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Ending the Anomaly: Achieving Low Latency and Airtime Fairness in WiFi
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.
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2017 (English)Conference paper, (Refereed)
Abstract [en]

With more devices connected, delays and jitter at the WiFi hop become more prevalent, and correct functioning during network congestion becomes more important. However, two important performance issues prevent modern WiFi from reaching its potential: increased latency under load caused by excessive queueing (i.e. bufferbloat) and the 802.11 performance anomaly.

To remedy these issues, we present a novel two-part solution. We design a new queueing scheme that eliminates bufferbloat in the wireless setting. Leveraging this queueing scheme, we then design an airtime fairness scheduler that operates at the access point and doesn't require any changes to clients.

We evaluate our solution using both a theoretical model and experiments in a testbed environment, formulating a suitable analytical model in the process. We show that our solution achieves an order of magnitude reduction in latency under load, large improvements in multi-station throughput, and nearly perfect airtime fairness for both TCP and downstream UDP traffic. Further experiments with application traffic confirm that the solution provides significant performance gains for real-world traffic.We develop a production quality implementation of our solution in the Linux kernel, the platform powering most access points outside of the managed enterprise setting. The implementation has been accepted into the mainline kernel distribution, making it available for deployment on billions of devices running Linux today.

Place, publisher, year, edition, pages
USENIX - The Advanced Computing Systems Association, 2017.
National Category
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-47000OAI: oai:DiVA.org:kau-47000DiVA: diva2:1043930
Conference
2017 USENIX Annual Technical Conference (USENIX ATC 17)
Available from: 2016-11-01 Created: 2016-11-01 Last updated: 2017-05-31
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. 20 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2016:49
Keyword
Bufferbloat, WiFi, AQM, queueing, network measurement, performance evaluation, fairness
National Category
Computer Science
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: 2016-11-16Bibliographically approved

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