RFC1525

From RFC-Wiki

Network Working Group E. Decker Request for Comments: 1525 cisco Systems, Inc. Obsoletes: 1286 K. McCloghrie Category: Standards Track Hughes LAN Systems, Inc.

                                                         P. Langille
                                                                 DEC
                                                      A. Rijsinghani
                                                                 DEC
                                                      September 1993
               Definitions of Managed Objects for
                     Source Routing Bridges

Status of this Memo

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

Introduction

This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in TCP/IP based internets. In particular, it defines objects for managing source routing and source routing transparent bridges. These bridges are also required to implement relevant groups in the Bridge MIB [6].

This MIB supersedes the dot1dSr group of objects published in an earlier version of the Bridge MIB, RFC 1286. Changes have primarily been made to track changes in the IEEE 802.5M SRT Addendum to the IEEE 802.1D Standard for MAC Bridges.

The Network Management Framework

The Internet-standard Network Management Framework consists of three components. They are:

  o    STD 16, RFC 1155 which defines the SMI, the mechanisms used for
       describing and naming objects for the purpose of
       management.  STD 16, RFC 1212 defines a more concise description
       mechanism, which is wholly consistent with the SMI.
  o    STD 17, RFC 1213 defines MIB-II, the core set of managed objects
       for the Internet suite of protocols.
  o    STD 15, RFC 1157 which defines the SNMP, the protocol used for
       network access to managed objects.

The Framework permits new objects to be defined for the purpose of experimentation and evaluation.

Object Definitions

Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. Objects in the MIB are defined using the subset of Abstract Syntax Notation One (ASN.1) defined in the SMI. In particular, each object object type is named by an OBJECT IDENTIFIER, an administratively assigned name. The object type together with an object instance serves to uniquely identify a specific instantiation of the object. For human convenience, we often use a textual string, termed the descriptor, to refer to the object type.

Overview

A common device present in many networks is the Bridge. This device is used to connect Local Area Network segments below the network

layer. There are two major modes defined for this bridging; transparent and source route. The transparent method of bridging is defined in the IEEE 802.1d MAC Bridge specification [11]. Source route bridging has been defined by I.B.M. and is described in the Token Ring Architecture Reference [12], as well as the IEEE 802.5M SRT Bridge Operations Addendum [14] to 802.1d. This memo defines objects needed for management of a source routing bridge, and is an extension to the SNMP Bridge MIB [6].

An explicit attempt was made to keep this MIB as simple as possible. This was accomplished by applying the following criteria to objects proposed for inclusion:

  (1)  Start with a small set of essential objects and add only
       as further objects are needed.
  (2)  Require objects be essential for either fault or
       configuration management.
  (3)  Consider evidence of current use and/or utility.
  (4)  Limit the total of objects.
  (5)  Exclude objects which are simply derivable from others in
       this or other MIBs.
  (6)  Avoid causing critical sections to be heavily
       instrumented.  The guideline that was followed is one
       counter per critical section per layer.

Structure of MIB

Objects in this MIB are arranged into groups. Each group is organized as a set of related objects. The overall structure and assignment of objects to their groups is shown below. Where appropriate, the corresponding management object name found in IEEE 802.1d [11] and IEEE 802.5M [14] is also included.

SR Bridge MIB Name              IEEE Name
  dot1dSr
    PortTable
      Port
      HopCount                    SourceRoutingPort
                                    .PortHopCount
      LocalSegment                  .SegmentNumber
      BridgeNum                     .BridgeNumber
      TargetSegment
      LargestFrame                  .LargestFrameSize
      STESpanMode                   .LimitedBroadcastMode
      SpecInFrames                BridgePort
                                    .ValidSRFramesReceived
      SpecOutFrames                 .ValidSRForwardedOutbound
      ApeInFrames
      ApeOutFrames                  .BroadcastFramesForwarded
      SteInFrames
      SteOutFrames                  .BroadcastFramesForwarded
      SegmentMismatchDiscards       .DiscardInvalidRI
      DuplicateSegmentDiscards      .LanIdMismatch
      HopCountExceededDiscards      .FramesDiscardedHopCountExceeded

The following IEEE management objects have not been included in the SR Bridge MIB for the indicated reasons.

