rfc1252.txt

RFC 的详细文档！

Network Working Group                                          F. Baker
Request for Comments: 1252                                          ACC
Obsoletes: RFC 1248                                           R. Coltun
                                                Computer Science Center
                                                            August 1991


               OSPF Version 2 Management Information Base

Status of this Memo

   This RFC specifies an IAB standards track protocol for the Internet
   community, and requests discussion and suggestions for improvements.
   Please refer to the current edition of the "IAB Official Protocol
   Standards" for the standardization state and status of this protocol.
   This memo replaces RFC 1248 which contained some minor errors in
   referring to "experimental" and "standard-mib" in Section 5.
   Distribution of this memo is unlimited.

Table of Contents

   1. Abstract .............................................    2
   2. The Network Management Framework......................    2
   3. Objects ..............................................    2
   3.1 Format of Definitions ...............................    3
   4. Overview .............................................    3
   4.1 Textual Conventions .................................    3
   4.2 Structure of MIB ....................................    3
   4.2.1 General Variables .................................    4
   4.2.2 Area Data Structure and Area Stub Metric Table ....    4
   4.2.3 Link State Database ...............................    4
   4.2.4 Address Table and Host Tables .....................    4
   4.2.5 Interface and Interface Metric Tables .............    4
   4.2.6 Virtual Interface Table ...........................    4
   4.2.7 Neighbor and Virtual Neighbor Tables ..............    4
   4.3 Conceptual Row Creation .............................    5
   4.4 Default Configuration ...............................    5
   5. Definitions ..........................................    7
   5.1 OSPF General Variables ..............................    8
   5.2 OSPF Area Data Structure ............................   11
   5.3 OSPF Area Default Metric Table ......................   14
   5.4 OSPF Link State Database ............................   16
   5.5 OSPF Address Range Table ............................   19
   5.6 OSPF Host Table .....................................   21
   5.7 OSPF Interface Table ................................   23
   5.8 OSPF Interface Metric Table .........................   28
   5.9 OSPF Virtual Interface Table ........................   31
   5.10 OSPF Neighbor Table ................................   34



Baker & Coltun                                                  [Page 1]

RFC 1252                   OSPF Version 2 MIB                August 1991


   5.11 OSPF Virtual Neighbor Table ........................   38
   6. Acknowledgements .....................................   40
   7. References ...........................................   40
   8. Security Considerations...............................   41
   9. Authors' Addresses....................................   42

1.  Abstract

   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 OSPF Version 2.

2.  The Network Management Framework

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

      RFC 1155 which defines the SMI, the mechanisms used for describing
      and naming objects for the purpose of management.  RFC 1212
      defines a more concise description mechanism, which is wholly
      consistent with the SMI.

      RFC 1156 which defines MIB-I, the core set of managed objects for
      the Internet suite of protocols.  RFC 1213, defines MIB-II, an
      evolution of MIB-I based on implementation experience and new
      operational requirements.

      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.

3.  Objects

   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) [7]
   defined in the SMI.  In particular, each object has a name, a syntax,
   and an encoding.  The name is an object identifier, an
   administratively assigned name, which specifies an object type.  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 OBJECT
   DESCRIPTOR, to also refer to the object type.

   The syntax of an object type defines the abstract data structure
   corresponding to that object type.  The ASN.1 language is used for



Baker & Coltun                                                  [Page 2]

RFC 1252                   OSPF Version 2 MIB                August 1991


   this purpose.  However, the SMI [3] purposely restricts the ASN.1
   constructs which may be used.  These restrictions are explicitly made
   for simplicity.

   The encoding of an object type is simply how that object type is
   represented using the object type's syntax.  Implicitly tied to the
   notion of an object type's syntax and encoding is how the object type
   is represented when being transmitted on the network.

   The SMI specifies the use of the basic encoding rules of ASN.1 [8],
   subject to the additional requirements imposed by the SNMP.

3.1.  Format of Definitions

   Section 5 contains contains the specification of all object types
   contained in this MIB module.  The object types are defined using the
   conventions defined in the SMI, as amended by the extensions
   specified in [9].

4.  Overview

4.1.  Textual Conventions

   Several new data types are introduced as a textual convention in this
   MIB document.  These textual conventions enhance the readability of
   the specification and can ease comparison with other specifications
   if appropriate.  It should be noted that the introduction of the
   these textual conventions has no effect on either the syntax nor the
   semantics of any managed objects.  The use of these is merely an
   artifact of the explanatory method used.  Objects defined in terms of
   one of these methods are always encoded by means of the rules that
   define the primitive type.  Hence, no changes to the SMI or the SNMP
   are necessary to accommodate these textual conventions which are
   adopted merely for the convenience of readers and writers in pursuit
   of the elusive goal of clear, concise, and unambiguous MIB documents.

   The new data types are AreaID, RouterID, TOSType, Metric, BigMetric,
   TruthValue, Status, Validation, PositiveInteger, HelloRange,
   UpToMaxAge, InterfaceIndex, and DesignatedRouterPriority.

4.2.  Structure of MIB

   The MIB is composed of the following sections:

          General Variables
          Area Data Structure
          Area Stub Metric Table
          Link State Database



Baker & Coltun                                                  [Page 3]

RFC 1252                   OSPF Version 2 MIB                August 1991


          Address Range Table
          Host Table
          Interface Table
          Interface Metric Table
          Virtual Interface Table
          Neighbor Table
          Virtual Neighbor Table

4.2.1.  General Variables

   The General Variables are about what they sound like; variables which
   are global to the OSPF Process.

4.2.2.  Area Data Structure and Area Stub Metric Table

   The Area Data Structure describes the OSPF Areas that the router
   participates in.  The Area Stub Metric Table describes the metrics
   advertised into a stub area by the default router(s).

