stems (see [Coh79, Ott84, BBJ99]). One performance measure, which is often considered in the context of processor sharing and which is specifically interesting for link dimensioning, is the sojourn time. It denotes the expected time, which a job spends in the system until it is fully served. It is apparent that this time depends on the number of other jobs, which are served during the same time period. Each new job that enters the system reduces the available rate for the existing jobs. A finished job, on the other side, increases it again for the remaining ones. For the objective of link dimensioning, the processor sharing model is interpreted differently. Here it means that, the bandwidth of a link is shared by a number of elastic flows. What was referred to as a job in the original sense, denotes a single transaction process, i.e. the transmission of an individual file by one TCP connection. Due to the TCP flow control mechanisms as explained in the section 6.3.1, the transmission rate of a file transaction is controlled by TCP to adapt it to the available bandwidth provided by the networks. This dynamic behavior of TCP leads to the 'elastic' property of the traffic flow. If TCP works ideally, i.e. assuming that TCP's feedback and control mechanism is perfect and absolutely fair, the bandwidth of a common bottleneck link would be shared equally among all active TCP flows (connections) traversing that link ([Fan02, RBPP00]). Whenever a new TCP flow starts sending data, all TCP connections, which are already in progress, instantaneously reduce their rate in order to provide a fair share for the new one. When a TCP connection finishes its file transmission, the remaining ones increase their rates to fully utilize the available bandwidth. Therefore, a common link, which is traversed by multiple elastic TCP flows, can be modeled as a processor sharing system [Rie04]. It shall be noticed that processor sharing in this context refers to the flow or connection level. There is no processor sharing at packet level. The 