A method to reduce the external blocking in the Batcher banyan network with incomplete copy network

Multicast ATM switch is in great demand for the future communication networ k. We have proposed the Batcher banyan network with cell copy preparation s tages as a transit switch. It performs cell replication with small hardware increase. On the trunkline, multicast traffic is quite little, thus hardwa re for cell copy can be sustained small. In those previous works, the effec t of the external blocking was omitted. In this paper, we propose a multica st switching network which adopts the incomplete copy network that we have proposed, and examine several strategics to prevent the external blocking f or this switching network. Namely, the input buffer method with an arbitrat ion network is applied. For multicast usage, we propose two modifications. One is to arbitrate after cell replication for the sake of simple control a nd small hardware. The other is to annex a cell distribution network for sm oothing biased cell arrival. Biased cell arrival occurs because the output of the incomplete copy network is riot uniform. Simulation results show the effectiveness of the proposal method.