Active delay control for TCP

Active delay control is a novel extension for TCP, where TCP endpoints impose delays on the transmission of packets to improve performance. The amount of delay can be calculated by routers from the level of congestion, or by endpoints from the received congestion signals. In particular, when there are many TCP flows competing for the bandwidth of a link, they can reduce their transmission rates to arbitrary degrees by increasing delays, without experiencing TCP time-outs. Active delay control is therefore useful for those long-lived TCP-based applications that cannot tolerate time-outs. Examples of such applications are video streaming and storage networks. It is also useful for short-lived flows that require short transfer time. Examples of such applications are HTTP transactions. We present the concept and motivation behind active delay control, and evaluate them by simulation.