RE: Why MSDP?

["Mike Luby" <luby@digitalfountain.com>]

John,
One of the things that I think we might have come to consensus on at the
IETF on Tuesday is to start calling the multicast service model defined in
RFC 1112 as "Any-Source Multicas" (ASM) hereafter (instead of ISM or
anything else).  This was raised by Dave Meyer in the SSM working group
meeting, and after a short discussion the consensus seemed to be that nobody
liked the term Internet Standard Multicast (ISM) because of its connotations
towards other models of multicast (as not being Internet Standards), that
there was a strong need for a common name for this service model, and that
although ASM was not the first choice of all people, ASM is the first choice
of quite a number of people and nobody had strong objections to ASM.

Michael Luby
Chief Technical Officer
Digital Fountain, Inc.
600 Alabama Street
San Francisco, CA  94110


www.digitalfountain.com
luby@digitalfountain.com
(415) 401-2100 (main)
(415) 401-2120 (direct)
(415) 401-2199 (fax)

-----Original Message-----
From: John M. Zwiebel [mailto:jzwiebel@cisco.com]
Sent: Thursday, March 22, 2001 1:54 PM
To: Nagesh Chintada
Cc: SSM; pim@catarina.usc.edu; msdp@network-services.uoregon.edu
Subject: Re: Why MSDP?


MSDP is required for ISM - or "internet standard multicast".
ISM is not SSM in that it allows building of shared-trees within
an AS which SSM does not.  The receiver does not need to know
who the senders to a given group are.

SSM builds only shortest-path trees because the host can signal
to the last hop router the specific hosts (senders) it wants to
listen to.  This rendezvous mechanism is outside of the PIM
protocol and can be discovered any way the application writer
wants it to be.

MSDP is not required (and not used) to support SSM groups.

Host routes are not needed in MBGP to be able to join toward the
shortest-path across the internet.

 ^ Greetings,
 ^
 ^ I have a very basic question:
 ^
 ^ First, the context:
 ^ For inter-domain Multicasting, one would typically deploy
 ^ PIM-SM/MBGP/MSDP protocols.....
 ^ MBGP for announcing  routes that include subnets containing multicast
 ^ sources, and MSDP
 ^ to announce sources.
 ^
 ^ Since MBGP already has the capability to announce multicast routes, why
 ^ not announce host routes of multicast sources as well, using MBGP? If
 ^ necessary, one can think of a simple extension to MBGP to mark the host
 ^ route as a "source route". IMHO, this will make it much easier to deploy
 ^ Multicast without having to worry about delpoying MSDP.
 ^
 ^ Any comments?
 ^
 ^ Best Regards,
 ^ Nagesh
 ^

----------------------------------------------------------------------------
--
	John Zwiebel                       Phone: 408-526-5303
	Cisco Systems Inc.
	IP Multicast Group