Mboned                                                    M. Abrahamsson
Internet-Draft                                                 T-Systems
Intended status: Best Current Practice                          T. Chown
Expires: April 25, 2019                                             Jisc
                                                             L. Giuliano
                                                  Juniper Networks, Inc.
                                                               T. Eckert
                                                        October 22, 2018

               Deprecating ASM for Interdomain Multicast


   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 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 organisation or domain and
   are especially easy to adopt in these existing intradomain ASM

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in "Key words for use in
   RFCs to Indicate Requirement Levels" [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 25, 2019.

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Copyright Notice

   Copyright (c) 2018 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
   2.  Multicast routing protocols . . . . . . . . . . . . . . . . .   3
     2.1.  ASM routing protocols . . . . . . . . . . . . . . . . . .   4
     2.2.  SSM Routing protocols . . . . . . . . . . . . . . . . . .   4
   3.  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Observations on ASM and SSM deployments . . . . . . . . .   5
     3.2.  Advantages of SSM for interdomain multicast . . . . . . .   6
   4.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Deprecating use of ASM for interdomain multicast  . . . .   7
     4.2.  Including network support for IGMPv3 / MLDv2  . . . . . .   7
     4.3.  Building application support for SSM  . . . . . . . . . .   8
     4.4.  Preferring SSM applications intradomain . . . . . . . . .   8
     4.5.  Documenting an ASM/SSM protocol mapping mechanism . . . .   8
     4.6.  Not filtering ASM addressing between domains  . . . . . .   9
     4.7.  Not precluding Intradomain ASM  . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

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

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   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 ASM for interdomain multicast, leaving SSM as
   the recommended interdomain mode of multicast.  This recommendation
   thus also implicitly states that all hosts and routers that are
   expected to support interdomain multicast applications fully support

   This document does not make any statement on the use of ASM within a
   single domain or organisation, 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
   support.  Many applications are initially deployed for intradomain
   use and are later deployed interdomain.  Therefore, this document
   recommends applications support SSM, even when they are initially
   intended for intradomain use.  As explained below, SSM applications
   are readily compatible with existing intradomain ASM deployments as
   SSM is merely a subset of ASM.

2.  Multicast routing protocols

   Any-Source Multicast (ASM) and Source-Specific Multicast (SSM) are
   the two multicast service models in use today.  In ASM, as originally
   described in [RFC1112], receivers express interest in joining a
   multicast group address and routers use multicast routing protocols
   to deliver traffic from the sender(s) to the receivers.  If there are
   multiple senders for a given group, traffic from all senders will be
   delivered to the receiver.  Since receivers specify only the group
   address, the network, and therefore the multicast routing protocols,
   are responsible for source discovery.  In SSM, by contrast, receivers
   specify both group and source when expressing interest in joining a
   multicast stream.  Source discovery in SSM is handled by some out-of-
   band mechanism (ie, the application layer), which drastically
   simplifies the network and how the multicast routing protocols

   IANA has reserved specific ranges of IPv4 and IPv6 address space for
   multicast addressing.  Guidelines for IPv4 multicast address
   assignments can be found in [RFC5771], while guidelines for IPv6
   multicast address assignments can be found in [RFC2375] and
   [RFC3307].  The IPv6 multicast address format is described in

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2.1.  ASM routing protocols

   The most commonly deployed ASM routing protocol is Protocol
   Independent Multicast - Sparse Mode, or PIM-SM, as detailed in
   [RFC7761].  PIM-SM, as the name suggests, was designed to be used in
   scenarios where the subnets with receivers are sparsely distributed
   throughout the network.  Because it does not know sender addresses in
   advance, PIM-SM uses the concept of a Rendezvous Point (RP) as a
   'meeting point' for sources and receivers, and all routers in a PIM-
   SM domain are configured to use specific RP(s), either explicitly or
   through dynamic RP discovery protocols.

   To enable PIM-SM to work between multiple domains, an inter-RP
   signalling protocol known as Multicast Source Discovery Protocol
   (MSDP) [RFC3618] is used to allow an RP in one domain to learn the
   existence of a source in another domain.  Deployment scenarios for
   MSDP are given in [RFC4611].  MSDP floods information about all
   active sources for all multicast streams to all RPs in all the
   domains - even if there is no receiver for a given application in a
   domain.  As a result of this key scalability and security issue,
   along with other deployment challenges with the protocol, MSDP was
   never extended to support IPv6 and remains an Experimental protocol.

