A simple method of estimating mean delay by counting arrivals and departures

A simple method is presented for estimating mean delay (sojourn time in queuing terminology) of a cell-processing processor in communication switching systems by observing the actual behavior of the systems. It is shown that Little´s formula leads to the estimation of the mean delay from the number of arrivals and departures. Hence, counters for these numbers are required. The method is easy to apply to real systems because measuring times of arrivals and departures, which is difficult for a call-processing processor, is not required. The accuracy of this method is evaluated for an M/G/1 queue