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rfc: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

Case, Fedor, Schoffstall, & Davin [Page 1] RFC 1157 SNMP May 1990

 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

Case, Fedor, Schoffstall, & Davin [Page 2] RFC 1157 SNMP May 1990

 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

Case, Fedor, Schoffstall, & Davin [Page 3] RFC 1157 SNMP May 1990

 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.

Case, Fedor, Schoffstall, & Davin [Page 4] RFC 1157 SNMP May 1990

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:

Case, Fedor, Schoffstall, & Davin [Page 5] RFC 1157 SNMP May 1990

    (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.

Case, Fedor, Schoffstall, & Davin [Page 6] RFC 1157 SNMP May 1990

 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.

Case, Fedor, Schoffstall, & Davin [Page 7] RFC 1157 SNMP May 1990

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

Case, Fedor, Schoffstall, & Davin [Page 8] RFC 1157 SNMP May 1990

 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

Case, Fedor, Schoffstall, & Davin [Page 9] RFC 1157 SNMP May 1990

         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.

Case, Fedor, Schoffstall, & Davin [Page 10] RFC 1157 SNMP May 1990

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

Case, Fedor, Schoffstall, & Davin [Page 11] RFC 1157 SNMP May 1990

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

Case, Fedor, Schoffstall, & Davin [Page 12] RFC 1157 SNMP May 1990

 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.

Case, Fedor, Schoffstall, & Davin [Page 13] RFC 1157 SNMP May 1990

 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

Case, Fedor, Schoffstall, & Davin [Page 14] RFC 1157 SNMP May 1990

 "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.

Case, Fedor, Schoffstall, & Davin [Page 15] RFC 1157 SNMP May 1990

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;
  1. - 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
                   }

Case, Fedor, Schoffstall, & Davin [Page 16] RFC 1157 SNMP May 1990

  1. - 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
                        }
  1. - the individual PDUs and commonly used
  2. - 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

Case, Fedor, Schoffstall, & Davin [Page 17] RFC 1157 SNMP May 1990

           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.

Case, Fedor, Schoffstall, & Davin [Page 18] RFC 1157 SNMP May 1990

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:
  1. - request/response information
                RequestID ::=
                        INTEGER
                ErrorStatus ::=
                        INTEGER {
                            noError(0),
                            tooBig(1),
                            noSuchName(2),
                            badValue(3),
                            readOnly(4)
                            genErr(5)
                        }
                ErrorIndex ::=
                        INTEGER
  1. - 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

Case, Fedor, Schoffstall, & Davin [Page 19] RFC 1157 SNMP May 1990

 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

Case, Fedor, Schoffstall, & Davin [Page 20] RFC 1157 SNMP May 1990

           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,

Case, Fedor, Schoffstall, & Davin [Page 21] RFC 1157 SNMP May 1990

                            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

Case, Fedor, Schoffstall, & Davin [Page 22] RFC 1157 SNMP May 1990

 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,

Case, Fedor, Schoffstall, & Davin [Page 23] RFC 1157 SNMP May 1990

                       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,

Case, Fedor, Schoffstall, & Davin [Page 24] RFC 1157 SNMP May 1990

                            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,

Case, Fedor, Schoffstall, & Davin [Page 25] RFC 1157 SNMP May 1990

           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.

Case, Fedor, Schoffstall, & Davin [Page 26] RFC 1157 SNMP May 1990

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.

Case, Fedor, Schoffstall, & Davin [Page 27] RFC 1157 SNMP May 1990

 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

Case, Fedor, Schoffstall, & Davin [Page 28] 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.

Case, Fedor, Schoffstall, & Davin [Page 29] RFC 1157 SNMP May 1990

5. Definitions

   RFC1157-SNMP DEFINITIONS ::= BEGIN
    IMPORTS
        ObjectName, ObjectSyntax, NetworkAddress, IpAddress, TimeTicks
            FROM RFC1155-SMI;
  1. - 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
                }
  1. - 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
                        }

Case, Fedor, Schoffstall, & Davin [Page 30] RFC 1157 SNMP May 1990

  1. - 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,

Case, Fedor, Schoffstall, & Davin [Page 31] RFC 1157 SNMP May 1990

                    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
                }
  1. - variable bindings
        VarBind ::=
                SEQUENCE {
                    name
                        ObjectName,
                    value
                        ObjectSyntax
                }
       VarBindList ::=
                SEQUENCE OF
                   VarBind
       END

Case, Fedor, Schoffstall, & Davin [Page 32] RFC 1157 SNMP May 1990

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 [Page 33] 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 [Page 34] 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:  case@CS.UTK.EDU
 Mark Fedor
 Performance Systems International
 Rensselaer Technology Park
 125 Jordan Road
 Troy, NY 12180
 Phone:  (518) 283-8860
 Email:  fedor@patton.NYSER.NET
 Martin Lee Schoffstall
 Performance Systems International
 Rensselaer Technology Park
 165 Jordan Road
 Troy, NY 12180
 Phone:  (518) 283-8860
 Email:  schoff@NISC.NYSER.NET

Case, Fedor, Schoffstall, & Davin [Page 35] 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:  jrd@ptt.lcs.mit.edu

Case, Fedor, Schoffstall, & Davin [Page 36]

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