ABSTRACT
In the models considered in the previous chapters, note that there was only a single class of customers in the system. However, there are several applications where customers can be differentiated into classes and each class has its own characteristics. For example, consider a hospital emergency ward. The patients can be classified into emergency, urgent, and regular cases with varying arrival rates and service requirements. The question to ask is: In what order should the emergency ward serve its patients? It is natural to give highest priority to critical cases and serve them before others. But how does that impact the quality of service for each class? We seek to address such questions in this chapter. We begin by describing some introductory remarks, then evaluate performance measures of various service disciplines, and finally touch upon the notion of optimal policies to decide the order of service.
