Optimum cell duplication or replication for multicast applications

Many multicast ATM switch architectures have been proposed which differ greatly in the method in which replication of cells is handled. Depending on the switch architecture, the processing overhead incurred due to the cell copy function may be non-negligible. We develop a queueing model for a multicast switching node which accounts for this overhead. In the model, the source sends some number of duplicate cells, each of which is replicated at the switch to yield the total number of required copies. We use constrained optimization to determine the optimal amount of source duplication which minimizes the mean response time of the system. It is found that higher source duplication is favored when the copy function overhead is comparable to the service time of a single cell. The model is then enhanced to account for errors and retransmissions for reliable multicast