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  • 151.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    On Packet Aggregation for VoIP in Wireless Meshed Networks2007Konferensbidrag (Refereegranskat)
  • 152.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Method and System for Centralized Control of User Associations in Wireless Mesh Networks2012Patent (Övrig (populärvetenskap, debatt, mm))
  • 153.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    Optimization of WLAN associations considering handover costs2012Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In Wireless Local Area Network (WLAN) hotspots the coverage areas of Access Points (APs) often overlap considerably. Current state of the art optimization models find the optimal AP for each user station by balancing the load across the network. Recent studies have shown that in typical commercial WLAN hotspots the median connection duration is short. In such dynamic network settings the mentioned optimization models might cause many handovers between APs to accommodate for user arrivals or mobility. We introduce a new mixed integer linear optimization problem that allows to optimize handovers but takes into account the costs of handovers such as signaling and communication interruption. Using our model and extensive numeric simulations we show that disregarding the handover costs leads to low performance. Based on this insight we design a new optimization scheme that uses estimates of future station arrivals and mobility patterns. We show that our scheme outperforms current optimization mechanisms and is robust against estimation errors

  • 154.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    Chow, Lawrence
    Stanford University.
    Collins, Bradley
    Stanford University.
    Bambos, Nicholas
    Stanford University.
    Daniel, Mellado
    Miguel, Sanchez
    A Software Defined Networking Approach for Handover Management with Real-Time Video in WLANs2012Konferensbidrag (Refereegranskat)
  • 155.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Sivchenko, Dmitry
    Method and system for deriving an aggregation delay for packet aggregation in a wireless network2011Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    System and method for deriving an aggregation delay for a packet aggregation in a wireless network comprising a controller for deriving an optimal aggregation delay at a network node depending on information relating to the channel quality related parameters at the network node in the wireless network.

  • 156.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Bayer, Nico
    Einsiedler, Hans-Joachim
    Sivchenko, Dmitry
    FUZPAG: A Fuzzy-Controlled Packet Aggregation Scheme for Wireless Mesh Networks2010Ingår i: Proceedings of the International Conference on Fuzzy Systems and Knowledge Discovery (FSKD'10), IEEE , 2010, s. 778-782Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless mesh networks (WMNs) are wireless multi-hop backhaul networks in which mesh routers relay traffic on behalf of clients or other routers. Due to large MAC layer overhead, applications such as Voice over IP, which send many small packets, show poor performance in WMNs. Packet aggregation increases the capacity of IEEE 802.11-based WMNs by aggregating small packets into larger ones and thereby reducing overhead. In order to have enough packets to aggregate, packets need to be delayed and buffered. Current aggregation mechanisms use fixed buffer delays or do not take into account the delay characteristics of the saturated IEEE 802.11 MAC layer. In this work, we present FUZPAG, a novel packet aggregation architecture for IEEE 802.11-based wireless mesh networks. It uses fuzzy control to determine the optimum aggregation buffer delay under the current channel utilization. By cooperation among neighboring nodes FUZPAG distributes the buffer delay in a fair way. We implemented and evaluated the system in a wireless mesh testbed. For different network topologies we show that FUZPAG outperforms standard aggregation in terms of end-to-end latency under a wide range of traffic patterns.

  • 157.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Bayer, Nico
    Sivchenko, Dmitry
    An Experimental Comparison of Burst Packet Transmission Schemes in IEEE 802.11-based Wireless Mesh Networks2010Ingår i: Proceedings of IEEE Global Telecommunications Conference (GLOBECOM) 2010, IEEE , 2010, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless mesh networks (WMNs) are wireless multihop networks comprised of mesh routers, which relay traffic on behalf of clients and other nodes. Using the standard IEEE 802.11 distributed coordination function (DCF) as MAC layer, a node needs to contend for the medium each time it wants to transmit a packet. This creates high overhead in particular for small packets and leads to poor performance for real-time applications such as Voice over IP (VoIP) or online gaming. Burst packet transmission can increase the efficiency. For example, with the Transmission Opportunity limit (TXOPlimit) in IEEE 802.11e, a station may transfer several packets without contending for the channel in between. Similarly, IP packet aggregation combines several IP packets together and sends them as one MAC Service Data Unit. Originally, both schemes have been developed for singlehop networks only. Thus the impact on WMNs is unclear if the packets need to contend over multiple hops. In this paper, we use measurements from a 9-node WMN testbed to compare TXOPs and IP packet aggregation for VoIP in terms of fairness, network capacity and quality of user experience. We show that for low networks loads, both TXOPs and IP packet aggregation increase the VoIP quality compared to IEEE 802.11 DCF. However, in highly loaded networks IP packet aggregation outperforms the other schemes.

