Differentiation and Interaction of Traffic: A Flow Level Study

We study what kind of differentiation can be achieved using DiffServ without admission control using a relative services approach, i.e. the rate of the flow should be in proportion to the contracted rate. We model analytically differentiation mechanisms proposed in such proposals as AF and Simple Integrated Media Access (SIMA) with emphasis on modelling the interaction between various differentiation mechanisms and traffic flows of type TCP and UDP. We first review main results of an earlier and more detailed packet level model and then introduce more abstract flow level models. As a result we show how the flow level models are powerful models for explaining how marking thresholds and mechanisms determine the differentiation in a network. The flow level models are able to produce results similar to the packet level models, and can be used as an abstraction of a DiffServ network and give system level guidelines for both network and differentiation design.