Multi-Source Application Support Using Single-Source Multicast


IP multicast still faces considerable address allocation and scalability challenges a decade after its inception, inhibiting the deployment of large- scale multimedia applications such as Internet TV. Explicitly-Requested Single- Source (EXPRESS) Multicast is a recent proposal that addresses many of these issues, but it removes multi-source multicast primitives from the network layer. Many multicast applications are multi-source, even those that logically have a single sender (because of the use of RTCP), and thus are not directly supported by the EXPRESS model.

The premise of this work is that large-scale multi-source multicast sessions can be supported efficiently in a network with only single-source multicast primitives, through the use of application-level relays. These relays subsume the functionality of network-level rendezvous points and, since they exist at the application layer, application-level knowledge can be used to: determine the placement of relays on a per-session basis, determine the specific relay(s) to be used on a per-client basis, and allow relay points to enforce dynamic floor control decisions.