Progress Toward Optimal

Over the last several years, a variety of multipoint virtual circuit switching systems have been proposed for use in Asynchronous Transfer Mode (ATM) networks. The inherent exibility of ATM networking and the desire to apply this technology to a wide range of diierent applications makes it impractical to rely on statistical traac models when engineering a system. This motivates a renewed interest in networks which are nonblocking with respect to requests to create or modify multipoint virtual circuits. While the various multipoint switching system architectures can all be conngured to achieve nonblocking operation, for most, the cost of the nonblocking connguration quickly becomes prohibitive. We examine the complexity characteristics of a variety of mul-tipoint switch architectures, taking into account the switching network, the memory required for routing multipoint virtual circuits and the eeort required to create or modify a virtual circuit. In particular, we show that a very simple architecture, based on the concept of cell recycling, can be conngured to be nonblocking with optimal complexity in all three dimensions. This architecture exempliies a class of networks which we refer to as reroutably nonblocking.