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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: ACM Digital Library, 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.
    Andersson, Jan-Olof
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Offloading INTCollector Events with P42019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In-Band Network Telemetry (INT) is a new technique in the area of Software-defined networking (SDN) for monitoring SDN enabled networks. INT monitoring provides fine-grained INT data with less load on the control plane since monitoring is done directly at the data plane. The collected INT data is added as packet headers "In-band" at each INT device along the flow path. The INT data is later composed into telemetry packets which are sent to a collector that is responsible for processing the INT data. The collector of the INT data needs to have good performance since there is a large amount of data that has to be processed quickly. INTCollector, a high performance collector of INT data, is a response to this challenge. The performance of INTCollector is optimized by implementing critical parts in eXpress Data Path (XDP), enabling fast packet processing. INTCollector is, moreover, able to reduce processing of INT data and the need for storage space since it employs a strategy where only important INT data is collected, decided by an internal event detection mechanism.The event detection mechanism in INTCollector can however be offloaded to the INT device itself, with possible perfomance benefits for the collector. Programming Protocol-Independent Packet Processors (P4) opens up this possibility by providing a language for programming network devices. This thesis presents an implementation of INT in P4 with offloaded event detection. We use a programmable P4 testbed to perform an experimental evaluation, which reveal that offloading does indeed benefit INTCollector in terms of performance. Offloading also comes with the advantage of  allowing parameters of the event detection logic at the data plane to be accessible to the control plane.

  • 3.
    Bernhard, David
    et al.
    University of Bristol, UK.
    Oksana, Kulyk
    Technische Universität Darmstadt, Germany.
    Volkamer, Melanie
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). Technische Universität Darmstadt, Germany.
    Security proofs for Participation privacy, receipt-freeness and ballot privacy for the helios voting scheme2017In: ARES '17 Proceedings of the 12th International Conference on Availability, Reliability and Security, New York: Association for Computing Machinery (ACM), 2017, article id UNSP 1Conference paper (Refereed)
    Abstract [en]

    The Helios voting scheme is well studied including formal proofs for verifiability and ballot privacy. However, depending on its version, the scheme provides either participation privacy (hiding who participated in the election) or verifiability against malicious bulletin board (preventing election manipulation by ballot stuffing), but not both at the same time. It also does not provide receipt-freeness, thus enabling vote buying by letting the voters construct receipts proving how they voted. Recently, an extension to Helios, further referred to as KTV-Helios, has been proposed that claims to provide these additional security properties. However, the authors of KTV-Helios did not prove their claims. Our contribution is to provide formal definitions for participation privacy and receipt-freeness that we applied to KTV-Helios. In order to evaluate the fulfillment of participation privacy and receipt-freeness, we furthermore applied the existing definition of ballot privacy, which was also used for evaluating the security of Helios, in order to show that ballot privacy also holds for KTV-Helios

  • 4.
    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

  • 5.
    Eklund, Johan
    et al.
    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.
    Grinnemo, Karl-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).
    Using multiple paths in SCTP to reduce latency for signaling traffic2018In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 129, p. 184-196Article in journal (Refereed)
    Abstract [en]

    The increase in traffic volumes as well as the heterogeneity in network infrastructure in the upcoming 5G cellular networks will lead to a dramatic increase in volumes of control traffic, i.e., signaling traffic, in the networks. Moreover, the increasing number of low-power devices with an on-off behavior to save energy will generate extra control traffic. These increased traffic volumes for signaling traffic, often generated as bursts of messages, will challenge the signaling application timing requirements on transmission. One of the major transport protocols deployed for signaling traffic in cellular networks is the Stream Control Transmission Protocol (SCTP), with support for multiple paths as well as for independent data flows. This paper evaluates transmission over several paths in SCTP to keep the latency low despite increasing traffic volumes. We explore different transmission strategies and find that concurrent multipath transfer over several paths will significantly reduce latency for transmission over network paths with the same or similar delay. Still, over heterogeneous paths, careful, continuous sender scheduling is crucial to keep latency low. To this end, we design and evaluate a sender scheduler that considers path characteristics as well as queuing status and data flows of different priority to make scheduling decisions. Our results indicate that by careful dynamic sender scheduling, concurrent multipath transfer could lead to reduced latency for signaling traffic irrespective of path or traffic characteristics.

