1.3.6.1.2.1.1.1.0
  identifies the one and only instance of sysDescr.

3.2.6.3.1. ifTable Object Type Names

  The name of a subnet interface, s, is the OBJECT IDENTIFIER value of
  the form i, where i has the value of that instance of the ifIndex
  object type associated with s.

  For each object type, t, for which the defined name, n, has a prefix
  of ifEntry, an instance, i, of t is named by an OBJECT IDENTIFIER of
  the form n.s, where s is the name of the subnet interface about which
  i represents information.

  For example, suppose one wanted to identify the instance of the
  variable ifType associated with interface 2.  Accordingly, ifType.2
  would identify the desired instance.

3.2.6.3.2. atTable Object Type Names

  The name of an AT-cached network address, x, is an OBJECT IDENTIFIER
  of the form 1.a.b.c.d, where a.b.c.d is the value (in the familiar
  "dot" notation) of the atNetAddress object type associated with x.

  The name of an address translation equivalence e is an OBJECT
  IDENTIFIER value of the form s.w, such that s is the value of that
  instance of the atIndex object type associated with e and such that w
  is the name of the AT-cached network address associated with e.

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  For each object type, t, for which the defined name, n, has a prefix
  of atEntry, an instance, i, of t is named by an OBJECT IDENTIFIER of
  the form n.y, where y is the name of the address translation
  equivalence about which i represents information.

  For example, suppose one wanted to find the physical address of an
  entry in the address translation table (ARP cache) associated with an
  IP address of 89.1.1.42 and interface 3.  Accordingly,
  atPhysAddress.3.1.89.1.1.42 would identify the desired instance.

3.2.6.3.3. ipAddrTable Object Type Names

  The name of an IP-addressable network element, x, is the OBJECT
  IDENTIFIER of the form a.b.c.d such that a.b.c.d is the value (in the
  familiar "dot" notation) of that instance of the ipAdEntAddr object
  type associated with x.

  For each object type, t, for which the defined name, n, has a prefix
  of ipAddrEntry, an instance, i, of t is named by an OBJECT IDENTIFIER
  of the form n.y, where y is the name of the IP-addressable network
  element about which i represents information.

  For example, suppose one wanted to find the network mask of an entry
  in the IP interface table associated with an IP address of 89.1.1.42.
  Accordingly, ipAdEntNetMask.89.1.1.42 would identify the desired
  instance.

3.2.6.3.4. ipRoutingTable Object Type Names

  The name of an IP route, x, is the OBJECT IDENTIFIER of the form
  a.b.c.d such that a.b.c.d is the value (in the familiar "dot"
  notation) of that instance of the ipRouteDest object type associated
  with x.

  For each object type, t, for which the defined name, n, has a prefix
  of ipRoutingEntry, an instance, i, of t is named by an OBJECT
  IDENTIFIER of the form n.y, where y is the name of the IP route about
  which i represents information.

  For example, suppose one wanted to find the next hop of an entry in
  the IP routing table associated  with the destination of 89.1.1.42.
  Accordingly, ipRouteNextHop.89.1.1.42 would identify the desired
  instance.

3.2.6.3.5. tcpConnTable Object Type Names

  The name of a TCP connection, x, is the OBJECT IDENTIFIER of the form
  a.b.c.d.e.f.g.h.i.j such that a.b.c.d is the value (in the familiar

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  "dot" notation) of that instance of the tcpConnLocalAddress object
  type associated with x and such that f.g.h.i is the value (in the
  familiar "dot" notation) of that instance of the tcpConnRemoteAddress
  object type associated with x and such that e is the value of that
  instance of the tcpConnLocalPort object type associated with x and
  such that j is the value of that instance of the tcpConnRemotePort
  object type associated with x.

  For each object type, t, for which the defined name, n, has a prefix
  of  tcpConnEntry, an instance, i, of t is named by an OBJECT
  IDENTIFIER of the form n.y, where y is the name of the TCP connection
  about which i represents information.

