Blocking probability of bicast connections in a rearrangeable Clos network

Clos networks, which are ubiquitous in large capacity switches, have been widely studied for unicast connection requests. But most of these results do not hold when the switch has to support multicast connections. Our interest is specifically in bicast connections which are required for setting up backup protected circuits in optical backbone networks. In this work we have studied the nonblocking properties of rearrangeable Clos switches. Furthermore, we have developed expressions to estimate the blocking probability when the nonblocking conditions are not met. We have also run simulations to determine the blocking probability which correspond well with the estimates. We have considered two ways of realizing a bicast connection - by splitting the circuit at the outer stage or at the middle stage.