  • 6.
    Fredriksson, Sofia
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Organizational adaptation towards artificial intelligence: A case study at a public organization2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Artificial intelligence has become commercialized and has created a huge demand on the market. However, few people know what the technology means and even scientist struggle to find a universal definition. The technology is complex and versatile with elements making it controversial. The concept of artificial intelligence has been studied in the technical field and several publications has made efforts to predict the impact that the technology will have on our societies in the future. Even if the technology has created a great demand on the market, empirical findings of how this technology is affecting organizations is lacking. There is thus no current research to help organizations adapt to this new technology.The purpose of this study is to start cover that research gap with empirical data to help organizations understand how they are affected by this paradigm shift in technology. The study is conducted as a single case study at a public organization with middle technological skills. Data has been collected through interviews, observations and reviewing of governing documents. Seventeen interviews were held with employees with different work roles in the administration. The data was then analyzed from a combined framework including technology, organizational adaptation and social sustainability.The study found that the organization is reactive in its adaptation process and lacking an understanding of the technology. The findings show that the concept of artificial intelligence is hard to understand but applicable and tangible examples facilitates the process. A better information flow would help the investigated organization to become more proactive in its adaptation and better utilize its personnel. The findings also show that there are ethical issues about the technology that the organization needs to process before beginning an implementation. The researcher also argues the importance of a joint framework when analyzing the organizational impact of artificial intelligence due to its complexity.

  • 7.
    Fritsch, Lothar
    et al.
    Norwegian Computing Center, Oslo.
    Groven, Arne-Kristian
    Norwegian Comp Ctr, Oslo, Norway..
    Strand, Lars
    Norwegian Comp Ctr, Oslo, Norway..
    A holistic approach to Open-Source VoIP security: Preliminary results from the EUX2010sec project2009In: Networks, 2009. ICN '09. Eighth International Conference on / [ed] Robert Bestak, Laurent George, Vladimir S. Zaborovsky, Cosmin Dini, IEEE , 2009, p. 275-280Conference paper (Refereed)
    Abstract [en]

    This paper describes the approach and preliminary results from the research project EUX2010sec. The project works closely with Voice-over-IP (VoIP) companies and users. It aims at providing better security of opera source VoIP installations. The work towards this goal is organized by gathering researchers and practitioners around several scientific activities that range from security modeling and verification up to testbed testing. The expected outcomes of the project are a solid scientific and practical understanding of the security options for setting tip VoIP infrastructures, particular guidance on secure, typical setups of such infrastructures, The project's special focus is on producing results relevant to the practitioners in the project, aiming at the stimulation of innovation and the provision of highest quality in open-source based VoIP products and services.

  • 8.
    Grunzke, Richard
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Risk Analysis of the applied RFID system: Project Stolpen2007Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [en]

    This thesis will be a risk analysis of a RFID-system for a logistical application. The system works as follows: Around Karlstad in Sweden there are three new weighing machines for lorries. The load weight will be measured for the police to control overweight and for logistical reasons such as issuing invoices and optimising the supply chain. The lorries do not have to stop to be weighed. They have to drive slowly over the weighing machine, so the loss of time is minimal. The lorries will be identified via RFID-tags. So every time a lorry will be driven over the weighing machine, the identification number and the measured weight will be logged and send to a database. In the future it is planed to store the weight on the tag itself. The task is now to analyse the RFID-communication and the transmission to the database. The thesis will contain several parts. First RFID in general and how RFID will be used in the application-scenario will be described. Next sections will be about the security and privacy requirements and the risks in detail. Then possible solutions are outlined and concrete suggestions are presented. Finally a conclusion will be drawn, which will show that the application has a low level of security.

