Abstract: A novel mechanism for performing Ethernet noise source characterization including monitoring and analyzing several Ethernet impairments, including Ethernet 1000Base-T impairments. Time domain and frequency domain analysis techniques are used to characterize cable performance, supportable transmission rate and to determine whether cable performance and specification requirements are being met. Various noise sources are characterized including: echo signal, NEXT signal, FEXT signal, insertion loss, alien NEXT/external noise source and residual noise. Using time domain analysis, the power of the interfering signal is measured and compared to a pre-defined allowed reference limit. Alternatively, the filter tap values used in the receive signal processing blocks, e.g., echo canceller, NEXT canceller, FEXT detector/canceller, etc., can be used. In addition, the energy of the actual filtered output generated within the receiver from these processing blocks may be used as well.