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INTERNET-DRAFT                                   David Meyer
draft-ietf-mboned-ssm232-05.txt                  Rob Rockell
                                               Greg Shepherd
Category                               Best Current Practice
Expires: November 2003                              May 2003


        Source-Specific Protocol Independent Multicast in 232/8
                   <draft-ietf-mboned-ssm232-05.txt>



Status of this Document

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   This document is a product of the .  Comments should be addressed to
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Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.











Meyer, Rockell, and Shepherd                                    [Page 1]


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                                Abstract


   IP Multicast group addresses in the 232/8 (232.0.0.0 to
   232.255.255.255) range are designated as source-specific multicast
   [SSM] destination addresses and are reserved for use by source-
   specific applications and protocols [IANA]. This document defines
   operational recommendations to ensure source-specific behavior within
   the 232/8 range.

   The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED,
   SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined
   in RFC 2119 [RFC2119].






































Meyer, Rockell, and Shepherd                                    [Page 2]


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                           Table of Contents


   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2. Operational practices in 232/8 . . . . . . . . . . . . . . . .   4
    2.1. Preventing local sources from sending to shared tree. . . .   4
    2.2. Preventing remote sources from being learned/joined via MSDP. 4
    2.3. Preventing receivers from joining the shared tree . . . . .   5
    2.4. Preventing RP's as candidates for 232/8 . . . . . . . . . .   5
   3. Intellectual Property. . . . . . . . . . . . . . . . . . . . .   5
   4. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . .   6
   5. Security Considerations. . . . . . . . . . . . . . . . . . . .   6
   6. IANA Considerations. . . . . . . . . . . . . . . . . . . . . .   6
   7. References . . . . . . . . . . . . . . . . . . . . . . . . . .   7
    7.1. Normative References. . . . . . . . . . . . . . . . . . . .   7
    7.2. Informative References. . . . . . . . . . . . . . . . . . .   7
   8. Author's Addresses . . . . . . . . . . . . . . . . . . . . . .   7
   9. Full Copyright Statement . . . . . . . . . . . . . . . . . . .   7



1.  Introduction


   Current PIM Sparse Mode (PIM-SM) [RFC2362] relies on the shared
   Rendezvous Point (RP) tree to learn about active sources for a group
   and to support group-generic (not source specific) data distribution.
   The IP Multicast group address range 232/8 has been designated for
   source-specific [SSM] applications and protocols [IANA] and SHOULD
   support source-only trees only, precluding the requirement of an RP
   and a shared tree; active sources in the 232/8 range will be
   discovered out of band. PIM Sparse Mode Designated Routers (DR), with
   local membership, are capable of joining the shortest path tree for
   the source directly using Source-Specific PIM [SSM].

   Operational best common practices in the 232/8 group address range
   are necessary to ensure shortest path source-only trees across
   multiple domains in the Internet [SSM], and to prevent data from
   sources sending to groups in the 232/8 range from arriving via shared
   trees. This avoids unwanted data arrival, and allows several sources
   to use the same group address without conflict at the receivers.







Meyer, Rockell, and Shepherd                        Section 1.  [Page 3]


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   The operational practices SHOULD

    o Prevent local sources from sending to shared tree

    o Prevent remote sources from being learned/joined via MSDP [MSDP]

    o Prevent receivers from joining the shared tree

    o Prevent RP's as candidates for 232/8




2.  Operational practices in 232/8




2.1.  Preventing local sources from sending to shared tree


   Eliminating the use of shared trees for groups in 232/8, while
   maintaining coexistence with PIM-SM, behavior of the RP and/or the DR
   needs to be modified. This can be accomplished by

    - preventing data for 232/8 groups from being sent encapsulated to
      the RP by the DR

    - preventing the RP from accepting registers for 232/8 groups from
      the DR

    - preventing the RP from forwarding accepted data down (*,G)
      tree for 232/8 groups




2.2.  Preventing remote sources from being learned/joined via MSDP


   PIM-SS does not require active source announcements via MSDP. All
   source announcements are received out of band, the the last hop
   router is responsible for sending (S,G) joins directly to the source.
   To prevent propagation of SAs in the 232/8 range, an RP SHOULD

    - never originate an SA for any 232/8 groups

    - never accept or forward an SA for any 232/8 groups.



Meyer, Rockell, and Shepherd                      Section 2.2.  [Page 4]


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2.3.  Preventing receivers from joining the shared tree


   Local PIM domain practices need to be enforced to prevent local
   receivers from joining the shared tree for 232/8 groups. This can be
   accomplished by

    - preventing DR from sending (*,G) joins for 232/8 groups

    - preventing RP from accepting (*,G) join for 232/8 groups

   However, within a local PIM domain, any last-hop router NOT
   preventing (*,G) joins may trigger unwanted (*,G) state toward
   the RP which intersects an existing (S,G) tree, allowing the
   receiver on the shared tree to receive the data, breaking the
   source-specific [SSM] service model. It is therefore recommended
   that ALL routers in the domain MUST reject AND never originate
   (*,G) joins for 232/8 groups.

   In those cases in which an ISP is offering its customers (or
   others) the use of the ISP's RP, the ISP SHOULD NOT allow (*,G)
   joins in the 232/8 range.




2.4.  Preventing RP's as candidates for 232/8


   Because PIM-SS does not require an RP, all RPs SHOULD NOT offer
   themselves as candidates in the 232/8 range. This can be accomplished
   by

    - preventing RP/BSR from announcing in the 232/8 range

    - preventing ALL routers from accepting RP delegations in the
      232/8 range

    - precluding RP functionality on RP for the 232/8 range


3.  Intellectual Property


   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights



Meyer, Rockell, and Shepherd                        Section 3.  [Page 5]


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   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.



4.  Acknowledgments


   This document is the work of many people in the multicast community,
   including (but not limited to) Dino Farinacci, John Meylor, John
   Zwiebel, Tom Pusateri, Dave Thaler, Toerless Eckert, Leonard
   Giuliano, Mike McBride, and Pekka Savola.



5.  Security Considerations


   This document describes operational practices that introduce no new
   security issues to either PIM-SM or PIM-SSM.



6.  IANA Considerations


   This document creates a no new requirements on IANA namespaces
   [RFC2434].










Meyer, Rockell, and Shepherd                        Section 6.  [Page 6]


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7.  References

7.1.  Normative References

   [MSDP]      Meyer, D. and B. Fenner (Editors), "The Multicast
               Source Discovery Protocol (MSDP)",
               draft-ietf-msdp-spec-20.txt. Work in Progress.

   [SSM]       Holbrook, H., and B. Cain,, "Source-Specific Multicast",
               draft-ietf-ssm-arch-03.txt. Work in Progress.

   [RFC2362]   D. Estrin, et. al., "Protocol Independent Multicast-Sparse
               Mode (PIM-SM): Protocol Specification", RFC 2362, June,
               1998.




7.2.  Informative References

   [IANA]      http://www.iana.org

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


8.  Author's Addresses



   David Meyer
   Email: dmm@1-4-5.net

   Robert Rockell
   Sprint
   Email: rrockell@sprint.net

   Greg Shepherd
   Procket
   Email: shep@procket.com



9.  Full Copyright Statement

   Copyright (C) The Internet Society (2003). All Rights Reserved.





Meyer, Rockell, and Shepherd                        Section 9.  [Page 7]


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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.




























Meyer, Rockell, and Shepherd                        Section 9.  [Page 8]


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