2.5.11 Source-Specific Multicast (ssm)

NOTE: This charter is a snapshot of the 49th IETF Meeting in San Diego, California. It may now be out-of-date. Last Modified: 27-Oct-00


Hugh Holbrook <holbrook@cisco.com>
Supratik Bhattacharyya <supratik@sprintlabs.com>

Routing Area Director(s):

David Oran <oran@cisco.com>
Rob Coltun <rcoltun@redback.com>

Routing Area Advisor:

Rob Coltun <rcoltun@redback.com>

Mailing Lists:

General Discussion:ssm-interest@external.cisco.com
To Subscribe: mailer@cisco.com
In Body: subscribe ssm-interest
Archive: TBA

Description of Working Group:

The purpose of the SSM working group is to standardize and clearly elucidate the definition of source-specific multicast in such a way as to provide unambiguous semantics to the designers of the protocols and host interfaces used in conjunction with source-specific multicast.

We intend SSM to be a short-lived, highly-focused working group. The working group will handle the following four work items related to SSM:

1) A concise standards-track RFC that clearly defines the source-specific multicast model and its relation to RFC 1112 multicast. This document will specify of the host interfaces to be used for source-specific multicast, the rules that hosts, routers, and protocols must follow when allocating and using source-specific addresses. This document will serve as a reference to RFC authors designing protocols and host interfaces that implement SSM. This document will be parented in the Internet Area, although it will be a product of this working group.

2) A short standards-track RFC that formally allocates the address space to source-specific multicast. (Similar to RFC1918 and to Admin-Scope.), "ratifying" the IANA allocation and referring to the above document for the semantics of the address range.

3) An informational RFC providing an overview of source-specific multicast. This document will serve as a starting point for parties interested in source-specific multicast.

4) SSM can be implemented in routers with slight modifications to the PIM-SM protocol and vendors have implementations in progress. The PIM-SM specification will be rewritten to serve as both a PIM-SM and a "PIM-SSM" specification. The SSM and PIM working groups chairs will jointly submit an IETF last call for this document.

Other SSM-related documents may be taken on as work items by other multicast working groups that have more specific expertise, namely pim, mboned, or idmr. For instance, a document describing IGMPv3 modifications for SSM will (likely) be adopted by IDMR. The SSM working group chairs will cooperate with chairs of the related working groups and the Area Directors to determine the appropriate location of SSM-related documents that arise during the working group's lifetime.

A significant amount of work on SSM has already occurred, therefore we believe that the SSM working group can quickly complete all of its work items.

Goals and Milestones:

Aug 00


First meeting

Aug 00


Submit I-D to alloctate address space to source-specific multicast

Aug 00


Submit source-specific multicast model as internet-draft

Aug 00


Submit I-D for source-specific multicast

Sep 00


Reach consensus on source-specific multicast model and alloctate address space to source-specific multicast

Oct 00


Submit I-Ds on source-specific multicast model and alloctate address space to source-specific multicast to IESG for consideration as RFCs

Mar 01


Submit I-D on source-specific multicast to IESG for consideration as an Informational RFC

No Current Internet-Drafts
No Request For Comments

Current Meeting Report

None received.


None received.