Support for Multicast over UNI 3.0/3.1 based ATM Networks
RFC 2022

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Network Working Group                                        G. Armitage
Request for Comments: 2022                                      Bellcore
Category: Standards Track                                  November 1996

       Support for Multicast over UNI 3.0/3.1 based ATM Networks.

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

   Mapping the connectionless IP multicast service over the connection
   oriented ATM services provided by UNI 3.0/3.1 is a non-trivial task.
   This memo describes a mechanism to support the multicast needs of
   Layer 3 protocols in general, and describes its application to IP
   multicasting in particular.

   ATM based IP hosts and routers use a Multicast Address Resolution
   Server (MARS) to support RFC 1112 style Level 2 IP multicast over the
   ATM Forum's UNI 3.0/3.1 point to multipoint connection service.
   Clusters of endpoints share a MARS and use it to track and
   disseminate information identifying the nodes listed as receivers for
   given multicast groups. This allows endpoints to establish and manage
   point to multipoint VCs when transmitting to the group.

   The MARS behaviour allows Layer 3 multicasting to be supported using
   either meshes of VCs or ATM level multicast servers. This choice may
   be made on a per-group basis, and is transparent to the endpoints.

Armitage                    Standards Track                     [Page 1]
RFC 2022          Multicast over UNI 3.0/3.1 based ATM     November 1996

Table of Contents

   1. Introduction.................................................   4
    1.1 The Multicast Address Resolution Server (MARS).............   5
    1.2 The ATM level multicast Cluster............................   5
    1.3 Document overview..........................................   6
    1.4 Conventions................................................   7
   2. The IP multicast service model...............................   7
   3. UNI 3.0/3.1 support for intra-cluster multicasting...........   8
    3.1 VC meshes..................................................   9
    3.2 Multicast Servers..........................................   9
    3.3 Tradeoffs..................................................  10
    3.4 Interaction with local UNI 3.0/3.1 signalling entity.......  11
   4. Overview of the MARS.........................................  12
    4.1 Architecture...............................................  12
    4.2 Control message format.....................................  12
    4.3 Fixed header fields in MARS control messages...............  13
      4.3.1 Hardware type..........................................  14
      4.3.2 Protocol type..........................................  14
      4.3.3 Checksum...............................................  15
      4.3.4 Extensions Offset......................................  15
      4.3.5 Operation code.........................................  16
      4.3.6 Reserved...............................................  16
   5. Endpoint (MARS client) interface behaviour...................  16
    5.1 Transmit side behaviour....................................  17
      5.1.1 Retrieving Group Membership from the MARS..............  18
      5.1.2 MARS_REQUEST, MARS_MULTI, and MARS_NAK messages........  20
      5.1.3 Establishing the outgoing multipoint VC................  22
      5.1.4 Monitoring updates on ClusterControlVC.................  24
        5.1.4.1 Updating the active VCs............................  24
        5.1.4.2 Tracking the Cluster Sequence Number...............  25
      5.1.5 Revalidating a VC's leaf nodes.........................  26
        5.1.5.1 When leaf node drops itself........................  27
        5.1.5.2 When a jump is detected in the CSN.................  27
      5.1.6 'Migrating' the outgoing multipoint VC.................  27
    5.2. Receive side behaviour....................................  29
      5.2.1 Format of the MARS_JOIN and MARS_LEAVE Messages........  30
        5.2.1.1 Important IPv4 default values......................  32
      5.2.2 Retransmission of MARS_JOIN and MARS_LEAVE messages....  33
      5.2.3 Cluster member registration and deregistration.........  34
    5.3 Support for Layer 3 group management.......................  34
    5.4 Support for redundant/backup MARS entities.................  36
      5.4.1 First response to MARS problems........................  36
      5.4.2 Connecting to a backup MARS............................  37
      5.4.3 Dynamic backup lists, and soft redirects...............  37
    5.5 Data path LLC/SNAP encapsulations..........................  40