   To this day, there is no IETF Proposed Standard level interdomain
   solution for IPv4 ASM multicast because MSDP was the "best" component
   for the interdomain source discovery problem, and it is Experimental.
   Other protocol options where investigated at the same time but were
   never implemented or deployed and are now historic (e.g: [RFC3913]).

   Due to the availability of more bits in an IPv6 address than in IPv4,
   an IPv6-specific mechanism was able to be designed in support of
   interdomain ASM with PIM-SM.  Embedded-RP [RFC3956] allows routers
   supporting the protocol to determine the RP for the group without any
   prior configuration or discovery protocols, simply by observing the
   unicast RP address that is embedded (included) in the IPv6 multicast
   group address.  Embedded-RP allows PIM-SM operation across any IPv6
   network in which there is an end-to-end path of routers supporting
   the mechanism.

2.2.  SSM Routing protocols

   SSM is detailed in [RFC4607].  Note that there is no separate
   document for PIM-SSM as it merely leverages a subset of [RFC7761].

   PIM-SSM expects that the sender's source address(es) is known in
   advance by receivers by some out-of-band mechanism (typically in the
   application layer), and thus the receiver's designated router can

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   send a PIM JOIN directly towards the source without needing to use an

   IPv4 addresses in the 232/8 ( to range are
   designated as source-specific multicast (SSM) destination addresses
   and are reserved for use by source-specific applications and
   protocols.  See [RFC4607].  For IPv6, the address prefix FF3x::/32 is
   reserved for source-specific multicast use.

3.  Discussion

3.1.  Observations on ASM and SSM deployments

   In enterprise and campus scenarios, ASM in the form of PIM-SM is
   likely the most commonly deployed multicast protocol.  The
   configuration and management of an RP (including RP redundancy)
   within a single domain is a well understood operational practice.
   However, if interworking with external PIM domains is needed in IPv4
   multicast deployments, interdomain MSDP is required to exchange
   information about sources between domain RPs.  Deployment experience
   has shown MSDP to be a complex and fragile protocol to manage and
   troubleshoot (complex flooding RPF rules, state attack protection,
   filtering of undesired sources, ...).

   PIM-SM is a general purpose protocol that can handle all use cases.
   In particular, it was designed for cases such as videoconferencing
   where multiple sources may come and go during a multicast session.
   But for cases where a single, persistent source for a group is used,
   and receivers can be configured to know of that source, PIM-SM has
   unnecessary complexity.  Therefore, SSM eliminates the most
   components of PIM-SM.

   As explained above, MSDP was not extended to support to IPv6.
   Instead, the proposed interdomain ASM solution for PIM-SM with IPv6
   is Embedded-RP, which allows the RP address for a multicast group to
   be embedded in the group address, making RP discovery automatic for
   all routers on the path between a receiver and a sender.  Embedded-RP
   can support lightweight ad-hoc deployments.  However, it relies on a
   single RP for an entire group that could only be made resilient
   within one domain.  While this approach solves the MSDP issues, it
   does not solve the problem of unauthorised sources sending traffic to
   ASM multicast groups; this security issues is one of biggest problem
   of interdomain multicast.

   As stated in RFC 4607, SSM is particularly well-suited to
   dissemination-style applications with one or more senders whose
   identities are known (by some oob mechanism) before the application
   starts running or applications that utilize some signaling to

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   indicate the source address of the multicast stream (eg, electronic
   programming guide in IPTV applications).  PIM-SSM is therefore very
   well-suited to applications such as classic linear broadcast TV over

   SSM requires applications, host operating systems and the designated
   routers connected to receiving hosts to support IGMPv3 [RFC3376] and
   MLDv2 [RFC3810].  Support for IGMPv3 and MLDv2 has become widespread
   in common OSes for several years (Windows, MacOS, Linux/Android) and
   is no longer an impediment to SSM deployment.

