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  • 51.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Effects of Loss Notification and Loss Differentiation on DCCP and TCP Performance2004Conference paper (Refereed)
    Abstract [en]

    This paper examines the effects of non-congestion related wireless link errors on transport protocol performance.

    Although link-level retransmissions to a large extent can alleviate this problem for TCP, delay-sensitive applications using DCCP may not be well served by link-level retransmissions. The loss differentiation and loss notification mechanisms in DCCP are discussed, and the TFRC congestion control is numerically evaluated for wireless loss sensitivity. The results show that the use of loss differentiation can be critical for high rate senders.

    The results, however, also show that the blind use of DCCP loss differentiation for low rate senders may be inefficient considering the communications and computational overheads involved. Further, a TCP implementation modified to provide loss differentiation and loss notification is experimentally examined. As expected there are considerable gains from using loss differentiation.

  • 52.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Efficient Image Transfer for Wireless Networks2000Conference paper (Refereed)
  • 53.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Impact of Partial Reliability on Web Image Transport Performance2002Conference paper (Refereed)
    Abstract [en]

    This paper reports on experiments with a web-browsing application using

    PRTP, a new TCP-based protocol. With PRTP it is possible for an application to

    specify, and receive, a more flexible transport service than with TCP or UDP. A web

    application using PRTP is presented, and experiments examining the performance implications

    of using PRTP instead of TCP are discussed. The experiments used actual

    implementations of TCP and PRTP to conduct web page transfers over a network capable

    of emulating different network characteristics. The JPEG part of the web pages

    were recoded using a robust JPEG coding and transmitted using the partially reliable

    transport service made possible by PRTP. A novelty in these experiments was that the

    packet loss could be controlled in detail, allowing specific packets in a stream to be lost as opposed to losing packets with a certain probability. The experiments were performed for five different network characteristics each at six different loss ratios using three different web pages. The results show that using a partially reliable transport service in conjunction with the presented application provides throughput gains in the

    majority of cases, at the expense of slightly degraded image quality. The gains relative to TCP are up to 41% with a mean of 7.2%.

  • 54.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Issues with TCP-friendly Rate Control in DCCP2004Conference paper (Refereed)
    Abstract [en]

    TCP-Friendly Rate Control (TFRC) is a congestion control mechanism that is proposed to be used together with the new DCCP protocol. This paper provides an overview of the issues surrounding the use of TFRC for interactive media applications. Most issues are related to speci_c TFRC mechanisms, and to the use of smaller-than-MSS packets. An analytical examination of TFRCs behavior in the presence of wireless bit errors is also presented. The results show that DCCP's builtin loss differentiation can potentially be disabled for resourceconstrained devices in order to reduce overhead

  • 55.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Progressive Parsing Transcoding of JPEG Images2000Conference paper (Refereed)
  • 56.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Transcoding of Image Data2004Chapter in book (Other academic)
  • 57.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Transport Layer Loss Differentiation and Loss Notification2003Conference paper (Refereed)
  • 58.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Conchon, Emmanuel
    LAAS-CNRS / ENSICA, Toulouse, France.
    Perennou, Tanguy
    LAAS-CNRS / ENSICA, Toulouse, France.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    KauNet: Improving Reproducibility for Wireless and Mobile Research2007Conference paper (Refereed)
    Abstract [en]

    This paper presents the KauNet emulation system that provides pattern-based emulation. KauNet enables bit precise placement of bit-errors, exact and repeatable packet losses, delays and bandwidth variations. The design and performance of KauNet is discussed. An example is also provided of how it can be integrated in a specific emulation framework to enhance emulation for mobile and wireless systems

  • 59.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hjärtquist, Peter
    Hofmann, Johann
    Ulges, Adrian
    Sokolov, Strahil
    FIVES D5.1: Design Specification2009Report (Refereed)
  • 60.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hofmann, Johann
    FIVES D4.1: User requirements report with HCI and GUI guidelines2009Report (Refereed)
    Abstract

    This user requirements report collects the results from a comprehensive on-line end-user survey that were conducted by the FIVES project. The survey was composed of 50 questions divided into a number of topical areas. In addition to the user survey results, this report also provides guidelines for Human-Computer Interaction (HCI) aspects of systems with a special focus on issues relevant to the task of large volume image classification, which is a major task in many investigations.

