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  • 1.
    Alay, Özgü
    et al.
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    Peón-Quirós, Miguel
    IMDEA Networks Institute, Spain.
    Mancuso, Vincenzo
    IMDEA Networks Institute, Spain.
    Hirsch, Thomas
    Celerway Communications, Norway.
    Evensen, Kristian
    Celerway Communications, Norway.
    Hansen, Audun
    Celerway Communications, Norway.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Karlsson, Jonas
    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).
    Safari Khatouni, Ali
    Politecnico di Torino, Italy.
    Mellia, Marco
    Politecnico di Torino, Italy.
    Ajmone Marsan, Marco
    IMDEA Networks Institute, Spain and Politecnico di Torino, Italy.
    Experience: An open platform for experimentation with commercial mobile broadband networks2017In: MobiCom '17 Proceedings of the 23rd Annual International Conference on Mobile Computing and Networking, New York: Association for Computing Machinery (ACM), 2017, p. 70-78Conference paper (Refereed)
    Abstract [en]

    Open experimentation with operational Mobile Broadband (MBB) networks in the wild is currently a fundamental requirement of the research community in its endeavor to address the need of innovative solutions for mobile communications. Even more, there is a strong need for objective data about stability and performance of MBB (e.g., 3G/4G) networks, and for tools that rigorously and scientifically assess their status. In this paper, we introduce the MONROE measurement platform: an open access and flexible hardware-based platform for measurements and custom experimentation on operational MBB networks. The MONROE platform enables accurate, realistic and meaningful assessment of the performance and reliability of 11 MBB networks in Europe. We report on our experience designing, implementing and testing the solution we propose for the platform. We detail the challenges we overcame while building and testing the MONROE testbed and argue our design and implementation choices accordingly. We describe and exemplify the capabilities of the platform and the wide variety of experiments that external users already perform using the system

  • 2.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Impact of TCP Congestion Control on Bufferbloat in Cellular Networks2013In: Proceedings of the 14th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2013) / [ed] Angelos Lazaris, Balaji Rengarajan, IEEE Press, 2013Conference paper (Refereed)
    Abstract [en]

    The existence of excessively large and too filled network buffers, known as bufferbloat, has recently gained attention as a major performance problem for delay-sensitive applications. One important network scenario where bufferbloat may occur is cellular networks.

    This paper investigates the interaction between TCP congestion control and buffering in cellular networks. Extensive measurements have been performed in commercial 3G, 3.5G and 4G cellular networks, with a mix of long and short TCP flows using the CUBIC, NewReno and Westwood+ congestion control algorithms. The results show that the completion times of short flows increase significantly when concurrent long flow traffic is introduced. This is caused by increased buffer occupancy from the long flows. In addition, for 3G and 3.5G the completion times are shown to depend significantly on the congestion control algorithms used for the background flows, with CUBIC leading to significantly larger completion times.

  • 3.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Observations of Bufferbloat in Swedish Cellular Networks2013In: Proceedings of the 9th Swedish National Computer Networking Workshop (SNCNW 2013) / [ed] Bengt Ahlgren, 2013Conference paper (Refereed)
  • 4.
    Berthold, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Inter-temporal Privacy Metrics2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Informational privacy of individuals has significantly gained importance after information technology has become widely deployed. Data, once digitalised, can be copied, distributed, and long-term stored at negligible costs. This has dramatic consequences for individuals that leave traces in the form of personal data whenever they interact with information technology, for instance, computers and phones; or even when information technology is recording the personal data of aware or unaware individuals. The right of individuals for informational privacy, in particular to control the flow and use of their personal data, is easily undermined by those controlling the information technology.

    The objective of this thesis is to study the measurement of informational privacy with a particular focus on scenarios where an individual discloses personal data to a second party which uses this data for re-identifying the individual within a set of other individuals. We contribute with privacy metrics for several instances of this scenario in the publications included in this thesis, most notably one which adds a time dimension to the scenario for modelling the effects of the time passed between data disclosure and usage. The result is a new framework for inter-temporal privacy metrics.

  • 5.
    Berthold, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Lundin, Reine
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Re-identification revisitedManuscript (preprint) (Other academic)
  • 6.
    Bozakov, Zdravko
    et al.
    Dell EMC, Ireland.
    Mangiante, Simone
    Dell EMC, Ireland.
    Hernandez Benet, Cristian
    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). Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Santos, Ricardo
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Buckley, Donagh
    Dell EMC, Ireland.
    A NEAT framework for enhanced end-host integration in SDN environments2017In: 2017 IEEE Conference on Network Function Virtualization and Software Defined Networks (NFV-SDN), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    SDN aims to facilitate the management of increasingly complex, dynamic network environments and optimize the use of the resources available therein with minimal operator intervention. To this end, SDN controllers maintain a global view of the network topology and its state. However, the extraction of information about network flows and other network metrics remains a non-trivial challenge. Network applications exhibit a wide range of properties, posing diverse, often conflicting, demands towards the network. As these requirements are typically not known, controllers must rely on error-prone heuristics to extract them. In this work, we develop a framework which allows applications deployed in an SDN environment to explicitly express their requirements to the network. Conversely, it allows network controllers to deploy policies on end-hosts and to supply applications with information about network paths, salient servers and other relevant metrics. The proposed approach opens the door for fine grained, application-aware resource optimization strategies in SDNs

  • 7.
    Budzisz, Łukasz
    et al.
    Technische Universität Berlin, Berlin, Germany.
    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).
    Ferrús, Ramon
    Universitat Politècnica de Catalunya, Barcelona, Spain.
    A taxonomy and survey of SCTP research2012In: ACM Computing Surveys, ISSN 0360-0300, E-ISSN 1557-7341, Vol. 44, no 4, p. -36, article id 18Article in journal (Refereed)
    Abstract [en]

    The Stream Control Transmission Protocol (SCTP) is a relatively recent general-purpose transport layer protocol for IP networks that has been introduced as a complement to the well-established TCP and UDP transport protocols. Although initially conceived for the transport of PSTN signaling messages over IP networks, the introduction of key features in SCTP, such as multihoming and multistreaming, has spurred considerable research interest surrounding SCTP and its applicability to different networking scenarios. This article aims to provide a detailed survey of one of these new features—multihoming—which, as it is shown, is the subject of evaluation in more than half of all published SCTP-related articles. To this end, the article first summarizes and organizes SCTP-related research conducted so far by developing a four-dimensional taxonomy reflecting the (1) protocol feature examined, (2) application area, (3) network environment, and (4) study approach. Over 430 SCTP-related publications have been analyzed and classified according to the proposed taxonomy. As a result, a clear perspective on this research area in the decade since the first protocol standardization in 2000 is given, covering both current and future research trends. On continuation, a detailed survey of the SCTP multihoming feature is provided, examining possible applications of multihoming, such as robustness, handover support, and loadsharing.