  • 158.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Cavalcanti de Castro, Marcel
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Paolo Delia, Francesco
    Avallone, Stefano
    OLSR and Net-X as a Framework for Channel Assignment Experiments: Poster Presentation2009Ingår i: Proceedings of the 4th ACM international workshop on Experimental evaluation and characterization WiNTECH 09, NewYork: ACM , 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a software framework for channel assingment and routing experiments in multi-channel/multi-radio wireless mesh networks.Based on a plug-in architecture we develop a traffic demand-aware channel assignment algorithm. The evaluation in KAUMesh - an experimental multi-radio mesh network - shows around 30% throughput improvement with respect to a traffic un-aware channel assignment scheme

  • 159.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    Software Defined Networking for the Management and Operation of WLANs2013Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 160.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Sivchenko, Dmitry
    Theoretical and Experimental Analysis of the Channel Busy Fraction in IEEE 802.112010Ingår i: Proceedings of Future Network & Mobile Summit 2010, IEEE , 2010, s. 1-9Konferensbidrag (Refereegranskat)
    Abstract [en]

    Optimizing the operation of IEEE 802.11 networks requires to estimate the load of the wireless channel. The channel busy fraction, which is the fraction of time in which the wireless channel is sensed busy due to successful or unsuccessful transmissions, can be used as such indicator. It can be obtained from e.g. the IEEE 802.11k channel load report or hardware-specific interfaces. Previously, the channel busy fraction has been used as a metric for different purposes such as routing and admission control. However, a thorough evaluation of the relationship between the busy fraction and other important characteristics such as the collision probability and throughput is missing. In this paper, we present an analytical model to study the channel busy fraction in non-saturated IEEE 802.11 networks. We validate the model with measurements in a testbed. The predictions from the model match measurements well. Furthermore, we demonstrate how to apply the model to estimate the available link bandwidth. Using measurements obtained from a testbed operated at 6 Mbit/s, we show that the channel busy fraction allows an accurate prediction of the available bandwidth with an error smaller than 70 Kbit/s.

  • 161.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Staehle, Barbara
    Staehle, Dirk
    Pries, Rastin
    Hirth,, Matthias
    Measuring One-Way Delay in Wireless Mesh Networks: An Experimental Investigation2009Ingår i: Proceedings of the 4th ACM workshop on Performance monitoring and measurement of heterogeneous wireless and wired networks, New York: ACM , 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless Mesh networks are multi-hop networks mostly based on IEEE 802.11 technology and are considered as a viable alternative for providing broadband wireless Internet access. As a consequence, they require support for Quality of Service or advanced mechanisms for selecting Internet gateways. One important requiredinformation is the one-way delay between different nodes. In this paper, we have developed, implemented, and evaluated an one-way delay estimation technique for wireless mesh networks which is based on estimating intra node queuing and inter node forwarding delay. An IP-header option field is used to accumulate the per hop delay estimate to provide an end-to-end estimate. We also outline problems with the implementation and compare results with real one-way delays obtained from a 14 node mesh testbed.We show how estimation accuracy depends on network load and provide insights into further improvements

  • 162.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Vestin, Jonathan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    CloudMAC - Using OpenFlow to Process 802.11 MAC Frames in the Cloud2013Ingår i: PIK - Praxis der Informationsverarbeitung und Kommunikation, ISSN 0930-5157, Vol. 36, nr 1, s. 53-Artikel i tidskrift (Refereegranskat)
  • 163.
    Dely, Peter
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Vestin, Jonathan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Bayer, Nico
    Telekom Innovation Laboratories.
    Einsiedler, Hans
    Telekom Innovation Laboratories.
    Peylo, Christoph
    Telekom Innovation Laboratories.
    CloudMAC: An OpenFlow based Architecture for 802.11 MAC Layer Processing in the Cloud2012Ingår i: 2012 IEEE Globecom Workshops (GC Wkshps 2012): Proceedings of a meeting held 3-7 December 2012, Anaheim, California, USA, IEEE conference proceedings, 2012, s. 186-191Konferensbidrag (Refereegranskat)
  • 164.
    Di Felice, Marco
    et al.
    Department of Computer Science, University of Bologna, Italy.
    Chowdhury, Kaushik
    Department of Electrical and Computer Engineering, Northeastern University, Boston, USA.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Bononi, Luciano
    Department of Computer Science, University of Bologna, Italy.
    Adaptive Sensing Scheduling and Spectrum Selection in Cognitive Wireless Mesh Networks2011Ingår i: Proceedings of 20th International Conference on Computer Communications and Networks (ICCCN), IEEE conference proceedings, 2011, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cognitive Radio (CR) technology constitutes a promising approach to increase the capacity of Wireless Mesh Networks (WMNs). Using this technology, Mesh Routers (MRs) and the attached Mesh Clients (MCs) are allowed to opportunistically transmit on the licensed band, but under the constraint not to interfere with the Primary Users (PUs) of the spectrum. Thus, the effective deployment of CR- WMNs require that each MR must be able to: sense the current spectrum, select an available PU-free channel and perform the spectrum handoff to a new channel in case of PU arrival on the current one. How to coordinate these actions in the optimal way which maximizes the performance of the CR-WMNs while minimizing the interference to the PUs constitutes an open research issue in CR systems. In this paper, we propose an adaptive spectrum scheduling and allocation scheme which allows a MR to identify the best schedule of (i) when to sense the current channel, (ii) when to transmit, (iii) when to perform a spectrum handoff. Due the large number of parameters involved, we propose Reinforcement Learning (RL) techniques to allow a MR to learn by itself the optimal balance between spectrum sensing-exploitation- exploration actions based on network feedbacks coming from the MCs. We perform extensive simulations which confirm the adaptivity and efficiency of our approach in terms of increased throughput when compared with non-learning based schemes for CR-WMNs.