  • 9.
    Hedman Fallquist, Mattias
    et al.
    Karlstad University. Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Johansson, Fredrik
    Karlstad University. Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Utvärdering av enhetstestning för Palasso2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The market-leading wage and PA-.system for the Swedish public sector Palasso is developed in Karlstad. In order to achieve the highest quality of code , the developing team behind Palasso has been conducting extensive testing. Testing is done to ensure that the software does what it should do. However, the testing has been done at a high level. In order to continue to evolve, the group that develops Palasso has started to look at the new development methods that have become popular in the computer industry in recent years. These methods are based on the use of tests as low as possible so-called unit tests.

    To examine the possibility for Palasso to use unit testing, the study has been divided into two parts. First, a study of existing frameworks to find the best suited one for Palasso. Then, by using the selected framework, a second study is conducted to see if it is possible integrate unit testing with the Palasso system. This part was divided into two methods.

    In the first method a existing functionality was redeveloped to show how the code should be structured and implemented to be suitable for unit tests. In the second method unit testing was introduced on legacy code to prove that it was possible to introduce unit test and that small changes can make the code more testable.

    The best suited framework for Palasso was TestNG. TestNG was chosen because it was easy to use and it had scalability. The second study showed that it is possible to integrate unit tests with the Palasso system. But it should be introduced when new modules are developed or when existing code is modified. The introduction of unit testing provides many advantages. It is concluded that the quality of the Palassos system would benefit from using unit testing.

  • 10. Larson, Ulf E.
    et al.
    Jonsson, Erland
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Guidance for Selecting Data Collection Mechanisms for Intrusion Detection2014In: Handbook of Research on Emerging Developments in Data Privacy / [ed] Manish Gupta, Hershey, PA, USA: IGI Global, 2014, p. 343-374Chapter in book (Refereed)
  • 11.
    Lundin, Reine
    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.
    Lindskog, Stefan
    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.
    An Investigation of Entropy of Selectively Encrypted Bitmap Images2012In: Computational Aspects of Social Networks (CASoN), 2012 Fourth International Conference on, IEEE, 2012, p. 238-243Conference paper (Refereed)
    Abstract [en]

    Selective encryption is a concept in which the main goal is to reduce computational cost while providing confidentiality by encrypting only chosen parts of the information to be protected. Previous work on selective encryption has mainly been aimed towards multimedia applications in order to reduce the overhead induced by encryption while still making the information perceptually secure to a desired protection level. This was accomplished by utilizing the fact that different parts of the information have different impacts on our perception senses, i.e., eyes and ears. How computationally secure the information is when using selective encryption has however only briefly been mentioned or rudimentarily analyzed. In this paper, we therefore investigate the security implications of selective encryption by generalizing the work on entropy of selectively encrypted strings to several dimensions and applying it to bitmap images. The generalization is done by constructing information neighborhoods that capture and model information dependencies in several dimensions.

  • 12.
    Mesodiakaki, Agapi
    et al.
    Department of Informatics, Aristotle University of Thessaloniki, Greece.
    Zola, Enrica
    UPC-BarcelonaTECH, Barcelona, Spain.
    Santos, Ricardo
    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.

  • 13. Paintsil, Ebenezer
    et al.
    Fritsch, Lothar
    Norsk Regnesentral.
    A Taxonomy of Privacy and Security Risks Contributing Factors2011In: IFIP Advances in Information and Communication Technology, ISSN 1868-4238, Vol. 352, p. 52-63Article in journal (Refereed)
  • 14. Paintsil, Ebenezer
    et al.
    Fritsch, Lothar
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Executable Model-Based Risk Analysis Method for Identity Management Systems: Using Hierarchical Colored Petri Nets Executable Model-Based Risk Assessment Method for Identity Management Systems2013In: Trust, Privacy, and Security in Digital Business: 10th International Conference, TrustBus 2013, Prague, Czech Republic, August 28-29, 2013. Proceedings / [ed] Furnell, S., Lambrinoudakis, C. & Lopez, J., Springer , 2013, p. 48-61Conference paper (Refereed)
    Abstract [en]

