Performance of Buuered Multistage Interconnection Networks in a Non Uniform Traac Environment 1

Multistage interconnection networks (MIN) are used to connect processors to memories in shared memory multiprocessor systems. They have also been proposed as switching fabrics in ATM switches in Broadband ISDN networks. A multistage network consists of several stages of switching elements (SE) connected by a permutation function. Since routing connicts among packets at the SEs cause blocking and reduce the performance of the network, analytical models have been developed and simulation studies carried out for performance evaluation of MINs in the presence of uniform traac in the network. Buuers are used at SEs to increase the performance of the network. Performance degradation of buuered MINs due to hot spot traac has been demonstrated by previous researchers using computation intensive simulation studies. The suitability of two existing models for possible use in the presence of a hot spot is investigated in this paper. Results show that errors from the models are large. In this paper, we propose a new and eecient Markov chain model for performance evaluation of a single buuered Omega network in the presence of a hot spot. Results obtained from the existing models and the proposed model for the uniform and the hot spot traac pattern are presented. It is shown that the proposed model is better than existing models in the presence of hot spot traac. While the existing models produce small errors in the case of low blocking in the network, the errors become prominent with increased blocking. The proposed model produces accurate results in the more general case of hot spot traac, whereas the existing models produce accurate results only in the special case of uniform traac.