three-phase algorithm  proposed by Hui, which uses probe, acknowledge
and send approach.  In this algorithm, first a small packet called
probe containing only the input and output port addresses is sent by
the input ports with active packets.  The probe packets are routed
through the batcher-banyan network as in Starlite switch.  However,
the excess probe packets are rejected, and not recirculated.  The
output ports receiving a probe packet send an acknowledgement packet
to the corresponding input ports using the addresses contained in the
received probe packets.  The acknowledgements are sent through the
same batcher-banyan network.  The input ports receiving
acknowledgements then send packets to the output ports.  If necessary,
the probing process can be repeated to reduce HOL blocking before
transmitting packets.   assume there is no HOL
blocking.


Assuming (i)packets are continuously arriving at the input ports at a
bit rate of 100 Mbps, (ii)packets arriving at the switch are ATM
cells, (iii)delay in the router as well as sorter is 1-bit per stage,
and, (iv)the switch size is 515´512, determine the minimum speed at
the which the above three-phase switch must operate.