A combined group/tree approach for scalable many-to-many reliable multicast

We present the design, implementation, and performance analysis of group-aided multicast (GAM), a scalable many-to-many reliable multicast transport protocol. GAM achieves high quality ACK trees while keeping the tree maintenance overhead reasonably low in the presence of dynamic group membership and route changes. It is supported by a group configuration mechanism organizing the members in a multicast session into multiple small groups and a tree configuration mechanism maintaining logical trees according to the underlying multicast routing trees. With the two mechanisms, GAM builds a two-layer hierarchy of multi-level logical trees from which high-quality per-source ACK trees are generated. Simulation results show that the GAM protocol is more scalable than a NACK suppression protocol in terms of processing time for request/repair messages and recovery latency.