Closed queueing networks with finite capacity queues: approximate analysis

Queueing networks with finite capacity queues and blocking are applied to model systems with finite resources and population constraints, such as computer and communication systems, as well as traffic, production and manufacturing systems. Various blocking types can be defined to represent different system behaviors. When a customer attempts to enter a full capacity queue blocking occurs. The analysis of queueing networks with finite capacity queues is often based on approximate methods and simulation, since exact analytical techniques cannot be applied because of the synchronization constraint, except for a few special cases. Various approximate analytical methods have been proposed in literature and provide a solution in terms of average performance indices such as throughput and mean response time. These methods have different characteristics including model assumptions and constraints, type of blocking, algorithm accuracy and efficiency. We present a comparison of some significant approximate methods to analyze closed queueing networks with finite capacity queues. By experimental results we identify the condition under which one can appropriately select a given solution method. Experimental comparisons have been performed by the Queueing Networks with Blocking Analyzer (QNBA), a software tool developed for modelling and analysis of queueing network models with finite capacity queues and blocking.