  • 8.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Architectures and Algorithms for Future Wireless Local Area Networks2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Future Wireless Local Area Networks (WLANs) with high carrier frequencies and wide channels need a dense deployment of Access Points (APs) to provide good performance. In densely deployed WLANs associations of stations and handovers need to be managed more intelligently than today.

    This dissertation studies when and how a station should perform a handover and to which AP from a theoretical and a practical perspective. We formulate and solve optimization problems that allow to compute the optimal AP for each station in normal WLANs and WLANs connected via a wireless mesh backhaul. Moreover, we propose to use software defined networks and the OpenFlow protocol to optimize station associations, handovers and traffic rates. Furthermore, we develop new mechanisms to estimate the quality  of a link  between a station and an AP. Those mechanisms allow optimization algorithms to make better decisions about when to initiate a handover. Since handovers in today’s WLANs are slow and may disturb real-time applications such as video streaming, a faster procedure is developed in this thesis.

    Evaluation results from wireless testbeds and network simulations show that our architectures and algorithms significantly increase the performance of WLANs, while they are backward compatible at the same time.

  • 9.
    di stasi, Giovanni
    et al.
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Karlsson, Jonas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Avallone, Stefano
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Canonico, Roberto
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Kassler, Andreas
    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.
    Combining Multi-Path Forwarding and Packet Aggregation for Improved Network Performance in Wireless Mesh Networks2014In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 68, p. 26-37Article in journal (Refereed)
    Abstract [en]

    Wireless mesh networks (WMNs) based on the IEEE 802.11 standard are becoming increasingly popular as a viable alternative to wired networks. WMNs can cover large or difficult to reach areas with low deployment and management costs. Several multi-path routing algorithms have been proposed for such kind of networks with the objective of load balancing the traffic across the network and providing robustness against node or link failures. Packet aggregation has also been proposed to reduce the overhead associated with the transmission of frames, which is not negligible in IEEE 802.11 networks. Unfortunately, multi-path routing and packet aggregation do not work well together, as they pursue different objectives. Indeed, while multi-path routing tends to spread packets among several next-hops, packet aggregation works more efficiently when several packets (destined to the same next-hop) are aggregated and sent together in a single MAC frame. In this paper, we propose a technique, called aggregation aware forwarding, that can be applied to existing multi-path routing algorithms to allow them to effectively exploit packet aggregation so as to increase their network performance. In particular, the proposed technique does not modify the path computation phase,but it just influences the forwarding decisions by taking the state of the sending queues into account.We demonstrated our proposed technique by applying it to Layer-2.5, a multi-path routing and forwarding paradigm for WMNs that has been previously proposed.We conducted a thorough performance evaluation by means of the ns-3 network simulator, which showed that our technique allows to increase the performance both in terms of network throughput and end-to-end delay.

  • 10.
    Eklund, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Grinnemo, Karl-Johan
    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.
    Stream-aware Scheduling to Improve Latency for Signaling Traffic using CMT-SCTP2016Conference paper (Refereed)
    Abstract [en]

    To mitigate delay spikes during transmission ofbursty signaling traffic, concurrent multipath transmission(CMT) over several paths in parallel could be an option. Still,unordered delivery is a well known problem when transmittingover asymmetric network paths, leading to extra delay due toHead-of-Line Blocking (HoLB). The Stream Control TransmissionProtocol (SCTP) is designed as a carrier for signaling trafficover IP to reduce the impact of HoLB. SCTP has support fortransmission of separate flows, called SCTP streams. SCTP iscurrently being extended with support for CMT (CMT-SCTP). Inthis paper, we address sender scheduling to optimize latency forsignaling traffic over CMT-SCTP. We present dynamic streamaware(DS) scheduling, which utilizes the SCTP stream concept,and continuously considers the current network status as well asthe data load to make scheduling decisions. We implement a DSScheduler and compare it against a dynamic path (DP) schedulerthat does not consider streams. Our investigation shows that DSscheduling could significantly reduce latency compared to a DPscheduler.

  • 11.
    Fida, Mah-Rukh
    et al.
    University of Edinburgh, UK.
    Kousias, Konstantinos
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    Rajiullah, Mohammad
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alay, Özgü
    Simula Research Laboratory, Norway.
    Brunström, Anna
    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).
    Argyriou, Antonios
    University of Thessaly, Greece.
    Demo: experimentation in controlled and operational LTE settings with FLEX-MONROE2017In: Proceedings of the 11th Workshop on Wireless Network Testbeds, Experimental evaluation & Characterization WiNTECH '17, Association for Computing Machinery (ACM), 2017, p. 93-94Conference paper (Refereed)
    Abstract [en]

    This demo paper presents FLEX-MONROE, a platform that facilitates better understanding of current LTE Mobile Broadband(MBB) networks and enables performance improvementsby allowing experimentation with controllable LTE parameters. The platform enables investigating impact oflow-level network parameter tweaks in LTE infrastructure onthe application performance. We argue that FLEX-MONROEis crucial to provide guidelines on improving application performance both in the current and future MBB networks

  • 12.
    Fischer, Andreas
    et al.
    University of Passau.
    De Meer, Hermann
    University of Passau.
    Generating Virtual Network Embedding Problems with Guaranteed Solutions2016In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 13, no 3, p. 504-517Article in journal (Refereed)
    Abstract [en]

    The efficiency of network virtualization depends on the appropriate assignment of resources. The underlying problem, called Virtual Network Embedding, has been much discussed in the literature, and many algorithms have been proposed, attempting to optimize the resource assignment in various respects. Evaluation of those algorithms requires a large number of randomly generated embedding scenarios. This paper presents a novel scenario generation approach and demonstrates how to produce scenarios with a guaranteed exact solution, thereby facilitating better evaluation of embedding algorithms.

