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Analyzing the Latency of Sparse Flows in the FQ-CoDel Queue Management Algorithm
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
2018 (English)In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, no 11, p. 2266-2269Article in journal (Refereed) Published
Abstract [en]

The FQ-CoDel queue management algorithm was recently published as an IETF RFC.It achieves low latency especially for low-volume (or sparse) traffic flowscompeting with bulk flows. However, the exact conditions for when a particularflow is considered to be sparse has not been well-explored.

In this work, we analyse the performance characteristics of the sparse flowoptimisation of FQ-CoDel, formulating the constraints that flows must satisfy tobe considered sparse in a given scenario. We also formulate expressions for theexpected queueing latency for sparse flows.

Then, using a numerical example, we show that for a given link and a given typeof sparse flows (VoIP traffic), the number of sparse flows that a givenbottleneck can service with low sparse flow latency is only dependent on thenumber of backlogged bulk flows at the bottleneck. Furthermore, as long as themaximum number of sparse flows is not exceeded, all sparse flows can expect avery low queueing latency through the bottleneck.

Place, publisher, year, edition, pages
IEEE, 2018. Vol. 22, no 11, p. 2266-2269
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-69414DOI: 10.1109/LCOMM.2018.2871457ISI: 000449977700022OAI: oai:DiVA.org:kau-69414DiVA, id: diva2:1251687
Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2018-11-29Bibliographically 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
Projects
HITS, 4707
Funder
Knowledge Foundation
Note

Paper 6 was published as manuscript in the thesis.

The revised fulltext is identical to the original version with the exception that printing errors have been removed.

Available from: 2018-10-26 Created: 2018-09-27 Last updated: 2020-06-09Bibliographically approved

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Høiland-Jørgensen, Toke

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