In this paper, we present a performance study of an input/output buffered type ATM switch with backpressure mechanism with a MMPP process as input. The backpressure is exerted at the Head of Line (HOL) level to prevent output buffer cell loss fig1 (a)(b). MMPP process is chosen due to its bursty nature able to capture multimedia source characteristics such as data and voice. We propose an approximate method to calculate the total waiting time in the switch. Numerical examples will be given for two states MMPP to quantitatively show the effects of output buffer size b on performance switch. Using structured stochastic matrices of M/G/1 type does the analysis and the obtained results extend those related to scalar case (Poisson process). Voir le lien ici