  • 165.
    Di Felice, Marco
    et al.
    Department of Computer Science, University of Bologna, Italy.
    Chowdhury, Kaushik Roy
    Department of Electrical and Computer Engineering, Northeastern University, Boston, USA.
    Kim, Wooseong
    Department of Computer Science, University of California, Los Angeles, USA.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Bononi, Luciano
    Department of Computer Science, University of Bologna, Italy.
    End-to-end Protocols for Cognitive Radio Ad Hoc Networks: An Evaluation Study2010Ingår i: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, Vol. 68, nr 9, s. 859-875Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cognitive radio ad hoc networks (CRAHNs) constitute a viable solution to solve the current problems of inefficiency in the spectrum allocation, and to deploy highly reconfigurable and self-organizing wireless networks. Cognitive radio (CR) devices are envisaged to utilize the spectrum in an opportunistic way by dynamically accessing different licensed portions of the spectrum. To this aim, most of the recent research has mainly focused on devising spectrum sensing and sharing algorithms at the link layer, so that CR devices can operate without interfering with the transmissions of other licensed users, also called primary users (PUs). However, it is also important to consider the impact of such schemes on the higher layers of the protocol stack, in order to provide efficient end-to-end data delivery. At present, routing and transport layer protocols constitute an important yet not deeply investigated area of research over CRAHNs. This paper provides three main contributions on the modeling and performance evaluation of end-to-end protocols (e.g. routing and transport layer protocols) for CRAHNs. First, we describe NS2-CRAHN, an extension of the NS-2 simulator, which is designed to support realistic simulation of CRAHNs. NS2-CRAHN contains an accurate yet flexible modeling of the activities of PUs and of the cognitive cycle implemented by each CR user. Second, we analyze the impact of CRAHNs characteristics over the route formation process, by considering different routing metrics and route discovery algorithms. Finally, we study TCP performance over CRAHNs, by considering the impact of three factors on different TCP variants: (i) spectrum sensing cycle, (ii) interference from PUs and (iii) channel heterogeneity. Simulation results highlight the differences of CRAHNs with traditional ad hoc networks and provide useful directions for the design of novel end-to-end protocols for CRAHNs.

  • 166.
    di stasi, Giovanni
    et al.
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Karlsson, Jonas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    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
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Combining Multi-Path Forwarding and Packet Aggregation for Improved Network Performance in Wireless Mesh Networks2014Ingår i: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 68, s. 26-37Artikel i tidskrift (Refereegranskat)
    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.

  • 167.
    Doolin, Kevin
    et al.
    Waterford Institute of Technology, Ireland.
    Pashalidis, Andreas
    NEC Europe Ltd., Heidelberg, Germany.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Mota, Telma
    PT Inovação S.A., Portugal.
    Context-Aware Multimedia Services in a Pervasive Environment: The Daidalos Approach2008Ingår i: Proceedings of the 2008 Ambi-Sys workshop on Software Organisation and MonIToring of Ambient Systems, ICST , 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    There is a clear trend towards making multimedia applications context-aware so as to customize them by taking into account any collection of information which may be relevant, such as e.g. user location. However, current multimedia services are dominated by IMS, which is seen as a service platform that uses the SIP protocol to access all services that the internet can provide. In this paper, we describe the Daidalos approach on making IMS based multi-media services context-aware. We also demonstrate, how generic sensor networks can be integrated into the context management system of our platform thus enabling sensor network detected events to influence behavior of context-aware multimedia applications

  • 168.
    Ehlert, Sven
    et al.
    Fraunhofer FOKUS, Berlin, Germany.
    Zhang, Ge
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Magedanz, Thomas
    Fraunhofer FOKUS, Berlin, Germany.
    Increasing SIP firewall performance by ruleset size limitation2008Ingår i: Proceedings of the IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2008), IEEE conference proceedings, 2008, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    To protect SIP communication networks from attacks, especially flooding attacks like denial-of-service or message spam, intrusion detection systems (IDS) are deployed at the ingress point of the network to filter potential malicious traffic. A key issue of IDS performance is the operation of its firewall to block malicious user requests. Depending on the complexity of the firewall ruleset, filtering performance of the IDS can decrease considerably during high-load flooding situations. In this paper we propose a scheme to increase IDS firewall performance by merging several similar rules into more general ones and ignoring lesser relevant rules to limit the number of firewall rules. We formalise a mathematical model to compute new firewall rules and show exemplary with traffic from SIP VoIP communication networks how the calculation can be performed. If applied to a VoIP IDS, the scheme can increase firewall thoughput considerably, while retaining most of its effectiveness.

  • 169.
    Eklund, Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Evaluation of Emulab as Experimental Platform by comparing TCP and SCTP2004Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    To be able to evaluate new protocols it is important to have access to good experimental environments. Several experiments are needed to verify different aspects of protocol performance as well as robustness under various network conditions. Emulab is a new public experimental platform which is available for remote users. The ambition is that Emulab should offer the user the possibility to perform both simulation and emulation of a network. In addition, Emulab offers access to an experimental live network. This thesis presents a study where a series of tests are performed on the Emulab platform and also gives an introduction to SCTP. The first objective of the thesis is to obtain practical experience and to evaluate the usability of Emulab and the second objective is to compare the throughput between the transport protocols TCP and SCTP. The experiences from using Emulab are very positive. The results show that Emulab is a reliable and robust platform with high availability. The throughput comparison did not reveal significant differences between SCTP and TCP under moderate traffic load. Further tests and analyses are necessary to obtain a clear view of the situation in a heavily loaded network

  • 170.
    Eklund, Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    On Switchover Performance in Multihomed SCTP2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The emergence of real-time applications, like Voice over IP and video conferencing, in IP networks implies a challenge to the underlying infrastructure. Several real-time applications have requirements on timeliness as well as on reliability and are accompanied by signaling applications to set up, tear down and control the media sessions. Since neither of the traditional transport protocols responsible for end-to-end transfer of messages was found suitable for signaling traffic, the Stream Control Transmission Protocol (SCTP) was standardized. The focus for the protocol was initially on telephony signaling applications, but it was later widened to serve as a general purpose transport protocol. One major new feature to enhance robustness in SCTP is multihoming, which enables for more than one path within the same association.

