Overview of the Internet Multicast Routing Architecture
RFC 5110

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Network Working Group                                          P. Savola
Request for Comments: 5110                                     CSC/FUNET
Category: Informational                                     January 2008

        Overview of the Internet Multicast Routing Architecture

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   This document describes multicast routing architectures that are
   currently deployed on the Internet.  This document briefly describes
   those protocols and references their specifications.

   This memo also reclassifies several older RFCs to Historic.  These
   RFCs describe multicast routing protocols that were never widely
   deployed or have fallen into disuse.

Table of Contents

   1. Introduction ....................................................3
      1.1. Multicast-Related Abbreviations ............................4
   2. Multicast Routing ...............................................4
      2.1. Setting up Multicast Forwarding State ......................5
           2.1.1. PIM-SM ..............................................5
           2.1.2. PIM-DM ..............................................5
           2.1.3. Bidirectional PIM ...................................6
           2.1.4. DVMRP ...............................................6
           2.1.5. MOSPF ...............................................7
           2.1.6. BGMP ................................................7
           2.1.7. CBT .................................................7
           2.1.8. Interactions and Summary ............................7
      2.2. Distributing Topology Information ..........................8
           2.2.1. Multiprotocol BGP ...................................8
           2.2.2. OSPF/IS-IS Multi-Topology Extensions ................9
           2.2.3. Issue: Overlapping Unicast/Multicast Topology .......9
           2.2.4. Summary ............................................10
      2.3. Learning (Active) Sources .................................10
           2.3.1. SSM ................................................11
           2.3.2. MSDP ...............................................11
           2.3.3. Embedded-RP ........................................11
           2.3.4. Summary ............................................12

Savola                       Informational                      [Page 1]
RFC 5110               Multicast Routing Overview           January 2008

      2.4. Configuring and Distributing PIM RP Information ...........12
           2.4.1. Manual RP Configuration ............................12
           2.4.2. Embedded-RP ........................................13
           2.4.3. BSR and Auto-RP ....................................13
           2.4.4. Summary ............................................14
      2.5. Mechanisms for Enhanced Redundancy ........................14
           2.5.1. Anycast RP .........................................14
           2.5.2. Stateless RP Failover ..............................14
           2.5.3. Bidirectional PIM ..................................15
           2.5.4. Summary ............................................15
      2.6. Interactions with Hosts ...................................15
           2.6.1. Hosts Sending Multicast ............................15
           2.6.2. Hosts Receiving Multicast ..........................15
           2.6.3. Summary ............................................16
      2.7. Restricting Multicast Flooding in the Link Layer ..........16
           2.7.1. Router-to-Router Flooding Reduction ................16
           2.7.2. Host/Router Flooding Reduction .....................17
           2.7.3. Summary ............................................18
   3. Acknowledgements ...............................................18
   4. IANA Considerations ............................................18
   5. Security Considerations ........................................19
   6. References .....................................................19
      6.1. Normative References ......................................19
      6.2. Informative References ....................................20
   Appendix A. Multicast Payload Transport Extensions.................24
      A.1. Reliable Multicast.........................................24
      A.2. Multicast Group Security...................................24

Savola                       Informational                      [Page 2]
RFC 5110               Multicast Routing Overview           January 2008

1.  Introduction

   This document provides a brief overview of multicast routing
   architectures that are currently deployed on the Internet and how
   those protocols fit together.  It also describes those multicast