  For example, suppose one wanted to find the state of a TCP connection
  between the local address of 89.1.1.42 on TCP port 21 and the remote
  address of 10.0.0.51 on TCP port 2059.  Accordingly,
  tcpConnState.89.1.1.42.21.10.0.0.51.2059 would identify the desired
  instance.

3.2.6.3.6. egpNeighTable Object Type Names

  The name of an EGP neighbor, x, is the OBJECT IDENTIFIER of the form
  a.b.c.d such that a.b.c.d is the value (in the familiar "dot"
  notation) of that instance of the egpNeighAddr object type associated
  with x.

  For each object type, t, for which the defined name, n, has a prefix
  of egpNeighEntry, an instance, i, of t is named by an OBJECT
  IDENTIFIER of the form n.y, where y is the name of the EGP neighbor
  about which i represents information.

  For example, suppose one wanted to find the neighbor state for the IP
  address of 89.1.1.42.  Accordingly, egpNeighState.89.1.1.42 would
  identify the desired instance.

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4. Protocol Specification

  The network management protocol is an application protocol by which
  the variables of an agent's MIB may be inspected or altered.

  Communication among protocol entities is accomplished by the exchange
  of messages, each of which is entirely and independently represented
  within a single UDP datagram using the basic encoding rules of ASN.1
  (as discussed in Section 3.2.2).  A message consists of a version
  identifier, an SNMP community name, and a protocol data unit (PDU).
  A protocol entity receives messages at UDP port 161 on the host with
  which it is associated for all messages except for those which report
  traps (i.e., all messages except those which contain the Trap-PDU).
  Messages which report traps should be received on UDP port 162 for
  further processing.  An implementation of this protocol need not
  accept messages whose length exceeds 484 octets.  However, it is
  recommended that implementations support larger datagrams whenever
  feasible.

  It is mandatory that all implementations of the SNMP support the five
  PDUs:  GetRequest-PDU, GetNextRequest-PDU, GetResponse-PDU,
  SetRequest-PDU, and Trap-PDU.

   RFC1157-SNMP DEFINITIONS ::= BEGIN

    IMPORTS
         ObjectName, ObjectSyntax, NetworkAddress, IpAddress, TimeTicks
                 FROM RFC1155-SMI;

    -- top-level message

            Message ::=
                    SEQUENCE {
                         version        -- version-1 for this RFC
                            INTEGER {
                                version-1(0)
                            },

                        community      -- community name
                            OCTET STRING,

                        data           -- e.g., PDUs if trivial
                            ANY        -- authentication is being used
                    }

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    -- protocol data units

            PDUs ::=
                    CHOICE {
                        get-request
                            GetRequest-PDU,

                        get-next-request
                            GetNextRequest-PDU,

                        get-response
                            GetResponse-PDU,

                        set-request
                            SetRequest-PDU,

                        trap
                            Trap-PDU
                         }

    -- the individual PDUs and commonly used
    -- data types will be defined later

    END

4.1. Elements of Procedure

  This section describes the actions of a protocol entity implementing
  the SNMP. Note, however, that it is not intended to constrain the
  internal architecture of any conformant implementation.

  In the text that follows, the term transport address is used.  In the
  case of the UDP, a transport address consists of an IP address along
  with a UDP port.  Other transport services may be used to support the
  SNMP.  In these cases, the definition of a transport address should
  be made accordingly.

  The top-level actions of a protocol entity which generates a message
  are as follows:

       (1)  It first constructs the appropriate PDU, e.g., the
            GetRequest-PDU, as an ASN.1 object.

       (2)  It then passes this ASN.1 object along with a community
            name its source transport address and the destination
            transport address, to the service which implements the
            desired authentication scheme.  This authentication

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            service returns another ASN.1 object.

       (3)  The protocol entity then constructs an ASN.1 Message
            object, using the community name and the resulting ASN.1
            object.

       (4)  This new ASN.1 object is then serialized, using the basic
            encoding rules of ASN.1, and then sent using a transport
            service to the peer protocol entity.