    Furthermore, the aspect of Graphical User Interface (GUI) design is also discussed from the context of FIVES needs.

  • 61.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hofmann, Johann
    FIVES D4.2 Test plan for end user tests2010Report (Other academic)
  • 62.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Holleboom, Thijs Jan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Retention of Micro-fragments in Cluster Slack: A First Model2009In: First IEEE International Workshop on Information Forensics and Security (WIFS 2009), London, UK: IEEE Signal Processing Society, 2009, p. 31-35Conference paper (Refereed)
    Abstract [en]

    In current forensic practice it is regularly needed to determine whether some set of files have been present on a storage medium or not. File carving techniques are readily used as a tool in such examinations. However, if all clusters holding the files searched for have been overwritten, remains of the previous files only resides in the cluster slack. In this work we elaborate on the factors that influence how many such cluster slack ¿micro-fragments¿ that can be expected to be detected. We identify a set of factors that influence the micro-fragment retention characteristics. One such characteristic is the file size distribution of the files overwriting the original files. We derive analytical expressions for three different file size distributions, which allows us to examine the retention characteristics even if the overwriting files come from different sources.

  • 63.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Deterministic network emulation using KauNetEm2016Conference paper (Other academic)
    Abstract [en]

    This paper presents KauNetEm, an extension to the Linux-based NetEm emulator that provides deterministic network emulation. KauNetEm enables precise and repeatable placement of NetEm emulation effects, a functionality that canconsiderably simplify several aspects of protocol evaluation. KauNetEm can be instructed to drop specific packets, apply a configurable delay or other emulation effects at predefinedpoints in time. The motivation for deterministic emulation, the overall design of KauNetEm, and usage examples are provided

  • 64.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Getting What You Want When You Want It: Deterministic Network Emulation2016Conference paper (Refereed)
    Abstract [en]

    This paper presents KauNetEm, an extension to the Linux-based NetEm emulator that provides deterministic network emulation. KauNetEm enables precise and repeatable placement of NetEm emulation effects, a functionality that can considerably simplify several aspects of protocol evaluation. KauNetEm can be instructed to drop specific packets, apply a configurable delay or other emulation effects at predefined points in time. The motivation for deterministic emulation, the overall design of KauNetEm, and usage examples are provided.

  • 65.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    KauNet: A Versatile and Flexible Emulation System2008Conference paper (Refereed)
  • 66.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    KauNet: Design and Usage2008Report (Refereed)
    Abstract [en]

    KauNet is an emulation system that allows deterministic placement of packet losses and bit-errors as well as more precise control over bandwidth and delay changes. KauNet is an extension to the well-known Dummynet emulator in FreeBSD and allows the use of pattern and scenario files to increase control and repeatability. This report provides a comprehensive description of the usage of KauNet, as well as a technical description of the design and implementation of KauNet

  • 67.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    KauNet: Design and Usage2008Report (Other academic)
    Abstract [en]

    KauNet is an emulation system that allows deterministic placement of packet losses and bit-errors as well as more precise control over bandwidth and delay changes. KauNet is an extension to the well-known Dummynet emulator in FreeBSD and  allows the use of pattern and scenario files to increase control and repeatability. This report provides a comprehensive description of the usage of KauNet, as well as a technical description of the design and implementation of KauNet.

