Subject: I-D ACTION:draft-rigotti-rvm-00.txt

From: [email-masked]
Date: Tue, 01 Jun 1999 08:57:23 -0400

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

	Title		: Reversed Multicast (RVM)
	Author(s)	: G. Rigotti
	Filename	: draft-rigotti-rvm-00.txt
	Pages		: 8
	Date		: 28-May-99
	
This memo presents extensions to IP that enable the use of source-based
distribution trees (such as those established by DVMRP[1] or PIM-DM[2])
to deliver multicast packets generated by members of a multicast group
in the opposite direction to packets originated by the source (S).
Packets generated by a member M of a group G are forwarded (unicast)
from an in-tree router to another, towards the source S.
In addition to send the packet to its upstream, each in-tree router 
injects it into the multicast tree (S,G). This enables packets to reach 
the rest of the receivers, as S would originate them.
The 'reversed' use of the distribution tree is intended for sending of
low volume feedback information produced by receivers in applications
such as RTP/RTCP[3] and reliable multicast.
This feature diminish the overhead in routers in case of applications
with a source and many receivers sending feedback, because only one
distribution tree, rooted at the sender S must be maintained, in place
of one per member.
In addition, multicast packets originated by receivers,travel through
the inverse path of information ones in the distribution tree.
This can be exploited by multicast transport protocols to localize
processes to subtrees or to reduce exposure.

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