  Similarly, the top-level actions of a protocol entity which receives
  a message are as follows:

       (1)  It performs a rudimentary parse of the incoming datagram
            to build an ASN.1 object corresponding to an ASN.1
            Message object. If the parse fails, it discards the
            datagram and performs no further actions.

       (2)  It then verifies the version number of the SNMP message.
            If there is a mismatch, it discards the datagram and
            performs no further actions.

       (3)  The protocol entity then passes the community name and
            user data found in the ASN.1 Message object, along with
            the datagram's source and destination transport addresses
            to the service which implements the desired
            authentication scheme.  This entity returns another ASN.1
            object, or signals an authentication failure.  In the
            latter case, the protocol entity notes this failure,
            (possibly) generates a trap, and discards the datagram
            and performs no further actions.

       (4)  The protocol entity then performs a rudimentary parse on
            the ASN.1 object returned from the authentication service
            to build an ASN.1 object corresponding to an ASN.1 PDUs
            object.  If the parse fails, it discards the datagram and
            performs no further actions.  Otherwise, using the named
            SNMP community, the appropriate profile is selected, and
            the PDU is processed accordingly.  If, as a result of
            this processing, a message is returned then the source
            transport address that the response message is sent from
            shall be identical to the destination transport address
            that the original request message was sent to.

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4.1.1. Common Constructs

  Before introducing the six PDU types of the protocol, it is
  appropriate to consider some of the ASN.1 constructs used frequently:

                 -- request/response information

                 RequestID ::=
                         INTEGER

                 ErrorStatus ::=
                         INTEGER {
                             noError(0),
                             tooBig(1),
                             noSuchName(2),
                             badValue(3),
                             readOnly(4)
                             genErr(5)
                         }

                 ErrorIndex ::=
                         INTEGER

                 -- variable bindings

                 VarBind ::=
                         SEQUENCE {
                             name
                                 ObjectName,

                             value
                                 ObjectSyntax
                         }

                 VarBindList ::=
                         SEQUENCE OF
                             VarBind

  RequestIDs are used to distinguish among outstanding requests.  By
  use of the RequestID, an SNMP application entity can correlate
  incoming responses with outstanding requests.  In cases where an
  unreliable datagram service is being used, the RequestID also
  provides a simple means of identifying messages duplicated by the
  network.

  A non-zero instance of ErrorStatus is used to indicate that an

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  exception occurred while processing a request.  In these cases,
  ErrorIndex may provide additional information by indicating which
  variable in a list caused the exception.

  The term variable refers to an instance of a managed object.  A
  variable binding, or VarBind, refers to the pairing of the name of a
  variable to the variable's value.  A VarBindList is a simple list of
  variable names and corresponding values.  Some PDUs are concerned
  only with the name of a variable and not its value (e.g., the
  GetRequest-PDU).  In this case, the value portion of the binding is
  ignored by the protocol entity.  However, the value portion must
  still have valid ASN.1 syntax and encoding.  It is recommended that
  the ASN.1 value NULL be used for the value portion of such bindings.

4.1.2. The GetRequest-PDU

            The form of the GetRequest-PDU is:
                 GetRequest-PDU ::=
                     [0]
                         IMPLICIT SEQUENCE {
                             request-id
                                 RequestID,

                             error-status        -- always 0
                                 ErrorStatus,

                             error-index         -- always 0
                                 ErrorIndex,

                             variable-bindings
                                 VarBindList
                         }

  The GetRequest-PDU is generated by a protocol entity only at the
  request of its SNMP application entity.

  Upon receipt of the GetRequest-PDU, the receiving protocol entity
  responds according to any applicable rule in the list below:

       (1)  If, for any object named in the variable-bindings field,
            the object's name does not exactly match the name of some
            object available for get operations in the relevant MIB
            view, then the receiving entity sends to the originator
            of the received message the GetResponse-PDU of identical
            form, except that the value of the error-status field is
            noSuchName, and the value of the error-index field is the
            index of said object name component in the received

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            message.

