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  • 1.
    Afzal, Zeeshan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Lindskog, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Partial Signature Matching in an MPTCP World using Insert-only Levenshtein DistanceManuscript (preprint) (Other academic)
  • 2.
    Afzal, Zeeshan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Lindskog, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Slice Distance: An Insert-Only Levenshtein Distance with a Focus on Security Applications2018In: Proceedings of NTMS 2018 Conference and Workshop, New York: IEEE, 2018, p. 1-5Conference paper (Refereed)
    Abstract [en]

    Levenshtein distance is well known for its use in comparing two strings for similarity. However, the set of considered edit operations used when comparing can be reduced in a number of situations. In such cases, the application of the generic Levenshtein distance can result in degraded detection and computational performance. Other metrics in the literature enable limiting the considered edit operations to a smaller subset. However, the possibility where a difference can only result from deleted bytes is not yet explored. To this end, we propose an insert-only variation of the Levenshtein distance to enable comparison of two strings for the case in which differences occur only because of missing bytes. The proposed distance metric is named slice distance and is formally presented and its computational complexity is discussed. We also provide a discussion of the potential security applications of the slice distance.

  • 3.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Impact of TCP Congestion Control on Bufferbloat in Cellular Networks2013In: Proceedings of the 14th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2013) / [ed] Angelos Lazaris, Balaji Rengarajan, IEEE Press, 2013Conference paper (Refereed)
    Abstract [en]

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

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

  • 4.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Observations of Bufferbloat in Swedish Cellular Networks2013In: Proceedings of the 9th Swedish National Computer Networking Workshop (SNCNW 2013) / [ed] Bengt Ahlgren, 2013Conference paper (Refereed)
  • 5.
    Asplund, Katarina
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Garcia, Johan
    Karlstad University, Division for Information Technology.
    Schneyer, Sean
    Karlstad University, Division for Information Technology.
    Grinnemo, Karl-Johan
    Karlstad University, Division for Information Technology.
    PRTP: A Partially Reliable Transport Protocol for Multimedia Applications: Background, Information and Analysis1999Report (Other academic)
  • 6.
    Asplund, Katarina
    et al.
    Karlstad University, Division for Information Technology.
    Garcia, Johan
    Brunstrom, Anna
    Schneyer, Sean
    Decreasing Transfer Delay Through Partial ReliabilityManuscript (preprint) (Other (popular science, discussion, etc.))
  • 7.
    Asplund, Katarina
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Schneyer, S.
    Decreasing Transfer Delay Through Partial Reliability2000Conference paper (Refereed)
  • 8.
    Beckman, Claes
    et al.
    KTH, Center for Wireless Systems.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    On the Impact of Velocity on the Train-to-Earth MIMO Propagation Channel: Statistical Observations and Qualitative Analysis2017In: 2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, IEEE, 2017, p. 1865-1866Conference paper (Refereed)
    Abstract [en]

    We provide measured data collected from 97 trains completing over 7000 journeys in Sweden showing that the throughput over LTE is impacted by train velocity. In order to explain these observations we assume that the underlying causes can be found in the implementation of the MIMO system into LTE Rel. 8 and the diffuse scattering of signals from ground reflections.

  • 9.
    Brunström, Anna
    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.
    Alfredsson, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    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.
    NEWCOM DR6.2: First report on frameworks/models matching Department 6 needs2005Report (Refereed)
    Abstract [en]

    During the first phase of NEWCOM the focus areas of Department 6 were identified and refined. A number of relevant knowledge gaps were identified for the areas transport protocols, architectures and cross-layer aspects, and modelling. In this deliverable we describe a first set of frameworks/models to support research integration within the Department. The integration approach and the defined models/frameworks are described for each one of the selected knowledge gaps. The deliverable also includes a report on tools, software libraries and traces that can be shared between the partners

  • 10.
    Brunström, Anna
    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.
    Asplund, Katarina
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Enhancing TCP Performance by Allowing Controlled Loss2000Conference paper (Refereed)
  • 11.
    Brunström, Anna
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    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.
    NEWCOM DR6.4: Proceedings of the Newcom Department 6 Second Technical Workshop2005Report (Refereed)
    Abstract [en]

    The Second Newcom Department 6 Technical Workshop was organized in Barcelona on September 16-17, 2005. The workshop program contained 6 presentations and provided a good overview of ongoing research integration activities within the department. All of the three areas of the department, transport protocols, architectures and cross-layer aspects, and modelling were represented with presentations. This deliverable contains the presentation material from the workshop. The included presentations are:



