Push-out of low priority signals from switch buffers

Abstract

An apparatus and method for push-out of signals from switch buffers ensures that a high percentage of the highest priority input signals are accepted by the switch by using the switch resources to remove lower priority input signals from the switch buffer in order to accommodate higher priority input signals. Signals of any priority may be pushed out of the switch buffer. The apparatus requires a queue with simultaneous read and write capability and a switch that performs one read operation to N write operations, N being the number of input ports. It pushes signals out of the buffer by performing additional 'dummy' read operations to read out signals of the specified priority, and then discards the signals by preventing them from entering the parallel-to-serial shift registers. A preferred embodiment of the invention utilizes an ATM CAM-controlled switch fabric, where the CAM receives the arrival number and priority of each cell in the buffer. The location of low priority cells is found by activating a dummy read priority line and addressing the CAM.