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.
Table of Contents
1. Introduction ......................................... 2 2. The Network Management Framework ..................... 2 2.1 Object Definitions .................................. 2 3. Overview ............................................. 2 3.1 Structure of MIB .................................... 3 3.1.1 The dot1dSr Group ................................. 4 3.1.2 The dot1dPortPair Group ........................... 4 3.2 Relationship to Other MIBs .......................... 5 3.2.1 Relationship to the Bridge MIB .................... 5 3.2.2 Relationship to the 'system' group ................ 5 3.2.3 Relationship to the 'interfaces' group ............ 5 4. Changes from RFC 1286 ................................ 6 5. Definitions .......................................... 7 5.1 Groups in the SR MIB ................................ 7 5.2 The dot1dSr Group Definitions ....................... 7 5.3 The dot1dPortPair Group Definitions ................. 14 6. Acknowledgments ...................................... 16 7. References ........................................... 16 8. Security Considerations .............................. 18 9. Authors' Addresses ................................... 18
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.
2. 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.
2.1. 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.
3. 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.
3.1. 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.
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
3.1.1. 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.
3.1.2. 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.
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].
3.2.1. 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.
3.2.2. 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.
3.2.3. 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.
4. 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.
-- 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 }
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.
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 }
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 }
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 }
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 }
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
6. 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.
7. 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).