  • 68.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    The Effect of Packet Loss on the Response Times of Web Services2007In: Proceedings of 3rd International Conference on Web Information Systems and Technologies (WebIST2007), INSTICC Press, 2007Conference paper (Refereed)
  • 69.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Korhonen, Topi
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Efficient Distribution-Derived Features for High-Speed Encrypted Flow Classification2018In: NetAI'18 Proceedings of the 2018 Workshop on Network Meets AI & ML, New York: Association for Computing Machinery (ACM), 2018, p. 21-27Conference paper (Refereed)
    Abstract [en]

    Flow classification is an important tool to enable efficient network resource usage, support traffic engineering, and aid QoS mechanisms. As traffic is increasingly becoming encrypted by default, flow classification is turning towards the use of machine learning methods employing features that are also available for encrypted traffic. In this work we evaluate flow features that capture the distributional properties of in-flow per-packet metrics such as packet size and inter-arrival time. The characteristics of such distributions are often captured with general statistical measures such as standard deviation, variance, etc. We instead propose a Kolmogorov-Smirnov discretization (KSD) algorithm to perform histogram bin construction based on the distributional properties observed in the data. This allows for a richer, histogram based, representation which also requires less resources for feature computation than higher order statistical moments. A comprehensive evaluation using synthetic data from Gaussian and Beta mixtures show that the KSD approach provides Jensen-Shannon distance results surpassing those of uniform binning and probabilistic binning. An empirical evaluation using live traffic traces from a cellular network further shows that when coupled with a random forest classifier the KSD-constructed features improve classification performance compared to general statistical features based on higher order moments, or alternative bin placement approaches.

  • 70.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Korhonen, Topi
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    On Runtime and Classification Performance of the Discretize-Optimize (DISCO) Classification Approach2018In: Performance Evaluation Review, ISSN 0163-5999, E-ISSN 1557-9484, Vol. 46, no 3, p. 167-170Article in journal (Refereed)
    Abstract [en]

    Using machine learning in high-speed networks for tasks such as flow classification typically requires either very resource efficient classification approaches, large amounts of computational resources, or specialized hardware. Here we provide a sketch of the discretize-optimize (DISCO) approach which can construct an extremely efficient classifier for low dimensional problems by combining feature selection, efficient discretization, novel bin placement, and lookup. As feature selection and discretization parameters are crucial, appropriate combinatorial optimization is an important aspect of the approach. A performance evaluation is performed for a YouTube classification task using a cellular traffic data set. The initial evaluation results show that the DISCO approach can move the Pareto boundary in the classification performance versus runtime trade-off by up to an order of magnitude compared to runtime optimized random forest and decision tree classifiers.

  • 71.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Korhonen, Topi
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Andersson, Ricky
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Västlund, Filip
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Towards Video Flow Classification at a Million Encrypted Flows Per Second2018In: Proceedings of 32nd International Conference on Advanced Information Networking and Applications (AINA) / [ed] Leonard Barolli, Makoto Takizawa, Tomoya Enokido, Marek R. Ogiela, Lidia Ogiela & Nadeem Javaid, Krakow: IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    As end-to-end encryption on the Internet is becoming more prevalent, techniques such as deep packet inspection (DPI) can no longer be expected to be able to classify traffic. In many cellular networks a large fraction of all traffic is video traffic, and being able to divide flows in the network into video and non-video can provide considerable traffic engineering benefits. In this study we examine machine learning based flow classification using features that are available also for encrypted flows. Using a data set of several several billion packets from a live cellular network we examine the obtainable classification performance for two different ensemble-based classifiers. Further, we contrast the classification performance of a statistical-based feature set with a less computationally demanding alternate feature set. To also examine the runtime aspects of the problem, we export the trained models and use a tailor-made C implementation to evaluate the runtime performance. The results quantify the trade-off between classification and runtime performance, and show that up to 1 million classifications per second can be achieved for a single core. Considering that only the subset of flows reaching some minimum flow length will need to be classified, the results are promising with regards to deployment also in scenarios with very high flow arrival rates.

