Traffic and delay in a circular data network

The operation and traffic behavior of a data transmission system using a loop topology are studied. A mathematical model is developed for evaluating system load and buffer delay. This model accommodates an arbitrary number of stations for a symmetric traffic pattern. Intrinsic to the model is a recognition of the bursty nature of data sources. Other factors that are taken into account are line and source rates as well as the blocking of data into fixed-size packets. Formulas are derived from which approximations to average message delay induced by traffic in the loop (a critical parameter in buffered systems) can be calculated. The results of the study are presented in a set of curves where normalized delay due to traffic within specific system configurations is plotted as a function of the number of stations and source activity. Simulation results for single loops of 5 and 50 stations are presented which indicate good agreement with the analytical approaches. A major conclusion is that, in certain quite reasonable circumstances, the delay is not large even for high line activity.