IEEE Object                     Disposition
SourceRoutingPort
                                The following objects were NOT
                                included in this MIB because they
                                are redundant or not considered
                                useful.
    .LimitedBroadcastEnable
    .DiscardLackOfBuffers
    .DiscardErrorDetails
    .DiscardTargetLANInoperable
    .ValidSRDiscardedInbound
    .BroadcastBytesForwarded
    .NonBroadcastBytesForwarded
    .FramesNotReceivedDueToCongestion
    .FramesDiscardedDueToInternalError

The dot1dSr Group

This group contains the objects that describe the entity's state with respect to source route bridging. If source routing is not supported, this group will not be implemented. This group is applicable to source route only, and SRT bridges.

The dot1dPortPair Group

Implementation of this group is optional. This group is implemented by those bridges that support the port-pair multiport model of the source route bridging mode as defined in the IEEE 802.5M SRT Addendum to 802.1d.

Relationship to Other MIBs

As described above, some IEEE 802.1d management objects have not been included in this MIB because they overlap with objects in other MIBs applicable to a bridge implementing this MIB. In particular, it is assumed that a bridge implementing this MIB will also implement (at least) the Bridge MIB and the 'system' group and the 'interfaces' group defined in MIB-II [4].

Relationship to the Bridge MIB

The Bridge MIB [6] must be implemented by all bridges, including transparent, SR and SRT bridges. The SR bridge MIB is an extension to the Bridge MIB.

Relationship to the 'system' group

In MIB-II, the 'system' group is defined as being mandatory for all systems such that each managed entity contains one instance of each object in the 'system' group. Thus, those objects apply to the entity as a whole irrespective of whether the entity's sole functionality is bridging, or whether bridging is only a subset of the entity's functionality.

Relationship to the 'interfaces' group

In MIB-II, the 'interfaces' group is defined as being mandatory for all systems and contains information on an entity's interfaces, where each interface is thought of as being attached to a `subnetwork'. (Note that this term is not to be confused with `subnet' which refers to an addressing partitioning scheme used in the Internet suite of protocols.) The term 'segment' is used in this memo to refer to such a subnetwork.

Implicit in this MIB is the notion of ports on a bridge. Each of these ports is associated with one interface of the 'interfaces' group, and in most situations, each port is associated with a different interface. However, there are situations in which multiple ports are associated with the same interface. An example of such a situation would be several ports, each corresponding one-to-one with several X.25 virtual circuits, but all on the same interface.

Each port is uniquely identified by a port number. A port number has no mandatory relationship to an interface number, but in the simple case, a port number will have the same value as the corresponding interface's interface number.

Some entities provide other services in addition to bridging with respect to the data sent and received by their interfaces. In such situations, only a subset of the data sent/received on an interface is within the domain of the entity's bridging functionality. This subset is considered to be delineated according to a set of protocols, with some protocols being bridged, and other protocols not being bridged. For example, in an entity which exclusively performed bridging, all protocols would be considered as being bridged, whereas in an entity which performed IP routing on IP datagrams and only bridged other protocols, only the non-IP data would be considered as being bridged.

Thus, this MIB (and in particular, its counters) are applicable only to that subset of the data on an entity's interfaces which is sent/received for a protocol being bridged. All such data is sent/received via the ports of the bridge.

Changes from RFC 1286

In addition to being separated from the Bridge MIB into a separate document, the following changes were implemented as a result of feedback from IEEE 802.5M:

      (1)  Changed syntax of dot1dSrPortLargestFrame to INTEGER in
           order to allow for having 64 possible values as described
           in draft 7 of the SR Addendum.  Listed all legal values
           in description.
      (2)  Updated syntax of dot1dSrPort, used to index into
           dot1dSrPortTable, to use the range (1..65535).
      (3)  Added a counter to dot1dSrPortTable to count occurrences
           of duplicate LAN IDs or Tree errors.
      (4)  Added a counter to dot1dSrPortTable to count LAN ID
           mismatches.
      (5)  Added text to dot1dSrPortSpecInFrames and
           dot1dSrPortSpecOutFrames clarifying that they are also
           referred to as Source Routed Frames.
      (6)  Added text to dot1dSrPortApeInFrames and
           dot1dSrPortApeOutFrames clarifying that they are also
           referred to as All Routes Explorer frames.
      (7)  Added a scalar variable to the dot1dSr group to indicate
           whether the bridge uses 3 bit or 6 bit length negotiation
           fields.
      (8)  Added dot1dPortPairGroup to allow representation of port
           pairs as defined in the IEEE 802.5M SRT Addendum.

