Layered queueing is a small and elegant extension to queueing networks, to model complex resources that are held in groups when a program executes. Upper-layer servers include the use of lower layers in their service times. The interpretation of results (such as bottleneck identification) is different in layered systems, whether they are solved by analytic techniques or by simulation, or even viewed from measurements.
Layered queueing occurs in all real systems, although the layered effects may be small enough to be ignored, giving the usual "flat" models.
The model concept originated in the "active server" model of Woodside (1984), which was a systematic layered application of the surrogate delays of Jacobson and Lazowska (1983). Contributions have come from a broad group of researchers. Developments include
The Carleton University group that publishes this page has been developing
techniques to solve layered models and also to build them and to exploit
their results. While our work is fully described here, we want to spread
the interest in this approach and include other ideas, tools, and results.