Research On Optimization And Blocking Probability In Three Stage Clos Network

Three stage Clos network is the most commonly used network topology which uses basic switch modules to build large-scale switching network. It can implement strictly nonblocking network, wide-sense nonblocking network and rearrangeable nonblocking network in some communication types such as permutation, multicast and multi-source multicast etc. So three stage Clos network can commendably meet design requirements of large-scale network. Thus, researching on the optimization and analysis of blocking probability in three stage Clos network not only has a very important significance in theory, but also has great applicable value.The research work presented in the dissertation is mainly focused on reducing the hardware cost of three stage Clos network and constructing the unifying model of blocking probability.Firstly, considering the problem that the hardware cost of strictly nonblocking multicast three stage Clos network is relatively bigger, a method is proposed for optimizing it. By calculating the differential of the hardware cost, the conditions that make minimizing the hardware cost are obtained. Then the hardware cost after optimizing the network is get. Through analyzing and comparing, the hardware cost of strictly nonblocking multicast three stage Clos network is efficiently reduced after optimizing the network.Secondly, considering the problem that the existing probability analysis model of three stage Clos network is only a single unicast and multicast model, a unifying model of probability analysis is proposed which uses Hwang's unifying approach and Pattavina's method. Compared to previous results the newly proposed unifying model can more correctly and comprehensively describes the blocking behavior of the multicast three stage Clos network.Thirdly, through the tradeoff between blocking probability and the hardware cost, the three stage Clos network model with small blocking probability and low hardware cost is obtained. By the comparisons between different sizes of network, it can be concluded that the hardware cost of the designed network is less approximate 50% than that of corresponding strictly nonblocking network but the probability is very small.Finally, a method to optimize hardware cost of WDM optical network based on three stage Clos network is proposed. According to the restricted condition, the optimization method is obtained by the third chapter's results. By analyses and comparisons it is validated that the proposed optimization method can efficiently reduce the hardware cost of WDM optical network based on three stage Clos network.