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Multicast Extensions to OSPF (RFC1584)

IP.com Disclosure Number: IPCOM000002418D
Original Publication Date: 1994-Mar-01
Included in the Prior Art Database: 2019-Feb-13

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Moy: AUTHOR

Related Documents

10.17487/RFC1584: DOI

Abstract

This memo documents enhancements to the OSPF protocol enabling the routing of IP multicast datagrams. [STANDARDS-TRACK]

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 2% of the total text.

Network Working Group J. Moy Request for Comments: 1584 Proteon, Inc. Category: Standards Track March 1994

Multicast Extensions to OSPF

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 documents enhancements to the OSPF protocol enabling the routing of IP multicast datagrams. In this proposal, an IP multicast packet is routed based both on the packet’s source and its multicast destination (commonly referred to as source/destination routing). As it is routed, the multicast packet follows a shortest path to each multicast destination. During packet forwarding, any commonality of paths is exploited; when multiple hosts belong to a single multicast group, a multicast packet will be replicated only when the paths to the separate hosts diverge.

OSPF, a link-state routing protocol, provides a database describing the Autonomous System’s topology. A new OSPF link state advertisement is added describing the location of multicast destinations. A multicast packet’s path is then calculated by building a pruned shortest-path tree rooted at the packet’s IP source. These trees are built on demand, and the results of the calculation are cached for use by subsequent packets.

The multicast extensions are built on top of OSPF Version 2. The extensions have been implemented so that a multicast routing capability can be introduced piecemeal into an OSPF Version 2 routing domain. Some of the OSPF Version 2 routers may run the multicast extensions, while others may continue to be restricted to the forwarding of regular IP traffic (unicasts).

Please send comments to mospf@gated.cornell.edu.

Moy [Page 1]

RFC 1584 Multicast Extensions to OSPF March 1994

Table of Contents

1 Introduction ........................................... 4 1.1 Terminology ............................................ 5 1.2 Acknowledgments ........................................ 6 2 Multicast routing in MOSPF ............................. 6 2.1 Routing characteristics ................................ 6 2.2 Sample path of a multicast datagram .................... 8 2.3 MOSPF forwarding mechanism ............................ 10 2.3.1 IGMP interface: the local group database .............. 10 2.3.2 A datagram’s shortest-path tree ....................... 14 2.3.3 Support for Non-broadcast networks .................... 16 2.3.4 Details concerning forwarding cache entries ........... 16 3 Inter-area multicasting ............................... 18 3.1 Extent of group-membership-LSAs ....................... 19 3.2 Building inter-area datagram shortest-path trees ...... 22 4 Inter-AS multicasting ................................. 27 4.1 Building inter-AS datagram shortest-path trees ....

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