  • 13.
    Garcia, Johan
    et al.
    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).
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Delay metrics and delay characteristics: A study of four Swedish HSDPA+ and LTE networks2015In: 2015 European Conference on Networks and Communications (EuCNC), IEEE, 2015, p. 234-238Conference paper (Refereed)
    Abstract [en]

    Network delays and user perceived latencies are of major importance in many applications in cellular networks. Delays can be measured with multiple approaches and at different protocol layers. This work involves a detailed examination of several delay metrics from a network, transport, and application perspective. The study explores base delay as well as latency under load, capturing also the effect of buffering. The examination is based on a comprehensive active measurement campaign performed in the networks of four Swedish operators. The results show that the delay captured by different metrics can vary significantly, with delay captured from the TCP three-way-handshake and adaptive ping measurements giving the most consistent results for base network delay in our measurements. As expected, when background traffic is introduced measured delay increases by an order of magnitude due to buffering in the network, highlighting the importance of also capturing latency under load when describing network performance. Finally, using an analytic model of flow completion time, we show that well-selected network measurements can provide a good prediction of higher layer delay performance.

  • 14.
    Garcia, Johan
    et al.
    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).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Estimating data transfer capacity for intermittent connectivity: A transport aware model2016In: 2016 IEEE 27th Annual International Symposium On Personal, Indoor, And Mobile Radio Communications (PIMRC), New York: IEEE, 2016, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Communication performed with mobile devices will experience varying levels of connectivity as the communication device moves in and out of coverage. A subset of mobile communication devices operate under conditions where the connectivity is characterized by relatively short contact periods occurring intermittently. In this paper we propose a model to predict the amount of data that can be transferred during such short contact periods. The model includes aspects of the transport layer slow-start behavior and is validated using data from a long-running measurement campaign in the networks of four Swedish cellular networks. Further validation of the modeling assumptions is performed by employing a numerical optimization technique based on non-linear least squares regression using the iterative Levenberg-Marquardt approach. The model is then used to explore the relevant parameter space.

  • 15.
    Garcia, Johan
    et al.
    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).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Examining TCP Short Flow Performance in Cellular Networks Through Active and Passive Measurements2015In: AllThingsCellular '15 Proceedings of the 5th Workshop on All Things Cellular: Operations, Applications and Challenges / [ed] David Choffnes and Kobus Van der Merwe, Association for Computing Machinery (ACM), 2015, p. 7-12Conference paper (Refereed)
    Abstract [en]

    In this study we examine the conditions in a current cellular network by examining data passively collected in the core of a cellular operator during a 24-hour period. More than 2 billion traffic measurement data points from over 500,000 cellular users are analyzed. The analysis characterizes the Time-of-Day (ToD) variations for traffic intensity and session length and serves as a complement to the active measurements also performed. A comprehensive active measurement campaign was completed in the HSDPA+ and LTE networks of the four major Swedish operators. We collect around 50,000 data points from stationary cellular modems and analyze the ToD variation pattern for underlying network layer metrics such as delay and throughput. In conjunction with the time-varying session size distribution obtained from the passive measurements, we then analyze the ToD impact on TCP flows of varying sizes. The ToD effects are examined using time series analysis with Lomb-Scargle periodograms and differential Bayesian Information Criterion to allow comparison of the relative impact of the network ToD effects. The results show that ToD effects are predominantly impacting longer-running flows, and although short flows are also impacted they are mostly constrained by other issues such as protocol efficiency.

  • 16.
    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

  • 17.
    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.

  • 18.
    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. 

  • 19.
    Hassan, Ahmad
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT. Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hoque, Ahsanul
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Automated Microwave Antenna Alignment of Base Transceiver Station2011Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This master’s thesis is intended for the solution of Microwave (MW) link alignment which has several applications in modern communication systems. MW communication is used for point to point links with small wavelength and simultaneously compact antenna dimensions. Assuring the automated alignment of antennas provides a better communication between switching stations and allow its subscribers to communicate ceaselessly. In the first part of the work; effects of downtime on a network are discussed and at later stage a mechanism is investigated which will reduce the downtime. MW antenna used in communication systems is regularly affected by environmental factor and generally by wear and tear of mounts. These factors cause the precisely directed antennas to be perturbed from respective main lobes. Larger antennas with narrow main lobes require more sophisticated designing while smaller antennas have a broader main lobe. An automated antenna alignment that works without human intervention can decrease the down time and ensure a reliable communication between the near end and far end terminals of the Base Transceiver Station (BTS). The focus has been laid on a system that works autonomously and for that LabVIEW design and RCX Robonics Kit is used.  Results are presented to indicate antenna alignment in automatically synchronized manner.

  • 20.
    Hernandez Benet, Cristian
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Nasim, Robayet
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alizadeh Noghani, Kyoomars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    OpenStackEmu - A Cloud Testbed Combining Network Emulation with OpenStack and SDN2017In: Consumer Communications & Networking Conference (CCNC), 2017 14th IEEE Annual, IEEE, 2017, p. 566-568Conference paper (Refereed)
    Abstract [en]

    OpenStack has been widely acknowledged to be one of the most important open source cloud platforms. In order to perform experimentally driven research in the area of cloud and cloud networking, there is however a big gap, because most researchers do not have access to a large cloud deployment and cannot change networking or compute infrastructure in order to test their algorithms and protocols on a large-scale. We developed OpenStackEmu, which is to the best of our knowledge the first attempt that combines OpenStack infrastructure with a Software Defined Networking (SDN) based controller such as OpenDaylight and a large-scale network emulator CORE (Common Open Research Emulator). The OpenStack compute and control nodes are connected to the CORE emulation server using TUN/TAP interfaces that inject the control (e.g. for VM migration) and data (VM-to-VM traffic) packets into a customizable network topology that is emulated using configurable Open vSwitches using CORE emulator. Experimenters can define e.g. fat-tree or distributed data center topologies and study the behavior of real VMs and services in those VMs under different background loads and SDN routing policies. We integrated the data center traffic generator DCT2Gen that allows to generate realistic background traffic based on traces from real data centers. Experimenters can study the performance impact of different VM migration strategies or different routing and load balancing schemes on real VM and application performance using different emulated topologies. We believe that OpenStackEmu is an important tool for both the SDN and OpenStack community in order to evaluate the performance of novel algorithms and protocols in the area of cloud networking.

