rfc2864.txt

RFC 的详细文档！

Network Working Group                                      K. McCloghrie
Request for Comments: 2864                                 Cisco Systems
Category: Standards Track                                      G. Hanson
                                                  ADC Telecommunications
                                                               June 2000


     The Inverted Stack Table Extension to the Interfaces Group MIB

Status of this Memo

   This document 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" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Table of Contents

   1 Introduction ..................................................  1
   2 The SNMP Network Management Framework .........................  1
   3 Interface Sub-Layers and the ifStackTable .....................  3
   4 Definitions ...................................................  4
   5 Acknowledgements ..............................................  7
   6 References ....................................................  7
   7 Security Considerations .......................................  8
   8 Authors' Addresses ............................................  9
   9 Notice on Intellectual Property ............................... 10
   10 Full Copyright Statement ..................................... 11

1.  Introduction

   This memo defines a portion of the Management Information Base (MIB)
   for use with network management protocols in the Internet community.
   In particular, it describes managed objects which provide an inverted
   mapping of the interface stack table used for managing network
   interfaces.

2.  The SNMP Network Management Framework

   The SNMP Management Framework presently consists of five major
   components:





McCloghrie & Hanson         Standards Track                     [Page 1]

RFC 2864              Inverted Stack Extension MIB             June 2000


    o An overall architecture, described in RFC 2571 [1].

    o Mechanisms for describing and naming objects and events for the
      purpose of management.  The first version of this Structure of
      Management Information (SMI) is called SMIv1 and described in STD
      16, RFC 1155 [2], STD 16, RFC 1212 [3] and RFC 1215 [4].  The
      second version, called SMIv2, is described in STD 58, which
      consists of RFC 2578 [5], RFC 2579 [6] and RFC 2580 [7].

    o Message protocols for transferring management information.  The
      first version of the SNMP message protocol is called SNMPv1 and
      described in STD 15, RFC 1157 [8].  A second version of the SNMP
      message protocol, which is not an Internet standards track
      protocol, is called SNMPv2c and described in RFC 1901 [9] and RFC
      1906 [10].  The third version of the message protocol is called
      SNMPv3 and described in RFC 1906 [10], RFC 2572 [11] and RFC 2574
      [12].

    o Protocol operations for accessing management information.  The
      first set of protocol operations and associated PDU formats is
      described in STD 15, RFC 1157 [8].  A second set of protocol
      operations and associated PDU formats is described in RFC 1905
      [13].

    o A set of fundamental applications described in RFC 2573 [14] and
      the view-based access control mechanism described in RFC 2575
      [15].

   A more detailed introduction to the current SNMP Management Framework
   can be found in RFC 2570 [18].

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using the mechanisms defined in the SMI.

   This memo specifies a MIB module that is compliant to the SMIv2.  A
   MIB conforming to the SMIv1 can be produced through the appropriate
   translations.  The resulting translated MIB must be semantically
   equivalent, except where objects or events are omitted because no
   translation is possible (e.g., use of Counter64).  Some machine
   readable information in SMIv2 will be converted into textual
   descriptions in SMIv1 during the translation process.  However, this
   loss of machine readable information is not considered to change the
   semantics of the MIB.







McCloghrie & Hanson         Standards Track                     [Page 2]

RFC 2864              Inverted Stack Extension MIB             June 2000


3.  Interface Sub-Layers and the ifStackTable

   MIB-II [16] defines objects for managing network interfaces by
   providing a generic interface definition together with the ability to
   define media-specific extensions.  The generic objects are known as
   the 'interfaces' group.

   Experience in defining media-specific extensions showed the need to
   distinguish between the multiple sub-layers beneath the
   internetwork-layer.  Consider, for example, an interface with PPP
   running over an HDLC link which uses a RS232-like connector.  Each of
   these sub-layers has its own media-specific MIB module.

   The latest definition of the 'interfaces' group in the IF-MIB [17]
   satisfies this need by having each sub-layer be represented by its
   own conceptual row in the ifTable.  It also defines an additional MIB
   table, the ifStackTable, to identify the "superior" and "subordinate"
   sub-layers through ifIndex "pointers" to the appropriate conceptual
   rows in the ifTable.

   Each conceptual row in the ifStackTable represents a relationship
   between two interfaces, where this relationship is that the "higher-
   layer" interface runs "on top" of the "lower-layer" interface.  For
   example, if a PPP module operated directly over a serial interface,
   the PPP module would be a "higher layer" to the serial interface, and
   the serial interface would be a "lower layer" to the PPP module.
   This concept of "higher-layer" and "lower-layer" is the same as
   embodied in the definitions of the ifTable's packet counters.

   The ifStackTable is INDEX-ed by the ifIndex values of the two
   interfaces involved in the relationship.  By necessity, one of these
   ifIndex values must come first, and the IF-MIB chose to have the
   higher-layer interface first, and the lower-layer interface second.
   Due to this, it is straight-forward for a Network Management
   application to read a subset of the ifStackTable and thereby
   determine the interfaces which run underneath a particular interface.
   However, to determine which interfaces run on top of a particular
   interface, a Network Management application has no alternative but to
   read the whole table.  This is very inefficient when querying a
   device which has many interfaces, and many conceptual rows in its
   ifStackTable.

