Effect of topology on performance of reliable multicast communication

In this paper we examine the performance implications of providing reliability in conjunction with multicast transport over a high speed wide area network. We use a block based acknowledgement and selective retransmission protocol to evaluate the impact of the loss rate and the multicast tree topology on the achievable throughput. Our results show that even when the buffer overflow probability at switches and receivers is low, the cumulative loss probability seen by a source may be quite high. We also demonstrate that the average throughput increases significantly if the transport protocol delivers packets to the application layer out-of-sequence. We investigate the scaling properties of the error control mechanism and show that the multicast tree topology that results in minimum transfer time is not necessarily the same as the one constructed using minimal bandwidth or shortest path algorithms.