Scalable multicast data distribution for different transport service classes

Not all of the problems of large scale multicast can be addressed by automated repeat request (ARQ) based multicast protocols. Simulation studies have shown that independent packet loss among receivers is a worst case situation, where ARQ based protocols scale poorly and react with throughput degradation. Software based forward error correction (FEC) techniques are therefore a good solution and can be used to enhance the throughput efficiency by controlling the packet loss rate. A new method for implementing FEC at the transport layer is presented and performance measurements are shown. The difference between the restricted reliable multicast protocol (RRMP) and existing ARQ/FEC based multicast protocols is the flexibility and adaptability the RRMP provides by offering different transport service classes for different application needs. An application is able to choose the transport service, which best meets the requirements for efficiency, latency, delay, scalability etc. The design and implementation decisions for the FEC and ARQ based error recovery are outlined. Performance measurements demonstrate the suitability of FEC for real-time data transmissions.