On the scaling of feedback algorithms for very large multicast groups

Abstract

Feedback from multicast group members is vital for many multicast protocols. In order to avoid feedback implosion in very large groups feedback algorithms with well-behaved scaling-properties must be chosen. In this paper, we analyse the performance of three typical feedback algorithms described in the literature. Apart from the basic trade-off between feedback latency and response duplicates we especially focus on the algorithms’ sensitivity to the quality of the group size estimation. Based on this analysis we propose a generalised framework for feedback algorithms and especially give recommendations for the choice of well-behaved feedback mechanisms that are suitable for very large groups.