Subject: Small Group Multicast (SGM) BoF

From: "David Oran" <[email-masked]>
Date: Mon, 19 Jun 2000 11:44:08 -0400

A number of people in the Internet community have been advocating that the
IETF consider standardizing a method for handling multicast to small groups,
where "small" is generally understood to be in the range of 3-10 or so
participants. The rationale for this is twofold:

1) there are alleged to be a number of very important applications which
have a small numbers of participants per group (e.g. classic audio and video
conferencing, collaboration tools, etc.) with an extremely large number of
such groups simultaneously active on the Internet.

2) Existing IP multicast methods, including newer specialized schemes like
Source Specific Multicast (SSM) are generally thought to have scaling
problems when there are a very large nubmer of groups, because of per-group
state in all the intermediate routers.

Because of the range of possible approaches to this problem and the
potential widespread impact on portions of the IP protocol suite, router
implementation, operational practices, etc. of the Internet, the BoF is
being jointly hosted by the Routing and Internet areas, and will be chaired
by Randy Bush of the OPS area.

The BoF's goals are to:
a) assess interest in forming a Working Group on Small Group Multicast
b) produce a crisp problem statement which could be used as the
   basis for a Working Group Charter
c) reach consensus on a set of constraints on the solution space (see below)
d) examine existing work for possible solutions (see below)

In order to have a technically sound and deployable solution, it is
particularly important the scope of changes to the Internet architecturte,
protocols, host & router implementations, and operational management be
understood and hopefully minimized. Some of these possible constraints
include:

- Host API (e.g. sockets interface) changes allowed?
- Host protocol implementation changes allowed?
- IP packet header changes allowed? If so, effect on router forwarding
  speed?
- New routing protocols needed? Modifications to existing multicast
  and/or unicast routing protocols?

In order to stimulate discussion in advance of the BoF, we will use an
existing mailing list set up by the folks who have been working on a set of
approaches to SGM which are collectively known as explicit multicast, or
"xcast". The mailing list is:
	[email-masked]
and may be subscribed to by via [email-masked]

A detailed agenda will be provided in the next couple of weeks after initial
discussion on the mailing list.

An initial reading list for people interested in the discussion follows:

1) "Connectionless  Multicast",  draft-ooms-cl-multicast-01.txt
2) "Small Group Multicast",
   http://www.icair.org/main_projects_infrast_sgm.html
3) "Multiple Destination  option  on  IPv6",  draft-imai-mdo6-00.txt
4) "Distributed Core Multicast: a  routing  protocol  for
    many small groups with application  to  mobile  IP
    telephony", draft-blazevic-dcm-mobility-00.txt
5)  "Datagram  Routing  for  Internet  Multicasting",  L.
    Aguilar, Sigcomm84, March 1984
6) "IPv4 option  for  Sender  Directed  Multi-Destination
    Delivery", C. Graff, RFC1770