MONITORING THE PERFORMANCE OF COMMERCIAL T1-RATE TRANSMISSION SERVICE

This paper gathers the scattered empirical and theoretical elements of the performance-management problem for commercial T1-rate transmission service and integrates these elements in a useful way. We propose two variants of a time-based performance-monitoring 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 metallic-conductor 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.