This article considers three-stage switching networks able to support multicast traffic, that is, connections in which one inlet is connected to more than one output at the same time. The nonblocking conditions for this network are studied under the assumption of absence of any optimized routing of the connections inside the structure (the so-called strict-sense nonblocking networks). The theoretical nonblocking condition for such network under point-to-point traffic is the well known Clos condition. We give here the necessary and sufficient conditions for such network to be strict-sense nonblocking under multicast traffic. © 2005 Wiley Periodicals, Inc. NETWORKS, Vol. 46(4), 163–170 2005

This paper considers three-stage switching networks able to support multicast traffic, i.e. connections in which one inlet is connected to more than one output at the same time. The nonblocking conditions for this network are studied under the assumption of absence of any optimized routing of the connections inside the structure (the so-called strict-sense nonblocking networks). An analytical model is developed here that provides not only the nonblocking conditions of three-stage multicast networks, but also the evaluation of the blocking probability when such conditions are not satisfied. Unlike previous well-known approaches, our model takes into account the correlation between occupancy events in links belonging to different interstage patterns. The results being found also provide a more stringent condition of network nonblocking for multicast traffic which disproves some of the claimed results recently published in the technical literature.

This paper considers three-stage switching networks for which nonblocking conditions with point-to-point traffic are given by the well known Clos (1953) theorem, under the assumption of absence of any optimized routing of the connections inside the network. We give the conditions for such a network to be strict-sense nonblocking under multicast traffic, by showing also that previously published papers, although claiming the same result, only provided sufficient conditions.