Performance Evaluation of Combined Input Output Queued Switch with Finite Input and Output Buffers

It has recently been shown that a combined input output queued (CIOQ) switch with a speedup factor of 2 can exactly emulate an output-queued (OQ) switch [1]-[6]. In particular, the maximal matching algorithm, named Least Cushion First/Most Urgent First (LCF/MUF) algorithm presented in [6], can be executed in parallel to achieve exact emulation. However, the buffer size at every input and output port was assumed to be of infinite size. This assumption is obviously unrealistic in practice. In this paper, we investigate via computer simulation the performance of the LCF/MUF algorithm with finite input and output buffers. We found that, under uniform traffic, a CIOQ switch behaves almost like an OQ switch if the buffer sizes at every input and output ports are 3 and 9 cells respectively. For correlated traffic, to achieve similar performance, the input and output buffer sizes have to be increased to about 7 and 11 times of the mean burst size, respectively.