New Error Recovery Structures for Reliable Multicasting

shown in Fig. 3, which plot the maximum throughput achieved by each protocol when the number of receivers goes from 0 to 2000. The probability of a packet being lost is set to 0.02 and 0.1 in Fig. 3(a) and Fig. 3(b), respectively. We do not compare ELRP with the maximum throughout for tree-based protocols, because in a local group, a tree-based protocol is likely to have a single parent connected with all the receivers in the local group as its immediate children, which corresponds to the sender-initiated, receiver-initiated, or RINA cases we already consider It is clear that ELRP with unicast NAK is the best choice, with E-DNKA being the second best. This establishes the case for using ELRP in local groups interconnected with a backbone ACK tree, which is what HRMP does. It also makes the use of NAK avoidance questionable in general, since ELRP is better and just as simple to implement in local groups, and maintaining accurate NAK avoidance timers over extended internet regions becomes expensive. 6. Conclusion We have presented ELRP, a ring-based protocol for reliable multicasting that scales well with the number of receivers. We have shown that its maximum attainable throughput is constant with respect to the number of receivers. According to our analysis, the maximum throughput of ELRP is higher than the maximum throughput attainable by any sender-initiated protocol, receiver-initiated protocol, receiver-initiated with NAK avoidance (RINA) protocol, and other ring-based protocols. We have introduced a deterministic NAK avoidance strategy for ring-based protocols, which we call DNKA, we have shown that it incurs a smaller average delay than the traditional NAK avoidance scheme based on random timers. Because of the long-latency and token-management problems in ring protocols over long distances, we have introduced a hybrid structure that combines trees and rings called HRMP. HRMP uses an ACK tree as a backbone connecting local domains using ELRP. We have shown theat HRMP achieves the same or larger throughput than tree-based protocols in local domains. HRMP does not place any strong restrictions on the number of receivers that can be the children of a given node in the ACK tree, because receivers in a local group are organized as one virtual node according to ELRP. References [1] S. Deering, "RFC-1112: Host extension for IP multicasting" Aug. 1989.