  • 21.
    Hurtig, Per
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Alay, Ozgu
    Simula Research Laboratory.
    Ferlin, Simone
    Simula Research Laboratory.
    Yedugundla, Kiran
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Reducing Transport Latency using Multipath Protocols2015Conference paper (Refereed)
  • 22.
    Hurtig, Per
    et al.
    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.
    Enhanced Metric Caching for Short TCP Flows2012In: Proceedings of the IEEE International Conference on Communications (ICC 2012), IEEE Press, 2012, p. 1209-1213Conference paper (Refereed)
    Abstract [en]

    Internet-based applications that require low latency are becoming more common. Such applications typically generate traffic consisting of short, or bursty, TCP flows. As TCP, instead, is designed to optimize the throughput of long bulk flows there is an apparent mismatch. To overcome this, a lot of research has recently focused on optimizing TCP for short flows as well. In this paper, we identify a performance problem for short flows caused by the metric caching conducted by the TCP control block interdependence mechanisms. Using this metric caching, a single packet loss can potentially ruin the performance for all future flows to the same destination by making them start in congestion avoidance instead of slow-start. To solve this, we propose an enhanced selective caching mechanism for short flows. To illustrate the usefulness of our approach, we implement it in both Linux and FreeBSD and experimentally evaluate it in a real test-bed. The experiments show that the selective caching approach is able to reduce the average transmission time of short flows by up to 40%.

  • 23.
    Hurtig, Per
    et al.
    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.
    Petlund, Andreas
    Simula Research Laboratory AS.
    Welzl, Michael
    University of Oslo.
    TCP and Stream Control Transmission Protocol (SCTP) RTO Restart2016In: Internet RFCs, ISSN 2070-1721, no 7765Article in journal (Refereed)
    Abstract [en]

    This document describes a modified sender-side algorithm for managing the TCP and Stream Control Transmission Protocol (SCTP) retransmission timers that provides faster loss recovery when there is a small amount of outstanding data for a connection. The modification, RTO Restart (RTOR), allows the transport to restart its retransmission timer using a smaller timeout duration, so that the effective retransmission timeout (RTO) becomes more aggressive in situations where fast retransmit cannot be used. This enables faster loss detection and recovery for connections that are short lived or application limited.

  • 24.
    Hurtig, Per
    et al.
    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.
    Kassler, Andreas
    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.
    MPTCP PathFinder: Datacenter Bandwidth Aggregation2014Conference paper (Refereed)
  • 25.
    Høiland-Jørgensen, Toke
    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).
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    The Good, the Bad and the WiFi: Modern AQMs in a residential setting2015In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 89, p. 90-106Article in journal (Refereed)
    Abstract [en]

    Several new active queue management (AQM) and hybrid AQM/fairness queueing algorithms have been proposed recently. They seek to ensure low queueing delay and high network goodput without requiring parameter tuning of the algorithms themselves. However, extensive experimental evaluations of these algorithms are still lacking. This paper evaluates a selection of bottleneck queue management schemes in a test-bed representative of residential Internet connections of both symmetrical and asymmetrical bandwidths as well as WiFi. Latency under load and the performance of VoIP and web traffic patterns are evaluated under steady state conditions. Furthermore, the impact of the algorithms on fairness between TCP flows with different RTTs, and also the transient behaviour of the algorithms at flow startup is examined. The results show that while the AQM algorithms can significantly improve steady state performance, they exacerbate TCP flow unfairness. In addition, the evaluated AQMs severely struggle to quickly control queueing latency at flow startup, which can lead to large latency spikes that hurt the perceived performance. The fairness queueing algorithms almost completely alleviate the algorithm performance problems, providing the best balance of low latency and high throughput in the tested scenarios. However, on WiFi the performance of all the tested algorithms is hampered by large amounts of queueing in lower layers of the network stack inducing significant latency outside of the algorithms’ control.

  • 26.
    Kane, Bridget
    University of Dublin, Trinity College, Ireland.
    An Analysis of Multi-Disciplinary Medical Team Meeting Dynamics: An Investigation into Collaboration and Information Flow at Meetings and the Use of Information Communication Technology2010Book (Other academic)
  • 27.
    Kane, Bridget
    et al.
    University of Dublin, Trinity College, Ireland.
    Groth, Kristina
    Karolinska institutet.
    Randall, Dave
    Manchester university.
    Medical team meetings: utilising technology to enhance communication, collaboration and decision-making2011In: Behavior and Information Technology, ISSN 0144-929X, E-ISSN 1362-3001, Vol. 30, no 4, p. 437-442Article in journal (Other academic)
  • 28.
    Kane, Bridget
    et al.
    University of Dublin, Trinity College, Ireland.
    Luz, Saturnino
    University of Dublin, Trinity College, Ireland.
    Medical teamwork, collaboration and patient-centred care2015In: Journal of Behaviour and Information Technology, ISSN 0144-929X, Vol. 34, no 6, p. 543-547Article in journal (Other academic)
  • 29.
    Karlsson, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Transport-Layer Performance in Wireless Multi-Hop Networks2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless communication has seen a tremendous growth in the last decades. Continuing on this trend, wireless multi-hop networks  are nowadays used or planned for use in a multitude of contexts, spanning from Internet access at home to emergency situations.

    The Transmission Control Protocol (TCP) provides reliable and ordered delivery of a data and is used by major Internet applications such as web browsers, email clients and file transfer programs. TCP traffic is also the dominating traffic type on the Internet. However, TCP performs less than optimal in wireless multi-hop networks due to packet reordering, low link capacity, packet loss and variable delay.

    In this thesis, we develop novel proposals for enhancing the network and transport layer to improve TCP performance in wireless multi-hop networks. As initial studies, we experimentally evaluate the performance of different TCP variants, with and without mobile nodes. We further evaluate the impact of multi-path routing on TCP performance and propose packet aggregation combined with aggregation aware multi-path forwarding as a means to better utilize the available bandwidth. The last contribution is a novel extension to multi-path TCP to  enable single-homed hosts to fully utilize the network capacity.

