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Improving Performance in Heterogeneous Networks: A Transport Layer Centered Approach
Karlstad University, Faculty of Economic Sciences, Communication and IT.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The evolution of computer communications and the Internet has led to the emergence of a large number of communication technologies with widely different capabilities and characteristics. While this multitude of technologies provides a wide array of possibilities it also creates a complex and heterogeneous environment for higher-layer communication protocols. Specific link technologies, as well as overall network heterogeneity, can hamper user-perceived performance or impede end-to-end throughput.

In this thesis we examine two transport layer centered approaches to improve performance.

The first approach addresses the decrease in user satisfaction that occurs when web waiting times become too long. Increased transport layer flexibility with regards to reliability, together with error-resilient image coding, is used to enable a new trade-off. The user is given the possibility to reduce waiting times, at the expense of image fidelity.

An experimental examination of this new functionality is provided, with a focus on image-coding aspects. The results show that reduced waiting times can be achieved, and user studies indicate the usefulness of this new trade-off.

The second approach concerns the throughput degradations that can occur as a consequence of link and transport layer interactions. An experimental evaluation of the GSM environment shows that when negative interactions do occur, they are coupled to large variability in link layer round-trip times rather than simply to poor radio conditions. Another type of interaction can occur for link layers which expose higher layers to residual bit errors.

Residual bit errors create an ambiguity problem for congestion controlled transport layer protocols which cannot correctly determine the cause for a loss. This ambiguity leads to an unnecessary throughput degradation. To mitigate this degradation, loss differentiation and notification mechanisms are proposed and experimentally evaluated from both performance and fairness perspectives. The results show that considerable performance improvements can be realized. However, there are also fairness implications that need to be taken into account since the same mechanisms that improve performance may also lead to unfairness towards flows that do not employ loss differentiation.

Place, publisher, year, edition, pages
2005.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2005:27
Keywords [en]
transport protocols, partial reliability, image transfer, transcoding, loss differentiation, fairness, wireless networks, network emulation
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-2364ISBN: 91-85335-68-1 (print)OAI: oai:DiVA.org:kau-2364DiVA, id: diva2:24712
Public defence
2005-06-17, Agardh-salen, 11D 257, Karlstads universitetKarlstad, 13:15 (English)
Opponent
Supervisors
Available from: 2009-06-09 Created: 2009-06-09 Last updated: 2018-01-13Bibliographically approved
List of papers
1. Application and Transport Layer Flexibility - A User-influenced Web Browsing System
Open this publication in new window or tab >>Application and Transport Layer Flexibility - A User-influenced Web Browsing System
(English)Manuscript (preprint) (Other academic)
National Category
Computer Systems
Identifiers
urn:nbn:se:kau:diva-2365 (URN)
Available from: 2009-06-18 Created: 2009-06-18 Last updated: 2018-08-14Bibliographically approved
2. Impact of Partial Reliability on Web Image Transport Performance
Open this publication in new window or tab >>Impact of Partial Reliability on Web Image Transport Performance
2002 (English)In: Proceedings PromoteIT 2002, 2002Chapter in book (Other academic)
National Category
Computer Systems
Identifiers
urn:nbn:se:kau:diva-2366 (URN)
Available from: 2009-06-18 Created: 2009-06-18 Last updated: 2018-08-14Bibliographically approved
3. JPEG Transcoding - Efficiency and Robustness Aspects
Open this publication in new window or tab >>JPEG Transcoding - Efficiency and Robustness Aspects
2002 (English)In: JPEG transcoding : efficiency and robustness aspects, 2002Chapter in book (Other academic)
Identifiers
urn:nbn:se:kau:diva-2367 (URN)
Available from: 2009-06-18 Created: 2009-06-18Bibliographically approved
4. A GSM/GPRS Testbed for TCP Performance Evaluation
Open this publication in new window or tab >>A GSM/GPRS Testbed for TCP Performance Evaluation
2002 (English)In: Proceedings of International Workshop on Wired/Wireless Internet Communications / [ed] Hamid R. Arabnia, Youngsong Mun, CSREA Press, 2002, p. 19-26Conference paper, Published paper (Other academic)
Abstract [en]

Investigating the wireless Internet is a nontrivial task dueto the complexity of wireless systems and the many protocolinteractions that appear. In this paper we present a measurementtestbed that allows us to investigate the performanceof Internet traffic over a real GSM network but witha controlled radio environment and traffic load. A detailedperformance evaluation of TCP over GSM is presented. Arange of radio conditions are considered with a focus on theinteraction between TCP and the GSM link layer. With respectto efficient protocol layer interaction, the results showthat high variability in round trip times is more problematicthan poor radio conditions. How the testbed has been extendedfor GPRS and planned measurements for this systemare also discussed.

