TCP Performance Modeling

Allen B. Downey

This page describes two of my recent papers on TCP performance.

TCP Self-Clocking and Bandwidth Estimation

Abstract

We propose a simple queueing model for TCP transfers sharing a bottleneck link and examine its behavior when the buffer at the bottleneck is large compared to the bandwidth-delay product. This model explains some behaviors of TCP that have already been observed, and predicts other behaviors that are new. We present measurements that demonstrate the predicted behaviors in the current Internet.

Papers

This paper appeared in Computer Networks, Volume 51, Issue 13, 12 September 2007, Pages 3844-3863. Postscript, gzipped Postscript and PDF.

An earlier version of this paper, entitled "TCP Self-Clocking," is available as an Olin College Technical Report TR-2003-002, in Postscript, gzipped Postscript and PDF.

Slides

Here are the slides I used when I presented this work for the Boston University Network Research Group.

Software

Here is the simulator I used to generate some of the results in the paper. It provides a reference implementation of some of the algorithms described in the paper.

An empirical model of TCP performance

Abstract

We propose a model of TCP performance that captures the behavior of a set of network paths with diverse characteristics. The model uses more parameters than others, but we show that each feature of the model describes an effect that is important for at least some paths. We show that the model is sufficient to describe the datasets we collected with acceptable accuracy. Finally, we show that the model's parameters can be estimated using simple, application-level measurements.

Papers

This paper appeared in IEEE MASCOTS 2005. It is available here in Postscript, gzipped Postscript and PDF.

The slides I used when I presented this paper are here in Postscript, gzipped Postscript and PDF.

Here is the .bib file and the HTML version of the bibliography.

Slides

Here are the slides I used the last time I presented this work, available in Postscript, gzipped Postscript and PDF.

Datasets

The following directories contain figures from the paper and additional data:

Timing charts for a set of HTTP measurements.
Round trip time distributions.
Correlation of rtts.
Window sizes during slow start.
Predicted and actual transfer times, based on 100,000 bytes transfers.
Predicted and actual transfer times, based on 50,000 bytes transfers.

Explanations of these datasets are available in the paper itself.