Performance of shared-memory switches under multicast bursty traffic

Asynchronous transfer mode (ATM) is rapidly emerging as the switching technology of choice for broadband networks. We study shared-memory switches under multicast bursty traffic, and characterize the relation between their performance and the multicast distribution which defines the mix of multicast traffic arriving at the switches. We consider two schemes that have been used in practical realization of these switches to replicate multicast cells: (i) replication-at-receiving (RAR), where multiple copies of a multicast cell are stored in the buffer and served independently, and (ii) replication-at-sending (RAS), where a single instance of a multicast cell is stored in the buffer, and the cell is replicated as it is transmitted to the output ports. For both schemes, using simulation, we find upper bounds for the buffer requirements to achieve a desired packet loss rate. We show that these upper bounds, which are significantly larger than the buffer requirements under unicast traffic, are actually approached under any realistic multicast distribution, and even for small volumes of multicast traffic. We also study shared-memory switches with output demultiplexers, and characterize and compare the different multicasting schemes that are used in these ATM switches.