Place, publisher, year, edition, pages
CSREA Press, 2002
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-2368 (URN)1-892512-38-6 (ISBN)
Conference
International Conference on Internet Computing, Las Vegas, Nevada, USA
Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2018-08-14Bibliographically approved
5. Checksum-based Loss Differentiation
Open this publication in new window or tab >>Checksum-based Loss Differentiation
2002 (English)In: Proceedings 4th IEEE Conference on Mobile and Wireless Communications Networks, 2002Chapter in book (Other academic)
National Category
Computer Systems
Identifiers
urn:nbn:se:kau:diva-2369 (URN)
Available from: 2009-06-18 Created: 2009-06-18 Last updated: 2018-08-14Bibliographically approved
6. Evaluation of Transport Layer Loss Notification in Wireless Environments
Open this publication in new window or tab >>Evaluation of Transport Layer Loss Notification in Wireless Environments
2005 (English)In: Networking - ICN 2005: 4th International Conference on Networking, Reunion Island, France, April 17-21, 2005, Proceedings, Part I / [ed] Pascal Lorenz & Petre Dini, Springer Berlin/Heidelberg, 2005, p. 247-257Conference paper, Published paper (Other academic)
Abstract [en]

Residual bit-errors in wireless environments are well known to cause difficulties for congestion controlled protocols like TCP. In this study we focus on a receiver-based loss differentiation approach to mitigating the problems, and more specifically on two different loss notification schemes. The fully receiver-based 3-dupack scheme uses additional dupacks to implicitly influence the retransmission behavior of the sender. The second TCP option scheme uses a TCP option to explicitly convey a corruption notification. Although these schemes look relatively simple at first glance, when examining the details several issues exist which are highlighted and discussed. A performance evaluation based on a FreeBSD kernel implementation show that the TCP option scheme works well in all tested cases and provides a considerable throughput improvement. The 3-dupack scheme also provide performance gains in most cases, but the improvements varies more between different test cases, with some cases showing no improvement over regular TCP.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2005
Series
Lecture Notes in Computer Science, ISSN 0302-9743 ; 3420
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-2370 (URN)10.1007/978-3-540-31956-6_30 (DOI)978-3-540-25339-6 (ISBN)978-3-540-31956-6 (ISBN)
Conference
4th International Conference on Networking, Reunion Island, France, April 17-21, 2005
Available from: 2009-06-18 Created: 2009-06-18 Last updated: 2018-08-14Bibliographically approved
7. An Experimental Study on the Performance and Fairness of Loss Differentiation for TCP
Open this publication in new window or tab >>An Experimental Study on the Performance and Fairness of Loss Differentiation for TCP
2004 (English)In: ICETE (3), 2004Chapter in book (Other academic)
National Category
Computer Systems
Identifiers
urn:nbn:se:kau:diva-2371 (URN)
Available from: 2009-06-18 Created: 2009-06-18 Last updated: 2018-08-14Bibliographically approved
8. The Impact of Loss Generation on Emulation-Based Protocol Evaluation
Open this publication in new window or tab >>The Impact of Loss Generation on Emulation-Based Protocol Evaluation
2006 (English)In: PDCN'06 Proceedings of the 24th IASTED international conference on Parallel and distributed computing and networks / [ed] Fahringer, T., Anaheim, USA: ACTA Press, 2006, 1, p. 231-237Conference paper, Published paper (Refereed)
Abstract [en]

Network emulation has for a long time been an important tool for evaluating the performance of communication protocols. By emulating network characteristics, such as restricted bandwidth, delay and losses, knowledge about the behavior and performance of actual protocol implementations can be obtained. This paper focuses on the generation of losses in network emulators and shows the beneficial effects of being able to control the generation of losses in a precise way. Both the possibility to get additional knowledge about a protocol implementations behavior, as well as statistical benefits such as paired experiments are discussed. By extending the loss generation to also include bit-error generation, in addition to packet losses, a finer level of abstraction is provided. Deterministic bit-error generation allows detailed and repeatable studies of bit-error sensitive protocol behavior. TCP and a loss differentiating variant of TCP is used to illustrate the utility of improved loss generation.

Place, publisher, year, edition, pages
Anaheim, USA: ACTA Press, 2006 Edition: 1
Keywords
Networks, Network protocols, Protocol correctness
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-2340 (URN)0-88986-568-X (ISBN)
Conference
Parallel and Distributed Computing and Networks(PDCN 2006), February 14 – 16, 2006, Innsbruck, Austria
Available from: 2009-06-05 Created: 2009-06-05 Last updated: 2018-08-14Bibliographically approved

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