3.2.  Advantages of SSM for interdomain multicast

   A significant benefit of SSM is the reduced complexity that comes
   through eliminating the network-based source discovery required in
   ASM.  Specifically, SSM eliminates the need for RPs, shared trees,
   Shortest Path Tree (SPT) switchovers, PIM registers, MSDP, dynamic RP
   discovery mechanisms (BSR/AutoRP) and data-driven state creation.
   SSM simply utilizes a small subset of PIM-SM, alongside the
   integration with IGMPv3 / MLDv2, where the source address signaled
   from the receiver is immediately used to create (S,G) state.
   Eliminating network-based source discovery for interdomain multicast
   means the vast majority of the complexity of multicast goes away.

   This reduced complexity makes SSM radically simpler to manage,
   troubleshoot and operate, particularly for backbone network
   operators.  This is the main motivation for the recommendation to
   deprecate the use of ASM in interdomain scenarios.  Note that SSM
   operation is standardised in PIM-SM (RFC7761); there is no separate
   specification for PIM-SSM.

   RFC 4607 details many benefits of SSM, including:

      "Elimination of cross-delivery of traffic when two sources
      simultaneously use the same source-specific destination address;

      Avoidance of the need for inter-host coordination when choosing
      source-specific addresses, as a consequence of the above;

      Avoidance of many of the router protocols and algorithms that are
      needed to provide the ASM service model."

   Further discussion can also be found in [RFC3569].

   SSM is considered more secure in that it inherently supports access
   control.  That is, receivers only get packets from the sources they
   explicitly specify, as opposed to ASM where any host can send traffic

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   to a group address and have it transmitted to all receivers.  This
   topic is expanded upon in [RFC4609].

4.  Recommendations

4.1.  Deprecating use of ASM for interdomain multicast

   This document recommends that the use of ASM is deprecated for
   interdomain multicast, and thus implicitly, that hosts and routers
   that support such interdomain applications fully support SSM and its
   associated protocols.  Best current practices for deploying
   interdomain multicast using SSM are documented in [RFC8313].

   The recommendation applies to the use of ASM between domains where
   either MSDP (IPv4) or Embedded-RP (IPv6) is used.

   An interdomain use of ASM multicast in the context of this document
   is one where PIM-SM with RPs/MSDP/Embedded-RP is run on routers
   operated by two or more separate administrative entities (domains,

   The more inclusive interpretation of this recommendation is that it
   also extends to the case where PIM may only be operated in a single
   operator domain, but where user hosts or non-PIM network edge devices
   are under different operator control.  A typical example of this case
   is an SP providing IPTV (single operator domain for PIM) to
   subscribers operating an IGMP proxy home gateway and IGMPv3/MLDv2
   hosts (computer, tablets, set-top boxes).

4.2.  Including network support for IGMPv3 / MLDv2

   This document recommends that all hosts, router platforms and
   security appliances supporting multicast support IGMPv3 [RFC3376] and
   MLDv2 [RFC3810] (based on the version IP they intend to support).
   The updated IPv6 Node Requirements RFC [I-D.ietf-6man-rfc6434-bis]
   states that MLDv2 support is a MUST in all implementations.  Such
   support is already widespread in common host and router platforms.

   Further guidance on IGMPv3 and MLDv2 is given in [RFC4604].

   Multicast snooping is often used limit the flooding of multicast
   traffic in a layer 2 network.  With snooping, a L2 switch will
   monitor IGMP/MLD messages and only forward multicast traffic out host
   ports that have interested receivers connected.  Such snooping
   capability should therefore support IGMPv3 and MLDv2.  There is
   further discussion in [RFC4541].

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4.3.  Building application support for SSM

   The recommendation to use SSM for interdomain multicast means that
   applications should properly trigger the sending of IGMPv3/MLDv2
   messages.  It should be noted, however, there is a wide range of
   applications today that only support ASM.  In many cases this is due
   to application developers being unaware of the operational concerns
   of networks.  This document serves to provide clear direction for
   application developers to support SSM.

   It is often thought that ASM is required for multicast applications
   where there are multiple sources.  However, RFC 4607 also describes
   how SSM can be used instead of PIM-SM for multi-party applications:

      "SSM can be used to build multi-source applications where all
      participants' identities are not known in advance, but the multi-
      source "rendezvous" functionality does not occur in the network
      layer in this case.  Just like in an application that uses unicast
      as the underlying transport, this functionality can be implemented
      by the application or by an application-layer library."

