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Flent: The FLExible Network Tester
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). (DISCO)ORCID iD: 0000-0001-5241-6815
University of Modena and Reggio Emilia.
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). (DISCO)ORCID iD: 0000-0002-8731-2482
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). (DISCO)ORCID iD: 0000-0001-7311-9334
2017 (English)In: VALUETOOLS 2017: Proceedings of 11th EAI International Conference on Performance Evaluation Methodologies and Tools, New York, NY: ACM Digital Library, 2017, p. 1-6, article id 271973Conference paper, Published paper (Refereed)
Abstract [en]

Running network performance experiments on real systems is essential for a complete understanding of protocols and systems connected to the internet. However, the process of running experiments can be tedious and error-prone. In particular, ensuring reproducibility across different systems is difficult, and comparing different test runs from an experiment can be non-trivial.In this paper, we present a tool, called Flent, designed to make experimental evaluations of networks more reliable and easier to perform. Flent works by composing well-known benchmarking tools to, e.g., run tests consisting of several bulk data flows combined with simultaneous latency measurements. Tests are specified in source code, and several common tests are included with the tool. In addition, Flent contains features to automate test runs, collect relevant metadata and interactively plot and explore datasets.We showcase Flent's capabilities by performing a set of experiments evaluating the new BBR congestion control algorithm, using Flent's capabilities to reproduce experiments both in a controlled testbed and across the public internet. Our evaluation reveals several interesting features of BBR's performance.

Place, publisher, year, edition, pages
New York, NY: ACM Digital Library, 2017. p. 1-6, article id 271973
Keywords [en]
Network experimentation, Network performance analysis, Network measurement, Measurement tools
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-64766DOI: 10.1145/3150928.3150957ISBN: 978-1-4503-6346-4 (electronic)OAI: oai:DiVA.org:kau-64766DiVA, id: diva2:1151589
Conference
VALUETOOLS 2017, December 5–7, 2017, Venice, Italy
Available from: 2017-10-23 Created: 2017-10-23 Last updated: 2018-09-27Bibliographically approved
In thesis
1. Bufferbloat and Beyond: Removing Performance Barriers in Real-World Networks
Open this publication in new window or tab >>Bufferbloat and Beyond: Removing Performance Barriers in Real-World Networks
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The topic of this thesis is the performance of computer networks. While network performance has generally improved with time, over the last several years we have seen examples of performance barriers limiting network performance. In this work we explore such performance barriers and look for solutions.

The problem of excess persistent queueing latency, known as bufferbloat, serves as our starting point; we examine its prevalence in the public internet, and evaluate solutions for better queue management, and explore how to improve on existing solutions to make them easier to deploy.

Since an increasing number of clients access the internet through WiFi networks, examining WiFi performance is a natural next step. Here we also look at bufferbloat, as well as the so-called performance anomaly, where stations with poor signal strengths can severely impact the performance of the whole network. We present solutions for both of these issues, and additionally design a mechanism for assigning policies for distributing airtime between devices on a WiFi network. We also analyse the “TCP Small Queues” latency minimisation technique implemented in the Linux TCP stack and optimise its performance over WiFi networks.

Finally, we explore how high-speed network processing can be enabled in software, by looking at the eXpress Data Path framework that has been gradually implemented in the Linux kernel as a way to enable high-performance programmable packet processing directly in the operating system’s networking stack.

A special focus of this work has been to ensure that the results are carried forward to the implementation stage, which is achieved by releasing implementations as open source software. This includes parts that have been accepted into the Linux kernel, as well as a separate open source measurement tool, called Flent, which is used to perform most of the experiments presented in this thesis, and also used widely in the bufferbloat community.

Abstract [en]

The topic of this thesis is the performance of computer networks in general, and the internet in particular. While network performance has generally improved with time, over the last several years we have seen examples of performance barriers limiting network performance. In this work we explore such performance barriers and look for solutions.

Our exploration takes us through three areas where performance barriers are found: The bufferbloat phenomenon of excessive queueing latency, the performance anomaly in WiFi networks and related airtime resource sharing problems, and the problem of implementing high-speed programmable packet processing in an operating system. In each of these areas we present solutions that significantly advance the state of the art.

The work in this thesis spans all three aspects of the field of computing, namely mathematics, engineering and science. We perform mathematical analysis of algorithms, engineer solutions to the problems we explore, and perform scientific studies of the network itself. All our solutions are implemented as open source software, including both contributions to the upstream Linux kernel, as well as the Flent test tool, developed to support the measurements performed in the rest of the thesis.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2018
Series
Karlstad University Studies, ISSN 1403-8099 ; 2018:42
Keywords
Bufferbloat, AQM, WiFi, XDP, TSQ, Flent, network measurement, performance evaluation, fairness, queueing, programmable packet processing
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-69416 (URN)978-91-7063-878-7 (ISBN)978-91-7063-973-9 (ISBN)
Public defence
2018-11-23, 21A342, Eva Erikssonsalen, Karlstad, 09:15 (English)
Opponent
Supervisors
Available from: 2018-10-26 Created: 2018-09-27 Last updated: 2019-03-13Bibliographically approved

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Høiland-Jørgensen, TokeHurtig, PerBrunström, Anna

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