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The Impact of Loss Generation on Emulation-Based Protocol Evaluation
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.ORCID iD: 0000-0003-3461-7079
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.ORCID iD: 0000-0003-0368-9221
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.ORCID iD: 0000-0001-7311-9334
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, 1. p. 231-237
Keywords [en]
Networks, Network protocols, Protocol correctness
National Category
Computer Systems
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-2340ISBN: 0-88986-568-X (print)OAI: oai:DiVA.org:kau-2340DiVA, id: diva2:24679
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
In thesis
1. Improving Performance in Heterogeneous Networks: A Transport Layer Centered Approach
Open this publication in new window or tab >>Improving Performance in Heterogeneous Networks: A Transport Layer Centered Approach
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.

Series
Karlstad University Studies, ISSN 1403-8099 ; 2005:27
Keywords
transport protocols, partial reliability, image transfer, transcoding, loss differentiation, fairness, wireless networks, network emulation
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-2364 (URN)91-85335-68-1 (ISBN)
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
2. TCP in Wireless Networks: Challenges, Optimizations and Evaluations
Open this publication in new window or tab >>TCP in Wireless Networks: Challenges, Optimizations and Evaluations
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents research on transport layer behavior in wireless networks. As the Internet is expanding its reach to include mobile devices, it has become apparent that some of the original design assumptions for the dominant transport protocol, TCP, are approaching their limits. A key feature of TCP is the congestion control algorithm, constructed with the assumption that packet loss is normally very low, and that packet loss therefore is a sign of network congestion. This holds true for wired networks, but for mobile wireless networks non-congestion related packet loss may appear. The varying signal power inherent with mobility and handover between base-stations are two example causes of such packet loss. This thesis provides an overview of the challenges for TCP in wireless networks together with a compilation of a number of suggested TCP optimizations for these environments. A TCP modification called TCP-L is proposed. It allows an application to increase its performance, in environments where residual bit errors normally give a degraded throughput, by making a reliability tradeoff. The performance of TCP-L is experimentally evaluated with an implementation in the Linux kernel. The transport layer performance in a 4G scenario is also experimentally investigated, focusing on the impact of the link layer design and its parameterization. Further, for emulation-based protocol evaluations, controlled packet loss and bit error generation is shown to be an important aspect.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2005
Series
Karlstad University Studies, ISSN 1403-8099 ; 2005:13
Keywords
Wireless networks, TCP/IP, TCP-L, Network emulation
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-2335 (URN)91-85335-53-3 (ISBN)
Presentation
2005-05-18, Agardsalen, 11D 257, Karlstads universitetKarlstad, 13:15 (English)
Opponent
Supervisors
Available from: 2009-06-05 Created: 2009-04-08 Last updated: 2016-10-25Bibliographically approved

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http://portal.acm.org/citation.cfm?id=1168956

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Garcia, JohanAlfredsson, StefanBrunstrom, Anna

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