A Variable Buffer-Size Model and Its Use in Analyzing Closed Queueing Networks with Blocking

We present a model which enables efficient analysis of certain types of closed queueing networks with blocking due to limited buffer spaces. The networks analyzed are those in which the limited buffers occur in tandem subnetworks. A new model, with variable buffer-size, is introduced as a conceptual tool to model part of a tandem network with blocking, using only product-form submodels. Using this model we iteratively solve for the whole network. The technique is illustrated first for a simple system with tandem queues, and then for more complex systems. The method is compared with exact solutions or simulations, and found to be reasonably accurate. The method is easily implemented using standard software for closed queueing networks. Given the complexity of the blocking problem, our approach offers a simple and efficient alternative to exact analysis.