Date Added: Jul 2009
Recent advances in network coding research dramatically changed the underlying structure of optimal multicast routing algorithms and made them efficiently computable. While most such algorithm design assume a single file/layer being multicast, layered coding introduces new challenges into the paradigm due to its cumulative decoding nature. Layered coding is designed to handle heterogeneity in receiver capacities, and a node may decode layer k only if it successfully receives all layers in 1..k. The authors show that recently proposed optimization models for layered multicast do not correctly address this challenge. They argue that in order to achieve the absolute maximum throughput (or minimum cost), it is necessary to decouple application layer throughput from network layer throughput.