A Reliable Multicast data Distribution Protocol based on software FEC techniques

Applications requiring the reliable distribution of data to groups of clients would be supported perfectly by reliable multicast protocols. In many cases, the problem of congestion control (a major research issue otherwise) does not exist because downlink bandwidth is \owned" or can be preallo-cated to a particular server by independent means, but the problems of insuring reliable data delivery to large groups, and adaptability to heterogeneous clients, still remain. These problems can be solved at once with the clever use of FEC techniques. In this paper we show the design of a Reliable Multicast data Distribution Protocol (RMDP) that we have built using these techniques, and discuss the implementation tradeoos. Experimental results show that, albeit somewhat expensive, doing encoding/decoding in software is aaordable for speeds up to the MB/s range even on desktop PCs. Slower machines can still receive at high speed, thus optimizing network usage, by taking advantage of the fact that decoding needs not to be done in real time. Finally, our RMDP can work even without any feedback from the receivers, thus making it well suited to mobile/wireless systems. Full sources for the application and the encoding algorithm described in this paper are available from the authors.