n a multiple traffic class system, where there are different classes of services with various traffic and QoS demands into the network and each traffic class corresponds to a traffic stream, then the multi-dimensional Erlang-B formula can be applied for the dimensioning in this case. 6.2.6 Summary In section 6.2, dimensioning methodology for circuit-switched traffic was presented. In this thesis, the circuit-switched type of traffic with strict QoS requirements is subject to admission control. In order to guarantee its blocking probability, i.e. connection reject ratio, the Erlang-B model (for single traffic stream) and Multi-dimensional Erlang-B model (for multiple traffic streams) are suggested for dimensioning the lub link for the circuit-switched traffic. Dimensioning procedure is presented and the characteristics of the Erlang models are demonstrated. The presented results demonstrate the high accuracy of applying Erlang models for the dimensioning of the lub link for the circuit-switched traffic. 6.3 Dimensioning for Elastic Traffic This section presents analytical models, which allows the dimensioning of the single lub link for elastic traffic. As introduced in chapter 1.4, this type of traffic is generated by applications with non real time characteristics and is typically carried by TCP. The relevant QoS requirement for elastic traffic flows is application throughput (see section 4.1.2.1). Specifically, for a specific object size Xt the overall average transaction time should not go above a certain time threshold Tt. The respective throughput is calculated as X1 / Tt. Time T reflects a typical customer's waiting-time tolerance level, which certainly depends on its given maximum data rate and the type of applications. In this thesis, for meeting this QoS target of the elastic traffic, the proposed analytical dimensioning model is based on the processor sharing model, which considers the rate-sharing property of TCP. To apply the processor sharing model for dimensioning the lub link, several assumptions ar