Throttled-buffer ATM switch output control circuitry with CAM-based multicast support

The shared buffer switch chip uses a CAM-access approach. Cells are uniquely identified by a combination of sequence number and port for unicasts, or sequence number and multicast identifier (MCI) for multicasts. A Tag CAM is used to search for these identifiers, and a control throughput of47 Mcell/s is achieved. The multicast hardware employs a CAM (the McCAM) to query multicast destination bitmaps. Only one copy of both the tag and the cell is stored. The McCAM is searched for multicasts that are unobstructed by busy unicast ports. The McCAM also enables global multicast querying, so that multicast connections behind the head-of-line may be serviced.