   This MIB provides an inverted Interfaces Stack Table, the
   ifInvStackTable.  While it contains no additional information beyond
   that already contained in the ifStackTable, the ifInvStackTable has
   the ifIndex values in its INDEX clause in the reverse order, i.e.,
   the lower-layer interface first, and the higher-layer interface
   second.  As a result, the ifInvStackTable is an inverted version of



McCloghrie & Hanson         Standards Track                     [Page 3]

RFC 2864              Inverted Stack Extension MIB             June 2000


   the same information contained in the ifStackTable.  Thus, the
   ifInvStackTable provides an efficient means for a Network Management
   application to read a subset of the ifStackTable and thereby
   determine which interfaces run on top of a particular interface.

4.  Definitions

IF-INVERTED-STACK-MIB DEFINITIONS ::= BEGIN

IMPORTS
  MODULE-IDENTITY, OBJECT-TYPE, mib-2      FROM SNMPv2-SMI
  RowStatus                                FROM SNMPv2-TC
  MODULE-COMPLIANCE, OBJECT-GROUP          FROM SNMPv2-CONF
  ifStackGroup2,
  ifStackHigherLayer, ifStackLowerLayer    FROM IF-MIB;

ifInvertedStackMIB MODULE-IDENTITY
  LAST-UPDATED "200006140000Z"
  ORGANIZATION "IETF Interfaces MIB Working Group"
  CONTACT-INFO
          "   Keith McCloghrie
              Cisco Systems, Inc.
              170 West Tasman Drive
              San Jose, CA  95134-1706
              US

              408-526-5260
              [e-mail]"
  DESCRIPTION
          "The MIB module which provides the Inverted Stack Table for
          interface sub-layers."
  REVISION      "200006140000Z"
  DESCRIPTION
          "Initial revision, published as RFC 2864"
  ::= { mib-2 77 }

ifInvMIBObjects OBJECT IDENTIFIER ::= { ifInvertedStackMIB 1 }

--
--           The Inverted Interface Stack Group
--

ifInvStackTable  OBJECT-TYPE
   SYNTAX        SEQUENCE OF IfInvStackEntry
   MAX-ACCESS    not-accessible
   STATUS        current
   DESCRIPTION
          "A table containing information on the relationships between



McCloghrie & Hanson         Standards Track                     [Page 4]

RFC 2864              Inverted Stack Extension MIB             June 2000


          the multiple sub-layers of network interfaces.  In
          particular, it contains information on which sub-layers run
          'underneath' which other sub-layers, where each sub-layer
          corresponds to a conceptual row in the ifTable.  For
          example, when the sub-layer with ifIndex value x runs
          underneath the sub-layer with ifIndex value y, then this
          table contains:

            ifInvStackStatus.x.y=active

          For each ifIndex value, z, which identifies an active
          interface, there are always at least two instantiated rows
          in this table associated with z.  For one of these rows, z
          is the value of ifStackHigherLayer; for the other, z is the
          value of ifStackLowerLayer.  (If z is not involved in
          multiplexing, then these are the only two rows associated
          with z.)

          For example, two rows exist even for an interface which has
          no others stacked on top or below it:

            ifInvStackStatus.z.0=active
            ifInvStackStatus.0.z=active

          This table contains exactly the same number of rows as the
          ifStackTable, but the rows appear in a different order."
   REFERENCE
          "ifStackTable of RFC 2863"
   ::= { ifInvMIBObjects 1 }

ifInvStackEntry  OBJECT-TYPE
   SYNTAX        IfInvStackEntry
   MAX-ACCESS    not-accessible
   STATUS        current
   DESCRIPTION
          "Information on a particular relationship between two sub-
          layers, specifying that one sub-layer runs underneath the
          other sub-layer.  Each sub-layer corresponds to a conceptual
          row in the ifTable."
   INDEX { ifStackLowerLayer, ifStackHigherLayer }
   ::= { ifInvStackTable 1 }

IfInvStackEntry ::=
  SEQUENCE {
      ifInvStackStatus       RowStatus
   }

ifInvStackStatus  OBJECT-TYPE



McCloghrie & Hanson         Standards Track                     [Page 5]

RFC 2864              Inverted Stack Extension MIB             June 2000


  SYNTAX         RowStatus
  MAX-ACCESS     read-only
  STATUS         current
  DESCRIPTION
          "The status of the relationship between two sub-layers.

          An instance of this object exists for each instance of the
          ifStackStatus object, and vice versa.  For example, if the
          variable ifStackStatus.H.L exists, then the variable
          ifInvStackStatus.L.H must also exist, and vice versa.  In
          addition, the two variables always have the same value.

          However, unlike ifStackStatus, the ifInvStackStatus object
          is NOT write-able.  A network management application wishing
          to change a relationship between sub-layers H and L cannot
          do so by modifying the value of ifInvStackStatus.L.H, but
          must instead modify the value of ifStackStatus.H.L.  After
          the ifStackTable is modified, the change will be reflected
          in this table."
  ::= { ifInvStackEntry 1 }

-- conformance information

ifInvConformance OBJECT IDENTIFIER ::= { ifInvMIBObjects 2 }