       (2)  If, for any object named in the variable-bindings field,
            the object is an aggregate type (as defined in the SMI),
            then the receiving entity sends to the originator of the
            received message the GetResponse-PDU of identical form,
            except that the value of the error-status field is
            noSuchName, and the value of the error-index field is the
            index of said object name component in the received
            message.

       (3)  If the size of the GetResponse-PDU generated as described
            below would exceed a local limitation, then the receiving
            entity sends to the originator of the received message
            the GetResponse-PDU of identical form, except that the
            value of the error-status field is tooBig, and the value
            of the error-index field is zero.

       (4)  If, for any object named in the variable-bindings field,
            the value of the object cannot be retrieved for reasons
            not covered by any of the foregoing rules, then the
            receiving entity sends to the originator of the received
            message the GetResponse-PDU of identical form, except
            that the value of the error-status field is genErr and
            the value of the error-index field is the index of said
            object name component in the received message.

  If none of the foregoing rules apply, then the receiving protocol
  entity sends to the originator of the received message the
  GetResponse-PDU such that, for each object named in the variable-
  bindings field of the received message, the corresponding component
  of the GetResponse-PDU represents the name and value of that
  variable.  The value of the error- status field of the GetResponse-
  PDU is noError and the value of the error-index field is zero.  The
  value of the request-id field of the GetResponse-PDU is that of the
  received message.

4.1.3. The GetNextRequest-PDU

  The form of the GetNextRequest-PDU is identical to that of the
  GetRequest-PDU except for the indication of the PDU type.  In the
  ASN.1 language:

                 GetNextRequest-PDU ::=
                     [1]
                         IMPLICIT SEQUENCE {
                             request-id
                                 RequestID,

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                             error-status        -- always 0
                                 ErrorStatus,

                             error-index         -- always 0
                                 ErrorIndex,

                             variable-bindings
                                 VarBindList
                         }

  The GetNextRequest-PDU is generated by a protocol entity only at the
  request of its SNMP application entity.

  Upon receipt of the GetNextRequest-PDU, the receiving protocol entity
  responds according to any applicable rule in the list below:

       (1)  If, for any object name in the variable-bindings field,
            that name does not lexicographically precede the name of
            some object available for get operations in the relevant
            MIB view, then the receiving entity sends to the
            originator of the received message the GetResponse-PDU of
            identical form, except that the value of the error-status
            field is noSuchName, and the value of the error-index
            field is the index of said object name component in the
            received message.

       (2)  If the size of the GetResponse-PDU generated as described
            below would exceed a local limitation, then the receiving
            entity sends to the originator of the received message
            the GetResponse-PDU of identical form, except that the
            value of the error-status field is tooBig, and the value
            of the error-index field is zero.

       (3)  If, for any object named in the variable-bindings field,
            the value of the lexicographical successor to the named
            object cannot be retrieved for reasons not covered by any
            of the foregoing rules, then the receiving entity sends
            to the originator of the received message the
            GetResponse-PDU of identical form, except that the value
            of the error-status field is genErr and the value of the
            error-index field is the index of said object name
            component in the received message.

  If none of the foregoing rules apply, then the receiving protocol
  entity sends to the originator of the received message the
  GetResponse-PDU such that, for each name in the variable-bindings
  field of the received message, the corresponding component of the

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  GetResponse-PDU represents the name and value of that object whose
  name is, in the lexicographical ordering of the names of all objects
  available for get operations in the relevant MIB view, together with
  the value of the name field of the given component, the immediate
  successor to that value.  The value of the error-status field of the
  GetResponse-PDU is noError and the value of the errorindex field is
  zero.  The value of the request-id field of the GetResponse-PDU is
  that of the received message.

4.1.3.1. Example of Table Traversal

  One important use of the GetNextRequest-PDU is the traversal of
  conceptual tables of information within the MIB. The semantics of
  this type of SNMP message, together with the protocol-specific
  mechanisms for identifying individual instances of object types in
  the MIB, affords  access to related objects in the MIB as if they
  enjoyed a tabular organization.

