Switching using parallel input-output queued switches with no speedup

We propose an efficient parallel switching architecture that requires no speedup and guarantees bounded delay. Our architecture consists of k input-output-queued switches with first-in-first-out queues, operating at the line speed in parallel under the control of a single scheduler, with k being independent of the number N of inputs and outputs. Arriving traffic is demultiplexed (spread) over the k identical switches, switched to the correct output, and multiplexed (combined) before departing from the parallel switch. We show that by using an appropriate demultiplexing strategy at the inputs and by applying the same matching at each of the k parallel switches during each cell slot, our scheme guarantees a way for cells of a flow to be read in order from the output queues of the switches, thus, eliminating the need for cell resequencing. Further, by allowing the scheduler to examine the state of only the first of the k parallel switches, our scheme also reduces considerably the amount of state information required by the scheduler. The switching algorithms that we develop are based on existing practical switching algorithms for input-queued switches, and have an additional communication complexity that is optimal up to a constant factor.