A case for simplicity in providing network quality of service: class-based strict priority queueing

In this paper, we make a case for a simple alternative in providing quality of service (QoS) in packet-switched networks: class-based strict priority queueing. Simplicity here is meant in a multi-faceted sense with respect to (1) implementation complexity in routers, (2) service interface towards network users, (3) analytical tractability, and (4) configuration and management ease. We find basic properties of the worst-case behaviour in strict priority queueing systems using network calculus. Besides the newly derived worst-case characteristics, there are known results for the average behaviour of strict priority queueing systems from traditional queueing theory. These results are contrasted against the worst-case results by means of numerical investigations. They provide on the one hand a feeling for a provider as to how conservative the worst-case bounds are as well as on the other hand a hint for users on what service they can expect from the network on average. The rationale behind this work is the appealing simplicity as well as the almost ubiquitous availability of strict priority queueing in today´s routers and the thus promising applicability of our results for practical purposes in providing QoS in the Internet.