تجزیه و تحلیل عملکرد ترافیک دو درجه ای انتقال سوئیچ بافری ATM در طی کانال نامطمئن

In this article we analyze the performance of a space division output buffered switch operating in an ATM multimedia environment as follows. Fixed size packets arrive onto the switch inputs in each time slot. These packets are of two classes. Class-1 packets, representing real time communications, are sensitive to delay but insensitive to loss. Class-2 packets, representing nonreal time communications, are insensitive to delay but sensitive to loss. The switch transmits these two-class packets over communications channels which are unreliable. That is, the packets could be lost before reaching the other end. To respond to the class-1 delay sensitivity, the switch gives class-1 packets higher service priority over class-2 packets. And to respond to the class-2 loss sensitivity, the switch requires an acknowledgment for each class-2 packet it transmits. It is this latter response that is the major contribution of the article. In particular, it gives rise to two service times, rather than one as has usually been considered in the published literature. For the purpose of the analysis, the switch is modelled as a priority, discrete time, batch arrival, single server queueing system, with infinite buffer and two service times: one deterministic for class-1 and one geometric for class-2. Three performance measures are analyzed: occupancy, unfinished work, and waiting time.