    In this thesis we evaluate some of the mechanisms affecting transmission performance in case of a switchover between paths in a multihomed SCTP session. The major part of the evaluation concerns a failure situation, where the current path is broken. In case of failure, the endpoint does not get an explicit notification, but has to react upon missing acknowledgements. The challenge is to distinguish path failure from temporary congestion to decide  when to switch to an alternate path. A too fast switchover may be spurious, which could reduce transmission performance, while a too late switchover also results in reduced transmission performance. This implies a tradeoff which involves several protocol as well as network parameters and we elaborate among these to give a coherent view of the parameters and their interaction. Further, we present a recommendation on how to tune the parameters to meet  telephony signaling requirements, still without violating fairness to other traffic.

    We also consider another angle of switchover performance, the startup on the alternate path. Since the available capacity is usually unknown to the sender, the transmission on a new path is started at a low rate and then increased as acknowledgements of successful transmissions return. In case of switchover in the middle of a media session the startup phase after a switchover could cause problems to the application. In multihomed SCTP the availability of the alternate path makes it feasible for the end-host to estimate the available capacity on the alternate path prior to the switchover. Thus, it would be possible to implement a more efficient startup scheme. In this thesis we combine different switchover scenarios with relevant traffic. For these combinations, we analytically evaluate and quantify the potential performance gain from utilizing an ideal startup mechanism as compared to the traditional startup procedure.

  • 171.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Improving mSCTP-based Vertical Handovers by Increasing the Initial Congestion Window2011Ingår i: / [ed] Johan Eklund,Karl-Johan Grinnemo, Anna Brunstrom, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless networks play an increasingly important role in our daily lives. However, the wireless landscape comprises serveralnetwork technologies, and which technology to use is often context dependent and varies over time: In urban areas, WiFi viaa WiFi hotspot might be the preferred access technology, while in rural areas 3G, HSPA or some other 3GPP technologymight be the only viable alternative. To this end, a large number of vertical handover solutions, ranging from link-level toapplication-level solutions, has been proposed in the past several years.We believe that the Stream Control Transmission Protocol and its extension for Dynamic Address Reconfiguration (mSCTP)make up an attractive vertical handover solution, especially in cases where there are little or no economic incentives to modify orupgrade the existing network infrastructure. Currently, we are implementing an mSCTP-based mobility management frameworkfor Android smartphones and tablets, and as part of that work we are considering ways of mitigating the effects of a handoveron ongoing transport sessions.A mobile terminal with several network interfaces may traverse different types of networks (WLAN, UMTS, HSPA).A seamless handover between these networks may be achieved by the transport protocol, Stream Control TransmissionProtocol(SCTP), with its multihoming facility (mSCTP), in conjunction with a mobility manager monitoring the availablenetwork interfaces. SCTP, a reliable transport protocol, closely related to TCP, encompasses slow-start in the beginning of asession. This slow-start phase is also activated to probe for network capacity on the target path after a handover, which couldresult in unncessarily reduced throughput in case of spare capacity in the network. The throughput degradation in could becrucial for an ongoing real time session, like video conferencing. In this study we have conducted experiments on the benefitof increasing the initial congestion window to reduce the negative impact of the slow start phase. We have by experimentsquantified the performance gain from an increasd initial window, and have seen that there a reduction in maximum transfertime for a message of about 50 % in scenarios with real-time video, compared to the default initial congestion window. Theimprovement is most prominent in sessions with high transfer delays. One easy, and thus very attractive, way to improveon the handover performance is to increase the initial congestion window on the handover target path. Although a seeminglycontroversal proposition, one should bear in mind that researchers at Google and other cloud computing companies are currentlystrongly promoting a drastic increase of TCP’s initial congestion window within IETF.

  • 172.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Impact of SACK delay and link delay on Failover performance in SCTP2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Stream Control Transmission Protocol (SCTP) was developed

    to support the transfer of telephony signaling over

    IP networks. One of the ambitions when designing SCTP

    was to offer a robust transfer of traffic between hosts. For

    this reason SCTP was designed to support multihoming,

    which gives the possibility to set up several paths between

    the same hosts in the same session. If the primary path between

    a source machine and a destination machine breaks

    down, the traffic may still be sent to the destination by utilizing

    one of the alternate paths. The failover that occurs

    when changing path is to be transparent to the application.

    Consequently, the time between occurrence of a break on

    the primary path until the traffic is run smoothly on one of

    the alternate paths is important. This paper presents experimental

    results concerning SCTP failover performance. The

    focus in this paper is to evaluate the impact of the SACK

    delay and link delay on the failover time as well as on the

    maximum transfer time for a single message, which complements

    earlier studies in this area. The results show a

    significant performance impact of the SACK delay as well

    as of the link delay. This suggests that the SACK delay

    is an important parameter to tune to enhance application

    transparency in failure situations

  • 173.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Performance of Network Redundancy Mechanisms in SCTP2005Rapport (Refereegranskat)
    Abstract [en]

    One of the ambitions when designing the Stream Control Transmission Protocol was to offer a robust transfer of traffic between hosts. For this reason SCTP was designed to support multihoming, which presumes the possibility to set up several paths between the same hosts in the same session. If the primary path between a source machine and a destination machine breaks down, the traffic may still be sent to the destination, by utilizing one of the alternate paths. The failover that occurs when changing path is to be transparent to the application.



