Local Error Recovery in SRM: Comparison of Two Approaches

SRM is a framework for reliable multicast delivery. In order to maximize the collaboration among the group members in error recovery, both retransmission requests and replies are multicast to the entire group. SRM uses random timers to effectively suppress duplicate requests and replies. However, a few members with frequent losses can still cause frequent retransmissions to all the group members. To further improve the scalability of SRM, one must localize the scope of error recovery traffic. In this paper we present two approaches to local recovery: hop-based scope control and use of local recovery groups. The first approach uses hop count to limit the distribution of requests and replies, whereas the second approach confines error recovery traffic using separately addressed local recovery groups. The local recovery groups and hop count settings are automatically created and dynamically adjusted based on observed loss patterns. We use simulation experiments to examine the performance ..