Reliable sender-initiated multicast for improved QoS

Network support for reliable sender-initiated multicast can aid software distribution, server-pushing of web-pages as well as pushing of prerecorded audio and video. Currently, bandwidth availability and propagation delays between the sender and the different recipients differ by many orders of magnitude. Hence, an important problem which needs to be addressed for facilitating reliable sender-initiated multicast is this problem of network heterogeneity. Prior work in reliable multicast either presents solutions to transmit at the rate of the bottleneck link of the entire multicast tree, or assumes knowledge of static bandwidth to each of the recipients. We propose an algorithm which does not make these assumptions but partitions the set of recipients on the basis of the available bandwidths at the time when the multicast is started; it then transmits separately to each set of recipients sharing a common quality of service (QoS). To the best of our knowledge, this is a first such solution. To achieve these goals, we propose (i) an algorithm to divide the set of receivers into classes with similar QoS, and (ii) callbacks for error recovery in reliable multicast. Our algorithm makes use of L4 switching at the routers but assumes the state at the routers to be soft state. Using analysis, we show our algorithm to be scalable for certain restricted network characteristics.