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Abstract

A high impedance tap for monitoring traffic over a communication link of a fast Ethernet local area network (LAN). The circuit of the present invention is advantageously used for tapping into a fast Ethernet communication link (e.g., bi-directional communication channel) of a LAN using, for instance, 10/100 BaseT Ethernet communication protocol. The novel circuit is particularly useful in point to point communication links (e.g., supporting fast Ethernet communication) where two communication nodes are coupled together using a bi-directional communication link (e.g., two twisted pair cables). Unlike the prior art monitoring probes, the probe of the present invention does not insert itself in series between the communication link, but rather taps onto the communication link in parallel using a high impedance termination circuit thereby leaving the existing communication link undisturbed electrically. By leaving the communication link undisturbed electrically, the probe of the present invention does not introduce latency into the communication link nor does it interrupt the communication link for any reason (e.g., during auto-negotiation sessions or on power down, power interruption, etc.). The high impedance value selected for the present invention is approximately one order of magnitude greater than the individual termination impedance of the communication nodes. The particular termination circuit used can employ a parallel coupled resistor with optional capacitors coupled to each wire of a twisted pair cable. The probe can be attached to a number of different statistics gathering systems (e.g., of the RMOD and RMOD2 standard) or various types of traffic accounting systems.

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First Claim