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Abstract : |
The IP service model retains its simplicity and robustness by deferring reliability and congestion control to higher layers through end-to-end transport protocols. While the IP unicast service has proven successful, extending end-to-end adaptation to multicast has been a difficult problem. Unlike the unicast case, multicast protocols must support large and heterogeneous receiver sets. While proposed approaches to multicast transports attempt to localize problems and/or organize receivers into a hierarchy through a divide-and-conquer approach, this approach succeeds only if the resulting hierarchy is congruent with the underlying routing tree topology. This implies the need for some level of topological information at the end systems which the IP multicast service deliberately hides. In this paper, we explore the problem of inferring the required topological information using only observations made at the end hosts. To this end, we present a Group Formation Protocol (GFP) whereby receivers dynamically organize themselves into a multi-level hierarchy of multicast groups that corresponds to the underlying routing tree. GFP can serve as a core component across a wide range of multicast applications and protocols such as local recovery for reliable multicast, self organized transcoding, self organizing web caches, the optimal and dynamic placement of proxies, repeaters, designated receivers, recorders and so forth. Our simulations indicate that GFP structures receivers in accordance with the underlying topology for a range of workloads and network topologies. 1, |