  By the SNMP exchange sketched below, an SNMP application entity might
  extract the destination address and next hop gateway for each entry
  in the routing table of a particular network element. Suppose that
  this routing table has three entries:

        Destination                     NextHop         Metric

        10.0.0.99                       89.1.1.42       5
        9.1.2.3                         99.0.0.3        3
        10.0.0.51                       89.1.1.42       5

  The management station sends to the SNMP agent a GetNextRequest-PDU
  containing the indicated OBJECT IDENTIFIER values as the requested
  variable names:

  GetNextRequest ( ipRouteDest, ipRouteNextHop, ipRouteMetric1 )

  The SNMP agent responds with a GetResponse-PDU:

                GetResponse (( ipRouteDest.9.1.2.3 =  "9.1.2.3" ),
                        ( ipRouteNextHop.9.1.2.3 = "99.0.0.3" ),
                        ( ipRouteMetric1.9.1.2.3 = 3 ))

  The management station continues with:

                GetNextRequest ( ipRouteDest.9.1.2.3,
                        ipRouteNextHop.9.1.2.3,

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                        ipRouteMetric1.9.1.2.3 )

  The SNMP agent responds:

                GetResponse (( ipRouteDest.10.0.0.51 = "10.0.0.51" ),
                        ( ipRouteNextHop.10.0.0.51 = "89.1.1.42" ),
                        ( ipRouteMetric1.10.0.0.51 = 5 ))

  The management station continues with:

                GetNextRequest ( ipRouteDest.10.0.0.51,
                        ipRouteNextHop.10.0.0.51,
                        ipRouteMetric1.10.0.0.51 )

  The SNMP agent responds:

                GetResponse (( ipRouteDest.10.0.0.99 = "10.0.0.99" ),
                        ( ipRouteNextHop.10.0.0.99 = "89.1.1.42" ),
                        ( ipRouteMetric1.10.0.0.99 = 5 ))

  The management station continues with:

                GetNextRequest ( ipRouteDest.10.0.0.99,
                        ipRouteNextHop.10.0.0.99,
                        ipRouteMetric1.10.0.0.99 )

  As there are no further entries in the table, the SNMP agent returns
  those objects that are next in the lexicographical ordering of the
  known object names.  This response signals the end of the routing
  table to the management station.

4.1.4. The GetResponse-PDU

  The form of the GetResponse-PDU is identical to that of the
  GetRequest-PDU except for the indication of the PDU type.  In the
  ASN.1 language:

                 GetResponse-PDU ::=
                     [2]
                         IMPLICIT SEQUENCE {
                             request-id
                                 RequestID,

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                             error-status
                                 ErrorStatus,

                             error-index
                                 ErrorIndex,

                             variable-bindings
                                 VarBindList
                         }

  The GetResponse-PDU is generated by a protocol entity only upon
  receipt of the GetRequest-PDU, GetNextRequest-PDU, or SetRequest-PDU,
  as described elsewhere in this document.

  Upon receipt of the GetResponse-PDU, the receiving protocol entity
  presents its contents to its SNMP application entity.

4.1.5. The SetRequest-PDU

  The form of the SetRequest-PDU is identical to that of the
  GetRequest-PDU except for the indication of the PDU type.  In the
  ASN.1 language:

                 SetRequest-PDU ::=
                     [3]
                         IMPLICIT SEQUENCE {
                             request-id
                                 RequestID,

                             error-status        -- always 0
                                 ErrorStatus,

                             error-index         -- always 0
                                 ErrorIndex,

                             variable-bindings
                                 VarBindList
                         }

  The SetRequest-PDU is generated by a protocol entity only at the
  request of its SNMP application entity.

  Upon receipt of the SetRequest-PDU, the receiving entity responds
  according to any applicable rule in the list below:

       (1)  If, for any object named in the variable-bindings field,

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            the object is not available for set operations in the
            relevant MIB view, then the receiving entity sends to the
            originator of the received message the GetResponse-PDU of
            identical form, except that the value of the error-status
            field is noSuchName, and the value of the error-index
            field is the index of said object name component in the
            received message.