    - Westwood-SCTP: A Transport Protocol for Traffic Balancing on Multihomed Hosts

    - Transport Layer Handover using SCTP

    - The Optimization of Transport Protocol over Ad-Hoc Networks

    - Wireless Networks Emulation

    - An Analytical Model of Rate-Controlled MPEG Video Sources in a UMTS Network

    - An Analytical Model of a Rate-controlled MPEG-4 Video Source Capturing both Intra-frame and Inter-frame Correlation



    As an option, a supporting paper for the presentation could also be supplied by the authors. The

    deliverable contains supporting articles for two of the presentations

  • 12.
    Brunström, Anna
    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.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    NEWCOM DR6.6: Second report on common frameworks/models matching Department 62006Report (Refereed)
    Abstract [en]

    Work within Department 6 of NEWCOM is organized into the areas transport protocols, architectures and cross-layer aspects, and modelling. In this deliverable we provide a second report on the frameworks/models used to support research integration within the Department. The integration approach and the defined models/frameworks are described for each one of the three areas of the department. The deliverable also includes an updated report on tools, software libraries and traces that can be shared between the partners

  • 13.
    Brunström, Anna
    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.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    NEWCOM DR6.7: Proceedings of the Newcom Department 6 Second Technical Workshop2006Report (Refereed)
    Abstract [en]

    The Third Newcom Department 6 Technical Workshop was organized in Catania, Italy, on February 2, 2006. The workshop program contained 4 presentations and contained reports on ongoing integrated research activities as well as presentation intended to initiate additional joint research within the department. All of the three areas of the department, transport protocols, architectures and cross-layer

    aspects, and modelling were represented with presentations. This deliverable contains the presentation material from the workshop. The included presentations are:



    - P2P-based Video transmission in wireless networks

    - Transport Layer Handover using SCTP

    - WIPEMU 4G System Emulation and Sample Results

    - Wireless Networks Emulation



    Where available the presentation notes are also included with the presentations

  • 14.
    Brunström, Anna
    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.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    NEWCOM DR6.9: Proceedings of the Newcom Department 6 Fourth Technical Workshop2006Report (Refereed)
    Abstract [en]

    The Fourth Newcom Department 6 Technical Workshop was organized in Toulouse, France, on September 13-14, 2006. The workshop program contained 6 presentations and contained reports on ongoing integrated research activities as well as presentation intended to initiate additional joint research activities between the partners. All of the three areas of the department, transport protocols, architectures and cross-layer aspects, and modelling were represented with presentations. This deliverable contains the presentation material from the workshop. The included presentations are:



    - P2P Video Transmission over Heterogeneous Wired/Wireless Networks: A Starting Point for Integrated Research

    - DCCP Overview and First Experiments

    - Estimation of the SCTP Failover Time

    - Improving End to End Goodput of Ad Hoc Networks with SCTP Multihoming

    - A Taxonomy and Survey of SCTP Research

    - Integrating KAUnet and SWINE



    Where available the presentation notes are also included with the presentations

  • 15.
    Budzisz, Łukasz
    et al.
    Technische Universität Berlin, Berlin, Germany.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Ferrús, Ramon
    Universitat Politècnica de Catalunya, Barcelona, Spain.
    A taxonomy and survey of SCTP research2012In: ACM Computing Surveys, ISSN 0360-0300, E-ISSN 1557-7341, Vol. 44, no 4Article in journal (Refereed)
    Abstract [en]

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

  • 16. Conchon, Emmanuel
    et al.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Pérennou, Tanguy
    Diaz, Michel
    Improved IP-level Emulation for Mobile and Wireless Systems2007In: Proceedings IEEE Wireless Communications and Networking Conference (WCNC07), IEEE Communications Society, 2007, p. 3592-3597Conference paper (Refereed)
  • 17.
    Conchon, Emmanuel
    et al.
    Université de Toulouse.
    Pérennou, Tanguy
    Université de Toulouse.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Diaz, Michel
    W-NINE: A Two-stage Emulation Platform for Mobile and Wireless Systems2010In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2010, p. 1-20Article in journal (Refereed)
    Abstract [en]

    More and more applications and protocols are now running on wireless networks. Testing         the implementation of such applications and protocols is a real challenge as the position of the mobile terminals and environmental effects strongly affect the overall performance. Network emulation is often perceived as a good trade-off between experiments on operational wireless networks and discrete-event simulations on Opnet or ns-2. However, ensuring repeatability and realism in network emulation while taking into account mobility in a wireless environment is very difficult. This paper proposes a network emulation platform, called W-NINE, based on off-line computations preceding online pattern-based traffic shaping. The underlying concepts of repeatability, dynamicity, accuracy, and realism are defined in the emulation context. Two different simple case studies illustrate the validity of our approach with respect to these concepts.

