Wide-sense nonblocking multicast ATM switches

In ATM networks, upon a new call request, the connection admission control (CAC) checks whether enough resources are available on each link along the path from the source to the destination. Since there are many internal links between a pair of input-output ports within a switch node, the time constraint of setting up a call is not likely to be met if CAC also needs to check every internal link. In this paper, we consider nonblocking multicast ATM switches based on the Clos network where if the input port and destined output ports of a switch are available for a request, the request can immediately be accepted in that switch. In other words, the CAC does not need to consider the states of internal links. We derive the wide-sense nonblocking conditions for such switches and provide a simple connection algorithm by which it can be guaranteed that each connection will use no more than a preset number of middle switches. This can reduce the required number of middle switches.