Analysis of a Priority Polling System for Two-Way Traffic

Polling systems are a common mechanism for packet transmission in switching systems with distributed control, and computer communication systems, where data and signaling packets must be passed between a set of peripheral device controllers and a central control facility. Presented in this paper is the queueing analysis of the transmission delays for the two-way data traffic between the central control and a set of peripheral controllers, where the communication is based on a complex polling cycle giving effective priority to outgoing packets from the central control. The analysis takes fully into account the mutual dependence between incoming and outgoing packet delays. The delay analysis for the high-priority outgoing packets is exact, and for the lowpriority incoming packets it is approximate. Numerical results are presented to illustrate the analysis method, and are validated against computer simulations.