A queue management algorithm for intra-flow service differentiation in the “best effort” Internet

End-to-end QoS can be improved by exploiting knowledge about the flow structure to influence the flow within the network. This leads to a graceful degradation under congestion (“intra-flow” QoS). Typically this is accomplished by filtering higher-layer information within the network, which is both expensive in terms of resources, as well as undesirable with regard to network security. In this paper, we present a queue management algorithm called DiffRED (differential random early detection) that allows us to enhance intra-flow QoS without higher-layer filtering. The algorithm differentiates between packets marked by the sender as either more or less eligible to be dropped in comparison to unmarked packets. This gives the application some control over the packet loss process and thus enhances the performance of available end-to-end loss recovery mechanisms, end-to-end fairness and finally the perceived quality. The algorithm helps to bridge the huge gap between the current “best-effort” Internet and full deployment of inter-flow service differentiation. We introduce simple metrics to describe the loss process of individual flows and present simulation results for a voice service using the proposed scheme. We demonstrate how the algorithm provides a significant intra-flow QoS enhancement and evaluate the impact on conventional traffic