Scheduling Combined Unicast and Multicast Tra c in WDM Networks

We study the performance of various strategies for scheduling a combined load of unicast and multicast tra c in a broadcast WDM network. The performance measure of interest is schedule length, which directly a ects both aggregate network throughput and average packet delay. Three di erent scheduling strategies are presented, namely: separate scheduling of unicast and multicast tra c, treating multicast tra c as a number of unicast messages, and treating unicast tra c as multicasts of size one. The strategies are compared against each other using extensive simulation experiments in order to establish the regions of operation, in terms of a number of relevant system parameters, for which each strategy performs best. Our main conclusions are as follows.Multicast tra c can be treated as unicast tra c under very limited circumstances. On the other hand, treating unicast tra c as multicast tra c produces short schedules in most cases. Alternatively, scheduling and transmitting each tra c component separately is also a good choice.