Definitions

      SOURCE-ROUTING-MIB DEFINITIONS ::= BEGIN
      IMPORTS
              Counter, Gauge
                      FROM RFC1155-SMI
              dot1dBridge, dot1dSr
                      FROM BRIDGE-MIB
              OBJECT-TYPE
                      FROM RFC-1212;
      -- groups in the SR MIB
      -- dot1dSr is imported from the Bridge MIB
      dot1dPortPair   OBJECT IDENTIFIER ::= { dot1dBridge 10 }
      -- the dot1dSr group
      -- this group is implemented by those bridges that
      -- support the source route bridging mode, including Source
      -- Routing and SRT bridges.
      dot1dSrPortTable OBJECT-TYPE
          SYNTAX  SEQUENCE OF Dot1dSrPortEntry
          ACCESS  not-accessible
          STATUS  mandatory
          DESCRIPTION
                  "A table that contains information about every
                  port that is associated with this source route
                  bridge."
          ::= { dot1dSr 1 }
      dot1dSrPortEntry OBJECT-TYPE
          SYNTAX  Dot1dSrPortEntry
          ACCESS  not-accessible
          STATUS  mandatory
          DESCRIPTION
                  "A list of information for each port of a source
                  route bridge."
          INDEX   { dot1dSrPort }
          ::= { dot1dSrPortTable 1 }
      Dot1dSrPortEntry ::=
          SEQUENCE {
              dot1dSrPort
                  INTEGER,
              dot1dSrPortHopCount
                  INTEGER,
              dot1dSrPortLocalSegment
                  INTEGER,
              dot1dSrPortBridgeNum
                  INTEGER,
              dot1dSrPortTargetSegment
                  INTEGER,
              dot1dSrPortLargestFrame
                  INTEGER,
              dot1dSrPortSTESpanMode
                  INTEGER,
              dot1dSrPortSpecInFrames
                  Counter,
              dot1dSrPortSpecOutFrames
                  Counter,
              dot1dSrPortApeInFrames
                  Counter,
              dot1dSrPortApeOutFrames
                  Counter,
              dot1dSrPortSteInFrames
                  Counter,
              dot1dSrPortSteOutFrames
                  Counter,
              dot1dSrPortSegmentMismatchDiscards
                  Counter,
              dot1dSrPortDuplicateSegmentDiscards
                  Counter,
              dot1dSrPortHopCountExceededDiscards
                  Counter,
              dot1dSrPortDupLanIdOrTreeErrors
                  Counter,
              dot1dSrPortLanIdMismatches
                  Counter
          }
      dot1dSrPort OBJECT-TYPE
          SYNTAX  INTEGER (1..65535)
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The port number of the port for which this entry
                  contains Source Route management information."
          ::= { dot1dSrPortEntry 1 }
      dot1dSrPortHopCount OBJECT-TYPE
          SYNTAX  INTEGER
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "The maximum number of routing descriptors allowed
                  in an All Paths or Spanning Tree Explorer frames."
          ::= { dot1dSrPortEntry 2 }
      dot1dSrPortLocalSegment OBJECT-TYPE
          SYNTAX  INTEGER
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "The segment number that uniquely identifies the
                  segment to which this port is connected. Current
                  source routing protocols limit this value to the
                  range: 0 through 4095. (The value 0 is used by
                  some management applications for special test
                  cases.) A value of 65535 signifies that no segment
                  number is assigned to this port."
          ::= { dot1dSrPortEntry 3 }
      dot1dSrPortBridgeNum OBJECT-TYPE
          SYNTAX  INTEGER
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "A bridge number uniquely identifies a bridge when
                  more than one bridge is used to span the same two
                  segments.  Current source routing protocols limit
                  this value to the range: 0 through 15. A value of
                  65535 signifies that no bridge number is assigned
                  to this bridge."
          ::= { dot1dSrPortEntry 4 }
      dot1dSrPortTargetSegment OBJECT-TYPE
          SYNTAX  INTEGER
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "The segment number that corresponds to the target
                  segment this port is considered to be connected to
                  by the bridge.  Current source routing protocols
                  limit this value to the range: 0 through 4095.
                  (The value 0 is used by some management
                  applications for special test cases.) A value of
                  65535 signifies that no target segment is assigned
                  to this port."
          ::= { dot1dSrPortEntry 5 }
      -- It would be nice if we could use ifMtu as the size of the
      -- largest frame, but we can't because ifMtu is defined to be
      -- the size that the (inter-)network layer can use which can
      -- differ from the MAC layer (especially if several layers of
      -- encapsulation are used).
      dot1dSrPortLargestFrame OBJECT-TYPE
          SYNTAX  INTEGER
