reduction in performance is of the same magnitude as for the crossbar network, as evident from Figure E.2. The delay characteristics of Banyan networks are also evaluated by simulation with the assumptions already considered for the crossbar switch and d=2; the results are shown in Figure E.5. E.4 Other Switching Architectures Several properties that we have found for a crossbar switch fabric hold in general for every strictly nonblocking switch fabric. Some of them are Saturated throughput (Tout/Tin) Crossbar blocked packets discarded Discarded blocked packets Retransmitted blocked packet Switch dimension (log2(N)) FIGURE E.4 Normalized saturated throughput evaluated by simulation for output queueing Banyan network with two val- ues of the dimension of the base element. Results related to a crossbar matrix are also reported for comparison. Similar results can be obtained with input queueing. Appendix E: Space Division Switch Fabric Performance Evaluation Average delay (slots) Output Input queues queues Offered traffic (Pin) FIGURE E.5 Average delay in number of slots evaluated by simulation and analytically for output queueing and input queueing Banyan network with d=2. The curves are evaluated for large N and varying the traffic load. Input queueing is less performing than output queueing. The average delay does not depend on the switch fabric dimension if N is big. A threshold exists, evident on the delay plot, dividing abruptly the normal work- ing regime from the congestion regime. From a quantitative point of view, the crossbar switch fabric is in absolute the best per- former, both in terms of saturated throughput and in terms of delay, among the possible space division strictly nonblocking switching architectures. On the other hand, if through- put and delay are considered, Banyan networks are the worst performers among the space division switch fabrics that we have introduced in Chapter 5. Also this is an intuitive property. As far as the crossbar is concerned, it is the strictly nonblocking structure th