Nortel Networks Corporation

Sri Reddy

David Stevens

Robert W Smith

Van A Hunter

Ilan Raab

Tissa Senevirathne

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. Protection path switching occurs, for example, only when 10 errors occur on any one of the 36 primary switching fabric lines being received by four fabric access devices therein within a 100 millisecond window initiated at the detection of the first error on the communication line. If 10 errors are not detected within a defined communication window, in the described embodiment, the window is terminated and is only reinitiated upon the detection of the next line error.

Method and apparatus for switch core health monitoring and redundancy

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.

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Los Altos, CA, United States of America

Sri Reddy