The optimistic analytical results for performance analysis of buffered banyan networks are mainly due to certain independence assumptions used for simplifying analysis. To capture more effects of cell correlation, a refined analytical model for both single-buffered and multiple buffered banyan networks is proposed in this paper. When cell output contention occurs at a 2 2 switch element, two contention resolution schemes are used. One is based on randomly choosing the winning cell and another is to give priority to the cell which has been delayed in the current buffer for at least one stage cycle. The switch throughput, cell transfer delay and cell delay deviation for single-buffered banyan networks with and without using priority scheme are derived. Then the model is generalized to multiple buffered banyan networks where analytical expressions for throughput and delay are obtained. We show that using the priority scheme the cell delay deviation is reduced and the influence on throughput performance is insignificant. The results obtained from our analytical model are compared with the simulations and good agreement is observed. Comparisons with some proposed analytical models in the literature reveal that our model is more accurate and powerful in predicting the performance of buffered banyan networks.

A large-scale modular multicast ATM switch based on a three-stage Clos network architecture is proposed and its performance is studied in this paper. The complexity of our proposed switch is NN if the switch size is NN. The first stage of the proposed multicast switch consists of n sorting modules, where n=N. Each sorting module has n inputs and n outputs and is responsible for traffic distribution. The second and third stages consist of modified Knockout switches which are responsible for packet replication and switching. Although it is a multipath network, cell sequence is preserved because only output buffers are used in this architecture. The proposed multicast switch has the following advantages: 1) it is modular and suitable for large scale deployment; 2) no dedicated copy network is required since copying and switching are performed simultaneously; 3) two-stage packet replication is used which gives a maximum fan-out of n2; 4) translation tables are distributed which gives manageable table sizes; 5) high throughput performance for both uniform and nonuniform input traffic; 6) self-routing scheme is used. The performance of the switch under uniform and non-uniform input traffic is studied and numerical examples demonstrate that the cell loss probability is significantly improved when the distribution network is used. In a particular example, it is shown that for the largest cell loss probability in the second stage to be less then 10-11, the knockout expander, with the use of the distribution network, needs only be larger than 6. On the other hand, without the distribution network, the knockout expander must be larger than 13.