A Scalable and Robust Feedback Mechanism for Adaptive Multimedia Multicast Systems

We present a mechanism for providing feedback information to multicast sources of multimedia streams in a scalable and robust manner. The presented feedback mechanism is suitable for best-eeort unreliable networks such as the Internet. This mechanism is useful for controlling the transmission rate of multimedia sources in both cases of layered and single-rate multicast. It allows for determining the worst case state among a group of receivers, where each receiver may be in one of a set of nite states, and is applicable in receiver-driven as well as in sender-driven adaptive multimedia systems. Simulation results show that the presented feedback mechanism scales well for very large groups of thousands of participants. The eeciency of the proposed mechanism in eliminating the reply implosion problem, its robustness in facing losses in the network, as well as its responsiveness are illustrated. The advantages of the proposed feedback mechanism over feedback based on periodic reports is demonstrated.