On rate limitation mechanisms for TCP throughput: a longitudinal analysis

Paper type: 
Journal Paper
João Taveira Araújo, Raul Landa, Richard Clegg, George Pavlou, Kensuke Fukuda
Computer Networks, 2017
TCP remains the dominant transport protocol for Internet traffic. It is usually considered to have its sending rate covered by a sliding window congestion control mechanism. However, in addition to this normal congestion control, a number of other mechanisms limit TCP throughput. This paper analyzes the extent to which network, host and application settings define flow throughput over time and across autonomous systems. Our study draws on data from a longitudinal study spanning five years of passive traces collected from a single transit link. Mechanisms for this include limiting by application, interference with the TCP window control mechanism and artificial limitations on maximum window sizes by the operating system. This paper uses a large data set to assess the impact of each mechanism. We conclude that more than half of all heavy-hitter inbound traffic remains throttled by constraints beyond network capacity. For this data set, TCP congestion control is no longer the dominant mechanism that moderates throughput.
This paper is a considerably expanded version of the INFOCOM paper. Again it argues that TCP is no longer mainly controlled by loss and congestion but instead by algorithms and settings under the control of the sender or receiver deliberately or accidentally designed to restrict throughput for a variety of reasons (for example limiting video sending to the rate at which the viewer is watching). It contains extended discussion of the methodology and in particular how flight and RTT data was extracted from passive traces.
author={Araujo, J.T. and Landa, R. and Clegg, R.G. and Pavlou, G. and Fukuda, K.}, 
booktitle={Computer Networks -- to appear},
title={A longitudinal analysis of Internet rate limitations},