Bandwidth Sharing and Admission Control for Elastic Traac

We consider the performance of a network like the In-ternet handling so-called elastic traac where the rate of ows adjusts to ll available bandwidth. Realized throughput depends both on the way bandwidth is shared and on the random nature of traac. We assume traac consists of point to point transfers of individual documents of nite size arriving according to a Poisson process. Notable results are that weighted sharing has limited impact on perceived quality of service and that discrimination in favour of short documents leads to considerably better performance than fair sharing. In a linear network, max-min fairness is preferable to proportional fairness under random traf-c while the converse is true under the assumption of a static connguration of persistent ows. Admission control is advocated as a necessary means to maintain goodput in case of traac overload.