Decomposition of output queuing switches
H.S. Kim, Alberto Leon‐Garcia · IEE Proceedings I Communications Speech and Vision · 1991
A large switch is often constructed with multiple stages of switching elements to reduce the hardware complexity or the speedup. Multiple-stage structures allow either blocking or nonblocking configurations. The blocking configuration suffers from the congestion of packets in a part of the switch. The nonblocking configuration requires a centralised control to route the packets through the switch. A centralised control creates a bottleneck when the switch operates at a high data rate. The paper introduces a simple technique to reduce the complexity of the output queuing switch with a speedup without either losing the self-routing characteristic or allowing performance degradation under nonuniform traffic patterns. Any of the output queuing switches with a speedup can be used as a basic switching element. The switching elements are then interconnected with the distributors in multiple stages. By introducing the distributors between stages of switching elements, the packets can be evenly distributed to all the input ports of the switching elements in the following stages. Although the switch becomes blocking, it retains the self-routing property and achieves the maximum throughput of 100% with only a small additional delay.