    This paper describes the results from an experiment concerning SCTP failover performance, which means the time between occurrence of a break on the primary path until the traffic is run smoothly on the alternate path. The experiment is performed mainly to verify the Linux Kernel implementation of SCTP (LK-SCTP) and is run on the Emulab platform. The results will serve as a basis for further experiments.



    The experiment is performed in a network without concurrent traffic and in conclusion the results from the experiment correspond well to the values found in other studies and they are close to the theoretical best values. As expected the parameter Path.Max.Retrans has a great impact on the failover time. One observation is that the failover time and the max transfer time for a message are dependent upon the status in the network when the break of the primary path occurs.

  • 174.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Cheimonidis, Georgios
    Ismailov, Yuri
    Delay Penalty during SCTP Handover2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The rapidly growing interest in untethered Internet connections such as WLAN and 3G/4G mobile connections,calls for intelligent session management, not least in terms of handovers. As part of an effort to develop a SCTP-based session management framework, we are studying ways of improving the SCTP handover delay forreal-time traffic by optimizing the startup delay on the handover-target path. We have developed a theoretical model that predicts the transfer times of SCTP messages during the startup on a new path. This paper validates our model. It shows that the model can be used to predict message transfer times in variable bitrate flows. The paper further employs our model to study the startup delay penalty during handover for the spectrum of network conditions considered relevant for real-time traffic over mobile connections.

  • 175.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Cheimonidis, Georgios
    Ismailov, Yuri
    Impact of Slow Start on SCTP Handover Performance2011Ingår i: Proceedings of 20th International Conference on Computer Communications and Networks: ICCCN2011, IEEE conference proceedings, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The rapidly growing interest in untethered Internet connections, especially in terms of WLAN and 3G/4G mobile connections, calls for intelligent session management: a mobile device should be able to provide a reasonable end-user experience despite location changes, disconnection periods and, not least, handovers. As part of an effort to develop a SCTP-based session management framework that meets these criteria, we are studying ways of improving the SCTP handover delay for real-time traffic; especially the startup delay on the connection between a mobile device and the target access point. To obtain an appreciation of the theoretically feasible gains of optimizing the startup delay on the handover-target path, we have developed a model that predicts the transfer times of SCTP messages during slow start. This paper experimentally validates our model and demonstrates that it could be used to predict the message transfer times in a variable bitrate flow by approximating the variable flow with a constant dito. It also employs our model to obtain an appreciation of the startup delay penalties incured by slow start during handovers in typical mobile, real-time traffic scenarios.

  • 176.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    School of Information and Communication Technology, KTH Royal Institute of Technology.
    Baucke, Stephan
    Ericsson Research, Germany.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Tuning SCTP Failover for Carrier Grade Telephony Signaling2010Ingår i: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 54, nr 1, s. 133-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Stream Control Transmission Protocol (SCTP) has not only been selected as the signaling transport protocol of choice in IETF SIGTRAN, the architecture that bridges circuit-switched and IP-based mobile core networks, but also plays a pivotal role in SAE/LTE, the next-generation UMTS/HSPA networks. To meet the redundancy requirements of telecom signaling traffic, SCTP includes a failover mechanism that enables rerouting of traffic from an unreachable network path to a backup path. However, the recommendations provided by IETF on how to configure the SCTP failover mechanism to meet telecom signaling requirements are kept quite general and leave much of the tuning to the telecom equipment vendor and/or operator. Several works by us and others have been carried out to study the effect of different SCTP parameters on the failover performance. The main contribution of this paper is that it gives a coherent treatment of how to configure the SCTP failover mechanism for carrier-grade telephony signaling, and provides practically usable configuration recommendations. The paper also discusses an alternate or complementary way of optimizing the SCTP failover mechanism by relaxing the exponential backoff that foregoes a retransmission timeout in SCTP. Some results showing significantly reduced failover times by use of this mechanism, with only marginal deteriorating effects on a signaling network, are discussed and analyzed in the paper.

  • 177.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Efficient Scheduling to Reduce Latency for Signaling Traffic using CMT-SCTP2016Ingår i: 27th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), September 4-7, Valencia, Spain, IEEE, 2016, s. 2127-2132Konferensbidrag (Refereegranskat)
    Abstract [en]

    To mitigate delay spikes during transmission of bursty signaling traffic, concurrent multipath transmission (CMT) over several paths in parallel could be an option. Still, unordered delivery is a well known problem when concurrently transmitting data over asymmetric network paths, leading to extra delay due to Head-of-Line Blocking (HoLB). The Stream Control Transmission Protocol (SCTP), designed as a carrier for signaling traffic over IP, is currently being extended with support for CMT (CMT-SCTP). To reduce the impact of HoLB, SCTP has support for transmission of separate data flows, called SCTP streams. In this paper, we address sender scheduling to optimize latency for signaling traffic using CMT-SCTP. We present dynamic stream-aware (DS) scheduling, which utilizes the SCTP stream concept, and continuously considers the current network status as well as the data load to make scheduling decisions. We implement a DS scheduler and compare it against some existing schedulers. Our investigation suggests that DS scheduling could significantly reduce latency compared to dynamic path scheduling that does not consider streams. Moreover, we show that naive round-robin scheduling may provide low latency over symmetric network paths, but may transmit data on non-beneficial asymmetric network paths leading to increased latency. Finally, our results show that a static stream based approach, found beneficial for bulk traffic, is not appropriate for bursty signaling traffic. 

