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  1. E. Nyberg, How to achieve fair differentiation: Relating flow level QoS requirements to DiffServ packet level mechanisms, Licentiate thesis, Helsinki University of Technology, Networking Laboratory, 2002 (pdf)(bib)
    Abstract: Quality of Service (QoS) is a general notion of introducing different quality levels to the best-effort Internet. Differentiation of traffic is needed both to guarantee quality requirements for real-time applications as well as to offer different levels of priority inside traffic classes. Differentiated Services (DiffServ) is a set of mechanisms aiming at providing scalable differentiation, where quality treatment inside the network is done to aggregates of flows not to individual flows. Quality guarantees can be divided into two service models. In assured services the flow should receive a rate at least equal to the contracted rate, while in relative services the rate of the flow should be proportional to the contracted rate. The thesis models QoS mechanisms used and proposed for use in DiffServ networks. The modelling concentrates on the interaction between various differentiation mechanisms and traffic flows using a given transport protocol. This type of closed loop modelling of the dependency of the flow sending rate on the metering, marking, dropping and scheduling mechanisms has not been done before. The mechanisms are modelled and analyzed on two levels: flow level and packet level. Furthermore detailed simulation of the packet level are performed. The correspondence between the models is good, and each modelling approach is able to illustrate a different aspect of mechanism design, either through the choice of parameter values or through the choice between two complementary mechanisms. Based on the models, we study how well relative services can be achieved, i.e. in what proportion network bandwidth is divided, using DiffServ without admission control.