Internet Group Management Protocol, Version 3
RFC 3376

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Network Working Group                                            B. Cain
Request for Comments: 3376                               Cereva Networks
Obsoletes: 2236                                               S. Deering
Category: Standards Track                                    I. Kouvelas
                                                           Cisco Systems
                                                               B. Fenner
                                                    AT&T Labs - Research
                                                          A. Thyagarajan
                                                                Ericsson
                                                            October 2002

             Internet Group Management Protocol, Version 3

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 (2002).  All Rights Reserved.

Abstract

   This document specifies Version 3 of the Internet Group Management
   Protocol, IGMPv3.  IGMP is the protocol used by IPv4 systems to
   report their IP multicast group memberships to neighboring multicast
   routers.  Version 3 of IGMP adds support for "source filtering", that
   is, the ability for a system to report interest in receiving packets
   *only* from specific source addresses, or from *all but* specific
   source addresses, sent to a particular multicast address.  That
   information may be used by multicast routing protocols to avoid
   delivering multicast packets from specific sources to networks where
   there are no interested receivers.

   This document obsoletes RFC 2236.

Cain, et. al.               Standards Track                     [Page 1]
RFC 3376                         IGMPv3                     October 2002

Table of Contents

   1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  The Service Interface for Requesting IP Multicast Reception .   3
   3.  Multicast Reception State Maintained by Systems . . . . . . .   5
   4.  Message Formats . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Description of the Protocol for Group Members . . . . . . . .  19
   6.  Description of the Protocol for Multicast Routers . . . . . .  24
   7.  Interoperation with Older Versions of IGMP. . . . . . . . . .  35
   8.  List of Timers, Counters, and Their Default Values. . . . . .  40
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  43
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  47
   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  47
   12. Normative References. . . . . . . . . . . . . . . . . . . . .  47
   13. Informative References. . . . . . . . . . . . . . . . . . . .  47
       Appendix A. Design Rationale. . . . . . . . . . . . . . . . .  49
       Appendix B. Summary of changes from IGMPv2. . . . . . . . . .  50
       Authors' Addresses. . . . . . . . . . . . . . . . . . . . . .  52
       Full Copyright Statement. . . . . . . . . . . . . . . . . . .  53

1. Introduction

   The Internet Group Management Protocol (IGMP) is used by IPv4 systems
   (hosts and routers) to report their IP multicast group memberships to
   any neighboring multicast routers.  Note that an IP multicast router
   may itself be a member of one or more multicast groups, in which case
   it performs both the "multicast router part" of the protocol (to
   collect the membership information needed by its multicast routing
   protocol) and the "group member part" of the protocol (to inform
   itself and other, neighboring multicast routers of its memberships).

   IGMP is also used for other IP multicast management functions, using
   message types other than those used for group membership reporting.
   This document specifies only the group membership reporting functions
   and messages.

   This document specifies Version 3 of IGMP.  Version 1, specified in
   [RFC-1112], was the first widely-deployed version and the first
   version to become an Internet Standard.  Version 2, specified in
   [RFC-2236], added support for "low leave latency", that is, a
   reduction in the time it takes for a multicast router to learn that
   there are no longer any members of a particular group present on an
   attached network.  Version 3 adds support for "source filtering",
   that is, the ability for a system to report interest in receiving
   packets *only* from specific source addresses, as required to support
   Source-Specific Multicast [SSM], or from *all but* specific source
   addresses, sent to a particular multicast address.  Version 3 is
   designed to be interoperable with Versions 1 and 2.