Congestion at flow level and the impact of user behaviour

So-called elastic flows, corresponding to document transfers of various types, constitute the bulk of Internet traffic. This paper presents models of a single bottleneck link handling elastic traffic, accounting for random flow arrivals. The transport protocol and packet scheduling are taken into account approximately by assuming perfectly realized bandwidth sharing objectives. We refer to the demand as the product of the flow arrival rate and the average flow size. It is shown that per-flow throughput performance is generally satisfactory as long as demand is only slightly less than capacity. In overload, on the other hand, some flows must be abandoned. A fraction of link bandwidth is then wasted and performance critically depends on user behaviour. The models are useful in appraising the effectiveness of proposed schemes for Internet service differentiation.