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The Good, the Bad and the WiFi: Modern AQMs in a residential setting
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science. (DISCO)ORCID iD: 0000-0001-5241-6815
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science. (DISCO)ORCID iD: 0000-0002-8731-2482
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science. (DISCO)ORCID iD: 0000-0001-7311-9334
2015 (English)In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 89, p. 90-106Article in journal (Refereed) Published
Abstract [en]

Several new active queue management (AQM) and hybrid AQM/fairness queueing algorithms have been proposed recently. They seek to ensure low queueing delay and high network goodput without requiring parameter tuning of the algorithms themselves. However, extensive experimental evaluations of these algorithms are still lacking. This paper evaluates a selection of bottleneck queue management schemes in a test-bed representative of residential Internet connections of both symmetrical and asymmetrical bandwidths as well as WiFi. Latency under load and the performance of VoIP and web traffic patterns are evaluated under steady state conditions. Furthermore, the impact of the algorithms on fairness between TCP flows with different RTTs, and also the transient behaviour of the algorithms at flow startup is examined. The results show that while the AQM algorithms can significantly improve steady state performance, they exacerbate TCP flow unfairness. In addition, the evaluated AQMs severely struggle to quickly control queueing latency at flow startup, which can lead to large latency spikes that hurt the perceived performance. The fairness queueing algorithms almost completely alleviate the algorithm performance problems, providing the best balance of low latency and high throughput in the tested scenarios. However, on WiFi the performance of all the tested algorithms is hampered by large amounts of queueing in lower layers of the network stack inducing significant latency outside of the algorithms’ control.

Place, publisher, year, edition, pages
Elsevier, 2015. Vol. 89, p. 90-106
Keywords [en]
Active queue management, Fairness queueing, Bufferbloat, Latency, Performance measurement, Wireless networks
National Category
Communication Systems
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-37954DOI: 10.1016/j.comnet.2015.07.014ISI: 000361403600007OAI: oai:DiVA.org:kau-37954DiVA, id: diva2:854117
Available from: 2015-09-16 Created: 2015-09-16 Last updated: 2019-07-12Bibliographically approved
In thesis
1. On the Bleeding Edge: Debloating Internet Access Networks
Open this publication in new window or tab >>On the Bleeding Edge: Debloating Internet Access Networks
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

As ever more devices are connected to the internet, and applications turn ever more interactive, it becomes more important that the network can be counted on to respond reliably and without unnecessary delay. However, this is far from always the case today, as there can be many potential sources of unnecessary delay. In this thesis we focus on one of them: Excess queueing delay in network routers along the path, also known as bufferbloat.

We focus on the home network, and treat the issue in three stages. We examine latency variation and queueing delay on the public internet and show that significant excess delay is often present. Then, we evaluate several modern AQM algorithms and packet schedulers in a residential setting, and show that modern AQMs can almost entirely eliminate bufferbloat and extra queueing latency for wired connections, but that they are not as effective for WiFi links. Finally, we go on to design and implement a solution for bufferbloat at the WiFi link, and also design a workable scheduler-based solution for realising airtime fairness in WiFi.

Also included in this thesis is a description of Flent, a measurement tool used to perform most of the experiments in the other papers, and also used widely in the bufferbloat community.

Place, publisher, year, edition, pages
Karlstad: Karlstad University Press, 2016. p. 20
Series
Karlstad University Studies, ISSN 1403-8099 ; 2016:49
Keywords
Bufferbloat, WiFi, AQM, queueing, network measurement, performance evaluation, fairness
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-47001 (URN)978-91-7063-732-2 (ISBN)
Presentation
2016-12-06, 1B309 (Sjöströmsalen), Karlstads Universitet, Universitetsgatan 2, Karlstad, 13:15 (English)
Opponent
Supervisors
Available from: 2016-11-16 Created: 2016-11-01 Last updated: 2019-07-12Bibliographically approved
2. 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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Publisher's full texthttp://dx.doi.org/10.1016/j.comnet.2015.07.014

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