In this paper we present a comparative study of the nominee-based approach and consolidation-based approach to TCP-friendly reliable multicast. In this study, we find that TCP-friendliness may not be maintained in the nominee-based approach. The lack of flow control on recovery traffic is another drawback of nominee-based approach. On the other hand, throughput of the basic consolidation-based approach can be unacceptably low. A new consolidation-based protocol called the dual-track protocol is proposed. The sender maintains two sending tracks, namely the fast track and the slow track. The fast track tries to deliver packets to receivers at a higher pace whenever possible. Lost packets on the fast track are recovered via the slow track. By doing so, packet recovery is decoupled from the rate control so that unnecessary delay in the fast track can be avoided. We shall show that the dual-track protocol can significantly improve the throughput without compromising TCP-friendliness.
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