CLOS-KNOCKOUT - A LARGE-SCALE MODULAR MULTICAST ATM SWITCH

A large-scale modular multicast ATM switch based on a three-stage Clos network architecture is proposed and its performance is studied in th is paper. The complexity of our proposed switch is N root N if the swi tch size is N x N. The first stage of the proposed multicast switch co nsists of n sorting modules, where n = root N. Each sorting module has n inputs and n outputs and is responsible for traffic distribution. T he 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 bu ffers are used in this architecture. The proposed multicast switch has the following advantages: 1) it is modular and suitable for large sca le deployment: 2) no dedicated copy network is required since copying and switching are performed simultaneously: 3) two-stage packet replic ation is used which gives a maximum fan-out of n(2); 4) translation ta bles are distributed which gives manageable table sizes; 5) high throu ghput performance for both uniform and nonuniform input traffic: 6) se lf-routing scheme is used. The performance of the switch under uniform and non-uniform input traffic is studied and numerical examples demon strate that the cell loss probability is significantly improved when t he distribution network is used. In a particular example. it is shown that for the largest cell loss probability in the second stage to be l ess then 10(-11) the knockout expander, with the use of the distributi on network, needs only be larger than G. On the other hand, without th e distribution network. the knockout expander must be larger than 13.