e of a TCP source's transmission rate. Whenever TCP traffic traverses a bottleneck, where congestion occurs, the sources start regulating their transmission rates by adjusting the window size. As a consequence, TCP senders do not transmit data with a constant data rate. It varies in order to gain a certain share of the bottleneck capacity. The congestion avoidance mechanism is one of the fundamental causes of traffic "elasticity" as it 6 Dimensioning for Single ATM-Based lub forces TCP to adapt its transmission rate to the available bandwidth. The congestion avoidance algorithm together with the slow start mechanism provides the basis for the proposed processor sharing dimensioning model. 6.3.2 Related Work This section gives an overview of dimensioning methods for elastic traffic. Over the past years, there have been extensive researches on promoting processor sharing model for link dimensioning in IP networks, based on the fundamental behavior of bandwidth sharing property of TCP. Roberts proposes the use of processor sharing for network dimensioning in [Rob97]. In [RM98] Massoulié and Roberts suggest applying call admission control for elastic traffic in order to guarantee a minimum achievable throughput for all accepted flows. Lindberger again proves the processor sharing model as an appropriate means of network dimensioning in [Lin99]. He derives the formula to calculate the mean sojourn time of the M/G/R PS model for cases without flow blocking and introduces the "delay factor" as a QoS measure for elastic traffic. In addition, he proposes dimensioning for the cases of combined stream and elastic traffic. On the dimensioning for the cases of service integration, Núñez Queija, van den Berg, and Mandjes did further studies in [Qvd*99a, Qvd*99b]. They derive blocking probabilities and mean transfer times for different link sharing strategies between stream and elastic traffic flows. The computations for elastic traffic are based on processor sharing, while for stream traffic a blocking model is used. However, 