Deprecating Any-Source Multicast (ASM) for Interdomain Multicast
RFC 8815

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Internet Engineering Task Force (IETF)                    M. Abrahamsson
Request for Comments: 8815                                              
BCP: 229                                                        T. Chown
Category: Best Current Practice                                     Jisc
ISSN: 2070-1721                                              L. Giuliano
                                                  Juniper Networks, Inc.
                                                               T. Eckert
                                             Futurewei Technologies Inc.
                                                             August 2020

    Deprecating Any-Source Multicast (ASM) for Interdomain Multicast

Abstract

   This document recommends deprecation of the use of Any-Source
   Multicast (ASM) for interdomain multicast.  It recommends the use of
   Source-Specific Multicast (SSM) for interdomain multicast
   applications and recommends that hosts and routers in these
   deployments fully support SSM.  The recommendations in this document
   do not preclude the continued use of ASM within a single organization
   or domain and are especially easy to adopt in existing deployments of
   intradomain ASM using PIM Sparse Mode (PIM-SM).

Status of This Memo

   This memo documents an Internet Best Current Practice.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   BCPs is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8815.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Background
     2.1.  Multicast Service Models
     2.2.  ASM Routing Protocols
       2.2.1.  PIM Sparse Mode (PIM-SM)
       2.2.2.  Embedded-RP
       2.2.3.  BIDIR-RP
     2.3.  SSM Routing Protocols
   3.  Discussion
     3.1.  Observations on ASM and SSM Deployments
     3.2.  Advantages of SSM for Interdomain Multicast
       3.2.1.  Reduced Network Operations Complexity
       3.2.2.  No Network-Wide IP Multicast Group-Address Management
       3.2.3.  Intrinsic Source-Control Security
   4.  Recommendations
     4.1.  Deprecating Use of ASM for Interdomain Multicast
     4.2.  Including Network Support for IGMPv3/MLDv2
     4.3.  Building Application Support for SSM
     4.4.  Developing Application Guidance: SSM, ASM, Service
           Discovery
     4.5.  Preferring SSM Applications Intradomain
     4.6.  Documenting an ASM/SSM Protocol Mapping Mechanism
     4.7.  Not Filtering ASM Addressing between Domains
     4.8.  Not Precluding Intradomain ASM
     4.9.  Evolving PIM Deployments for SSM
   5.  Future Interdomain ASM Work
   6.  Security Considerations
   7.  IANA Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

   IP Multicast has been deployed in various forms, within private
   networks, the wider Internet, and federated networks such as national
   or regional research networks.  While a number of service models have
   been published, and in many cases revised over time, there has been
   no strong recommendation made by the IETF on the appropriateness of
   those models to certain scenarios, even though vendors and
   federations have often made such recommendations.

   This document addresses this gap by making a BCP-level recommendation
   to deprecate the use of Any-Source Multicast (ASM) for interdomain
   multicast, leaving Source-Specific Multicast (SSM) as the recommended
   interdomain mode of multicast.  Therefore, this document recommends
   that all hosts and routers that support interdomain multicast
   applications fully support SSM.

   This document does not make any statement on the use of ASM within a
   single domain or organization and, therefore, does not preclude its
   use.  Indeed, there are application contexts for which ASM is
   currently still widely considered well suited within a single domain.

   The main issue in most cases with moving to SSM is application