4.2.3.  Link State Database

   The Link State Database is provided primarily to provide detailed
   information for network debugging.

4.2.4.  Address Table and Host Tables

   The Address Range Table and Host Table are provided to view
   configured Network Summary and Host Route information.

4.2.5.  Interface and Interface Metric Tables

   The Interface Table and the Interface Metric Table together describe
   the various IP interfaces to OSPF.  The metrics are placed in
   separate tables in order to simplify dealing with multiple types of
   service, and to provide flexibility in the event that the IP TOS
   definition is changed in the future.  A Default Value specification
   is supplied for the TOS 0 (default) metric.

4.2.6.  Virtual Interface Table

   Likewise, the Virtual Interface Table describe virtual links to the
   OSPF Process.

4.2.7.  Neighbor and Virtual Neighbor Tables

   The Neighbor Table and the Virtual Neighbor Table describe the
   neighbors to the OSPF Process.




Baker & Coltun                                                  [Page 4]

RFC 1252                   OSPF Version 2 MIB                August 1991


4.3.  Conceptual Row Creation

   For the benefit of row-creation in "conceptual" (see [9]) tables,
   DEFVAL (Default Value) clauses are included in the definitions in
   section 5, suggesting values which an agent should use for instances
   of variables which need to be created due to a Set-Request, but which
   are not specified in the Set- Request.  DEFVAL clauses have not been
   specified for some objects which are read-only, implying that they
   are zeroed upon row creation.  These objects are of the SYNTAX
   Counter or Gauge.

   For those objects not having a DEFVAL clause, both management
   stations and agents should heed the Robustness Principle of the
   Internet (see RFC-791):

      "be liberal in what you accept, conservative in what
      you send"

   That is, management stations should include as many of these columnar
   objects as possible (e.g., all read-write objects) in a Set-Request
   when creating a conceptual row; agents should accept a Set-Request
   with as few of these as they need (e.g., the minimum contents of a
   row creating SET consists of those objects for which, as they cannot
   be intuited, no default is specified.).

   There are numerous read-write objects in this MIB, as it is designed
   for SNMP management of the protocol, not just SNMP monitoring of its
   state.  However, in the absence of a standard SNMP Security
   architecture, it is acceptable for implementations to implement these
   as read-only with an alternative interface for their modification.

4.4.  Default Configuration

   OSPF is a powerful routing protocol, equipped with features to handle
   virtually any configuration requirement that might reasonably be
   found within an Autonomous System.  With this power comes a fair
   degree of complexity, which the sheer number of objects in the MIB
   will attest to.  Care has therefore been taken, in constructing this
   MIB, to define default values for virtually every object, to minimize
   the amount of parameterization required in the typical case.  That
   default configuration is as follows:

   Given the following assumptions:

            - IP has already been configured

            - The ifTable has already been configured




Baker & Coltun                                                  [Page 5]

RFC 1252                   OSPF Version 2 MIB                August 1991


            - ifSpeed is estimated by the interface drivers

            - The OSPF Process automatically discovers all IP
            Interfaces and creates corresponding OSPF Interfaces

            - The TOS 0 metrics are autonomously derived from
            ifSpeed

            - The OSPF Process automatically creates the Areas
            required for the Interfaces

     The simplest configuration of an OSPF process requires that:

            - The OSPF Process be Enabled.

     This can be accomplished with a single SET:

                       ospfAdminStat := enabled.

     The configured system will have the following attributes:

            - The RouterID will be one of the IP addresses of the
            device

            - The device will be neither an Area Border Router nor
            an Autonomous System Border Router.

            - Every IP Interface, with or without an address, will
            be an OSPF Interface.

            - The AreaID of each interface will be 0.0.0.0, the
            Backbone.

            - Authentication will be disabled

            - All Broadcast and Point to Point interfaces will be
            operational.  NBMA Interfaces require the configuration
            of at least one neighbor.

            - Timers on all direct interfaces will be:
                     Hello Interval:        10 seconds
                     Dead Timeout:          40 Seconds
                     Retransmission:         5 Seconds
                     Transit Delay:          1 Second
                     Poll Interval:        120 Seconds

           - no direct links to hosts will be configured.




Baker & Coltun                                                  [Page 6]

RFC 1252                   OSPF Version 2 MIB                August 1991


           - no addresses will be summarized

           - Metrics, being a measure of bit duration, are
           unambiguous and intelligent.

           - No Virtual Links will be configured.

5.  Definitions


     RFC1252-MIB DEFINITIONS ::= BEGIN

     IMPORTS
             Counter, Gauge, IpAddress
                     FROM RFC1155-SMI
             mib-2
                     FROM RFC1213-MIB
             OBJECT-TYPE
                     FROM RFC-1212;

     --  This MIB module uses the extended OBJECT-TYPE macro as
     --  defined in [9].

             ospf OBJECT IDENTIFIER ::= { mib-2 13 }

     --  The Area ID, in OSPF, has the same format as an IP Address,
     --  but has the function of defining a summarization point for
     --  Link State Advertisements

             AreaID ::= IpAddress

     --  The Router ID, in OSPF, has the same format as an IP Address,
     --  but identifies the router independent of its IP Address.

             RouterID ::= IpAddress

     --  The OSPF Metric is defined as an unsigned value in the range

             Metric    ::= INTEGER (1..'FFFF'h)
             BigMetric ::= INTEGER (1..'FFFFFF'h)

     --  Boolean Values

             TruthValue ::= INTEGER { true (1), false (2) }

     --  Status Values

             Status ::= INTEGER { enabled (1), disabled (2) }