Performance analysis of large multicast switches with multicast virtual output queues

In multicast switches, the accommodation of multicast traffic in multiple queues per input buffer reduces the throughput degradation caused by head-of-line (HOL) blocking. Such an arrangement, called multicast virtual output queuing (MC-VOQ), is very promising in theory but can only be implemented in practice with heavy approximation. Complete avoidance of the HOL blocking problem would in fact require a distinct queue for each fanout set possible, leading to an exponential growth of the number of queues needed with the switch size. If only a limited number of queues can be used per input buffer, criteria must be identified for setting the number of queues, for associating the fanout sets with the individual queues, and for scheduling the transmission of packets out of the queues. This paper presents an analytical model for the investigation of saturation throughput and packet delay in MC-VOQ multicast switches. The model relies on the assumption of Poisson-distributed uniform input traffic and random queuing and scheduling policies. Extensive simulation experiments validate the results of the analysis for large switch sizes.