Static round-robin dispatching schemes for Clos-network switches

The Clos-network is widely recognized as a scalable architecture for high-performance switches and routers. One of the key challenges in designing a Clos-network switch for a high-speed environment is the design of the dispatching/scheduling so as to be efficient for a wide range of traffic patterns, yet practical to be implemented in hardware. Based on the static round-robin scheduling technique, we propose the SRRD cell dispatching algorithm and its variants for Clos-network switches in this paper. Our algorithms are based on the request-grant-accept (RGA) handshaking scheme, which can be implemented using simple distributed arbiters at the input and output of the Clos-network. The intuition behind our SRRD schemes is to desynchronize the pointers of the arbiters in a static way and by to use a rotating-search technique to improve the performance under non-uniform traffic. Our simulation results demonstrate that our algorithms achieve the lowest delay and highest throughput among all other related schemes. In addition, their hardware implementations seem to be even simpler than that of related algorithms.