Combined unicast and multicast scheduling

Abstract

A method and system for combined unicast and multicast scheduling. Data cells are assigned at each input to one unicast input queue for each output or to a single multicast input queue. Each input makes two requests for scheduling to each output for which it has a queued data cell, one unicast request and one multicast request. Each output grants up to one request, choosing highest priority requests first and giving precedence to one such highest priority request using an output precedence pointer. The output precedence pointer is either an individual output precedence pointer specific to that output for unicast data cells or a group output precedence pointer generic to all outputs for multicast data cells. Each input accepts up to one grant for unicast data cells or as many grants as possible for multicast data cells, choosing highest priority grants first and giving precedence to one such highest priority grant using an input precedence pointer. In one embodiment, the individual output precedence pointers each implement a round-robin precedence technique in which the most recent input to transmit a data cell has the lowest precedence; the pointer is incremented to point to a next input each time a data cell is transmitted from the pointed-to input.