Analytic solution of an integrated performance model of a computer communication network with window flow control

A method for analyzing the performance of computer communication networks using queueing network models (QNM's) is presented in this paper. The user/computer sites are interconnected by a wide-area network with an end-to-end window flow-control mechanism. The QNM for the system including the communication subnet and the host computers is intractable because of blocking due to window flow control and memory constraints at computer systems, even under otherwise analytically favorable assumptions. The approximate solution method, which is based on iteration and decomposition, combines several recently developed computationally inexpensive algorithms to compute user response times, taking into account the delay in the communication network and the processing time at computer systems. We also introduce a fast non-iterative procedure to analyze QNM's with external arrivals and with population size constraints, such that blocked customers are queued. The effect of the choice of window sizes and minimum link/bifurcated routing on system performance is investigated.