Method of and system for pre-fetching input cells in ATM switch

摘要

An ATM switch with multicast capability uses a feedback mechanism for resolving contentions. A multicast network reads N cells from an input queue, replicates multicast cells and translates their addresses in accordance with an external look-up table. The processed N cells are stored in a temporary buffer until information regarding the number (F) of cells fed back due to contention in the previous switching cycle is available. A rotator positions N-F cells from the temporary buffer on inputs of an output network so as to assign the cells from the temporary buffer a lower priority than a priority of the feed back cells. The output network selects the cells that can be switched to their destinations and transfers them to output ports. The cells that cannot be switched due to contention are fed back to be presented for the output network consideration in the next switching cycle. At the same time, a pointer of the input queue is decremented by a factor depending on the number of feedback cells, and the number of multicast and unicast cells in the current switching cycle.