time voice traffic. And the discarded packets of elastic traffic will trigger TCP retransmissions, which leads to degradation of the throughput of elastic traffic flows. However, the PS model does not consider packet losses and resultant retransmissions. Thus, the calculated results do not include this degradation on the transfer delays. But, the relative error of the theoretical estimations shown in the right diagram is below 10%, which is acceptable for dimensioning purpose, when the link utilization is within 80%. 6.3.9 Dimensioning Procedures This section describes in detail the dimensioning procedures, i.e. how to utilize the presented processor sharing models for the purposes of lub dimensioning. In this chapter, the dimensioning process only considers a single lub link as illustrated in Figure 6.35(a). The objective of dimensioning is to determine necessary lub link bandwidth for guaranteeing a desired QoS target with the highest cost-efficiency (i.e. maximum utilization). Figure 6.35(b) shows the input and output parameters of the process sharing models. r peak RTT lub link C PS Model Node B (x, ,T,), D1 , f (a) Network Scenario (b) Analytical Approach Figure 6.35. lub link dimensioning with processor sharing (PS) models 6.3 Dimensioning for Elastic Traffic At first, the amount of elastic traffic p, which traverses the lub link, has to be given. It can be derived from the mean flow arrival rate and mean object size, including the overheads from applications, TCP/IP protocols, as well as from UMTS networks. Furthermore, possible rate limitations confining individual flows (i.e. peak rate of the used RAB type) have to be identified. And in addition, the round trip times experienced under a low lub link utilization needs to be estimated. At last, an appropriate QoS target much be specified. This can either be a desired average transfer time Tt for an amount of data of size Xt (including all related overheads), or a desired average application throughput D which is equal to Xt IT1, or simply a value for the d