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. A large multicast ATM switch with external structure of output queueing and internal structure of buffered MINs ลฝ . ลฝ . multistage interconnection networks is considered in the paper, where the buffered MIN also called switching network is ลฝ . composed of switching elements with shared buffer output queueing. The cell replication while routing CRWR scheme is used in the switch to implement multicast function. In this paper, we study the performance of the switch with multicast traffic, mainly via computer simulations. The multicast traffic can be random and bursty. We found that compared to unicast traffic, multicast traffic with truncated geometric distribution of cell fanouts has only a slightly worse impact on the performance of switching elements in isolation or in the last stage of the switching network. The multicast traffic has no worse effect on the switch output buffer behavior and cell delay in the switching network. Moreover, using multiple MINs in parallel can substantially improve the switching network performance for highly bursty traffic. Some analytical approximations are given which could be useful in the dimensioning of switching networks. q 1998 Elsevier Science B.V.