Scalable Fair Reliable Multicast Using Active Services

Scalability is of paramount importance in the design of reliable multicast transport protocols , and requires a careful consideration of a number of problems such as feedback implosion, retransmission scoping, distributed loss recovery, and congestion control. In this paper, we present a reliable multicast architecture that invokes active services at strategic locations inside the network to comprehensively address these challenges. Active services provide the ability to quickly and eeciently recover from loss at the point of loss. They also exploit the physical hierarchy for feedback aggregation and eeective retransmission scoping with minimal router support. We present two protocols, one for packet loss recovery and another for congestion control, and describe an experimental testbed where these have been implemented. Analysis, simulation, and experimental results are used to demonstrate that our active services architecture improves resource usage, reduces latency for loss recovery and provides \TCP-friendly" congestion control.