  • 72.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Sundberg, Simon
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Beckman, Claes
    Icomera AB, Gothenburg, Sweden.
    Interactions Between Train Velocity andCellular Link Throughput - An Extensive Study2019In: 2019 IEEE 30th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2019Conference paper (Refereed)
    Abstract [en]

    Providing reliable internet connectivity to train passengers can be handled with onboard aggregation routers that use multiple external antennas to simultaneously convey user traffic over multiple links. This work studies the operational characteristics of a large-scale deployment of such a system. The examination focuses on how train velocity is associated with achieved link throughput, and how various interaction effects influence the relationship. A large data set collected over three years is analyzed, indicating that there is a systematic association between train velocity and link throughput that varies over the radio conditions and which is also linked to differences between operators.

  • 73.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Ulges, A
    Jansohn, C
    Hofmann, J
    Gluhchev, G
    FIVES M7.1: Image and Video Processing Survey2009Report (Refereed)
  • 74.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Vermaas, Oscar
    Hofmann, Johann
    FIVES D5.2a Architectural Description and API Description2010Report (Refereed)
  • 75.
    Gineste, Mathieu
    et al.
    LAAS-CNRS, Univ. of Toulouse/ISAE.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Programmable active emulation of wireless systems: A DVB-RCS Example2008In: 6th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks and Workshops, 2008. WiOPT 2008., IEEE conference proceedings, 2008, p. 2-7Conference paper (Refereed)
    Abstract [en]

    This paper presents a DVB-RCS satellite emulation system built using the NPBox programmable network emulation system. NPBox allows system components to be modeled both at a higher abstraction level using a finite-state-machine like abstraction, and also at a lower level using customized event guards and actions. Comparison experiments show that the emulated performance is similar to that of a complex low-level emulator.

  • 76.
    Grinnemo, Karl-Johan
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Garcia, Johan
    Karlstad University, Division for Information Technology.
    A Taxonomy and Survey of Retransmission Based Partially Reliable Transport Protocols2002Report (Other academic)
    Abstract [en]

    The mismatch between the services offered by the two standard transport protocols inthe Internet, TCP and UDP, and the services required by distributed multimedia applicationshas led to the development of a large number of partially reliable transportprotocols. That is, protocols which in terms of reliability places themselves betweenTCP and UDP. This paper presents a taxonomy for retransmission based, partially reliabletransport protocols, i.e., the subclass of partially reliable transport protocols thatperforms error recovery through retransmissions. The taxonomy comprises two classificationschemes: one that classifies retransmission based, partially reliable transportprotocols with respect to the reliability service they offer and one that classifies themwith respect to their error control scheme. The objective of our taxonomy is fourfold:to introduce a unified terminology; to provide a framework in which retransmissionbased, partially reliable transport protocols can be examined, compared, and contrasted;to make explicit the error control schemes used by these protocols; and, finally, to gainnew insights into these protocols and thereby suggest avenues for future research. Basedon our taxonomy, a survey was made of existing retransmission based, partially reliabletransport protocols. The survey shows how protocols are categorized according to ourtaxonomy, and exemplifies the majority of reliability services and error control schemesdetailed in our taxonomy.

  • 77.
    Grinnemo, Karl-Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Taxonomy and Survey of Retransmission-based Partially Reliable Transport Protocols2004In: Elsevier Computer Communications, ISSN 0140-3664, Vol. 27, no 15, p. 1441-1452Article in journal (Refereed)
  • 78.
    Hall, Tomas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Performance Evaluation of KauNet in Physical and Virtual Emulation Environments2012Report (Other academic)
    Abstract [en]

    Evaluation of applications and protocols in the context of computer networking is often necessary to determine the efficiency and level of service they can provide. In practical testing, three different options are available for the evaluation; using a physical network as a testbed, using an emulator to simplify the infrastructure, or using a simulator to remove reliance on infrastructure entirely. As a real network is costly and difficult or even impossible to create for every scenario, emulation and simulation is often used to approximate the behavior of a network with considerably less resources required. However, while a simulator is limited only by the time required to perform the simulation, an emulator is also limited by the hardware and software used. It is therefore important to evaluate the performance of the emulator itself, to determine its ability to emulate the desired network topologies.

