Module-First Matching Schemes for Scalable Input-Queued Space-Space-Space Clos-Network Packet Switches

Clos-network switches were proposed as a scalable architecture for the implementation of large-capacity circuit switches. In packet switching, the three-stage Clos-network architecture uses small switches as modules to assemble a switch with large number of ports or aggregated ports with high data rates. Current schemes for configuration of input-queued three- stage Clos-network (IQC) switches involve port matching and path routing assignment, in that order. The implementation of a scheduler capable of matching thousands of ports in large-size switches is complex because of the large port count. To decrease the scheduler complexity for such switches (e.g., 1024 ports or more), we propose a configuration scheme for IQC switches that hierarchizes the matching process. In a practical scenario our scheme performs routing first and port matching thereafter. This approach applies the reduction concept of Clos networks to the matching process. The application of this approach results in a feasible size of schedulers for up to Exabit-capacity switches, an independent configuration of the middle stage modules from port matches, a reduction of the matching communication overhead between different stages, and a release of the switching function to the last-stage modules in a 3-stage switch. We show that the switching performance of the proposed approach using weight- based and weightless selection schemes is high under uniform and nonuniform traffic.