PIM Source Discovery for ASM Deployments
draft-mankamana-pim-source-discovery-00

PIM Working Group                                              M. Mishra
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                            20 July 2026
Expires: 21 January 2027

                PIM Source Discovery for ASM Deployments
                draft-mankamana-pim-source-discovery-00

Abstract

   This document discusses the operational challenges of Any-Source
   Multicast deployments that use PIM Sparse Mode and explores whether
   PIM extensions can simplify source discovery and operational behavior
   while preserving the host-facing ASM service model.

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   This Internet-Draft will expire on 21 January 2027.

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Table of Contents

   1.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   3
   6.  Capability Discovery  . . . . . . . . . . . . . . . . . . . .   3
   7.  PIM Source Discovery Extensions . . . . . . . . . . . . . . .   3
   8.  Router Behavior . . . . . . . . . . . . . . . . . . . . . . .   3
   9.  Relationship to Existing ASM Mechanisms . . . . . . . . . . .   4
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   4
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   12. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . .   4
   13. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     14.1.  Normative References . . . . . . . . . . . . . . . . . .   4
     14.2.  Informative References . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Problem Statement

   [RFC7761] defines Protocol Independent Multicast - Sparse Mode (PIM-
   SM).  PIM-SM supports the Any-Source Multicast (ASM) service model by
   building shared trees rooted at a Rendezvous Point (RP) for multicast
   groups, and by optionally switching to source trees after sources are
   discovered.

   ASM has been widely deployed in operational networks.  In many
   deployments, especially IPTV deployments, the ASM service model is
   not only a network design choice but also part of the host and
   application behavior.  A network operator cannot always remove ASM
   simply by changing the network.  Moving away from ASM may require
   changes on receivers, applications, middleware, or customer premises
   devices.  In IPTV networks, the number of set-top boxes can be in the
   millions, so requiring all end hosts to be upgraded or replaced is
   often not operationally practical.

   The PIM architecture defines the RP as the point where receivers and
   sources meet in the ASM model.  Multiple mechanisms have been
   specified or deployed to configure or discover the RP, including
   static configuration and dynamic discovery mechanisms.  In addition,
   MSDP [RFC3618] has been defined to support source discovery across
   PIM-SM domains, allowing RPs in different domains to advertise active
   sources to one another.  These mechanisms solve important parts of
   the ASM problem space, but they also add operational dependencies
   around RP placement, RP discovery, inter-domain source discovery,
   filtering policy, scaling, and troubleshooting.

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   As a result, the overall ASM deployment experience can become
   difficult for operators.  The network may need to maintain RP state,
   source registration behavior, RP discovery behavior, MSDP peering and
   policy, and multicast forwarding state across many groups, sources,
   domains, and administrative boundaries.  When service behavior is
   incorrect, the operator often has to reason across several control-
   plane mechanisms before determining whether the issue is host
   signaling, RP discovery, source registration, MSDP source
   advertisement, PIM Join/Prune state, or multicast forwarding.

   There is therefore a need to explore whether the ASM deployment
   experience can be simplified without requiring a disruptive migration
   of existing end hosts away from ASM.  This document is intended to
   examine possible PIM extensions that can improve source discovery and
   operational behavior while preserving compatibility with deployed ASM
   host behavior.

2.  Requirements Language

   To be added.

3.  Terminology

   To be added.

4.  Applicability

   To be added.

5.  Protocol Overview

   To be added.

6.  Capability Discovery

   To be added.

7.  PIM Source Discovery Extensions

   To be added.

8.  Router Behavior

   To be added.

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9.  Relationship to Existing ASM Mechanisms

   To be added.

10.  Security Considerations

   To be added.

11.  IANA Considerations

   To be added.

12.  Open Issues

   To be added.

13.  Acknowledgements

   To be added.

14.  References

14.1.  Normative References

   [RFC7761]  Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
              Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
              Multicast - Sparse Mode (PIM-SM): Protocol Specification
              (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
              2016, <https://www.rfc-editor.org/info/rfc7761>.

14.2.  Informative References

   [RFC3618]  Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source
              Discovery Protocol (MSDP)", RFC 3618,
              DOI 10.17487/RFC3618, October 2003,
              <https://www.rfc-editor.org/info/rfc3618>.

Author's Address

   Mankamana Mishra
   Cisco Systems
   821 Alder Drive
   Milpitas, CA 95035
   United States of America
   Email: mankamis@cisco.com

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