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Abstract

A buffered crosspoint matrix (20) of an asynchronous transfer mode switch (10) includes a plurality of switching elements (38) for receiving and switching segments containing asynchronous transfer mode cells. Each switching element (38) receives segments at a plurality of multicast/routing elements (52). Each multicast/routing element generates insert enable signals for each segment to route segments to selected crosspoints (58) of a plurality of vertical bar elements (54). Each vertical bar element (54) includes a plurality of queuing systems (90) for receiving and storing segments within an associated common buffer area (94). Segments are prioritized according to class of service and segment locations within the common buffer area (94) are stored in subqueues (104) according to their corresponding class of service. Each queuing system (90) performs a first phase contention resolution tournament to determine an oldest segment of those segments at the head of the subqueue (104) list. An output selector (114) performs a second phase contention resolution tournament by determining a most aged segment from the oldest segments within each queuing system (90). The most aged segment is switched out of the corresponding vertical bar element (54). The buffered crosspoint matrix can be expanded by interconnecting switching elements (38) within a crossbar via expansion inputs (51). An alternative expansion method interconnects crossbars in a three stage matrix.

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