Performance of ATM switch fabric using cross-point buffers

Abstract

Multistage switches consisting of a number of stages of small switching elements (SE) are often used in ATM switch fabrics. An ATM switch fabric performs the functions of switching and buffering of cells. The location of buffers inside a fabric is critical in the performance of the switch. Output buffered SEs have a higher throughput than input buffered SEs. Moreover, output buffered SEs do not suffer from buffer hogging as found in shared buffered SEs operating in a nonuniform traffic environment. However, output-buffered SEs require internal speedup, thereby requiring high-speed buffers and complex buffer management hardware. Crosspoint buffering, however, enjoys the advantages of output buffering without requiring an internal speedup of its buffers. The objective of this paper is to study the performance of a crosspoint buffered ATM switch operating under uniform and nonuniform traffic patterns. The performance of the crosspoint buffered switch is compared with that of the output buffered switch. Analytical models based on the Markov chains are developed to facilitate the study. The results from the model are validated using simulation. It is shown that the model provides very accurate results.