Abstract: A method and apparatus selecting between primary switching fabric in an asynchronous transfer mode (ATM) network includes a Tap Mux controller that monitors the signals being transmitted to each of four fabric access devices. As each of the fabric access devices receives nine communication lines, the Tap Mux controller monitors a total for 36 communication lines on the primary switching fabric. Because the switching fabric is completely redundant, however, the Tap Mux controller also monitors a total of 36 communication lines on the protection switching fabric. The Tap Mux controller, therefore, includes logic that defines 72 state machines that each monitor one of the 72 lines. Each state machine, in the described embodiment, initiates a defined length time window and counts errors therein.

Abstract: A method and apparatus for monitoring the performance of a dedicated communications medium in a switched data networking environment wherein a probe having a bypass circuit allows promiscuous monitoring of all traffic between a switch and a network device, such as a file server, in either direction, and in full duplex mode. Additionally, the bypass circuit eliminates the requirement for a separate repeater between the switch and the network device.