  • 178.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Implications of using a Large Initial Congestion Window to Improve mSCTP Handover Delay2012Ingår i: MOBILITY 2012 : The Second International Conference on Mobile Services, Resources, and Users / [ed] Josef Noll, University of Oslo & Movation, Norway, Alessandro Bazzi, CNR - IEIIT, Italy, IARIA , 2012, , s. 6s. 116-121Konferensbidrag (Refereegranskat)
    Abstract [en]

    The currently rather heterogeneous wireless landscape makes handover between different network technologies, so-called vertical handover, a key to a continued success for wireless Internet access. Recently, an extension to the Stream Control Transmission Protocol (SCTP) – the Dynamic Address Reconfiguration (DAR) extension – was standardized by IETF. This extension enables the use of SCTP for vertical handover. Still, the way vertical handover works in SCTP with DAR makes it less suitable for real-time traffic. Particularly, it takes a significant amount of time for the traffic to ramp up to full speed on the handover target path. In this paper, we study the implications of an increased initial congestion window for real-time traffic on the handover target path when competing traffic is present. The results clearly show that an increased initial congestion window could significantly reduce the transfer delay for real-time traffic, provided the fair share of the available capacity on the handover target path is sufficiently higher than the send rate required by the real-time flow. Additionally, we notice that this performance gain comes without penalizing the competing traffic.

  • 179.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    Tieto Enator AB, Karlstad, Sweden.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    On the Relation Between SACK Delay and SCTP Failover Performance for Different Traffic Distributions2008Ingår i: Proceedings on the Fifth International Conference on Broadband Communications, Networks and Systems, IEEE , 2008, s. 577-584Konferensbidrag (Refereegranskat)
    Abstract [en]

    The stream control transmission protocol (SCTP) is an important component in the ongoing evolution towards IP in the fixed and mobile telephone networks. It is the transport protocol being used in the ongoing deployment of IETFpsilas signaling transport (SIGTRAN) architecture for tunneling of traditional telephony signaling traffic over IP. Further SCTP represents an alternative for future SIP signaling traffic. Key to the success of SCTP is its ability to recover from network failures, in particular failed network paths. SCTP includes multihoming and a failover mechanism which should swiftly shift from a failed or unavailable network path to a backup path. However, several studies have shown that SCTPpsilas failover performance is dependent on factors both related to protocol parameters and network conditions. This paper complements these studies by providing a comprehensive evaluation of the impact of SACK delay under various traffic distributions. The results show a clear relation between the traffic distribution and the impact of the SACK delay on SCTP failover performance. Severe negative effects are observed for low intensity traffic composed of individual signaling messages. On the other hand, our results show limited impact of SACK delay for high intensity and bursty traffic. Furthermore, the results show a limited increase in network traffic by reducing the SACK delay at low traffic intensities and even less impact on network traffic at high traffic intensities. Based on these results we recommend a decrease of the SCTP SACK timer to a small value in signaling scenarios

  • 180.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    On the Use of an Increased Initial Congestion Window to Improve mSCTP Handover Performance2012Ingår i: WAINA 2012: 26th International Conference on Advanced Information Networking and Applications Workshops / [ed] Leonard Barolli, Tomoya Enokido, Fatos Xhafa, Makoto Takizawa, IEEE Press, 2012, s. 1101-1106Konferensbidrag (Refereegranskat)
    Abstract [en]

    With the wireless landscape being ratherheterogeneous, handover between different networktechnologies, so-called vertical handover, becomes keyto a continued success for wireless Internet access.Recently, an extension to the Stream Control Trans-mission Protocol (SCTP) – the Dynamic Address Re-configuration (DAR) extension – was standardized bythe IETF. This extension enables the use of SCTPfor vertical handover. Still, the way vertical handoverworks in SCTP with DAR makes it less suitable for real-time traffic. Particularly, it takes a significant amountof time for the traffic to ramp up to full speed on thehandover target path. In this paper, we study the ex-tent to which an increased initial congestion window onthe handover target path decreases the transfer delayspikes in real-time video traffic experienced during avertical handover. The impact on both standard andhigh-definition video traffic is considered. The resultsof our study suggest that an increased initial congestionwindow does indeed significantly decrease the spikes inthe video traffic. However, the results also indicate thatit does not resolve the problem altogether.

  • 181.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    School of Information and Communication Technology, KTH Royal Institute of Technology.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Theoretical Analysis of an Ideal Startup Scheme in Multihomed SCTP2010Ingår i: Networked Services and Applications - Engineering, Control and Management: 16th EUNICE/IFIP WG 6.6 Workshop, EUNICE 2010, Trondheim, Norway, June 28-30, 2010 / [ed] Finn Arve Aagesen, Svein Johan Knapskog, Springer , 2010, s. 155-166Konferensbidrag (Refereegranskat)
    Abstract [en]

    SCTP congestion control includes the slow-start mechanism to probe the network for available bandwidth. In case of a path switch in a multihomed association, this mechanism may cause a sudden drop in throughput and increased message delays. By estimating the available bandwidth on the alternate path it is possible to utilize a more efficient startup scheme. In this paper, we analytically compare and quantify the degrading impact of slow start in relation to an ideal startup scheme. We consider three different scenarios where a path switch could occur. Further, we identify relevant traffic for these scenarios. Our results point out that the most prominent performance gain is seen for applications generating high traffic loads, like video conferencing. For this traffic, we have seen reductions in transfer time of more than 75% by an ideal startup scheme. Moreover, the results show an increasing impact of an improved startup mechanism with increasing RTTs

  • 182.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Stream-aware Scheduling to Improve Latency for Signaling Traffic using CMT-SCTP2016Konferensbidrag (Refereegranskat)
    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.