       (2)  If, for any object named in the variable-bindings field,
            the contents of the value field does not, according to
            the ASN.1 language, manifest a type, length, and value
            that is consistent with that required for the variable,
            then the receiving entity sends to the originator of the
            received message the GetResponse-PDU of identical form,
            except that the value of the error-status field is
            badValue, and the value of the error-index field is the
            index of said object name in the received message.

       (3)  If the size of the Get Response type message generated as
            described below would exceed a local limitation, then the
            receiving entity sends to the originator of the received
            message the GetResponse-PDU of identical form, except
            that the value of the error-status field is tooBig, and
            the value of the error-index field is zero.

       (4)  If, for any object named in the variable-bindings field,
            the value of the named object cannot be altered for
            reasons not covered by any of the foregoing rules, then
            the receiving entity sends to the originator of the
            received message the GetResponse-PDU of identical form,
            except that the value of the error-status field is genErr
            and the value of the error-index field is the index of
            said object name component in the received message.

  If none of the foregoing rules apply, then for each object named in
  the variable-bindings field of the received message, the
  corresponding value is assigned to the variable.  Each variable
  assignment specified by the SetRequest-PDU should be effected as if
  simultaneously set with respect to all other assignments specified in
  the same message.

  The receiving entity then sends to the originator of the received
  message the GetResponse-PDU of identical form except that the value
  of the error-status field of the generated message is noError and the
  value of the error-index field is zero.

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4.1.6. The Trap-PDU

  The form of the Trap-PDU is:

    Trap-PDU ::=
        [4]

             IMPLICIT SEQUENCE {
                enterprise          -- type of object generating
                                    -- trap, see sysObjectID in [5]
                    OBJECT IDENTIFIER,

                agent-addr          -- address of object generating
                    NetworkAddress, -- trap

                generic-trap        -- generic trap type
                    INTEGER {
                        coldStart(0),
                        warmStart(1),
                        linkDown(2),
                        linkUp(3),
                        authenticationFailure(4),
                        egpNeighborLoss(5),
                        enterpriseSpecific(6)
                    },

                specific-trap     -- specific code, present even
                    INTEGER,      -- if generic-trap is not
                                  -- enterpriseSpecific

                time-stamp        -- time elapsed between the last
                  TimeTicks,      -- (re)initialization of the network
                                  -- entity and the generation of the
                                     trap

                variable-bindings   -- "interesting" information
                     VarBindList
            }

  The Trap-PDU is generated by a protocol entity only at the request of
  the SNMP application entity.  The means by which an SNMP application
  entity selects the destination addresses of the SNMP application
  entities is implementation-specific.

  Upon receipt of the Trap-PDU, the receiving protocol entity presents
  its contents to its SNMP application entity.

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  The significance of the variable-bindings component of the Trap-PDU
  is implementation-specific.

  Interpretations of the value of the generic-trap field are:

4.1.6.1. The coldStart Trap

  A coldStart(0) trap signifies that the sending protocol entity is
  reinitializing itself such that the agent's configuration or the
  protocol entity implementation may be altered.

4.1.6.2. The warmStart Trap

  A warmStart(1) trap signifies that the sending protocol entity is
  reinitializing itself such that neither the agent configuration nor
  the protocol entity implementation is altered.

4.1.6.3. The linkDown Trap

  A linkDown(2) trap signifies that the sending protocol entity
  recognizes a failure in one of the communication links represented in
  the agent's configuration.

  The Trap-PDU of type linkDown contains as the first element of its
  variable-bindings, the name and value of the ifIndex instance for the
  affected interface.

4.1.6.4. The linkUp Trap

  A linkUp(3) trap signifies that the sending protocol entity
  recognizes that one of the communication links represented in the
  agent's configuration has come up.

  The Trap-PDU of type linkUp contains as the first element of its
  variable-bindings, the name and value of the ifIndex instance for the
  affected interface.

