A Novel Feedback Mechanism for Load Balanced Two-Stage Switches

A novel feedback mechanism is proposed in this paper to enhance the performance of load-balanced two-stage switches. The key idea is to properly select and coordinate the two sequences of TV deterministic configurations used by the two stages of switch fabrics, thereby forming a joint sequence with both staggered symmetry property and in-order packet delivery property. With a single-packet-buffer-per-middle-stage VOQ, a joint sequence with both properties is first constructed. Then based on it, an efficient feedback mechanism is designed to allow the right piece of middle-stage port occupancy information to be delivered to the right input port at the right time. In each time slot, an input selects a packet for sending based on its port-based scheduling algorithm. To this end, three simple port-based scheduling algorithms, RR, LQF and EDF, are also proposed. Simulation results show that with our proposed feedback mechanism, the three scheduling algorithms gives an unbeatable delay-throughput performance under various traffic conditions.