Internet Engineering Task Force G.Network Working Group Greg Shepherd
INTERNET-DRAFT Cisco Systems
INTERNET DRAFT Juniper Networks
Category Best Current Practices
Source-Specific Protocol Independent Multicast in 232/8
1. Status of this Memo
This document is specifies an Internet Draft Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of
RFC2026. RFC 2026.
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2. Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
IP Multicast group addresses in the 232/8 (184.108.40.206 to
220.127.116.11) range are designated as source-specific multicast
[SSM] destination addresses and are reserved for use by
specific applications and protocols [IANA-ALLOCATION]. [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].
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 source-
specific [SSM] applications and protocols [IANA-ALLOCATION] [IANA] and should 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
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]. [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 [PIM-SO], [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.
The operational practices should 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
5. Operational practices in 232/8
5.1. Preventing local sources from sending to shared tree Eliminatng
Eliminating the use of shared trees for groups in 232/8, while mainaining coexistance
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
- preventing the RP from forwarding accepted data down (*,G) tree
5.2. 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
- never originate an SA for any 232/8 groups
- never accept or forward an SA for any 232/8 groups.
5.3. 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
- preventing DR from sending (*,G) joins
- preventing RP from accepting (*,G) join
Within a local PIM domain, any last-hop router NOT preventing (*,G)
joins MAY tringer trigger (*,G) state toward the RP which intersects an
existing (S,G) tree, allowing the receiver on the shared tree to
receive the data. So if the last-hop routers are not preventing (*,G)
joins, then all routers in the domain must also prevent (*,G) joins.
5.4. Preventing RP's as candidates for 232/8
Because PIM-SS does not require an RP, all RPs SHOULD NOT offer themselves them-
selves 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 delegations in this range
- precluding RP functionality on RP for the 232/8 range
6. References Internet Assigned Numbers Authority,
[SSM] Holbrook, H., Cain, B., "Source-Specific Multicast for IP
draft-holbrook-ssm-00.txt, September, 2000. draft-holbrook-ssm-02.txt, March, 2001.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March, 1997.
[RFC2362] D. Estrin, et. al., "Protocol Independent Multicast-Sparse
Mode (PIM-SM): Protocol Specification", RFC 2362, June, 1998 Bhaskar, N.,
"Source Specific Protocol Independent Multicast (PIM-SS)", draft-
bhaskar-pim-ss-00.txt, March, 2000. Diot, C., Giuliano, L.,
Rockell, R., "Deployment of PIM-SO at Sprint (PIM-SO)", draft-
bhattach-diot-PIMSO-00.txt, March, 2000.
Farinacci, D., et. al.
[MSDP] D. Meyer, Editor, "Multicast Source Discovery Protocol
spec-05.txt, February, 2000. draft-ietf-msdp-spec-07.txt, April, 2001.
7. Author's Addresses
170 Tasman Drive San Jose, CA, 95134 Phone: +1 541
Email: email@example.com firstname.lastname@example.org
Ed Luczycki Broadcast.com
Sprint Internet Engineering Service Center
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