Path switching-a quasi-static routing scheme for large-scale ATM packet switches

A quasi-static routing scheme called path switching for large-scale ATM packet switch systems is proposed. Previously the Clos network has been used as the model for many large-scale ATM switch architectures, in which the most difficult issue is path and bandwidth assignment for each connection request. The static routing scheme, such as multirate circuit switching, does not fully exploit the statistical multiplexing gain. In contrast, the dynamic routing scheme, such as straight matching, requires slot-by-slot computation of route assignment. Path switching is a compromise of these two routing schemes. It uses a predetermined periodical connection pattern in the central stage, look-ahead selection in the input stage, and output queueing in the last stage. The scheduling of path switching consists of capacity assignment and route assignment. The capacity assignment is constrained by the quality of service of connection requests. The route assignment is based on the timespace interleaving of the coloring of bipartite multigraphs. We show that path switching can handle multirate and multimedia traffic effectively in the Clos network