RFC 1768 (rfc1768) - Page 2 of 45

Host Group Extensions for CLNP Multicasting

RFC 1768                   CLNP Multicasting                  March 1995


Table of Contents

   1.  Introduction ..........................................  2
   2.  Levels of Conformance..................................  3
   3.  Group Network Addresses................................  4
   4.  Model of a CLNP End System Multicast Implementation....  8
   5.  Extensions to the CLNP Protocol........................  8
   6.  Extensions to the ES-IS Routeing Protocol ............. 15
   7.  Security Considerations ............................... 39
   Appendix A.  Differences with RFC 1112 .................... 40
   Appendix B.  Issues Under Study ........................... 43
   References ................................................ 44
   Author's Address .......................................... 45

1.      Introduction

   This memo provides a specification for multicast extensions for CLNP
   in order to provide a CLNP based Internet the capabilities provided
   for IP by RFC 1112 (Host Extensions for IP Multicasting) [RFC 1112].
   This memo uses an outline similar to that of RFC 1112.

   Paraphrasing RFC 1112, "CLNP multicasting is the transmission of a
   CLNP datagram to a "host group", a set of zero or more End Systems
   identified by a single group Network address (GNA). A multicast
   datagram is delivered to all members of its destination host group
   with the same "best-efforts" reliability as regular unicast CLNP
   datagrams, i.e., the datagram is not guaranteed to arrive intact at
   all members of the destination group or in the same order relative to
   other datagrams.

   "The membership of a host group is dynamic; that is End Systems may
   join and leave groups at any time. There is no restrictions on the
   location or number of members in a host group. An End System may be a
   member of more than one group at a time. An End System need not be a
   member of a group to send datagrams to it.

   "A host group may be permanent or transient. A permanent group has an
   administratively assigned GNA. It is the address, not the membership
   of the group, that is permanent; at any time a permanent group may
   have any number of members, even zero.

   "Internetwork forwarding of CLNP multicast datagrams is handled by
   "multicast capable" Intermediate Systems which may be co-resident
   with unicast capable Intermediate Systems.

   The multicast extensions to the CLNP addressing structure defines
   group Network addresses which identify host groups.  The multicast
   extensions to CLNP provides a means for identifying a CLNP packet and



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