   Some useful considerations for multicast applications can be found in

4.4.  Preferring SSM applications intradomain

   If feasible, it is recommended for applications to use SSM even if
   they are initially only meant to be used in intradomain environments
   supporting ASM.  Because PIM-SSM is a subset of PIM-SM, existing
   intradomain PIM-SM networks are automatically compatible with SSM
   applications.  Thus, SSM applications can operate alongside existing
   ASM applications.  SSM's benefits of simplified address management
   and significantly reduced operational complexity apply equally to
   intradomain use.

   However, for some applications it may be prohibitively difficult to
   add support for source discovery, so intradomain ASM may still be

4.5.  Documenting an ASM/SSM protocol mapping mechanism

   In the case of existing ASM applications that cannot readily be
   ported to SSM, it may be possible to use some form of protocol
   mapping, i.e., to have a mechanism to translate a (*,G) join or leave
   to a (S,G) join or leave, for a specific source, S.  The general
   challenge in performing such mapping is determining where the
   configured source address, S, comes from.

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   There are existing vendor-specific mechanisms deployed that achieve
   this function, but none are documented in IETF documents.  This may
   be a useful area for the IETF to work on as an interim transition
   mechanism.  However, these mechanisms would introduce additional
   administrative burdens, along with the need for some form of address
   management, neither of which are required in SSM.  Hence, this should
   not be considered a a long-term solution.

4.6.  Not filtering ASM addressing between domains

   A key benefit of SSM is that the receiver specifies the source-group
   tuple when signaling interest in a multicast stream.  Hence, the
   group address need not be globally unique, so there is no need for
   multicast address allocation as long the reserved SSM range is used.

   Despite the deprecation of interdomain ASM, it is recommended that
   operators should not filter ASM group ranges at domain boundaries, as
   some form of ASM-SSM mappings may continue to be used for some time.

4.7.  Not precluding Intradomain ASM

   The use of ASM within a single multicast domain such as a campus or
   enterprise is still relatively common today.  There are even global
   enterprise networks that have successfully been using PIM-SM for many
   years.  The operators of such networks most often use Anycast-RP
   [RFC4610] or MSDP for RP resilience, at the expense of the extra
   operational complexity.  These existing practices are unaffected by
   this document.

   This document does not preclude continued use of ASM in the
   intradomain scenario.  If an organisation chooses to operate multiple
   multicast domains within its own administrative borders, it may then
   use MSDP or Embedded-RP internally within its own network.

5.  Security Considerations

   This document adds no new security considerations.  It instead
   removes security issues incurred by interdomain ASM with PIM-SM/MSDP
   such as infrastructure control plane attacks and application and
   bandwidth/congestion attacks from unauthorised sources sending to ASM
   multicast groups.  RFC 4609 describes the additional security
   benefits of using SSM instead of ASM.

6.  IANA Considerations

   This document makes no request of IANA.

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   Note to RFC Editor: this section may be removed upon publication as
   an RFC.

7.  Acknowledgments

   The authors would like to thank members of the IETF mboned WG for
   discussions on the content of this document, with specific thanks to
   the following people for their contributions to the document: Hitoshi
   Asaeda, Dale Carder, Jake Holland, Albert Manfredi, Mike McBride, Per
   Nihlen, Greg Shepherd, James Stevens, Stig Venaas, Nils Warnke, and
   Sandy Zhang.

8.  References

8.1.  Normative References

   [RFC1112]  Deering, S., "Host extensions for IP multicasting", STD 5,
              RFC 1112, DOI 10.17487/RFC1112, August 1989,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3307]  Haberman, B., "Allocation Guidelines for IPv6 Multicast
              Addresses", RFC 3307, DOI 10.17487/RFC3307, August 2002,

   [RFC3376]  Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
              Thyagarajan, "Internet Group Management Protocol, Version
              3", RFC 3376, DOI 10.17487/RFC3376, October 2002,

   [RFC3810]  Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
              Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
              DOI 10.17487/RFC3810, June 2004,

   [RFC3956]  Savola, P. and B. Haberman, "Embedding the Rendezvous
              Point (RP) Address in an IPv6 Multicast Address",
              RFC 3956, DOI 10.17487/RFC3956, November 2004,

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <https://www.rfc-editor.org/info/rfc4291>.