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "The maximum size of the INFO field (LLC and
                  above) that this port can send/receive.  It does
                  not include any MAC level (framing) octets.  The
                  value of this object is used by this bridge to
                  determine whether a modification of the
                  LargestFrame (LF, see [14]) field of the Routing
                  Control field of the Routing Information Field is
                  necessary.
                  64 valid values are defined by the IEEE 802.5M SRT
                  Addendum: 516, 635, 754, 873, 993, 1112, 1231,
                  1350, 1470, 1542, 1615, 1688, 1761, 1833, 1906,
                  1979, 2052, 2345, 2638, 2932, 3225, 3518, 3812,
                  4105, 4399, 4865, 5331, 5798, 6264, 6730, 7197,
                  7663, 8130, 8539, 8949, 9358, 9768, 10178, 10587,
                  10997, 11407, 12199, 12992, 13785, 14578, 15370,
                  16163, 16956, 17749, 20730, 23711, 26693, 29674,
                  32655, 35637, 38618, 41600, 44591, 47583, 50575,
                  53567, 56559, 59551, and 65535.
                  An illegal value will not be accepted by the
                  bridge."
          ::= { dot1dSrPortEntry 6 }
      dot1dSrPortSTESpanMode OBJECT-TYPE
          SYNTAX  INTEGER {
                      auto-span(1),
                      disabled(2),
                      forced(3)
                  }
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "Determines how this port behaves when presented
                  with a Spanning Tree Explorer frame.  The value
                  'disabled(2)' indicates that the port will not
                  accept or send Spanning Tree Explorer packets; any
                  STE packets received will be silently discarded.
                  The value 'forced(3)' indicates the port will
                  always accept and propagate Spanning Tree Explorer
                  frames.  This allows a manually configured
                  Spanning Tree for this class of packet to be
                  configured.  Note that unlike transparent
                  bridging, this is not catastrophic to the network
                  if there are loops.  The value 'auto-span(1)' can
                  only be returned by a bridge that both implements
                  the Spanning Tree Protocol and has use of the
                  protocol enabled on this port. The behavior of the
                  port for Spanning Tree Explorer frames is
                  determined by the state of dot1dStpPortState.  If
                  the port is in the 'forwarding' state, the frame
                  will be accepted or propagated.  Otherwise, it
                  will be silently discarded."
          ::= { dot1dSrPortEntry 7 }
      dot1dSrPortSpecInFrames OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of Specifically Routed frames, also
                  referred to as Source Routed Frames, that have
                  been received from this port's segment."
          ::= { dot1dSrPortEntry 8 }
      dot1dSrPortSpecOutFrames OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of Specifically Routed frames, also
                  referred to as Source Routed Frames, that this
                  port has transmitted on its segment."
          ::= { dot1dSrPortEntry 9 }
      dot1dSrPortApeInFrames OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of All Paths Explorer frames, also
                  referred to as All Routes Explorer frames, that
                  have been received by this port from its segment."
          ::= { dot1dSrPortEntry 10 }
      dot1dSrPortApeOutFrames OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of all Paths Explorer Frames, also
                  referred to as All Routes Explorer frames, that
                  have been transmitted by this port on its
                  segment."
          ::= { dot1dSrPortEntry 11 }
      dot1dSrPortSteInFrames OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of spanning tree explorer frames that
                  have been received by this port from its segment."
          ::= { dot1dSrPortEntry 12 }
      dot1dSrPortSteOutFrames OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of spanning tree explorer frames that
                  have been transmitted by this port on its
                  segment."
          ::= { dot1dSrPortEntry 13 }
      dot1dSrPortSegmentMismatchDiscards OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of explorer frames that have been
                  discarded by this port because the routing
                  descriptor field contained an invalid adjacent
                  segment value."
          ::= { dot1dSrPortEntry 14 }
      dot1dSrPortDuplicateSegmentDiscards OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of frames that have been discarded by
                  this port because the routing descriptor field
                  contained a duplicate segment identifier."
          ::= { dot1dSrPortEntry 15 }
      dot1dSrPortHopCountExceededDiscards OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of explorer frames that have been
