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  1. E. Kuumola, Analytical Model of AF PHB Node in DiffServ Network, Special Study, Networking Laboratory, Helsinki University of Technology, 2001 (pdf)(bib)
    Abstract: The current Internet offers only best-effort service for its users. Increase in the number of Internet users and the introduction of new Internet based services has increased the need for a Internet service quality differentiation. DiffServ architecture is one of the suggested methods to provide QoS into the Internet. In this report, a model is constructed for an Assured Forwarding (AF) PHB node in a DiffServ network with TCP and UDP traffic. The model describes two AF classes with three drop precedence levels. The parameters for AF packet classifier mechanism are adapted from the Simple Integrated Media Access (SIMA) nominal bit rate mechanism. The model is used in studying how the differentiation in bandwidth allocation between flows can be achieved with the AF PHB mechanism. The numerical results show that with AF PHB mechanism differentiation can be achieved. The bandwidth allocation ratio is not fixed, but depends on the network load. The results also show that by marking the TCP and UDP flows into separate AF classes, congestion sensitive TCP flows can be protected from bandwidth exhaustion of the UDP flows.