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   [RFC4607]  Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,

   [RFC4610]  Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol
              Independent Multicast (PIM)", RFC 4610,
              DOI 10.17487/RFC4610, August 2006,

   [RFC5771]  Cotton, M., Vegoda, L., and D. Meyer, "IANA Guidelines for
              IPv4 Multicast Address Assignments", BCP 51, RFC 5771,
              DOI 10.17487/RFC5771, March 2010,

   [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>.

8.2.  Informative References

   [RFC2375]  Hinden, R. and S. Deering, "IPv6 Multicast Address
              Assignments", RFC 2375, DOI 10.17487/RFC2375, July 1998,

   [RFC3170]  Quinn, B. and K. Almeroth, "IP Multicast Applications:
              Challenges and Solutions", RFC 3170, DOI 10.17487/RFC3170,
              September 2001, <https://www.rfc-editor.org/info/rfc3170>.

   [RFC3569]  Bhattacharyya, S., Ed., "An Overview of Source-Specific
              Multicast (SSM)", RFC 3569, DOI 10.17487/RFC3569, July
              2003, <https://www.rfc-editor.org/info/rfc3569>.

   [RFC3618]  Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source
              Discovery Protocol (MSDP)", RFC 3618,
              DOI 10.17487/RFC3618, October 2003,

   [RFC3913]  Thaler, D., "Border Gateway Multicast Protocol (BGMP):
              Protocol Specification", RFC 3913, DOI 10.17487/RFC3913,
              September 2004, <https://www.rfc-editor.org/info/rfc3913>.

   [RFC3973]  Adams, A., Nicholas, J., and W. Siadak, "Protocol
              Independent Multicast - Dense Mode (PIM-DM): Protocol
              Specification (Revised)", RFC 3973, DOI 10.17487/RFC3973,
              January 2005, <https://www.rfc-editor.org/info/rfc3973>.

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   [RFC4541]  Christensen, M., Kimball, K., and F. Solensky,
              "Considerations for Internet Group Management Protocol
              (IGMP) and Multicast Listener Discovery (MLD) Snooping
              Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006,

   [RFC4604]  Holbrook, H., Cain, B., and B. Haberman, "Using Internet
              Group Management Protocol Version 3 (IGMPv3) and Multicast
              Listener Discovery Protocol Version 2 (MLDv2) for Source-
              Specific Multicast", RFC 4604, DOI 10.17487/RFC4604,
              August 2006, <https://www.rfc-editor.org/info/rfc4604>.

   [RFC4609]  Savola, P., Lehtonen, R., and D. Meyer, "Protocol
              Independent Multicast - Sparse Mode (PIM-SM) Multicast
              Routing Security Issues and Enhancements", RFC 4609,
              DOI 10.17487/RFC4609, October 2006,

   [RFC4611]  McBride, M., Meylor, J., and D. Meyer, "Multicast Source
              Discovery Protocol (MSDP) Deployment Scenarios", BCP 121,
              RFC 4611, DOI 10.17487/RFC4611, August 2006,

   [RFC8085]  Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
              Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
              March 2017, <https://www.rfc-editor.org/info/rfc8085>.

   [RFC8313]  Tarapore, P., Ed., Sayko, R., Shepherd, G., Eckert, T.,
              Ed., and R. Krishnan, "Use of Multicast across Inter-
              domain Peering Points", BCP 213, RFC 8313,
              DOI 10.17487/RFC8313, January 2018,

              Chown, T., Loughney, J., and T. Winters, "IPv6 Node
              Requirements", draft-ietf-6man-rfc6434-bis-09 (work in
              progress), July 2018.

Authors' Addresses

   Mikael Abrahamsson

   Email: mikael.abrahamsson@t-systems.se

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Internet-Draft         Deprecating Interdomain ASM          October 2018

   Tim Chown
   Lumen House, Library Avenue
   Harwell Oxford, Didcot  OX11 0SG
   United Kingdom

   Email: tim.chown@jisc.ac.uk

   Lenny Giuliano
   Juniper Networks, Inc.
   2251 Corporate Park Drive
   Herndon, Virginia  20171
   United States

   Email: lenny@juniper.net

   Toerless Eckert
   Futurewei Technologies Inc.
   2330 Central Expy
   Santa Clara  95050

   Email: tte+ietf@cs.fau.de

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