                  discarded by this port because the Routing
                  Information Field has exceeded the maximum route
                  descriptor length."
          ::= { dot1dSrPortEntry 16 }
      dot1dSrPortDupLanIdOrTreeErrors OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of duplicate LAN IDs or Tree errors.
                  This helps in detection of problems in networks
                  containing older IBM Source Routing Bridges."
          ::= { dot1dSrPortEntry 17 }
      dot1dSrPortLanIdMismatches OBJECT-TYPE
          SYNTAX  Counter
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The number of ARE and STE frames that were
                  discarded because the last LAN ID in the routing
                  information field did not equal the LAN-in ID.
                  This error can occur in implementations which do
                  only a LAN-in ID and Bridge Number check instead
                  of a LAN-in ID, Bridge Number, and LAN-out ID
                  check before they forward broadcast frames."
          ::= { dot1dSrPortEntry 18 }
      -- scalar object in dot1dSr
      dot1dSrBridgeLfMode OBJECT-TYPE
          SYNTAX  INTEGER {
                      mode3(1),
                      mode6(2)
                  }
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "Indicates whether the bridge operates using older
                  3 bit length negotiation fields or the newer 6 bit
                  length field in its RIF."
          ::= { dot1dSr 2 }
      -- The Port-Pair Database
      -- Implementation of this group is optional.
      -- This group is implemented by those bridges that support
      -- the direct multiport model of the source route bridging
      -- mode as defined in the IEEE 802.5 SRT Addendum to
      -- 802.1d.
      -- Bridges implementing this group may report 65535 for
      -- dot1dSrPortBridgeNumber and dot1dSrPortTargetSegment,
      -- indicating that those objects are not applicable.
      dot1dPortPairTableSize OBJECT-TYPE
          SYNTAX  Gauge
          ACCESS  read-only
          STATUS  mandatory
          DESCRIPTION
                  "The total number of entries in the Bridge Port
                  Pair Database."
          ::= { dot1dPortPair 1 }
      -- the Bridge Port-Pair table
      -- this table represents port pairs within a bridge forming
      -- a unique bridge path, as defined in the IEEE 802.5M SRT
      -- Addendum.
      dot1dPortPairTable OBJECT-TYPE
          SYNTAX  SEQUENCE OF Dot1dPortPairEntry
          ACCESS  not-accessible
          STATUS  mandatory
          DESCRIPTION
                  "A table that contains information about every
                  port pair database entity associated with this
                  source routing bridge."
          ::= { dot1dPortPair 2 }
      dot1dPortPairEntry OBJECT-TYPE
          SYNTAX  Dot1dPortPairEntry
          ACCESS  not-accessible
          STATUS  mandatory
          DESCRIPTION
                  "A list of information for each port pair entity
                  of a bridge."
          INDEX   { dot1dPortPairLowPort, dot1dPortPairHighPort }
          ::= { dot1dPortPairTable 1 }
      Dot1dPortPairEntry ::=
          SEQUENCE {
              dot1dPortPairLowPort
                  INTEGER,
              dot1dPortPairHighPort
                  INTEGER,
              dot1dPortPairBridgeNum
                  INTEGER,
              dot1dPortPairBridgeState
                  INTEGER
          }
      dot1dPortPairLowPort OBJECT-TYPE
          SYNTAX  INTEGER (1..65535)
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "The port number of the lower numbered port for
                  which this entry contains port pair database
                  information."
          ::= { dot1dPortPairEntry 1 }
      dot1dPortPairHighPort OBJECT-TYPE
          SYNTAX  INTEGER (1..65535)
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "The port number of the higher numbered port for
                  which this entry contains port pair database
                  information."
          ::= { dot1dPortPairEntry 2 }
      dot1dPortPairBridgeNum OBJECT-TYPE
          SYNTAX  INTEGER
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "A bridge number that uniquely identifies the path
                  provided by this source routing bridge between the
                  segments connected to dot1dPortPairLowPort and
                  dot1dPortPairHighPort.  The purpose of bridge
                  number is to disambiguate between multiple paths
                  connecting the same two LANs."
          ::= { dot1dPortPairEntry 3 }
      dot1dPortPairBridgeState OBJECT-TYPE
          SYNTAX  INTEGER {
                      enabled(1),
                      disabled(2),
                      invalid(3)
                  }
          ACCESS  read-write
          STATUS  mandatory
          DESCRIPTION
                  "The state of dot1dPortPairBridgeNum.  Writing
                  'invalid(3)' to this object removes the
                  corresponding entry."
          ::= { dot1dPortPairEntry 4 }
      END