  • 30.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Di Stasi, Giovanni
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Avallone, Stefano
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    An Aggregation Aware Multi-path Forwarding Paradigm for Wireless Mesh Networks2011In: IEEE MASS 2011. Proceedings of the 8th IEEE International Conference on Mobile Ad-hoc and Sensor Systems, IEEE Computer Society, 2011, p. 765-770Conference paper (Refereed)
    Abstract [en]

    In multi-radio wireless mesh networks, a networkdevice simultaneously transmits packets over different channelsby using multiple radios. Such frequency diversity not only increasesthroughput but makes multi-path routing approaches extremelyinteresting. This is because the channel diversity reducesthe risk for intra- and inter-flow interference. A fundamentalproblem to solve is the forwarding strategy which determineswhich packets to be sent over what multi-path segments atany given time. Ideally, the forwarding strategy should scheduleflows according to the capacity constraints imposed by thechannel assignment. However, the possibility to improve MAClayer efficiency by aggregating small packets into larger onesis reduced when packets are forwarded to different next-hops.In this paper, we develop a novel packet forwarding strategyfor multi-radio mesh networks that combines the benefits ofmulti-path routing with packet aggregation. In our cross-layerapproach, we effectively trade-off aggregation opportunities withchannel diversity. Simulation results show that our approach canimprove network throughput and delay by up to 15 percentand 25 percent, respectively, compared with aggregation unawareforwarding strategies.

  • 31.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Di Stasi, Giovanni
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Avallone, Stefano
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    An Aggregation Aware Multi-path Forwarding Paradigm for Wireless Mesh Networks : AA-L2R Aggregation Aware Multi-path Routing2011Conference paper (Refereed)
  • 32.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Dimitrov, Velizar G.
    Department of Communication Networks, Technical University of Sofia, boulevard Kliment Ohridski 8, Sofia, Bulgaria.
    Kassler, Andreas
    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.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Nilsson, Jan
    Swedish Defence Research Agency (FOI), Box 1165, SE - 581 11 Linköping, Sweden.
    Hansson, Anders
    Swedish Defence Research Agency (FOI), Box 1165, SE - 581 11 Linköping, Sweden.
    Performance Evaluation for TCP in Tactical Mobile Ad hoc Networks2012In: Proceedings of International Conference on Wireless Information Networks and Systems, SciTePress, 2012, p. 277-282Conference paper (Refereed)
    Abstract [en]

    Tactical networks are used in military and rescue operations to provide timely and accurate information to operating teams.  Tactical networks have traditionally used long distance narrow band radio links. However, although these links provide robust real-time communication the limited bandwidth makes them less suited for high data-rate applications.  To support high-data rate TCP applications such as providing digital images and maps, emerging tactical networks use shorter range but higher data-rate wide band radio links and multi-hop.  Due to the requirement of cheap up-front cost, most MANET research has focused on Carrier Sense Multiple Access (CSMA) networks. However, in tactical networks, where bounded delays are important, Time Division Multiple Access (TDMA) can give better possibility to support the Quality of Service needed for real-time communication.  The purpose of this paper is to assess and compare the throughput of three state-of-the-art TCP versions and two routing protocols over TDMA based MANETs.

  • 33.
    Karlsson, Jonas
    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.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    MPTCP PathFinder - finding your ways to aggregated bandwidth2012Report (Other academic)
    Abstract [en]

    Many  networks are multi-path; mobile devices have multiple interfaces, data centers have redundant paths and ISPs forward traffic over disjoint paths to perform load-balancing. Multi-path TCP (MPTCP) is a new mechanism that transparently divides a TCP connection into subflows and distributes them over a host's network interfaces. While this enables multi-homed systems like e.g. smartphones to use several interfaces and thus different, and mostly disjoint, network paths for a single transmission, most end-systems are still single-homed. With one interface, standard MPTCP creates only a single subflow, making single-homed systems unable to benefit from MPTCP's functionality. In this paper we propose PathFinder, an MPTCP extension that tries to estimate the number of subflows required to fully utilize  the network capacity, enabling single-homed hosts to reap the benefits of MPTCP. We evaluate MPTCP with PathFinder and compare its performance to standard MPTCP. The evaluation shows that PathFinder is able to open a limited but sufficient amount of subflows to significantly increase the throughput when compared to using standard MPTCP.

  • 34.
    Karlsson, Jonas
    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.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    di Stasi, Giovanni
    University of Naples "Federico II", Italy.
    Impact of Multi-path Routing on TCP Performance2012In: 2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2012), Washington, DC: IEEE Press, 2012, p. 1-3Conference paper (Refereed)
    Abstract [en]

    Routing packets over multiple disjoint paths towards a destination can increase network utilization by load-balancing the traffic over the network. The drawback of load-balancing is that different paths might have different delay properties, causing packets to be reordered. This can reduce TCP performance significantly, as reordering is interpreted as a sign of congestion. Packet reordering can be avoided by letting the network layer route strictly on flow-level. This will, however, also limit the ability to achieve optimal network throughput. There are also several proposals that try to mitigate the effects of reordering at the transport layer. In this paper, we perform an initial evaluation of such TCP reordering mitigations in multi-radio multi-channel wireless mesh networks when using multi-path routing. We evaluate two TCP reordering mitigation techniques implemented in the Linux kernel. The transport layer mitigations are compared using different multi-path routing strategies. Our findings show that, in general, flow-level routing gives the best TCP performance and that transport layer reordering mitigations only marginally can improve performance.

  • 35.
    Karlsson, Jonas
    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.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    di Stasi, Giovanni
    (University of Naples "Federico II", Italy.
    Impact of Multi-path Routing on TCP Performance in Wireless Mesh Networks2012In: Proceedings of the 8th Swedish National Computer Networking Workshop (SNCNW 2012), 2012Conference paper (Refereed)
    Abstract [en]

    Routing packets over multiple disjoint paths to- wards a destination can increase network utilization by load- balancing the traffic over the network. The drawback of load-balancing is that different paths might have different delay properties, causing packets to be reordered. This can reduce TCP performance significantly, as reordering is interpreted as a sign of congestion. Packet reordering can be avoided by letting the network layer route strictly on flow-level. This will, however, also limit the ability to achieve optimal network throughput. There are also several proposals that try to mitigate the effects of reordering at the transport layer. In this paper, we perform an initial evaluation of such TCP reordering mitigations in multi-radio multi-channel wireless mesh networks when using multi-path routing. We evaluate two TCP reordering mitigation techniques implemented in the Linux kernel. The transport layer mitigations are compared using different multi-path routing strategies. Our findings show that, in general, flow-level routing gives the best TCP performance and that transport layer reordering mitigations only marginally can improve performance. 