  • 18. Endeshaw, T.
    et al.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Jakobsson, Andreas
    Fast Classification of Indecent Video by Low Complexity Repetitive Motion Detection2008Conference paper (Refereed)
  • 19.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    A clustering-based analysis of DPI-labeled video flow characteristics in cellular networks2017In: Proceedings of the IM 2017 - 2017 IFIP/IEEE International Symposium on Integrated Network Management, New York: IEEE, 2017, p. 1-4Conference paper (Refereed)
    Abstract [en]

    Using a specially instrumented deep packet inspection (DPI) appliance placed inside the core network of a commercial cellular operator we collect data from almost four million flows produced by a `heavy-hitter' subset of the customer base. The data contains per packet information for the first 100 packets in each flow, along with the classification done by the DPI engine. The data is used with unsupervised learning to obtain clusters of typical video flow behaviors, with the intent to quantify the number of such clusters and examine their characteristics. Among the flows identified as belonging to video applications by the DPI engine, a subset are actually video application signaling flows or other flows not carrying actual transfers of video data. Given that DPI-labeled data can be used to train supervised machine learning models to identify flows carrying video transfers in encrypted traffic, the potential presence and structure of such `noise' flows in the ground truth is important to examine. In this study K-means and DBSCAN is used to cluster the flows marked by the DPI engine as being from a video application. The clustering techniques identify a set of 4 to 6 clusters with archetypal flow behaviors, and a subset of these clusters are found to represent flows that are not actually transferring video data.

  • 20.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    A Fragment Hashing Approach for Scalable and Cloud-Aware Network File Detection2018In: Proceedings of NTMS 2018 Conference and Workshop, New York: IEEE, 2018, p. 1-5Conference paper (Refereed)
    Abstract [en]

    Monitoring networks for the presence of some particular set of files can, for example, be important in order to avoid exfiltration of sensitive data, or combat the spread of Child Sexual Abuse (CSA) material. This work presents a scalable system for large-scale file detection in high-speed networks. A multi-level approach using packet sampling with rolling and block hashing is introduced. We show that such approach together with a well tuned implementation can perform detection of a large number of files on the network at 10 Gbps using standard hardware. The use of packet sampling enables easy distribution of the monitoring processing functionality, and allows for flexible scaling in a cloud environment. Performance experiments on the most run-time critical hashing parts shows a single-thread performance consistent with 10Gbps line rate monitoring. The file detectability is examined for three data sets over a range of packet sampling rates. A conservative sampling rate of 0.1 is demonstrated to perform well for all tested data sets. It is also shown that knowledge of the file size distribution can be exploited to allow lower sampling rates to be configured for two of the data sets, which in turn results in lower resource usage.

  • 21.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    An Evaluation of Side-Information Assisted Forensic Hash Matching2014In: Computer Software and Applications Conference Workshops (COMPSACW), 2014 IEEE 38th International) / [ed] Chang, CK; Gao, Y; Hurson, A; Matskin, M; McMillin, B; Okabe, Y; Seceleanu, C; Yoshida, K, IEEE Press, 2014, p. 331-336Conference paper (Refereed)
    Abstract [en]

    Investigations involving digital forensics typically include file hash matching procedures at one or more steps in the examination. File hash matching is typically done by computing a complete file hash value for each file on a storage device and comparing that to a pre-computed hash list. This work examines how various improvements to the basic technique impact the time required to perform hash matching. Specifically, side-information assisted approaches are evaluated in this work. By utilizing side-information such as file sizes and pre-hashes in addition to the traditional hash values, we find that it is possible to considerably decrease the amount of time required to perform file hash matching. A simulation model is used to evaluate the potential time saving over a range of storage devices and using five different empirically derived file size distribution datasets totaling 36 million file sizes. The results indicate that side-information assisted hashing provides a considerable reduction of the time required, ranging between 5% and 99%, with the majority of cases providing reductions with more than 50%.

