Pipelined scheduling technique

Abstract

A pipelined scheduling system allowing suppressed unfairness among inputs and reduced fixed delay time is disclosed. Virtual output queues (VOQs) for each input port corresponding to respective ones of the output ports are stored. The VOQs are equally divided into a plurality of groups. Scheduling modules each corresponding to the groups performs a scheduling operation at a single time slot in a round robin fashion such that each of the scheduling modules reserves output ports at a predetermined future time slot for forwarding requests from logical queues of a corresponding group based on a reservation status received from a previous scheduling module, and then transfers an updated reservation status to an adjacent scheduling module. A crossbar switch connects each of the input ports to a selected one of the output ports depending on the reservation status at each time slot.