Optimal Nonblocking Multipoint Virtual Circuit Switching

Many multipoint virtual circuit switching systems have been proposed for use in ATM networks. The inherent exibility of ATM networks and the desire to use them for a wide range of di erent applications makes it impractical to rely upon statistical tra c models, motivating a renewed interest in nonblocking networks. While the various multipoint architectures can all be con gured to be nonblocking, for most, the cost quickly becomes prohibitive. We examine the complexity of several multipoint switch architectures, taking into account the switching network, the memory needed for routing and the e ort required to create or modify a virtual circuit. We show that a simple nonblocking architecture, based on the concept of cell recycling, achieves optimal complexity. This architecture exempli es a class of networks which we refer to as reroutably nonblocking. This work was supported by the National Science Foundation (grant DCI 8600947), Ascom Timeplex, Bell Communications Research, Bell Northern Research, Goldstar Information and Communications, Italtel SIT, NEC, NTT and SynOptics.