A comparison of the ShuffleNet and the banyan topologies for broadband packet switches

The performances of centralized, fast packet switches based on the ShuffleNet and on multistage banyans are compared. Two cost criteria are used, viz., the number of crosspoints and the number of pin-limited ICs. The analytic comparison of the two networks built with arbitrary size infinite buffered nodes shows their cost performance to be similar. The analysis also provides the optimal node sizes for both the topologies. The best throughput per crosspoint is obtained with small nodes, but the best throughput per pin-limited IC is obtained with the largest possible nodes that can be built on an IC. With the IC criterion, for both the networks, small nodes are found to give small minimum delays (inside the network). With finite buffered nodes and a simple back-pressure flow control (like the one for the banyan network), the ShuffleNet based switch can have problems of congestion. It is also prone to deadlocks