  • 22.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Application and Transport Layer Flexibility - An Image Transfer Example2002Report (Other academic)
  • 23.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Computer Assisted Reasoning as a Support for Knowledge Management2014In: ECKM 2014 - Proceedings og the 15th European Conference on Knowledge Management: Polytechnic Institute of Santarem Portugal 4-5 September 2014 / [ed] Vivas, C. & Sequeira, P., 2014, Vol. 3, p. 377-385Conference paper (Refereed)
  • 24.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Duplications and Misattributions of File Fragment Hashes in Image and Compressed Files2018In: Proceedings of NTMS 2018 Conference and Workshop, New York: IEEE, 2018, p. 1-5Conference paper (Refereed)
    Abstract [en]

    Hashing is used in a wide variety of security contexts. Hashes of parts of files, fragment hashes, can be used to detect remains of deleted files in cluster slack, to detect illicit files being sent over a network, to perform approximate file matching, or to quickly scan large storage devices using sector sampling. In this work we examine the fragment hash uniqueness and hash duplication characteristics of five different data sets with a focus on JPEG images and compressed file archives. We consider both block and rolling hashes and evaluate sizes of the hashed fragments ranging from 16 to 4096 bytes. During an initial hash generation phase hash metadata is created for each data set, which in total becomes several several billion hashes. During the scan phase each other data set is scanned and hashes checked for potential matches in the hash metadata. Three aspects of fragment hashes are examined: 1) the rate of duplicate hashes within each data set, 2) the rate of hash misattribution where a fragment hash from the scanned data set matches a fragment in the hash metadata although the actual file is not present in the scan set, 3) to what extent it is possible to detect fragments from files in a hashed set when those files have been compressed and embedded in a zip archive. The results obtained are useful as input to dimensioning and evaluation procedures for several application areas of fragment hashing.

  • 25.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Examining the Performance for Forensic Detection of Rare Videos Under Time Constraints2015In: SECRYPT 2015: Proceedings of the 12th International Conference on Security and Cryptography / [ed] Mohammad S. Obaidat, Pascal Lorenz, Pierangela Samarati, SciTePress, 2015, p. 419-426Conference paper (Refereed)
  • 26.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Explicit and Implicit Loss Notification for Error-prone Links2003Conference paper (Refereed)
    Abstract [en]

    In certain wireless environments the common transport protocol assumption that all packet losses are due to congestion may not hold true. If transport protocols react identically to both congestion and non-congestion related losses, performance will degrade. To avoid this performance problem, transport protocols must be able to differentiate between losses that are due to congestion and losses that are due to wireless link errors. Various loss differentiation techniques exist, some based on the sender side and some on the receiver side. If the loss differentiation is performed at the receiver, loss notification is needed to inform the sender of the loss cause. The sender use the loss notification information to adapt its retransmission and congestion avoidance behavior. The work in this paper examines the effectiveness of two different notification schemes that are to be used in conjunction with receiver based loss differentiation. The first scheme uses a TCP option to explicitly convey the a loss counter and the sequence number of the last corrupted packet. The second scheme uses the generation of additional dup-acks as a way to implicitly influence the retransmission and congestion behavior of the sender. The advantage of the second scheme is that it requires no changes at the sender side TCP implementation. However, since the second scheme can not change the basic loss behavior of halving the congestion window of TCP, its performance is reduced in relation to the first scheme. This paper provides a description of the design of these two loss notification schemes. Additionally, an experimental evaluation is presented, based on a FreeBSD kernel implementation of the two notification schemes in conjunction with checksum based loss differentiation

  • 27.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    FIVES and P2P-based Intelligence Gathering2009Conference paper (Other (popular science, discussion, etc.))
  • 28.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    FIVES D1.4: Annual report2010Report (Refereed)
  • 29.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Improving Performance in Heterogeneous Networks: A Transport Layer Centered Approach2005Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The evolution of computer communications and the Internet has led to the emergence of a large number of communication technologies with widely different capabilities and characteristics. While this multitude of technologies provides a wide array of possibilities it also creates a complex and heterogeneous environment for higher-layer communication protocols. Specific link technologies, as well as overall network heterogeneity, can hamper user-perceived performance or impede end-to-end throughput. In this thesis we examine two transport layer centered approaches to improve performance.