Acknowledgments

This document was produced on behalf of the Bridge MIB Working Group in the NM area of the Internet Engineering Task Force.

The authors wish to thank the members of the Bridge MIB Working Group for their many comments and suggestions which improved this effort.

References

[1] Cerf, V., "IAB Recommendations for the Development of Internet

   Network Management Standards", RFC 1052, NRI, April 1988.

[2] Cerf, V., "Report of the Second Ad Hoc Network Management Review

   Group", RFC 1109, NRI, August 1989.

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

   Management Information for TCP/IP-based internets", STD 16, RFC
   1155, Performance Systems International, Hughes LAN Systems, May
   1990.

[4] McCloghrie K., and M. Rose, Editors, "Management Information Base

   for Network Management of TCP/IP-based internets", STD 17, RFC
   1213, Performance Systems International, March 1991.

[5] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple

   Network Management Protocol", STD 15, RFC 1157, SNMP Research,
   Performance Systems International, Performance Systems
   International, MIT Laboratory for Computer Science, May 1990.

[6] Decker, E., Langille, P., Rijsinghani, A., and McCloghrie, K.,

   "Definitions of Managed Objects for Bridges", RFC 1493, cisco
   Systems, Digital Equipment Corporation, Digital Equipment
   Corporation, Hughes LAN Systems, July 1993.

[7] Information processing systems - Open Systems Interconnection -

   Specification of Abstract Syntax Notation One (ASN.1),
   International Organization for Standardization, International
   Standard 8824, December 1987.

[8] Information processing systems - Open Systems Interconnection -

   Specification of Basic Encoding Rules for Abstract Notation One
   (ASN.1), International Organization for Standardization,
   International Standard 8825, December 1987.

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

   STD 16, RFC 1212, Performance Systems International, Hughes LAN
   Systems, March 1991.
 [10] Rose, M., Editor, "A Convention for Defining Traps for use with
   the SNMP", RFC 1215, Performance Systems International, March
   1991.
 [11] ANSI/IEEE Standard 802.1D-1990 MAC Bridges, IEEE Project 802
   Local and Metropolitan Area Networks, (March 8, 1991).
 [12] I.B.M. Token Ring Architecture Reference.
 [13] ISO DIS 10038 MAC Bridges.
 [14] ANSI/IEEE P802.5M-Draft 7, "Source Routing Transparent Bridge
   Operation", IEEE Project 802 (1991).
 [15] ANSI/IEEE 802.1y, "Source Routing Tutorial for End System
   Operation", (September, 1990).

Security Considerations

Security issues are not discussed in this memo.

Authors' Addresses

Eric B. Decker cisco Systems, Inc. 1525 O'Brien Dr. Menlo Park, CA 94025

Phone: (415) 326-1941 Email: [email protected]

Keith McCloghrie Hughes LAN Systems, Inc. 1225 Charleston Road Mountain View, CA 94043

Phone: (415) 966-7934 EMail: [email protected]

Paul Langille Digital Equipment Corporation Digital Drive, MK02-2/K03 Merrimack, NH 03054

Phone: (603) 884-4045 EMail: [email protected]

Anil Rijsinghani Digital Equipment Corporation 550 King Street Littleton, MA 01460

Phone: (508) 486-6786 EMail: [email protected]