  • 36.
    Karlsson, Jonas
    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.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    di Stasi, Giovanni
    Department of Computer Science, University of Naples "Federico II", Italy.
    The Interaction Between TCP Reordering Mechanisms and Multi-path Forwarding in Wireless Mesh Networks2012In: 2012 IEEE 8th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob), IEEE Press, 2012, p. 276-283Conference paper (Refereed)
    Abstract [en]

    Routing packets over multiple disjoint paths towards a destination can increase network utilization by load-balancing the traffic over the network. In wireless mesh networks, multi-radio multi-channel nodes are often used to create a larger set of interference-free paths thus increasing the chance of load-balancing. The drawback of load-balancing is that different paths might have different delay properties, causing packets to be reordered. This can reduce TCP performance significantly, as reordering is interpreted as a sign of congestion. Packet reordering can be avoided by letting the network layer forward traffic strictly on flow-level. This would avoid the negative drawbacks of packet reordering, but will also limit the ability to achieve optimal network throughput. On the other hand, there are several proposals that try to mitigate the effects of reordering at the transport layer. In this paper, we perform an in-depth evaluation of such TCP reordering mitigations in multi-radio multi-channel wireless mesh networks when using multi-path forwarding. We evaluate two TCP reordering mitigation techniques implemented in the Linux kernel. The transport layer mitigations are compared using different multi-path forwarding strategies. Our findings show that, in general, flow-level forwarding gives the best TCP performance and that transport layer reordering mitigations only marginally can improve performance

  • 37.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    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.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    TCP Performance Evaluation in Wireless Mesh Networks using Packet Aggregation2012Manuscript (preprint) (Other academic)
    Abstract [en]

    Wireless Mesh Networks (WMNs) have attracted attention as a way to provide alternative wireless Internet connectivity. In a WMN, access points communicate with each other wirelessly, forming a wireless mesh backbone network. One major problem in WMNs is low performance due to MAC and PHY layer overhead for transmission of small packets. Around 44 percent of the packets in the Internet are smaller than 100 bytes and a majority of these packets are TCP packets. The capacity of WMNs can therefore be increased significantly by packet aggregation (concatenation) of TCP packets. In this paper, we evaluate the impact of packet aggregation on TCP performance in WMNs. Using both synthetic and trace based traffic distributions we demonstrate that packet aggregation can not only increase capacity for TCP in such networks but also reduce round trip times.

  • 38.
    Klockar, Annika
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Sternad, Mikael
    Uppsala University.
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Apelfröjd, Rikke
    Uppsala University.
    User-centric pre-selection and scheduling for coordinated multipoint systems2014In: 2014 11th International Symposium on Wireless Communications Systems (ISWCS 2014), IEEE, 2014, p. 888-894Conference paper (Refereed)
    Abstract [en]

    The data traffic volumes are constantly increasing in cellular networks. Furthermore, a larger part of the traffic is generated by applications that require high data rates. Techniques including Coordinated Multipoint transmission (CoMP) can increase the data rates, but at the cost of a high overhead. The overhead can be reduced if only a subset of the users is served with CoMP. In this paper, we propose a user selection approach, including pre-selection of CoMP users and short term scheduling, that takes user requirements into account. Users that require a high data rate to reach an acceptable level of service satisfaction are selected to use coherent joint processing CoMP in some of their downlink transmission bandwidth. Simulation results show that both the number of satisfied users and fairness are improved with the proposed user selection as compared to user selection that does not consider individual user requirements.

  • 39.
    Mesodiakaki, Agapi
    et al.
    Department of Informatics, Aristotle University of Thessaloniki, Greece.
    Zola, Enrica
    UPC-BarcelonaTECH, Barcelona, Spain.
    Santos, Ricardo
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Optimal User Association, Backhaul Routing and Switching off in 5G Heterogeneous Networks with Mesh Millimeter Wave Backhaul Links2018In: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 78, p. 99-114Article in journal (Refereed)
    Abstract [en]

    Next generation, i.e., fifth generation (5G), cellular networks will provide a significant higher capacity per area to support the ever-increasing traffic demands. In order to achieve that, many small cells need to be deployed that are connected using a combination of optical fiber links and millimeter-wave (mmWave) backhaul architecture to forward heterogeneous traffic over mesh topologies. In this paper, we present a general optimization framework for the design of policies that optimally solve the problem of where to associate a user, over which links to route its traffic towards which mesh gateway, and which base stations and backhaul links to switch off in order to minimize the energy cost for the network operator and still satisfy the user demands. We develop an optimal policy based on mixed integer linear programming (MILP) which considers different user distribution and traffic demands over multiple time periods. We develop also a fast iterative two-phase solution heuristic, which associates users and calculates backhaul routes to maximize energy savings. Our strategies optimize the backhaul network configuration at each timeslot based on the current demands and user locations. We discuss the application of our policies to backhaul management of mmWave cellular networks in light of current trend of network softwarization (Software-Defined Networking, SDN). Finally, we present extensive numerical simulations of our proposed policies, which show how the algorithms can efficiently trade-off energy consumption with required capacity, while satisfying flow demand requirements.

  • 40.
    Mohideen, Althaff C.
    et al.
    University of Aberdeen, UK.
    Rajiullah, Mohammad
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Secchi, Raffaello
    University of Aberdeen, UK.
    Fairhurst, Gorry
    University of Aberdeen, UK.
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Weinrank, Felix
    Münster University of Applied Sciences, Germany.
    Evaluating the impact of transport mechanisms on web performance for effective web access2019In: Journal of Network and Computer Applications, ISSN 1084-8045, E-ISSN 1095-8592, Vol. 137, p. 25-34Article in journal (Refereed)
    Abstract [en]

    This paper explores the design trade-offs required for an Internet transport protocol to effectively support web access. It identifies a set of distinct transport mechanisms and explores their use with a focus on multistreaming. The mechanisms are studied using a practical methodology that utilise the range of transport features provided by TCP and SCTP. The results demonstrate the relative benefit of key transport mechanisms and analyse how these impact web access performance. Our conclusions help identify the root causes of performance impairments and suggest appropriate choices guiding the design of a web transport protocol. Performing this analysis at the level of component transport mechanisms enables the results to be utilised in the design of new transport protocols, such as IETF QUIC.

