Analysis of demand-priority access using a priority queue with server vacations and message dependent switchover times

In this paper, we analyse the message waiting times in a local area network (LAN) that uses the demand-priority access method. This is a priority-base d round-robin arbitration method where the central controller (the repeater ) polls its connected ports to determine which have transmission requests p ending and the requests' priority classes. We model it as a 2-priority M/G/ 1 queue with multiple server vacations and switchover time between service periods. The service discipline is nonpreemptive and the length of the swit chover time is dependent upon the priority class of the preceding message s erved as well as that of the message to be served next. We provide an appro ximate analysis for the waiting times of both message classes and derive ex pressions for the Laplace-Stieltjes transforms (LST) of the stationary dist ributions and the mean waiting times. We conclude with numerical and simula tion results to show the applicability and accuracy of the analytical model .