OSCILLATIONS AND CHAOS IN A FLOW MODEL OF A SWITCHING-SYSTEM

Field data from digital switching systems in an access tandem environment indicate unexpectedly large queueing delays at moderate occupancies. We show that these delays are caused by an effect called "traffic synchronization," which is the batching of a system's workload caused by interactions between the system and incident traffic. We develop a flow model to study this effect, and show that a momentary overload can cause sustained oscillations in the system's queues. There are several steady-state modes of operation, and we show that for certain parameter ranges, the system is chaotic. Such oscillatory behavior can significantly lower the real-time capacity of the switching system, and we suggest controls to limit the synchronization effect. These controls are incorporated into the flow model and analyzed. The results described here are validated by numerical studies, simulations, and field data.