One document matched: draft-shepherd-ssm232-00.txt

Internet Engineering Task Force                              G. Shepherd
INTERNET-DRAFT                                             Cisco Systems
draft-shepherd-ssm232-00.txt                                 E. Luczycki
                                                           Broadcast.com
                                                              R. Rockell
                                                              Sprintlink
                                                             March, 2000
                                                  Expires September 2000

        Source-Specific Protocol Independent Multicast in 232/8

Status of this Memo

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
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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-ALLOCATION]. This
     document defines operational recommendations to ensure source-
     specific behavior within the 232/8 range.






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1.  Introduction

Current PIM Sparse Mode [PIM-SM] 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-ALLOCATION] 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. The
PIM Sparse Mode [PIM-SM] Designated Routers (DR), with local membership,
are capable of joining the shortest path tree for the source directly
using Source-Specific PIM [PIM-SS].

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 [PIM-SO], 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.

The operational practices should

 o Prevent local sources from sending to shared tree

 o Prevent remote sources from being learned/joined via 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

Eliminatng the use of shared trees for groups in 232/8, while mainaining
coexistance 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


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

PIM-SS does not require active source announcements via MSDP. All source



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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.


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
 - preventing RP from accepting (*,G) join


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 DRs from accepting deligations in this range
 - precluding RP functionality on RP for the 232/8 range


3.

References

IANA-ALLOCATION
     Internet Assigned Numbers Authority, http://www.isi.edu/in-
     notes/iana/assignments/multicast-addresses.

SSM  Holbrook, H., Cain, B., "Source-Specific Multicast for IP (SSM)",
     draft-holbrook-ssm-00.txt, September, 2000.

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

PIM-SSBhaskar, N., "Source-Specific Protocol Independent Multicast
     (PIM-SS)", draft-bhaskar-pim-ss-00.txt, March, 2000.

PIM-SODiot, C., Giuliano, L., Rockell, R., "Deployment of PIM-SO at
     Sprint (PIM-SO)", draft-bhattach-diot-PIMSO-00.txt, March, 2000.




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MSDP Farinacci, D., et. al. "Multicast Source Discovery Protocol
     (MSDP)", draft-ietf-msdp-spec-05.txt, February, 2000.

4.  Author's Addresses


   Greg Shepherd
   Cisco Systems
   170 Tasman Drive
   San Jose, CA, 95134
   Phone: +1 541 912 9758
   Email: shep@cisco.com

   Ed Luczycki
   Broadcast.com
   eds@yahoo-inc.com

   Robert Rockell
   Sprint Internet Service Center
   Reston, Virginia
   rrockell@sprintlink.net