Routing unit Switching and flow − control unit Transmission unit

Direct networks have become a popular way to interconnect processing nodes of todays larger commercial and research multiprocessors. The design of such direct networks is important, since it has a large eeect on the performance, cost, and the scalability of the system. The behavior of a direct network is determined primarily by how it does switching, routing and ow-control. This survey article presents systematically the key design issues of topology, switching, routing and ow-control in a tutorial style starting with a simple description of the issues and leading to recent trends and future research directions.