On the scaling of feedback algorithms for very large multicast groups

Feedback from multicast group members is vital for many multicast protocols . In order to avoid feedback implosion in very large groups feedback algori thms 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 recomm endations for the choice of well-behaved feedback mechanisms that are suita ble for very large groups. (C) 2001 Elsevier Science B.V, All rights reserv ed.