    The focus of this document is the KauNet emulator, an extension of Dummynet that adds several new features, primarily deterministic emulation of various network characteristics through the use of pre-generated patterns. A series of tests were per- formed using a testbed with KauNet in both physical and virtual environments, as well as a hybrid environment with both physical and virtual machines. While virtualization greatly increases the flexbility and utilization of resources compared to a pure physical setup, it may also reduce the overall performance and accuracy of the emulation.

    From the results achieved, KauNet performs well in a physical environment, with a high degree of accuracy even at high traffic loads. Virtualization on the other hand, clearly introduces several issues with both processing and packet loss that may make it undesirable for use in experiments, although it may still be sufficient for scenarios where the requirements for accuracy are lower. The hybrid environment represents a compromise, with both performance and flexibility midway between the physical and fully virtualized testbed. 

  • 79.
    Holleboom, Thijs Jan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Fragment Retention Characteristics in Slack Space: Analysis and Measurements2010In: Proceedings Security and Communication Networks (IWSCN), 2010 2nd International Workshop on  Security and Communication Networks, IEEE Computer Society, 2010Conference paper (Refereed)
    Abstract [en]

    When files are deleted, their information is not removed from the storage media. This is a well known fact, and there exist numerous undelete utilities to recover newly deleted files. When deleted files have been partly overwritten, the data from the part of the file that remains in unallocated space can be readily extracted by file carving. Such carving is often performed in forensic investigations. Furthermore, as a consequence of file system implementation specifics, there additionally exist small remains of the previous files in the space at the end of new files. In this paper we focus on these small remains of previous files, or micro-fragments, that exist even after all the space allocated to the previous file has been reallocated to new files. We derive expressions for modeling the number of micro-fragments that can be expected to be found, and perform experiments to evaluate the analytical model. The obtained results indicate good correspondence between the analytical predictions and the measured results.

  • 80.
    Hurtig, Per
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Loss Recovery in Short TCP/SCTP Flows2006Report (Other academic)
    Abstract [en]

    The Transmission Control Protocol (TCP) has been the dominant transport protocol within IP-based networks for many years, mainly due to the reliability it provide to its users and the congestion control it employs. However, as the amount of signaling traffic within IP-based networks have increased significantly in recent years, it has become clear that TCP is not suited for this kind of traffic. In order to meet the requirements of signaling traffic the Stream Control Transmission Protocol (SCTP) was developed by the Internet Engineering Task Force (IETF). SCTP is heavily influenced by TCP and is therefore similar to TCP in many ways. One example is the SCTP loss recovery and congestion control mechanisms which are almost identical to those of TCP. The primary purpose of this work is to study the performance and behavior of the TCP/SCTP loss recovery mechanisms for short flows. Using a simple client/server model, we evaluate the performance of these mechanism over a wide range of bandwidths, link delays and packet loss patterns. The experiments evaluate one TCP implementation and two SCTP implementations, and were conducted using network emulation. The experimental results show that there exist strong dependencies between the position of packet loss and the actual transmission time of the corresponding flow. In addition to these dependencies, we also found a number of implementation mistakes in the examined protocol implementations.

  • 81.
    Hurtig, Per
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Loss Recovery in Short TCP/SCTP Flows2006Report (Refereed)
    Abstract [en]

    The Transmission Control Protocol (TCP) has been the dominant transport protocol within IP-based networks for many years, mainly due to the reliability it provides to its users and the congestion control it employs. However, as the amount of signaling traffic within IP-based networks have increased significantly in recent years, it has become clear that TCP is not suited for this kind of traffic. In order to meet the requirements of signaling traffic the Stream Control Transmission Protocol (SCTP) was developed by the Internet Engineering Task Force (IETF). SCTP is heavily influenced by TCP and is therefore similar to TCP in many ways. One example is the SCTP loss recovery and congestion control mechanisms which are almost identical to those of TCP. The primary purpose of this work is to study the performance and behavior of the TCP/SCTP loss recovery mechanisms for short flows. Using a simple client/server model, we evaluate the performance of these mechanism over a wide range of bandwidths, link delays and packet loss patterns. The experiments evaluate one TCP implementation and two SCTP implementations, and were conducted using network emulation. The experimental results show that there exist strong dependencies between the position of packet loss and the actual transmission time of the corresponding flow. In addition to these dependencies, we also found a number of implementation mistakes in the examined protocol implementations

