This just came out: http://www.ietf.org/internet-drafts/draft-ietf-mboned-routingarch-00.txt
Overview of the Internet Multicast Routing Architecture
draft-ietf-mboned-routingarch-00.txt
Abstract
The lack of up-to-date documentation on IP multicast routing
protocols and procedures has caused a great deal of confusion. To
clarify the situation, this memo describes the routing protocols and
techniques currently (as of this writing) in use.
