. above certain utilization), processor sharing comes into play and thus degrades the overall flow performance. Therefore the individual flow performance is also a function of total link utilization, which is a result of the total traffic from all traffic classes. However, the impact of the link utilization on the application performance of individual traffic class still depends on the bearer type, i.e. delay factor is bearer specific. Nevertheless, in the highly congested states the experienced flow performance of various traffic classes converge since none of them can utilize its peak rate and a real fair sharing is available for each of them. Based on the above idea, for each traffic class an individual M/G/R-PS model is established with its own R. The individual M/G/R-PS model is then used to calculate the mean transfer delay or mean throughput of elastic traffic flows of individual traffic classes. The following variables are defined in Table 6.4. Variable Definitions index of a traffic class peak data rate for traffic class i Round Trip Time for traffic class i flow arrival rate of traffic class i delay factor (QoS target) of traffic class i E{xi} average file size of traffic class i offered traffic load for traffic class = calculated R in M/G/R-PS model for traffic class i TCP Maximum segment size link capacity Table 6.4: Defined variables for general M/G/R-PS Model For traffic class i, the corresponding M/G/R-PS model is based on R given by equation (6.30). It is a function of link capacity C and peak rate ri of this traffic class. (6.30) 6 Dimensioning for Single ATM-Based lub The total mean traffic load (from all traffic classes) p is calculated by equation (6.31). (6.31) bearers With the above Ri and total offered load p, the expected sojourn time (or mean transfer delay) E{T(xi)} for traffic class i to transfer an object of size Xi is calculated by generalizing the sojourn delay formula of the basic M/G/R-PS model: (6.32) Here delay factor fRi represents the increase of the average transfer time (or d