    Model-based risk analysis methods use graphical models to facilitate participation, risk communication and documentation and thereby improve the risk analysis process. Currently, risk analysis methods for identity management systems (IDMSs) mainly rely on time consuming and expensive manual inspections and lack graphical models. This article introduces the executable model-based risk analysis method (EM-BRAM) with the aim of addressing these challenges. The EM-BRAM employs graphical models to enhance risk analysis in IDMSs. It identifies risk contributing factors for IDMSs and uses them as inputs to a colored petri nets (CPNs) model of a targeted IDMS. It then verifies the system’s risk using CPNs’ state space analysis and queries. Currently, risk assessment methods for identity management systems (IDMSs) are lacking. This makes it difficult to compare IDMSs based on how they enhance privacy and security of system stakeholders. This article proposes the executable model-based risk assessment method (EM-BRAM) with the aim of addressing this challenge. The EM-BRAM identifies risk factors inherent in IDMSs and uses them as inputs to a colored petri nets (CPNs) model of a targeted IDMS. It then estimates or verifies the system’s security and privacy risks using CPNs’ state space analysis and queries.

  • 15.
    Persson, Robin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Ahlin, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Hemautomation: Spara energi genom att automatisera hemmet2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In today's society there is a significant focus on energy efficiency. Despite this, people leave lamps, televisions and computer screens etc. powered on unnecessarily. The goal of this project is to build a simple prototype for home automation where a user, via an application on a mobile phone, can switch on and off the power of an electrical products in the home and as well as being able to check whether such products are switched on or off. The prototype will also collect data on power consumption for these electrical products. This thesis describes the development of the prototype and addresses the choices made during the project. The project resulted in a prototype which after tests showed that there is potential to save energy by using home automation.

  • 16.
    Tjostheim, Ingvar
    et al.
    Norsk Regnesentral.
    Fritsch, Lothar
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Similar Information Privacy Behavior in 60-65s vs. 50-59ers - Findings From A European Survey on The Elderly2018In: Proceedings of the Mobile Privacy and Security for an Ageing Population workshop at the 20th International Conference on Human-Computer Interaction with Mobile Devices and Services (MobileHCI) 2018; September 3, 2018,  Barcelona, Spain, Barcelona: University of Bath; Cranfield university; Northumbria university, Newcastle; University of Portsmouth , 2018Conference paper (Other academic)
    Abstract [en]

    In this article, we presentfindings from a European survey with 10 countries on the subject sharing of personal information and concernsof the citizens. We compare the age group 60-65 years old with the age group 50-59, and in addition compare the Nordic region with the non-nordic population.There are more similarities than differences. The survey indicates that many of the elderly 60-65 take steps to protect their personal data.

  • 17.
    Towfik, Louie
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Häggmyr, Samuel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Mätverktyget Ping-Win2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Availability is important for a web service. It is therefore valuable to know when interferences occurs. With the help of monitoring of web services, one can acheive increased availability.Ping-Win is a monitoring service developed for the consultancy Knowit. Knowit is focusing on delivering web services for their clients. Ping-Win was developed with the purpose to monitor the services that Knowit are providing.The work was practised with an agile method, with five sprints in total, to be able to adjust the direction of the project  to fit the expectations that Knowit had on Ping-Win.The result was a web service with a complementing background service for continuous monitoring and also a database which was used to store the status messages.Ping-Win  was evaluated with a test were we let it monitor four websites during the Christmas holidays of 2017.

  • 18.
    Wahlberg, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Performance Comparison Study of Clusters on Public Clouds2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As cloud computing has become the more popular choice to host clusters in recent times there are multiple providers that offer their services to the public such as Amazon web services, Google cloud platform and Microsoft Azure. The decision of cluster provider is not only a decision of provider, it is also an indirect decision of cluster infrastructure. The indirect choice of infrastructure makes it important to consider any potential differences in cluster performance caused by the infrastructure in combination with the workload type, but also the cost of the infrastructure on the available public cloud providers.

