Sojourn times in queueing networks

From a customer's point of view, the most important performance measure in a queueing network is his sojourn time. This paper presents a survey of sojourn time results in queueing networks. Particular attention is paid to product-form networks, for which exact expressions for the joint distribution of a customer's successive sojourn times along a quasi overtake-free path are discussed. When the non-overtaking condition is violated, or when no product form exists, few analytical results are known. The paper mentions some of these results, as weil as approximation techniques for product-form networks. For networks without product form, the emphasis is put on computational techniques and on some quite general approximation methods which have recently been adapted to the sojourn time problem.