ANALYSIS OF BACKPRESSURE-TYPE PACKET SWITCHES WITH INPUT AND OUTPUT BUFFERING

The authors investigate the performance of packet loss and delay in a non-blocking backpressure-type packet switch with input and output que ueing that is able to transfer up to L packets per slot to a given swi tch output. The switching fabric allows limited queueing at the output ports. Overflow at the output queues is prevented by using a backpres sure mechanism and additional buffers at the input ports. The authors develop an analytical model of the switch architecture and analyse the impact of the back-pressure effect on the switch performance for arbi trary output and input buffer sizes and different speed-up factors. Th e model is based on the output contention process and Geom/PH/1/K inpu t queueing process. The output contention involved by packets at the h ead of input queues can be viewed as an independent phase type process . The result indicates that, when there are reasonable sizes of buffer s at both input and output port and the backpressure mechanism is used , the switch with output buffers having a relatively small capacity an d a speed-up factor of L = 2 approaches closely the ideal delay and pa cket loss performance of a pure output queueing switch at a reasonable input load condition.