Chapter Five – QUEUEING THEORY

Publisher Summary One of the most fruitful areas of applied probability theory for computer science applications is that of queueing theory or the study of waiting line phenomena. Similar to queues in daily lives, queues are also common in computer systems. Thus, there are queues of people waiting to use a computer terminal, queues of inquiry messages waiting for processing by the central computer system, queues of channel requests, and queues of input/output (I/O) requests. This chapter provides an overview of queueing theory and presents the elements of a queueing system pictorially. It highlights the fundamental ideas of queueing theory and discusses some of the basic queueing systems that are especially useful in computer science. It illustrates the use of these systems with a number of examples. For some computer systems, such as an on-line inquiry system, different parts of the system may be viewed as the essential queueing system, depending on where bottlenecks are felt to occur. Thus, if input and output message transmission times are negligible compared to the processing time at the central computer system, then the model of an on-line computer system may consist of the central computer system as the single server with the incoming inquiries playing the role of customers.