Methods and apparatus for quality of service control for TCP aggregates at a bottleneck link in the internet

Abstract

A network device that is inserted in the path of traffic in a packet network, and the associated procedures and controller algorithms for monitoring the performance of aggregates of short lived Transmission Control Protocol (TCP) Connections flowing over a bottleneck link and dynamically managing their performance. TCP operates by allowing a certain window of data to be outstanding between the source and the receiver of each transfer and if many transfers attempt to share the network, congestion occurs, thus reducing the transmission rate of ongoing transfers. The method and apparatus aim at the performance of an aggregate of short-lived connections and hence measure only the RTT (Round Trip Time) for the aggregate and determine a window for the aggregate. By setting a target performance for the entire aggregate a measurement is made over the aggregate to determine the current performance level for each value of control eg. A RD (Random Drop) probability, or a value of MWA (Modified window Advertisement). If MWA is used and the target is RTT then the algorithm update level and a running measurement of the minimum RTT, is maintained, which is taken to be RTPD (Round Trip Propagation Delay) hence giving the algorithm that computes minimum RTT a long but finite memory. This is achieved by carrying out the following set-ups at each instant update— (a) Measuring the average RTT over the previous measurement interval and subtracting from this the RTPD estimate to obtain queuing delay. (b) Adjusting MWA (Wk) in the just elapsed measurement interval as follows—Wk+1=Wk−9k−1x (measured delay-target queuing delay). (c) Applying the MWA Wk+1 over the next measurement.

Dependencies are inferred from the claim text.