rfc2127.txt

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Network Working Group                                 G. Roeck, Editor
Request for Comments: 2127                               cisco Systems
Category: Standards Track                                   March 1997


              ISDN Management Information Base using SMIv2

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.

Abstract

   This memo defines a portion of the Management Information Base (MIB)
   for use with network management protocols in the Internet community.
   In particular, it defines a minimal set of managed objects for SNMP-
   based management of ISDN terminal interfaces.  ISDN interfaces are
   supported on a variety of equipment (for data and voice) including
   terminal adapters, bridges, hosts, and routers.

   This document specifies a MIB module in a manner that is compliant to
   the SNMPv2 SMI.  The set of objects is consistent with the SNMP
   framework and existing SNMP standards.

   This document is a product of the ISDN MIB working group within the
   Internet Engineering Task Force.  Comments are solicited and should
   be addressed to the working group's mailing list at isdn-
   [e-mail] and/or the author.

   The current version of this document reflects changes made during the
   last call period and the IESG review.

Table of Contents

   1 The SNMPv2 Network Management Framework ......................    2
   2 Object Definitions ...........................................    2
   3 Overview .....................................................    3
   3.1 Structure of the MIB .......................................    3
   3.1.1 General Description ......................................    3
   3.2 Relationship to the Interfaces MIB .........................    4
   3.2.1 Layering Model ...........................................    4
   3.2.2 ifTestTable ..............................................    8
   3.2.3 ifRcvAddressTable ........................................    8
   3.2.4 ifEntry ..................................................    8



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   3.2.4.1 ifEntry for a Basic Rate hardware interface ............    8
   3.2.4.2 ifEntry for a B channel ................................    9
   3.2.4.3 ifEntry for LAPD (D channel Data Link Layer) ...........   10
   3.2.4.4 ifEntry for a signaling channel ........................   12
   3.3 Relationship to other MIBs .................................   14
   3.3.1 Relationship to the DS1/E1 MIB ...........................   14
   3.3.2 Relationship to the DS0 and DS0Bundle MIBs ...............   14
   3.3.3 Relationship to the Dial Control MIB .....................   14
   3.4 ISDN interface specific information and implementation hints
        ...........................................................   14
   3.4.1 ISDN leased lines ........................................   14
   3.4.2 Hyperchannels ............................................   15
   3.4.3 D channel backup and NFAS trunks .........................   16
   3.4.4 X.25 based packet-mode service in B and D channels .......   16
   3.4.5 SPID handling ............................................   17
   3.4.6 Closed User Groups .......................................   17
   3.4.7 Provision of point-to-point line topology ................   18
   3.4.8 Speech and audio bearer capability information elements ..   18
   3.4.9 Attaching incoming calls to router ports .................   19
   3.4.10 Usage of isdnMibDirectoryGroup and isdnDirectoryTable ...   20
   4 Definitions ..................................................   21
   5 Acknowledgments ..............................................   47
   6 References ...................................................   47
   7 Security Considerations ......................................   49
   8 Author's Address .............................................   49

1.  The SNMPv2 Network Management Framework

   The SNMPv2 Network Management Framework presently consists of three
   major components.  They are:

   o    the SMI, described in RFC 1902 [1] - the mechanisms used for
        describing and naming objects for the purpose of management.

   o    the MIB-II, STD 17, RFC 1213 [2] - the core set of managed
        objects for the Internet suite of protocols.

   o    the protocol, STD 15, RFC 1157 [3] and/or RFC 1905 [4], -
        the protocol for accessing managed objects.

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

2.  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)



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RFC 2127                        ISDN MIB                      March 1997


   defined in the SMI.  In particular, each 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

3.1.  Structure of the MIB

   For managing ISDN interfaces, the following information is necessary:

   o    Information for managing physical interfaces. In case of ISDN
        primary rate, this are usually T1 or E1 lines, being managed in
        the DS1/E1 MIB [12].  For Basic Rate lines, physical interfaces
        are managed by this MIB.

   o    Information for managing B channels.

   o    Information for managing signaling channels.

   o    Optionally, information for managing Terminal Endpoints (TE).
        A Terminal Endpoint is a link layer connection to a switch.

   o    Optionally, information for managing a list of directory numbers.

   In order to manage connections over ISDN lines, the management of
   peer information and call history information is required as well.
   This information is defined in the Dial Control MIB [15].

   The purpose for splitting the required information in two MIBs is to
   be able to use parts of this information for non-ISDN interfaces as
   well.  In particular, the Dial Control MIB might also be used for
   other types of interfaces, e.g. modems or X.25 virtual connections.

   Within this document, information has been structured into five
   groups, which are described in the following chapters.

3.1.1.  General Description

   This MIB controls all aspects of ISDN interfaces.  It consists of
   five groups.

   o    The isdnMibBasicRateGroup is used to provide information
        regarding physical Basic Rate interfaces.

   o    The isdnMibBearerGroup is used to control B (bearer) channels.