  • 82.
    Hurtig, Per
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Pérennou, Tanguy
    Université de Toulouse, France.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Using Triggers for Emulation of Opportunistic Networking2010In: Proceedings of the Second International Workshop on Mobile Opportunistic Networking, MobiOpp '10, Pisa, Italy: ACM Press, 2010, p. 155-158Conference paper (Refereed)
    Abstract [en]

    Opportunistic networks do not require the availability of an end-to-end path, but may instead take advantage of temporary connectivity opportunities. Opportunistic networks pose a challenge for network emulation as the traditional emulation setup where application/transport endpoints send/receive packets from the network following a black box approach is no longer applicable. Instead opportunistic networking protocols and applications need to react to the dynamics of the underlying network beyond what is conveyed through the exchange of packets. In order to support emulation evaluations for such challenging applications we in this paper introduce the concept of emulation triggers that can emulate arbitrary cross-layer feedback and that are synchronized with the emulated scenario. The design and implementation of triggers in the KauNet emulator are described. The use of triggers in the context of opportunistic networking is briefly sketched.

  • 83.
    Jalili, Leilia
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Parichehreh, Ali
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Efficient traffic offloading for seamless connectivity in 5G networks onboard high speed trains2017In: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, IEEE, 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Seamless wireless connectivity in high mobility scenarios (≥ 300 km/h), is one of the fundamental key requirements for the future 5G networks. High speed train (HST) is one of the preferred mid-range transportation systems, and highlights the challenges of providing wireless connectivity in high mobility scenarios for the 5G networks. Advanced version of Long Term Evolution (LTE-A) from the Third Generation Partnership Project (3GPP) with peak data rate up to 100 Mbps in high mobility scenarios paved the road toward high quality and cost effective onboard Internet in HSTs. However, frequent handovers (HO) of large number of onboard users increase the service interruptions that in turn inevitably decrease the experienced quality of service (QoS). In this paper, according to the two-tier architecture of the HST wireless connectivity, we propose a novel and practically viable onboard traffic offloading mechanism among the HST carriages that effectively mitigates the service interruptions caused by frequent HOs of massive number of onboard users. The proposed architecture does not imply any change on the LTE network standardization. Conclusions are supported by numerical results for realistic LTE parameters and current HST settings.

  • 84.
    Johan, Garcia
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    FIVES D1.4 Final Report 2011Report (Other (popular science, discussion, etc.))
  • 85. Perennou, Tanguy
    et al.
    Bouabdallah, Amine
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    IP-Level Satellite Link Emulation with KauNet2009In: International Workshop on Satellite and Space Communications, Siena, Italy: IEEE Communications Society, 2009Conference paper (Refereed)
    Abstract [en]

    Distributed applications and transport protocolscommunicating over a satellite link may react very strongly to conditions specific to that kind of link. Providing an evaluation framework to allow tests of real implementations of such software in that context is quite a challenging task. In this paper we show how the use of the general-purpose KauNet IP-level emulator combined with satellite-specific packet loss patterns can help by reproducing losses and delays experienced on a satellite link with a simple Ethernet LAN setup. We also describe a simple experimentation platform and how a typical demonstration is carried out. Such a platform is an essential tool for developers performing continuous testing as they provide new features for e.g. video codecs or transport-level software like DCCP and its congestion control components

  • 86. Popova, Antoaneta
    et al.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Neshov, Nikolay
    Bulgaria.
    Draganov, Ivo
    Bulgaria.
    Brodic, Darko
    Serbia.
    Finding URLs in images by text extraction in DCT domain, recognition and matching in dictionary2015In: International Journal of Reasoning-based Intelligent Systems, ISSN 1755-0556, Vol. 7, no 1/2, p. 78-92Article in journal (Refereed)
    Abstract [en]

