CRRD-OG: a packet dispatching algorithm with open grants for three-stage buffered clos-network switches

The clos-network architecture is well-known and widely described in the literature. It is very attractive because of its scalability. The clos-network in packet switching systems adopt the use of packet dispatching algorithms to avoid packet contention, which may occur while a packet is being routed in a switch fabric. The complexity of packet scheduling may be relaxed by providing buffers in the first and third stages in a three-stage clos network. Different dispatching schemes for buffered clos-network switches that provide 100% throughput under uniform traffic were proposed in many papers. In this paper the idea of open grants is introduced and an algorithm called concurrent round-robin dispatching with open grants (CRRD-OG) for three-stage buffered clos-network switches is proposed. This algorithm is an improved version of CRRD scheme by implementing an open grant rules and gives better performance results. The performance of CRRD-OG algorithm was evaluated and compared with results obtained for CRRD and CMSD (concurrent master-slave round-robin dispatching) schemes.