    The first approach addresses the decrease in user satisfaction that occurs when web waiting times become too long. Increased transport layer flexibility with regards to reliability, together with error-resilient image coding, is used to enable a new trade-off. The user is given the possibility to reduce waiting times, at the expense of image fidelity. An experimental examination of this new functionality is provided, with a focus on image-coding aspects. The results show that reduced waiting times can be achieved, and user studies indicate the usefulness of this new trade-off.



    The second approach concerns the throughput degradations that can occur as a consequence of link and transport layer interactions. An experimental evaluation of the GSM environment shows that when negative interactions do occur, they are coupled to large variability in link layer round-trip times rather than simply to poor radio conditions. Another type of interaction can occur for link layers which expose higher layers to residual bit errors. Residual bit-errors create an ambiguity problem for congestion controlled transport layer protocols which cannot correctly determine the cause for a loss. This ambiguity leads to an unnecessary throughput degradation. To mitigate this degradation, loss differentiation and notification mechanisms are proposed and experimentally evaluated from both performance and fairness perspectives. The results show that considerable performance improvements can be realized. However, there are also fairness implications that need to be taken into account since the same mechanisms that improve performance may also lead to unfairness towards flows that do not employ loss differentiation.

  • 30.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    JPEG Transcoding - Efficiency and Robustness Aspects2002Report (Other academic)
  • 31.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Quantifying the Benefits of File Size Information for Forensic Hash Matching2012In: Proceedings of the International Conference on Security and Cryptography (SECRYPT 2012) / [ed] Pierangela Samarati, Wenjing Lou, Jianying Zhou, Rome: INSTICC Press, 2012Conference paper (Refereed)
  • 32.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    The GATM Computer Assisted Reasoning Framework in a Security Policy Reasoning Context2014In: Proceedings of COGNITIVE 2014, The Sixth International Conference on Advanced Cognitive Technologies and Applications, International Academy, Research and Industry Association (IARIA), 2014, p. 215-219Conference paper (Refereed)
    Abstract [en]

    Humans are often faced with the need to make decisions regarding complex issues where multiple interests need to be balanced, and where there are a number of complex arguments weighing in opposite directions. The ability of humans to understand and internalize the underlying argumentation structure resulting from reasoning about complex issues is limited by the human cognitive ability. The cognitive limit can manifest itself both in relation to an inappropriate level and amount of detail in the presentation of information, as well as in the structuring of the information and the representation of the interrelationships between constituting arguments. The GATM model provides a structured way to represent reasoning, and can be useful both in the decision-making process as well as when communicating a decision. In this work a component-based overview of the GATM model is provided in the context of security policy reasoning, where previous work has shown that decision-making transparency and improved understanding of the reasoning behind a security policy may lead to a beneficial impact on policy compliance.

  • 33.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Delay metrics and delay characteristics: A study of four Swedish HSDPA+ and LTE networks2015In: 2015 European Conference on Networks and Communications (EuCNC), IEEE conference proceedings, 2015, p. 234-238Conference paper (Refereed)
    Abstract [en]

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

  • 34.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Estimating data transfer capacity for intermittent connectivity: A transport aware model2016In: 2016 IEEE 27th Annual International Symposium On Personal, Indoor, And Mobile Radio Communications (PIMRC), New York: IEEE, 2016, p. 1-6Conference paper (Refereed)
    Abstract [en]

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

  • 35.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Alfredsson, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    The Impact of Loss Generation on Emulation-Based Protocol Evaluation2006In: PDCN'06 Proceedings of the 24th IASTED international conference on Parallel and distributed computing and networks / [ed] Fahringer, T., Anaheim, USA: ACTA Press, 2006, 1, p. 231-237Conference paper (Refereed)
    Abstract [en]

    Network emulation has for a long time been an important tool for evaluating the performance of communication protocols. By emulating network characteristics, such as restricted bandwidth, delay and losses, knowledge about the behavior and performance of actual protocol implementations can be obtained. This paper focuses on the generation of losses in network emulators and shows the beneficial effects of being able to control the generation of losses in a precise way. Both the possibility to get additional knowledge about a protocol implementations behavior, as well as statistical benefits such as paired experiments are discussed. By extending the loss generation to also include bit-error generation, in addition to packet losses, a finer level of abstraction is provided. Deterministic bit-error generation allows detailed and repeatable studies of bit-error sensitive protocol behavior. TCP and a loss differentiating variant of TCP is used to illustrate the utility of improved loss generation.