    To evaluate whether or not there are any significant differences in either cluster cost or performance between the available public cloud providers, a performance comparison study was conducted. The study consisted of multiple clusters hosted on Amazon Web Services and the Google Cloud Platform. The clusters had access to five different instance types that each correspond to a specific number of available cores, amount of memory and storage. All clusters executed a CPU intensive, I/O intensive, and MapReduce workload while simultaneously having its performance monitored with regard to CPU, memory, and disk usage. The performance comparison study revealed that there are significant performance differences between clusters hosted on Amazon web services and Google cloud platform for the chosen workload types. Since there are significant differences it can be concluded that the choice of provider is crucial as it impacts the cluster performance. Comparing the selected instance types against each other with regard to performance and cost, reveals that a subset of them have better performance as well as lower cost. The instance types that is not a part of this subset, have either better performance or lower cost than its counterpart on the other provider.

  • 19.
    Yedugundla, Kiran
    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 Economic Sciences, Communication and IT, Centre for HumanIT.
    Probe or Wait: Handling tail losses using Multipath TCP2017In: 2017 IFIP Networking Conference (IFIP Networking) and Workshops, IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Packet losses are known to affect the performance of latency sensitive Internet applications such as media streaming and gaming. Transport protocols recover from packet loss in order to provide reliable end-to-end communication and improve user experience. The efficiency of loss recovery mechanisms influences the completion time of flows, and thus also the application performance as perceived by the end user. In this paper we focus on state-of-the-art loss recovery mechanisms for TCP and Multipath TCP. We use controlled tail loss scenarios to evaluate the performance of loss recovery mechanisms and, based on the observations, we propose an enhanced tail loss recovery mechanism for Multipath TCP, to improve the loss recovery time. Our experiment results, using the Linux Multipath TCP implementation, show consistent end-to-end latency performance improvement in considered scenarios.

  • 20. Zhang, Xiaojing
    et al.
    Lindberg, Therese
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Xiong, N.
    Vyatkin, Valeriy
    Mousavi, Atash
    Cooling Energy Consumption Investigation of Data Center IT Room with Vertical Placed Server2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 105, p. 2047-2052Article in journal (Refereed)
    Abstract [en]

    As energy consumption by cooling data center IT equipment can be over 40 % of total energy consumption, efficient cooling for large data centers is essential for reducing operation costs. Modern data centers are complex systems involving IT facilities, power system, cooling and ventilation systems. In our previous work, literature study was made to investigate available data center energy consumption models; and energy consumption models for data center IT room with distributed air flow control were developed. In this paper, the models are further extended and developed to cover the combined distributed air flow control and vertical placed servers in raised floor ventilation system. Simulation of the three types of ventilation systems with Even load, Idle server and Uneven load scenarios showed that significant cooling energy consumed by a traditional ventilation system can be saved by applying the proposed new concept and method. (C) 2017 The Authors. Published by Elsevier Ltd.

  • 21. Zola, Enrica
    et al.
    Kassler, Andreas
    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).
    Kim, Wooseong
    Joint User Association and Energy Aware Routing for Green Small Cell mmWave Backhaul Networks2017In: 2017 IEEE Wireless Communications and Networking Conference (WCNC), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    A dense deployment of small cells is one of the key characteristics envisioned for future 5G mobile networks in order to provide the required capacity increase. To cut cabling costs, small cells are foreseen to form multihop topologies using high capacity backhaul wireless links in the mmWave bands. Such small cells are deployed within the coverage area of a macro cell (eNB) to provide localized capacity where needed according to the well known Heterogeneous Network concept (HetNet). However, green networking will be very important because powering on unnecessarily a massive amount of small cells may lead to increased OPEX and CO2 emission. In this paper, we propose an optimization model that minimizes the total power consumption of 5G HetNets deployments while providing the required capacity and coverage. Our model jointly optimizes the user association, routing in the multihop backhaul and decides to power on or off the small cells to serve the user demands. Our numerical evaluation show significant power savings over a large range of traffic demand distributions while keeping the blocking probability low.

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