TCP-friendly window congestion control with dynamic grouping for reliable multicast

Congestion control for reliable multicast for large multicast groups has been a challenging issue for widespread deployment of reliable multicast services. We propose a receiver-driven window congestion control scheme with dynamic grouping for reliable multicast. The main objective is to improve multicast throughput performance and to solve the well-known "drop-to-zero" problem, i.e., to prevent a slow receiver from slowing down faster receivers in the same multicast group. For this purpose, we modify the window scheme and combine it with a new dynamic grouping scheme for local recovery to achieve high-throughput performance. The basic idea is two-fold. First, the sender can tune its window size according to the fastest receiver in a virtual group instead of the slowest receiver by taking advantage of the local recovery. Second, the sender can explicitly ask a worst-case group (WCG), which can be recorded in a simple list in cache or memory, to merge with others or unsubscribe from the multicast group. The proposed strategy is shown to be still TCP-friendly and scalable while eliminating the "drop-to-zero" problem. Some key related issues are also discussed.