  • 41.
    Nasim, Robayet
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Cost- and Performance-Aware Resource Management in Cloud Infrastructures2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    High availability, cost effectiveness and ease of application deployment have accelerated the adoption rate of cloud computing. This fast proliferation of cloud computing promotes the rapid development of large-scale infrastructures. However, large cloud datacenters (DCs) require infrastructure, design, deployment, scalability and reliability and need better management techniques to achieve sustainable design benefits. Resources inside cloud infrastructures often operate at low utilization, rarely exceeding 20-30%, which increases the operational cost significantly, especially due to energy consumption. To reduce operational cost without affecting quality of service (QoS) requirements, cloud applications should be allocated just enough resources to minimize their completion time or to maximize utilization. 

    The focus of this thesis is to enable resource-efficient and performance-aware cloud infrastructures by addressing above mentioned cost and performance related challenges. In particular, we propose algorithms, techniques, and deployment strategies for improving the dynamic allocation of virtual machines (VMs) into physical machines (PMs). 

    For minimizing the operational cost, we mainly focus on optimizing energy consumption of PMs by applying dynamic VM consolidation methods. To make VM consolidation techniques more efficient, we propose to utilize multiple paths to spread traffic and deploy recent queue management schemes which can maximize network resource utilization and reduce both downtime and migration time for live migration techniques. In addition, a dynamic resource allocation scheme is presented to distribute workloads among geographically dispersed DCs considering their location based time varying costs due to e.g. carbon emission or bandwidth provision. For optimizing performance level objectives, we focus on interference among applications contending in shared resources and propose a novel VM consolidation scheme considering sensitivity of the VMs to their demanded resources. Further, to investigate the impact of uncertain parameters on cloud resource allocation and applications’ QoS such as unpredictable variations in demand, we develop an optimization model based on the theory of robust optimization. Furthermore, in order to handle the scalability issues in the context of large scale infrastructures, a robust and fast Tabu Search algorithm is designed and evaluated.

  • 42.
    Nasim, Robayet
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Security Threats Analysis in Bluetooth-Enabled Mobile Devices2012In: International Journal of Network Security & Its Applications, ISSN 0975-2307, E-ISSN 0974-9330, Vol. 4, no 3, p. 41-56Article in journal (Refereed)
    Abstract [en]

    Exponential growth of the volume of Bluetooth-enabled devices indicates that it has become a popularway of wireless interconnections for exchanging information. The main goal of this paper is to analyzethe most critical Bluetooth attacks in real scenarios. In order to find out the major vulnerabilities inmodern Bluetooth-enabled mobile devices several attacks have performed successfully such as-Surveillance, Obfuscation, Sniffing, Unauthorized Direct Data Access (UDDA) and Man-in-the-MiddleAttack (MITM). To perform the testbed, several devices are used such as mobile phones, laptops,notebooks, wireless headsets, etc. and all the tests are carried out by pen-testing software like hcittml, braudit,spoafiooph, hridump, bluesnarfer, bluebugger and carwhisperer

  • 43.
    Nasim, Robayet
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    A Robust Tabu Search Heuristic for VM Consolidation under Demand Uncertainity in Virtualized Datacenters2017In: CCGrid '17 Proceedings of the 17th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing, IEEE, 2017, p. 170-180Conference paper (Refereed)
    Abstract [en]

    In virtualized datacenters (vDCs), dynamic consolidation of virtual machines (VMs) is used as one of the most common techniques to achieve both energy- and resource- utilization efficiency. Live migrations of VMs are used for dynamic consolidation but due to dynamic resource demand variation of VMs may lead to frequent and non-optimal migrations. Assuming deterministic workload of the VMs may ensure the most energy/resource efficient VM allocations but eventually may lead to significant resource contention or under-utilization if the workload varies significantly over time. On the other hand, adopting a conservative approach by allocating VMs depending on their peak demand may lead to low utilization, if the peak occurs infrequently or for a short period of time. Therefore, in this work we design a robust VM migration scheme that strikes a balance between protection for resource contention and additional energy costs due to powering on more servers while considering uncertainties on VMs resource demands. We use the theory of Gamma-robustness and derive a robust Mixed Integer Linear programming (MILP) formulation. Due to the complexity, the problem is hard to solve for online optimization and we propose a novel heuristic based on Tabu search. Using several scenarios, we show that that the proposed heuristic can achieve near optimal solution qualities in a short time and scales well with the instance sizes. Moreover, we quantitatively analyze the trade-off between energy cost versus protection level and robustness.

  • 44.
    Nasim, Robayet
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    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.
    Distributed Architectures for Intelligent Transport Systems: A Survey2012In: 2012 Second Symposium on Network Cloud Computing and Applications (NCCA), IEEE Press, 2012, p. 130-136Conference paper (Refereed)
    Abstract [en]

    Recently Intelligent Transport Systems (ITS) have acted as an efficient solution for improving the operational performance of traffic systems, reducing traffic congestion, and increasing safety for the travelers. But due to the inclusion of different distributed transport departments, heterogeneous devices, and diverse data sources, the architecture of ITS has become complex and costly. For an efficient and cost-effective architecture, ITS need to have easy and effective mechanisms for interacting among different transport subsystems. Recent technologies such as – service-oriented architectures (SOA), cloud or grid computing, provide a way of building a reliable and loosely-coupled distributed system. This paper surveys the promising solutions for distributed architectures of ITS and discusses opportunities and challenges in the context of ITS for public transport.