4.1.6.5. The authenticationFailure Trap

  An authenticationFailure(4) trap signifies that the sending protocol
  entity is the addressee of a protocol message that is not properly
  authenticated.  While implementations of the SNMP must be capable of
  generating this trap, they must also be capable of suppressing the
  emission of such traps via an implementation-specific mechanism.

4.1.6.6. The egpNeighborLoss Trap

  An egpNeighborLoss(5) trap signifies that an EGP neighbor for whom

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RFC 1157 SNMP May 1990

  the sending protocol entity was an EGP peer has been marked down and
  the peer relationship no longer obtains.

  The Trap-PDU of type egpNeighborLoss contains as the first element of
  its variable-bindings, the name and value of the egpNeighAddr
  instance for the affected neighbor.

4.1.6.7. The enterpriseSpecific Trap

  A enterpriseSpecific(6) trap signifies that the sending protocol
  entity recognizes that some enterprise-specific event has occurred.
  The specific-trap field identifies the particular trap which
  occurred.

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RFC 1157 SNMP May 1990

5. Definitions

    RFC1157-SNMP DEFINITIONS ::= BEGIN

     IMPORTS
         ObjectName, ObjectSyntax, NetworkAddress, IpAddress, TimeTicks
             FROM RFC1155-SMI;

         -- top-level message

         Message ::=
                 SEQUENCE {
                     version          -- version-1 for this RFC
                         INTEGER {
                             version-1(0)
                         },

                     community        -- community name
                         OCTET STRING,

                     data             -- e.g., PDUs if trivial
                         ANY          -- authentication is being used
                 }

         -- protocol data units

         PDUs ::=
                 CHOICE {
                             get-request
                                 GetRequest-PDU,

                             get-next-request
                                 GetNextRequest-PDU,

                             get-response
                                 GetResponse-PDU,

                             set-request
                                 SetRequest-PDU,

                             trap
                                 Trap-PDU
                         }

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         -- PDUs

         GetRequest-PDU ::=
             [0]
                 IMPLICIT PDU

         GetNextRequest-PDU ::=
             [1]
                 IMPLICIT PDU

         GetResponse-PDU ::=
             [2]
                 IMPLICIT PDU

         SetRequest-PDU ::=
             [3]
                 IMPLICIT PDU

         PDU ::=
                 SEQUENCE {
                    request-id
                         INTEGER,

                     error-status      -- sometimes ignored
                         INTEGER {
                             noError(0),
                             tooBig(1),
                             noSuchName(2),
                             badValue(3),
                             readOnly(4),
                             genErr(5)
                         },

                     error-index       -- sometimes ignored
                        INTEGER,

                     variable-bindings -- values are sometimes ignored
                         VarBindList
                 }

         Trap-PDU ::=
             [4]
                IMPLICIT SEQUENCE {
                     enterprise        -- type of object generating
                                       -- trap, see sysObjectID in [5]

                         OBJECT IDENTIFIER,

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                     agent-addr        -- address of object generating
                         NetworkAddress, -- trap

                     generic-trap      -- generic trap type
                         INTEGER {
                             coldStart(0),
                             warmStart(1),
                             linkDown(2),
                             linkUp(3),
                             authenticationFailure(4),
                             egpNeighborLoss(5),
                             enterpriseSpecific(6)
                         },

                     specific-trap  -- specific code, present even
                         INTEGER,   -- if generic-trap is not
                                    -- enterpriseSpecific

                     time-stamp     -- time elapsed between the last
                         TimeTicks, -- (re)initialization of the
                                       network
                                    -- entity and the generation of the
                                       trap

                      variable-bindings -- "interesting" information
                         VarBindList
                 }

         -- variable bindings

         VarBind ::=
                 SEQUENCE {
                     name
                         ObjectName,

                     value
                         ObjectSyntax
                 }

        VarBindList ::=
                 SEQUENCE OF
                    VarBind

        END

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6. Acknowledgements

  This memo was influenced by the IETF SNMP Extensions working
  group:

