RFC 3376 (rfc3376) - Page 2 of 53

Internet Group Management Protocol, Version 3

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.



Cain, et. al.               Standards Track