Subject: I-D ACTION:draft-ohta-static-multicast-01.txt

From: [email-masked]
Date: Tue, 03 Nov 1998 10:14:23 -0500

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title		: Static Multicast
	Author(s)	: M. Ohta, J. Crowcroft
	Filename	: draft-ohta-static-multicast-01.txt
	Pages		: 10
	Date		: 02-Nov-98
	
   The current IP Multicast model appears to achieve a level of
   simplicity by extending the IP unicast addressing model (historically
   the classful A,B, and C net numbers) from the mask and longest match
   schemes of CIDR, with a new classful address space, class D. The
   routing systems have been also built in a deceptively simple way in
   one of three manners - either broadcast and prune (DVMRP, Dense Mode
   PIM), destination list  based tree computation (MOSPF) or single
   centered trees (current sparse mode PIM and CBT). The multicast
   service creates the illusion of a spectrum that one can 'tune in to',
   as an application writer. Due to this view, many have seen the
   multicast pilot service, the Mbone, as a worldwide Ethernet, where
   simple distributed algorithms can be used to allocate 'wavelengths'
   and advertise them through 'broadcast' on a channel (the session
   directory), associated with a spectrum.
 
   These three pieces of the picture have tempted people to construct a
   distributed architecture for a number of next level services that
   cannot work at more than a modest scale, since they ignore the basic
   spirit of location independence for senders and receivers of IP
   packets, whether unicast or multicast. The problem is that many of
   these services are attempting to group activities at source, when it
   is only at join time that user grouping becomes apparent (if you
   like, multicast usage is a good example of very late binding). These
   services include Address Allocation and Session Creation,
   Advertisement and Discovery.
 
   This memo proposes approaches to solve some current multicast
   problems rather statically with DNS and URL based approach, and avoid
   the misguided pitfalls of trying to use address allocation to
   implement traffic aggregation for different sources or aggregation of
   multicast route policy control through control of such aggregated
   sources.

   Note that a minor level of aggregation occurs in applications which
   source cumulative layered data (e.g. audio/video/game data - ref
   vic/rat/rlc) - this memo is orthogonal to such an approach, which in
   any case only results in a small constant factor reduction in state.
 
   A lot of the IP multicast additional pieces of baggage are associated
   with the multimedia conferencing on Mbone - however, the commercial
   internet use of multicast includes many other applications - for
   these, SDR may not be the best directory model.

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