Performance analysis of feedback synchronization for multicast ABR flow control

We present a balanced and unbalanced binary-tree model to explore the delay performance of feedback synchronization algorithms for multicast ABR flow control. Using this model, we analyze the feedback-delay performance scalability of the soft-synchronization protocol (SSP), which derives a single "consolidated" RM (resource management) cell at each multicast branch-point from feedback RM cells of different downstream branches that are not necessarily responses to the same forward RM cell. In contrast with the other existing schemes, SSP is shown to be able to effectively support synchronization of feedback RM cell and make the effective RM cell roundtrip time (RTT) virtually independent of the multicast tree's topology. Also derived is the optimal RM-cell update interval for SSP to minimize RM-cell RTTs for a given multicast tree.