RED+ Gateways for Identification and Discrimination of Unfriendly Best-Effort Flows in the Internet

This paper proposes an add-on to the well known RED (Random Early Detection) algorithm called RED+. RED+ adds the functionality of identifying and discriminating high-bandwidth, unfriendly best-effort flows to RED gateways. It is based on the observation that unfriendly flows have higher arrival rates in times of congestion than friendly flows. Hence unfriendly flows can be discriminated if packets arriving at a router output-port are dropped as a function of RED’s average queue size and the arrival-rate of the packet’s flow. RED+ is scalable regarding the amount per flow information stored in routers as it only allocates per-flow state for the n highest bandwidth flows, where n is a configurable parameter. As shown by simulation, RED+ is able to identify and discriminate unresponsive flows avoiding problems of unfairness and congestion collapse.