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rfc:rfc2864

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
            kzm@cisco.com"
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 }

ifInvGroups OBJECT IDENTIFIER ::= { ifInvConformance 1 } ifInvCompliances OBJECT IDENTIFIER ::= { ifInvConformance 2 }

– compliance statements

ifInvCompliance MODULE-COMPLIANCE

STATUS  current
DESCRIPTION
        "The compliance statement for SNMP entities which provide
        inverted information on the layering of network interfaces."
MODULE  -- this module
    MANDATORY-GROUPS { ifInvStackGroup }
    OBJECT       ifInvStackStatus
    SYNTAX       INTEGER { active(1) }
    DESCRIPTION
        "Support is only required for 'active'."

McCloghrie & Hanson Standards Track [Page 6] RFC 2864 Inverted Stack Extension MIB June 2000

MODULE  IF-MIB
    MANDATORY-GROUPS { ifStackGroup2 }
::= { ifInvCompliances 1 }

– units of conformance

ifInvStackGroup OBJECT-GROUP

OBJECTS { ifInvStackStatus }
STATUS  current
DESCRIPTION
        "A collection of objects providing inverted information on
        the layering of MIB-II interfaces."
::= { ifInvGroups 1 }

END

5. Acknowledgements

 This memo has been produced by the IETF's Interfaces MIB working-
 group.

6. References

 [1]  Harrington, D., Presuhn, R. and B. Wijnen, "An Architecture for
      Describing SNMP Management Frameworks", RFC 2571, January 1998.
 [2]  Rose, M. and K. McCloghrie, "Structure and Identification of
      Management Information for TCP/IP-based Internets", STD 16, RFC
      1155, May 1990.
 [3]  Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD 16,
      RFC 1212, March 1991.
 [4]  Rose, M., "A Convention for Defining Traps for use with the
      SNMP", RFC 1215, March 1991.
 [5]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
      M. and S. Waldbusser, "Structure of Management Information
      Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
 [6]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
      M. and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
      RFC 2579, April 1999.
 [7]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
      M. and S. Waldbusser, "Conformance Statements for SMIv2", STD
      58, RFC 2580, April 1999.

McCloghrie & Hanson Standards Track [Page 7] RFC 2864 Inverted Stack Extension MIB June 2000

 [8]  Case, J., Fedor, M., Schoffstall, M. and J. Davin, "Simple
      Network Management Protocol", STD 15, RFC 1157, May 1990.
 [9]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S.
      Waldbusser, "Introduction to Community-based SNMPv2", RFC 1901,
      January 1996.
 [10] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S.
      Waldbusser, "Transport Mappings for Version 2 of the Simple
      Network Management Protocol (SNMPv2)", RFC 1906, January 1996.
 [11] Case, J., Harrington D., Presuhn R. and B. Wijnen, "Message
      Processing and Dispatching for the Simple Network Management
      Protocol (SNMP)", RFC 2572, January 1998.
 [12] Blumenthal, U. and B. Wijnen, "User-based Security Model (USM)
      for version 3 of the Simple Network Management Protocol
      (SNMPv3)", RFC 2574, January 1998.
 [13] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M. and S.
      Waldbusser, "Protocol Operations for Version 2 of the Simple
      Network Management Protocol (SNMPv2)", RFC 1905, January 1996.
 [14] Levi, D., Meyer, P. and B. Stewart, "SNMP Applications", RFC
      2573, January 1998.
 [15] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based Access
      Control Model (VACM) for the Simple Network Management Protocol
      (SNMP)", RFC 2575, January 1998.
 [16] McCloghrie, K. and M. Rose, "Management Information Base for
      Network Management of TCP/IP-based internets - MIB-II", STD 17,
      RFC 1213, March 1991.
 [17] McCloghrie, K. and F. Kastenholz, "The Interface Group MIB", RFC
      2863, June 2000.
 [18] Case, J., Mundy, R., Partain, D. and B. Stewart, "Introduction
      to Version 3 of the Internet-standard Network Management
      Framework", RFC 2570, April 1999.

7. Security Considerations

 There are no management objects defined in this MIB that have a MAX-
 ACCESS clause of read-write and/or read-create.  So, if this MIB is
 implemented correctly, then there is no risk that an intruder can
 alter or create any management objects of this MIB via direct SNMP
 SET operations.

McCloghrie & Hanson Standards Track [Page 8] RFC 2864 Inverted Stack Extension MIB June 2000

 SNMPv1 by itself is not a secure environment.  Even if the network
 itself is secure (for example by using IPSec), even then, there is no
 control as to who on the secure network is allowed to access and
 GET/SET (read/change/create/delete) the objects in this MIB.
 It is recommended that the implementers consider the security
 features as provided by the SNMPv3 framework.  Specifically, the use
 of the User-based Security Model RFC 2574 [12] and the View- based
 Access Control Model RFC 2575 [15] is recommended.
 It is then a customer/user responsibility to ensure that the SNMP
 entity giving access to an instance of this MIB, is properly
 configured to give access to the objects only to those principals
 (users) that have legitimate rights to indeed GET or SET
 (change/create/delete) them.

8. Authors' Addresses

 Keith McCloghrie
 Cisco Systems, Inc.
 170 West Tasman Drive
 San Jose, CA  95134-1706
 Phone: 408-526-5260
 EMail: kzm@cisco.com
 Gary Hanson
 ADC Telecommunications
 14375 NW Science Park Drive
 Portland, Oregon, 97229
 Phone: (800)733-5511 x6333
 EMail: gary_hanson@adc.com

McCloghrie & Hanson Standards Track [Page 9] RFC 2864 Inverted Stack Extension MIB June 2000

9. Notice on Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 intellectual property or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; neither does it represent that it
 has made any effort to identify any such rights.  Information on the
 IETF's procedures with respect to rights in standards-track and
 standards-related documentation can be found in BCP-11.  Copies of
 claims of rights made available for publication and any assurances of
 licenses to be made available, or the result of an attempt made to
 obtain a general license or permission for the use of such
 proprietary rights by implementors or users of this specification can
 be obtained from the IETF Secretariat.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights which may cover technology that may be required to practice
 this standard.  Please address the information to the IETF Executive
 Director.

McCloghrie & Hanson Standards Track [Page 10] RFC 2864 Inverted Stack Extension MIB June 2000

10. Full Copyright Statement

 Copyright (C) The Internet Society (2000).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

McCloghrie & Hanson Standards Track [Page 11]

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