Throughput analysis of tree-based protocols for many-to-many reliable multicast

Tree-based reliable multicast protocols are known to be most scalable for one-to-many sessions. However, there is still an open question whether these protocols are also scalable for many-to-many sessions. We categorize existing tree-based protocols into four classes according to the feedback/retransmission policies employed, and analyze and compare them on the basis of a proposed spatial loss model. This model considers the correlation of packet loss events for more realistic analysis, unlike previous work. The analysis reveals that, in many-to-many cases, a tree-based protocol with unicast NACK, unicast retransmission and periodic polling is most scalable with respect to throughput for practical session sizes. The protocol is also simple to implement.