Padded-frame Based in-sequence Dispatching Scheme for Memory-Memory-Memory (MMM) Clos-network

Compared with other types of Clos-netwok switch, the Memory-Memory-Memory (MMM) switch minimizes the time required to configure a Clos-network switch. However the use of buffers in the middle stage of an MMM switch can potentially cause the forwarding of cells to the outputs in out-of-sequence order. A novel scheduling algorithm, called Extended Padded Frame (EPF) scheme, is proposed, which provides in-sequence service for MMM Clos-network by adopting a frame-based approach. The new solution adopts a predetermined cyclic shift configuration at the first and third stages and the oldest-cell-first selection for arbitrations at the second stage. The algorithm is decentralized and requires no speedup. Analysis and simulation results show that the new algorithm is stable, that is to say, EPF can achieve 100% throughput under any admissible traffic patterns.