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        It supports configuration parameters as well as statistical
        information related to B channels.

   o    The isdnMibSignalingGroup is used to control D (delta) channels.
        There are three tables in this group. The isdnSignalingTable and
        isdnSignalingStatsTable support ISDN Network Layer configuration
        and statistics.  The isdnLapdTable supports ISDN Data Link Layer
        (LAPD) configuration and statistics.

   o    The optional isdnMibEndpointGroup can be used to specify
        Terminal Endpoints. It is required only if there are non-ISDN
        endpoints defined for a given D channel, or if additional
        information like Terminal Endpoint Identifier (TEI) values or
        Service Profile IDentifiers (SPID) is required to identify a
        given ISDN user.

   o    The optional isdnMibDirectoryGroup can be used to specify a
        list of directory numbers for each signaling channel.  It is
        required only if the directory numbers to be accepted differ
        from the isdnSignalingCallingAddress as specified in the
        isdnSignalingTable.

3.2.  Relationship to the Interfaces MIB

   This section clarifies the relationship of this MIB to the Interfaces
   MIB [11].  Several areas of correlation are addressed in the
   following subsections.  The implementor is referred to the Interfaces
   MIB document in order to understand the general intent of these
   areas.

3.2.1.  Layering Model

   An ISDN interface usually consists of a D channel and a number of B
   channels, all of which are layered on top of a physical interface.

   Furthermore, there are multiple interface layers for each D channel.
   There are Data Link Layer (LAPD) as well as Network Layer entities.

   This is accomplished in this MIB by creating a logical interface
   (ifEntry) for each of the D channel entities and a logical interface
   (ifEntry) for each of the B channels.  These are then correlated to
   each other and to the physical interface using the ifStack table of
   the Interfaces MIB [11].








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   The basic model, therefore, looks something like this:

       | |
    +--+ +--+
    | D ch. |
    |Layer 3|
    +--+ +--+
       | |        | |            | |    <== interface to upper
    +--+ +--+  +--+ +--+      +--+ +--+     layers, to be provided
    | D ch. |  |   B   |      |   B   |     by ifStack table
    |Layer 2|  |channel| .... |channel|
    +--+ +--+  +--+ +--+      +--+ +--+
       | |        | |            | |    <== attachment to physical
    +--+ +--------+ +------------+ +----+   interfaces, to be provided
    |         physical interface        |   by ifStack table
    |          (S/T, U or T1/E1)        |
    +-----------------------------------+
   Mapping of B/D channels to physical interfaces

   Each D channel can support multiple Terminal Endpoints.  Terminal
   Endpoints can either be one or multiple ISDN signaling channels, or
   channels supporting X.25 based packet mode services.

   To accomplish this, there can be multiple Network Layer entities on
   top of each ISDN Data Link Layer (LAPD) interface.  The detailed
   model therefore looks something like this, including interface types
   as examples:

  +------+  +----+  +----+
  |x25ple|  |isdn|  |isdn|    Terminal Endpoints (X.25 or ISDN)
  +--+---+  +-+--+  +-+--+
     |        |       |
     | +------+       |       |      |   <== Interface to upper layers,
     | | +------------+       |      |       to be provided by ifStack
     | | |                    |      |       table
    ++-+-++                 +-+-+  +-+-+
    |lapd | D channel       |ds0|  |ds0| B channels
    +--+--+ Data Link Layer +-+-+  +-+-+
       |                      |      |
    +--+----------------------+------+--------------------+
    |                 ds1 or isdns/isdnu                  |
    +-----------------------------------------------------+

   Detailed interface mapping

   IfEntries are maintained for each D channel Network Layer entity
   (Terminal Endpoint), for LAPD and for each B channel.




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   The ifType for a Terminal Endpoint can be isdn(63) for ISDN signaling
   channels or x25ple(40) for X.25 based packet mode services.  The
   ifType for D channel Data Link Layer (LAPD) interfaces is lapd(77).
   The ifType for B channels is ds0(81).  The ifType for physical
   interfaces is the matching IANA ifType, usually ds1(18) for Primary
   Rate interfaces or isdns(75)/isdnu(76) for Basic Rate interfaces.

   The ifStackTable is used to map B channels and LAPD interfaces to
   physical interfaces and to map D channel Network Layer interfaces
   (Terminal Endpoints) to LAPD.

   In the example given above, the assignment of index values could for
   example be as follows:

ifIndex ifType      ISDN MIB tables     Description
                    indexed by ifIndex

   1    isdns(75)   isdnBasicRateTable  Basic Rate physical interface
   2    lapd(77)    isdnLapdTable       LAPD interface
   3    x25ple(40)  isdnEndpointTable   X.25 Packet Layer
   4    isdn(63)    isdnSignalingTable  ISDN signaling channel #1
                    isdnEndpointTable
   5    isdn(63)    isdnSignalingTable  ISDN signaling channel #2
                    isdnEndpointTable
   6    ds0(81)     isdnBearerTable     B channel #1
   7    ds0(81)     isdnBearerTable     B channel #2
   8    ppp(23)                         peer entry #1 (see below)
   9    ppp(23)                         peer entry #2 (see below)























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   The corresponding ifStack table entries would then be:

        ifStackTable Entries