andwidth reservation on the IP-based lub link. As the concept of the CAC function is not changed, the derivation of the call blocking probability (i.e. CAC reject ratio) is still based on the Erlang-B formula (for single traffic stream) and multi-dimensional Erlang-B formula (for multiple traffic streams). The detailed calculation and application of the Erlang models for dimensioning can be referred to Chapter 6.2. 7.3 Dimensioning for Elastic Traffic This section presents analytical models for dimensioning the transport bandwidth on the single IP-based lub link transmitting elastic traffic that are carried by the TCP/IP. As introduced in section 3.4.2, the IP-based UTRAN network deploys an IP DiffServ-based QoS structure for performing QoS support and management. This QoS structure is based on DiffServ QoS scheme with an integrated Weighted Fair Queue (WFQ) and Strict Priority (SP) scheduling. For this IP QoS architecture, an analytical approach is proposed in this section for dimensioning the IP-based lub link for supporting a wide range of elastic service class each with different QoS requirements. For the elastic traffic, the relevant QoS for dimensioning is the end user application performance with respect to the average per user throughput or the mean delay for transferring a certain amount of data (see section 4.1.2.1). 7.3 Dimensioning for Elastic Traffic The objective of bandwidth dimensioning is to guarantee the desired QoS requirements of various services in a cost efficient way in terms of achieving a high transmission efficiency and maximal utilization of the IP transport bandwidth. 7.3.1 Analytical Models for the IP-Based Iub Dimensioning In the ATM-based lub, as presented in section 6.3, for the elastic traffic the proposed analytical dimensioning models to achieve the end user application performance are based on the M/G/R-PS model, which models the lub link traversed by a number of elastic TCP flows as a Process Sharing queuing system on the flow level. In the IP-based lub network, though the und