Frame based multicast scheduling for buffered Clos-network switches

Buffered Clos-network switches have advantages of modularity and simplicity; however, they are limited to serious out-of-sequence problems, especially when serving multicast traffic. In this study, a frame-based multicast scheduling algorithm for memory-memory-memory Clos networks (FMClos) is proposed. Multicast cells are replicated at the first and last stages based on address-copy technology, which eliminates head-of-line (HoL) blocking and improves throughput performance. The frame-based scheduling scheme performed at the input module, as well as the buffered crossbar switch element adopted by the central module, contributes to reducing the out-of-sequence (OOS) cells. Simulation results show that FMClos scheme can achieve nearly 100% throughput. In comparison with existing algorithms, the proposed method decreases the proportion of OOS cells and considerably reduces resequencing delay under heavy traffic load.