Multicast Feedback Suppression

For a reliable, ow-controlled multicast transport protocol to scale, it must avoid the feedback implosion problem 5], particularly if the protocol targets arbitrarily large multicast groups communicating over lossy networks. Most existing feedback control mechanisms based on probabilistic suppression address the feedback implosion problem by suppressing feedback using timers based on round-trip time (RTT) information. This approach requires that all receivers compute RTT to the data source. We present an algorithm whose major beneet derives from the fact that it does not need to compute RTT from receivers to the source, and does not require knowledge of group membership or network topology. We use a small set of representative receivers and probabilistic suppression to limit feedback. We believe that our approach will perform well in real networks. Simulations using randomly-generated network topologies of varying sizes with pessimistic network loss rates show that representatives considerably reduce the amount of feedback compared to a purely suppression-based scheme. For various multicast group sizes, a few representatives can keep the amount of feedback low while not degrading feedback timeliness.