Monitoring the performance of commercial T1-rate transmission service

This paper gathers the scattered empirical and theoretical elements of the performancemanagement problem for commercial T1-rate transmission service and integrates these elements in a useful way. We propose two variants of a time-based performancemonitoring algorithm that are Insensitive to the arrival pattern of transmission errors. The first variant compares a count of errored seconds accumulated over an interval of time to a fixed threshold, and Issues an alert to the network operator indicating degraded transmission performance whenever the count exceeds the threshold before the measurement Interval expires. The fixed-threshold test is calibrated with reference to the well-known Neyman model of transmission errors on metallicconductor systems. This calibration is then shown to be suitable as well for monitoring the performance of fiber-optic transmission systems where errored seconds follow the cumulative binomial distribution. The second variant of the new performance-monitoring algorithm replaces the fixed-threshold test with a dual-threshold test having a lower threshold that remains fixed and a higher threshold that floats in response to changes in error characteristics. An analysis based on the difference equations that describe the movement of the floating threshold shows that the dual-threshold test is more responsive than the fixed-threshold test in detecting nonstationary trends toward degraded transmission and in detecting stable but mediocre performance levels.