  • 183.
    Eldh, Sigrid
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Punnekkat, Sasikumar
    Mälardalens Högskola.
    Synergizing industrial needs and academic research for better software education2012Ingår i: Software Engineering Education based on Real-World Experiences (EduRex), 2012 First International Workshop, IEEE Press, 2012, s. 33-36Konferensbidrag (Refereegranskat)
    Abstract [en]

    The ubiquity of software is making every industry increasingly dependent on it for achieving their core products' functionality. The complexity in a telecommunication network requires not only thorough understanding of telecommunication per se, but software becomes equally interesting. This is the case with many industries, which rely more and more on software as their key enabler. Industry definitely needs a large number of software engineers with potential to be productive from day one. They are feeling impatient at the academic community for not being pragmatic. At the same time Academic community faces many challenges, which often make them thread a traditional path thus ignoring the industrial needs. We present some of these challenges from both the industrial and academic perspectives. We also present how we established a Master level advanced course on software verification and validation through mutual support and collaboration which became highly successful.

  • 184.
    Elsholz, Jan-Patrick
    et al.
    Institute of Distributed Systems, Ulm University, Germany.
    Schmidt, Holger
    Institute of Distributed Systems, Ulm University, Germany.
    Schober, Sven
    Institute of Distributed Systems, Ulm University, Germany.
    Hauck, Franz J
    Institute of Distributed Systems, Ulm University, Germany.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Instant-X: Towards a Generic API for Multimedia Middleware2009Ingår i: Proceedings of IEEE International Conference on Internet Multimedia Systems Architecture and Applications, IEEE Press, 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    The globalisation of our society leads to an increasing need for spontaneous communication. However, the development of such applications is a tedious and error-prone process. This results from the fact that in general only basic functionality is available in terms of protocol implementations and encoders/decoders. This leads to inflexible proprietary software systems implementing unavailable functionality on their own. In this work we introduce Instant-X, a novel component-based middleware platform for multimedia applications. Unlike related work, Instant-X provides a generic programming model with an API for essential tasks of multimedia applications with respect to signalling and data transmission. This API abstracts from concrete component implementations and thus allows replacing specific protocol implementations without changing the application code. Furthermore, Instant-X supports dynamic deployment, i.e., unavailable components can be automatically loaded at runtime. To show the feasibility of our approach we evaluated our Instant-X prototype regarding code complexity and performance.

  • 185. Endeshaw, T.
    et al.
    Garcia, Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Jakobsson, Andreas
    Fast Classification of Indecent Video by Low Complexity Repetitive Motion Detection2008Konferensbidrag (Refereegranskat)
  • 186. Escudero-Pascual, A.
    et al.
    Holleboom, Thijs Jan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Fischer Hübner, Simone
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Privacy for location data in mobile networks, a summary2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    EU Directive 2002/58/EC has introduced, by means of Art. 9, special protection for location data other than traffic data. In this paper, we argue that also location data within traffic data can contain sensitive information about the relative positioning and co-located displacements of mobile nodes and thus also

    requires special protection.



    Brief discussions are given to how mobility is supported in IP networks, to the level of privacy protection for location data that was introduced in the new European Union data protection directive, and to means of protecting privacy by technology. The concept of \textit{co-located displacements in

    MobileIP} is introduced and we show how the home agent will be able to determine whether or not a set of mobile nodes move in a co-located fashion.



    Finally we present how, also for location information within traffic data, privacy-enhancing technologies can be used to provide the level of privacy protection that is required by Art. 9 of the EU Directive 2002/58/EC for location data other than traffic data.

  • 187. Faigl, Zoltán
    et al.
    Fazekas, Péter
    Lindskog, Stefan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Analytical Analysis of the Performance Overheads of IPsec in Mobile IPv6 Scenarios2008Ingår i: Advances in Mobile and Wireless Communications: Views of the 16th IST Mobile and Wireless Communication Summit / [ed] István Frigyes, Janos Bito, and Péter Bakki, Berlin/Heidelberg, Germany: Springer-Verlag , 2008Kapitel i bok, del av antologi (Refereegranskat)
  • 188. Faigl, Zoltán
    et al.
    Fazekas, Péter
    Lindskog, Stefan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Performance Analysis of IPsec in MIPv6 Scenarios2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes an analysis of the performance overheads caused by the processing and space requirements of IPsec when protecting Mobile IPv6 (MIPv6) signaling. Signaling between the Mobile Nodes and the Home Agent (HA) in a large-scale reference scenario is considered. The analysis is based on queuing theory and focuses on the overall utilization of the HA by the MIPv6 signaling processes as well as the total mean response time for a mobility process in the network. The results can assist network designers in finding the most appropriate security configuration for their specific network and mobility scenario

  • 189. Faigl, Zoltán
    et al.
    Lindskog, Stefan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Experimental Evaluation of the Performance Costs of Different IKEv2 Authentication Methods2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an experimental evaluation of the costs of different IKEv2 authentication methods. The studied methods are pre-shared keys (PSK), extensible authentication protocol (EAP) using MD5 and TLS, which are typically referred to as EAP-MD5 and EAP-TLS, respectively. For the EAP-based methods RADIUS is used as AAA server. Different lengths of certification chains are studied in the EAP-TLS case. The paper first presents a brief overview of the considered authentication methods. Then, an experimental comparison of the costs for computations and messages transfers associated with the authentication methods are provided. The measurement results illustrate the practical costs involved for IKEv2 authentication, and show the performance implications of using different authentication methods. EAP-TLS is several times more demanding than both PSK and EAP-MD5. When EAP-TLS is used, the length of certificate chains also has a notable impact on performance

