Efficient Multicast Flow Control using Multiple Multicast Groups

Controlling the rate of multicast data transfer to a large number of receivers is difficult, due to the heterogeneity among the end-systems’ capabilities and their available network bandwidth. If the data transfer rate is too high, certain receivers will lose data, and retransmissions will be required. If the data transfer rate is too slow, an inordinate amount of time will be required to transfer the data. In this paper, we examine an approach towards multicast flow control in which the sender uses multiple multicast groups to transmit data at different rates to different sub-groups of receivers. Transmission rates for the multicast groups are chosen so as to minimize the average time needed to transfer data to all receivers. We present simple algorithms for determining the transmission rate associated with each multicast channel. Analysis and simulation are used to show that our techniques for rate selection and rate adjustment perform well for large and diverse receiver groups and make efficient use of network bandwidth. Moreover, we find that only a small number of multicast groups are needed to reap most of the performance benefits possible. This work was supported by the National Science Foundation under grant NCR-95-08274. The authors can be contacted at : [bhattach,kurose,[email protected] and [email protected].