Abstract

This paper presents the design of the scheduler for an M × N input-queued multicast switch. It is assumed that: (i) Each input maintains a single queue for arriving multicast cells, and (ii) Only the cell at the head of line (HOL) can be observed and scheduled at one time. The scheduler is required to be: (i) Work-conserving, which means that no output port may be idle as long as there is an input cell destined to it, and (ii) Fair, which means that no input cell may be held at HOL for more than a fixed number of cell times. The aim of our work is to find a work-conserving, fair policy that delivers maximum throughput and minimizes input queue latency, and yet is simple to implement in hardware. When a scheduling policy decides which cells to schedule, contention may require that it leave a residue of cells to be scheduled in the next cell time. The selection of where to place the residue uniquely defines the scheduling policy. Subject to

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