            Karl Auerbach, Epilogue Technology
            K. Ramesh Babu, Excelan
            Amatzia Ben-Artzi, 3Com/Bridge
            Lawrence Besaw, Hewlett-Packard
            Jeffrey D. Case, University of Tennessee at Knoxville
            Anthony Chung, Sytek
            James Davidson, The Wollongong Group
            James R. Davin, MIT Laboratory for Computer Science
            Mark S. Fedor, NYSERNet
            Phill Gross, The MITRE Corporation
            Satish Joshi, ACC
            Dan Lynch, Advanced Computing Environments
            Keith McCloghrie, The Wollongong Group
            Marshall T. Rose, The Wollongong Group (chair)
            Greg Satz, cisco
            Martin Lee Schoffstall, Rensselaer Polytechnic Institute
            Wengyik Yeong, NYSERNet

Case, Fedor, Schoffstall, & Davin

RFC 1157 SNMP May 1990

7. References

  [1] Cerf, V., "IAB Recommendations for the Development of
      Internet Network Management Standards", RFC 1052, IAB,
      April 1988.

  [2] Rose, M., and K. McCloghrie, "Structure and Identification
      of Management Information for TCP/IP-based internets",
      RFC 1065, TWG, August 1988.

  [3] McCloghrie, K., and M. Rose, "Management Information Base
      for Network Management of TCP/IP-based internets",
      RFC 1066, TWG, August 1988.

  [4] Cerf, V., "Report of the Second Ad Hoc Network Management
      Review Group", RFC 1109, IAB, August 1989.

  [5] Rose, M., and K. McCloghrie, "Structure and Identification
      of Management Information for TCP/IP-based Internets",
      RFC 1155, Performance Systems International and Hughes LAN
      Systems, May 1990.

  [6] McCloghrie, K., and M. Rose, "Management Information Base
      for Network Management of TCP/IP-based Internets",
      RFC 1156, Hughes LAN Systems and Performance Systems
      International, May 1990.

  [7] Case, J., M. Fedor, M. Schoffstall, and J. Davin,
      "A Simple Network Management Protocol", Internet
      Engineering Task Force working note, Network Information
      Center, SRI International, Menlo Park, California,
      March 1988.

  [8] Davin, J., J. Case, M. Fedor, and M. Schoffstall,
      "A Simple Gateway Monitoring Protocol", RFC 1028,
      Proteon, University of Tennessee at Knoxville,
      Cornell University, and Rensselaer Polytechnic
      Institute, November 1987.

  [9] Information processing systems - Open Systems
      Interconnection, "Specification of Abstract Syntax
      Notation One (ASN.1)", International Organization for
      Standardization, International Standard 8824,
      December 1987.

 [10] Information processing systems - Open Systems
      Interconnection, "Specification of Basic Encoding Rules
      for Abstract Notation One (ASN.1)", International

Case, Fedor, Schoffstall, & Davin

RFC 1157 SNMP May 1990

      Organization for Standardization, International Standard
      8825, December 1987.

 [11] Postel, J., "User Datagram Protocol", RFC 768,
      USC/Information Sciences Institute, November 1980.

Security Considerations

  Security issues are not discussed in this memo.

Authors' Addresses

  Jeffrey D. Case
  SNMP Research
  P.O. Box 8593
  Knoxville, TN 37996-4800

  Phone:  (615) 573-1434

  Email:  [email protected]

  Mark Fedor
  Performance Systems International
  Rensselaer Technology Park
  125 Jordan Road
  Troy, NY 12180

  Phone:  (518) 283-8860

  Email:  [email protected]

  Martin Lee Schoffstall
  Performance Systems International
  Rensselaer Technology Park
  165 Jordan Road
  Troy, NY 12180

  Phone:  (518) 283-8860

  Email:  [email protected]

Case, Fedor, Schoffstall, & Davin

RFC 1157 SNMP May 1990

  James R. Davin
  MIT Laboratory for Computer Science, NE43-507
  545 Technology Square
  Cambridge, MA 02139

  Phone:  (617) 253-6020

  EMail:  [email protected]

Case, Fedor, Schoffstall, & Davin