  • 45.
    Nasim, Robayet
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Maswood, Mirza Mohd Shahriar
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Medhi, Deep
    Cost-Efficient Resource Scheduling under QoS Constraints for Geo-Distributed Data Centers2018In: NOMS 2018 - 2018 IEEE/IFIP Network Operations and Management Symposium, IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    Geo-distributed Data Centers (DCs) are more and more common in order to provide scalability for the ever increasing compute demands of modern applications. When multiple distributed DCs can serve user requests, it is important to determine, which DC and server to select to fulfil the compute request, given that enough resources are available in terms of CPU and bandwidth. The problem is complicated as every DC has different operational costs associated, such as energy costs, carbon emission cost and bandwidth costs. In this paper, we develop a novel mathematical optimization model that guides the decision maker which DC to select, which server to use to host the compute demands and which DC gateway and network path to use to route the network traffic in order to satisfy the compute, bandwidth and latency demands. Our model includes the queuing delay depending on the traffic load in the model. Our extensive numerical evaluation based on real-world DC locations, demand patterns and resource provision costs shows how operational cost increases with traffic load, and we analyse the impact of different latency bounds on the performance of different virtual networks.

  • 46.
    Nasim, Robayet
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Taheri, Javid
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Optimizing Virtual Machine Consolidation in Virtualized Datacenters Using Resource Sensitivity2016In: Cloud Computing Technology and Science (CloudCom), 2016 IEEE International Conference on, IEEE, 2016, p. 168-175Conference paper (Refereed)
    Abstract [en]

    In virtualized datacenters (vDCs), dynamic consolidation of virtual machines (VMs) is used to achieve both energy-efficiency and load balancing among different physical machines (PMs). Using VM live migrations, we can consolidate VMs on a smaller number of hosts to power down unused PMs and save energy. Most migration schemes are however oblivious to the characteristics of services that run inside VMs, and thus may lead to migrations where VMs competing for the same resource type are packed on the same PM. As a result, VMs may suffer from significant resource contention and noticeable degradation in their performance. Using resource sensitivity values of VMs (ie, quantitative measures to reflect how much a VM is sensitive to its requested resources such as CPU, Mem, and Disk), we have designed a novel VM consolidation approach to optimize placement of VMs on available PMs. We validated our approach using five well-known applications/benchmarks with various resource demand signatures: varying from pure CPU/Mem/Disk-intensive to mixtures of them. Our extensive numerical evaluation illustrates that, for the same power consumption, our approach improve the performance of cloud services by 9 - 12\%, on average, when compared with current sensitivity oblivious approaches.

  • 47.
    Nasim, Robayet
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Zola, Enrica
    Universitat Politècnica de Catalunya (UPC), Spain..
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Robust Optimization for Energy-Efficient Virtual Machine Consolidation in Modern Datacenters2018In: Cluster Computing, ISSN 1386-7857, E-ISSN 1573-7543, Vol. 21, no 3, p. 1681-1709Article in journal (Refereed)
    Abstract [en]

    Energy efficient Virtual Machine (VM) consolidation in modern data centers is typically optimized using methods such as Mixed Integer Programming, which typically require precise input to the model. Unfortunately, many parameters are uncertain or very difficult to predict precisely in the real world. As a consequence, a once calculated solution may be highly infeasible in practice. In this paper, we use methods from robust optimization theory in order to quantify the impact of uncertainty in modern data centers. We study the impact of different parameter uncertainties on the energy efficiency and overbooking ratios such as e.g. VM resource demands, migration related overhead or the power consumption model of the servers used. We also show that setting aside additional resource to cope with uncertainty of workload influences the overbooking ratio of the servers and the energy consumption. We show that, by using our model, Cloud operators can calculate a more robust migration schedule leading to higher total energy consumption. A more risky operator may well choose a more opportunistic schedule leading to lower energy consumption but also higher risk of SLA violation.

  • 48.
    Nordling, Anders
    Karlstad University, Faculty of Arts and Education.
    Kompletterande undervisningsmaterial för gymnasiekursen Kommunikationsnät 12012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 49.
    Pieskä, Marcus
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    TCP Performance over 5G mmWave Links - Tradeoff between Capacity and Latency2017In: 2017 IEEE 13th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob), IEEE, 2017, p. 385-394Conference paper (Refereed)
    Abstract [en]

    Recently, 5G systems started to explore the usage of mmWave bands both for access and backhaul. Cellular systems operating at such frequencies would achieve a significantly higher capacity than current systems due to the large frequency block available. Due to the propagation characteristics, highly directional mmWave links may frequently switch between Line-of-sight, Non Line-of-sight and outage if the beam is blocked by obstacles. Such intermittent connectivity combined with high throughput causes TCP to perform very badly. In this paper, we study the performance of several TCP variants over intermittent mmWave links. We focus on latency aspects, use ns-3 with extensions for mmWave links and evaluate the TCP performance with real Linux TCP stacks using the Direct Code Execution (DCE) framework. We also investigate the benefit of bufferbloat solutions such as CoDel, with different TCP variants. We investigate the impact of CoDels configuration parameters and different RTTs on TCP throughput, fairness and queueing delay. The problem of slow recovery of TCP after NLOS periods is less pronounced when multiple flows coexist under CoDel only if some of the flows have very short RTTs. However, under presence of NLOS, the fairness between different flows with different RTT values is reduced.

  • 50.
    Rabitsch, Alexander
    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).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    A Stream-Aware Multipath QUIC Scheduler for Heterogeneous Paths2018In: EPIQ 2018 - Proceedings of the 2018 Workshop on the Evolution, Performance, and Interoperability of QUIC, Part of CoNEXT 2018, Association for Computing Machinery (ACM), 2018, p. 29-35Conference paper (Refereed)
    Abstract [en]

    Multipath communication is an attractive solution to the increasing need for improving web performance, by allowing devices to aggregate the capacity of different network paths, which can thus lead to lower latencies. However, path asymmetry is known to incur performance issues for multipath transport protocols, such as head-of-line blocking (HoLB), as well as other issues. We propose a proof-of-concept algorithm for a stream-aware packet scheduler for Multipath QUIC, called Stream-Aware Earliest Completion First (SA-ECF). SA-ECF schedules the sending of stream data so that the completion of individual streams are not delayed by slower paths, while providing a fair allocation of the aggregated bandwidth based on stream priority information from HTTP/2. We compare the performance of SA-ECF with other packet schedulers for MPQUIC using measurements from a virtualized testbed. Our results show that SA-ECF is able to handle path heterogeneity well, and can provide lower stream completion times than non stream-aware schedulers.

12 1 - 50 of 59
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