  • 190. Faigl, Zoltán
    et al.
    Lindskog, Stefan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    IKEv2 Performance when Protecting Mobile IPv6 Signaling2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes an analysis of the performance overheads caused by the processing and space requirements of the IKEv2 protocol using Diameter and EAP-TLS authentication when protecting Mobile IPv6 signaling. IKEv2 negotiation between mobile nodes, the home agent, and the AAA server in a large-scale reference scenario is considered. The analysis is based on queuing theory and focuses on the overall utilization of the home agent and the AAA server by the IKEv2 reauthentication processes as well as the total mean response time for such a process in the network

  • 191. Faigl, Zoltán
    et al.
    Lindskog, Stefan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Tóth, Katalin
    Providing Tunable Security in IEEE 802.11i Enabled Networks2006Rapport (Refereegranskat)
    Abstract [en]

    The basic idea of QoS is to provide mechanisms that can offer different service levels, which are expressed through well-defined parameters that are specified at run-time on the basis of need. Bit rate, throughput, delay, jitter, and packet loss rate are all examples of common QoS parameters suggested for packet networks. These parameters are all aimed to express (and guarantee) a certain service level with respect to reliability and/or performance. In this report, we investigate how security can be treated as yet another QoS parameter through the use of tunable security services. The main idea with this work is to let users specify a trade-off between security and performance through the choice of available security configuration(s). The performance metric used is latency. The concept is illustrated using the IEEE 802.11i wireless local area networking standard.

  • 192. Feiten, B.
    et al.
    Wolf, I.
    Guenkova-Luy, T.
    Schorr, A.
    Kassler, Andreas
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    New mode for rfc3640: AAC-BSAC with MPEG-21 gBSD: draft-feiten-avt-bsacmode-for-rfc3640-00.txt, Feb2005Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    This draft proposes a mode for RFC 3640 to support an MPEG-4 AAC-BSAC audio codec format with an optional attached bitstream description. The bitstream description employs the MPEG-21 generalized Bitstream Syntax Description Language (gBSDL). The description is attached as auxiliary header and can be used to support adaptation

  • 193. Fernández Gago, M. Carmen
    et al.
    Tountopoulos, Vassilis
    Fischer-Hübner, Simone
    Karlstads universitet, Institutionen för informationsteknologi.
    Nuñez, David
    Angulo, Julio
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för informatik och projektledning. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Pulls, Tobias
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Koulouris, Theo
    Tools for Cloud Accountability: A4Cloud Tutorial2015Ingår i: Privacy and Identity Management for the Future Internet in the Age of Globalisation: 9th IFIP WG 9.2, 9.5, 9.6/11.7, 11.4, 11.6/SIG 9.2.2 International Summer School, Patras, Greece, September 7-12, 2014, Revised Selected Papers / [ed] Jan Camenisch, Simone Fischer-Hübner, Marit Hansen, Cham: Springer, 2015, s. 219-236Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Cloud computing is becoming a key IT infrastructure technology being adopted progressively by companies and users. Still, there are issues and uncertainties surrounding its adoption, such as security and how users data is dealt with that require attention from developers, researchers, providers and users. The A4Cloud project tries to help solving the problem of accountability in the cloud by providing tools that support the process of achieving accountability. This paper presents the contents of the first A4Cloud tutorial. These contents include basic concepts and tools developed within the project. In particular, we will review how metrics can aid the accountability process and some of the tools that the A4Cloud project will produce such as the Data Track Tool (DTT) and the Cloud Offering Advisory Tool (COAT).

  • 194. Ferreira, Lucio
    et al.
    Perez-Romero, Jordi
    Tralli, Velio
    Fazekas, Peter
    Oliver, Miquel
    Lindskog, Stefan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Agustí, Ramón
    QoS Provision in Wireless Networks: Mobility, Security, and Radio Resource Management: An Overview2006Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 195.
    Fischer Hübner, Simone
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Anonymity2009Ingår i: Encyclopedia of Database Systems, Heidelberg: Springer , 2009, s. 90-91Kapitel i bok, del av antologi (Refereegranskat)
  • 196.
    Fischer Hübner, Simone
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    IT-Security and Privacy: Design and Use of Privacy-Enhancing Security Mechanisms2001Bok (Refereegranskat)
  • 197.
    Fischer Hübner, Simone
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Privacy and Security at Risk in the Global Information Society2000Rapport (Refereegranskat)
  • 198.
    Fischer Hübner, Simone
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Pseudonymity2009Ingår i: Encyclopedia of Database Systems / [ed] Liu, Ling; Özsu, M.Tamer, Heidelberg: Springer , 2009, s. 2207-Kapitel i bok, del av antologi (Refereegranskat)
  • 199.
    Fischer Hübner, Simone
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    The Conflict between Privacy and Digital Forensics2010Konferensbidrag (Refereegranskat)
  • 200.
    Fischer Hübner, Simone
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Unobservability2009Ingår i: Encyclopedia of Database Systems / [ed] Liu, Ling; Özsu, M.Tamer, Heidelberg: Springer , 2009, s. 3240-Kapitel i bok, del av antologi (Refereegranskat)
1234567 151 - 200 av 623
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