Bandwidth Analysis and Simulation of Reliable Multicast Transport Protocols

In this paper, an analytical bandwidth evaluation of generic reliable multicast protocols is presented. Our analysis is based on a realistic system model, including data packet and control packet loss, asynchronous local clocks and imperfect scope-limited local groups. Of particular importance are two new classes with aggregated acknowledgments. In contrast to other approaches, these classes provide reliability not only in case of message loss but also in case of node failures. Finally, we have analyzed the influence of the branching factor, i.e. the size of local groups in tree-based approaches, on a protocol's performance, which is an important parameter to improve performance. Our results prove that hierarchical approaches are superior. They provide higher throughput as well as lower bandwidth consumption. However, their performance is influenced by the optimal branching factor setting. The optimal branching factor depends mainly on the probability for receiving messages from other local groups. If this probability is zero, a small branching factor leads to the best results. On the other hand, if this probability is nonzero, which is likely if TTL scoping is used, larger local groups provide better performance. Finally, we have confirmed our analysis with simulation studies of XTP, SRM, RMTP and TMTP. [PUBLICATION ABSTRACT]