Modeling Non-homogeneous Terminal Systems Using MOSEL

In this paper we consider a stochastic queueing model for the performance evaluation of a real life computer system consisting of n terminals connected with a CPU. A user at terminal i has thinking and processing times depending on index i. First we discuss reliable models, and then unreliable models (i.e. the CPU and the terminals are subject to random breakdowns). The models described here are not new, they were studied earlier by different authors. This paper gives a detailed implementation of the models using MOSEL (MOdeling Specification and Evaluation Language), developed at the University of Erlangen, and it is shown that MOSEL is well suited for modeling such systems. We give some numerical examples, where the most important performance measures (such as utilization, response times, mean queue length) are calculated, to see what is the difference between the results of MOSEL and the ones published earlier. In the appendices we publish the source codes of the MOSEL programs mentioned in this paper.