    Automatic and fast detection of overlaid URLs and text in images and video with adult content can be an important aid for children protection in the internet. In this paper, we propose a method and associated algorithms for URL and text extraction from images and video frames based on combined processing in the compressed and spatial domains. It includes an improved approach for text detection and extraction in the discrete cosine transform (DCT) domain. It also includes an adaptive local binarisation with background compensation in the spatial domain to create an image appropriate for optical character recognition (OCR). As a final step, text recognition and verification is performed by matching to an URL dictionary. The proposed algorithms are quantitatively and qualitatively tested against other contemporary techniques, and encouraging results are obtained. Experimental tests over 3,000 images have been conducted highlighting the efficiency of the proposed approach.

  • 87. Pérennou, Tanguy
    et al.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hall, Tomas
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Emulating Opportunistic Networks with KauNet Triggers2011In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2011Article in journal (Refereed)
    Abstract [en]

    In opportunistic networks, the availability of an end-to-end path is no longer required. Instead opportunistic networks may take advantage of temporary connectivity opportunities. Opportunistic networks present a demanding environment for network emulation as the traditional emulation setup, where application/transport endpoints only send and receive packets from the network following a black box approach, is no longer applicable. Opportunistic networking protocols and applications additionally need to react to the dynamics of the underlying network beyond what is conveyed through the exchange of packets. In order to support IP-level emulation evaluations of applications and protocols that react to lower layer events, we have proposed the use of emulation triggers. Emulation triggers can emulate arbitrary cross-layer feedback and can be synchronized with other emulation effects. After introducing the design and implementation of triggers in the KauNet emulator, we describe the integration of triggers with the DTN2 reference implementation and illustrate how the functionality can be used to emulate a classical DTN data-mule scenario.

  • 88. Schneyer, S.
    et al.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Asplund, Katarina
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    PRTP: A Partially Reliable Transport Protocol for Multimedia Applications1999Conference paper (Refereed)
  • 89.
    Schneyer, Sean
    et al.
    Karlstad University, Division for Information Technology.
    Garcia, Johan
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Asplund, Katarina
    Karlstad University, Division for Information Technology.
    PRTP: A Partially Reliable Transport Protocol for Multimedia Applications1999In: Proceedings of ISIMADE, 1999Conference paper (Other academic)
  • 90.
    Wennström (Klockar), Annika
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Garcia, Johan
    Karlstad University, Division for Information Technology.
    Gustafsson, Jan H.
    Telia Mobile AB, Karlstad, Sweden.
    A GSM/GPRS Testbed for TCP Performance Evaluation2002In: Proceedings of International Workshop on Wired/Wireless Internet Communications / [ed] Hamid R. Arabnia, Youngsong Mun, CSREA Press, 2002, p. 19-26Conference 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.

  • 91.
    Wennström (Klockar), Annika
    et al.
    Karlstad University, Division for Information Technology.
    Garcia, Johan
    Karlstad University, Division for Information Technology.
    Brunström, Anna
    Karlstad University, Division for Information Technology.
    Gustafsson, Jan H.
    Telia Mobile AB, Karlstad, Sweden.
    TCP and GSM Link Layer Interactions: Implications for the Wireless Internet2001In: IEEE VTS 53rd Vehicular Technology Conference, 2001, IEEE conference proceedings, 2001, p. 2198-2202Conference paper (Refereed)
    Abstract [en]

    The demand for wireless access to the Internet has grown rapidly making the performance of TCP in wireless environments an important issue. We present experimental measurements of the performance of TCP over GSM. The measurements were captured over a real GSM network connected to a controlled radio environment. A range of radio conditions were considered with a focus on the interaction between TCP and the GSM link layer. Even for very poor radio conditions, only neglible negative interaction effects were found.

12 51 - 91 of 91
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