Queueing in Space-Division Packet Switching.

Because of the unscheduled nature of arrivals to a packet switch, two or more packets may arrive on different in-puts destined for the same output. The switch architecture may allow one of these packets to pass through to the output, but the others must be queued for later transmission. We study the performance of four different architectures that provide the queueing necessary to smooth fluctuations in packet arrivals to a space- division packet switch. They are (1) input queueing, where a separate first-in, first-out (FIFO) buffer is provided at each input to the switch; (2) input smoothing, where a frame of b packets is stored at each of the N input lines to the switch and simultaneously launched into a switch fabric of size Nb x Nb; (3) output queueing, where packets are queued in a separate FIFO buffer located at each output of the switch; and (4) completely shared buffering, where all queueing is done at the outputs and all buffers are completely shared among all the output lines.