  • 36.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    A Measurement Based Study of TCP Protocol Efficiency in Cellular Networks2014In: Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 2014 12th International Symposium on, IEEE Press, 2014, p. 131-136Conference paper (Refereed)
    Abstract [en]

    This paper examines the efficiency of resource utilization with respect to short-lived TCP flows in various cellular networks. The examination is done from the vantage point of an end-user who would like to use as much as possible of the cellular transmission resources that are available at any given time, thus minimizing the delays associated with communication. Based on a comprehensive measurement campaign we first derive network characteristics with regards to base RTT, RTT under load, and average throughput. A protocol efficiency metric is introduced to capture how efficiently short TCP flows are in fact able to use the instantaneously available transmission resources in a cellular network. The measurements show that short TCP connections have low efficiency in 3. SG (HSPA+) and 4G (LTE) mobile broadband networks, and that the improved latency and throughput characteristics of 4G in relation to 3. SG nevertheless results in lower short-flow efficiency for 4G.

  • 37.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alfredsson, Stefan
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Examining cellular access systems on trains: Measurements and change detection2017In: Proceedings of the 1st Network Traffic Measurement and Analysis Conference, New York: IEEE, 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Abstract:Access to reliable high-quality communication services on trains is important for today's mobile users. Train-mounted aggregation routers that provide WiFi access to train passengers and bundle external communication over multiple cellular modems/links is an efficient way of providing such services. Still, the characteristics of such systems have received limited attention in the literature. In this paper we examine the communication characteristics of such systems based on a large data set gathered over six months from an operational Swedish railway system. We characterize the conditions in terms of usage load, train velocity profiles, and observed throughput and delay as well as the relation between these parameters. Furthermore, we examine the data from an anomaly detection perspective. Based on a changepoint detection method, we examine how the collected metrics varies over the six months. Being able to detect shifts in the metrics over time can help detect anomalous changes in the hardware or environment, and also further helps explain the factors affecting the observed behaviors.

  • 38.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Examining TCP Short Flow Performance in Cellular Networks Through Active and Passive Measurements2015In: AllThingsCellular '15 Proceedings of the 5th Workshop on All Things Cellular: Operations, Applications and Challenges / [ed] David Choffnes and Kobus Van der Merwe, Association for Computing Machinery (ACM), 2015, p. 7-12Conference paper (Refereed)
    Abstract [en]

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

  • 39.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Beckman, Claes
    Center for Wireless Systems, KTH.
    Train Velocity and Data Throughput: A Large Scale LTE Cellular Measurements Study2017In: Proceedings of the 2017 IEEE 86th Vehicular Technology Conference (VTC Fall), New York: IEEE, 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Train-mounted aggregation routers that provide WiFi access to train passengers and bundle external communication over multiple cellular modems/links is an efficient way of providing communication services on trains. However, the characteristics of such systems have received limited attention in the literature. In this paper we address this gap by examining the communication characteristics of such systems based on a large data set gathered over six months from an operational Swedish railway system. We focus our examination on the relationship between per link throughput and train velocity. Using Levenberg- Marquardt non-linear regression a noticeable critical point is observed for an RS-SINR of around 12 dB. At this point the impact of increased train velocity on per link throughput changes from being negative to becoming positive. Using a machine learning approach we also explore the relative importance of several observed metrics in relation to per link throughput.

  • 40.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Brunstrom, Anna
    An Experimental Study on the Performance and Fairness of Loss Differentiation for TCP2004In: ICETE (3), 2004Chapter in book (Other academic)
  • 41.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Brunstrom, Anna
    Checksum-based Loss Differentiation2002In: Proceedings 4th IEEE Conference on Mobile and Wireless Communications Networks, 2002Chapter in book (Other academic)
  • 42.
    Garcia, Johan
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Evaluation of Transport Layer Loss Notification in Wireless Environments2005In: Networking - ICN 2005: 4th International Conference on Networking, Reunion Island, France, April 17-21, 2005, Proceedings, Part I / [ed] Pascal Lorenz & Petre Dini, Springer Berlin/Heidelberg, 2005, p. 247-257Conference paper (Other academic)
    Abstract [en]

    Residual bit-errors in wireless environments are well known to cause difficulties for congestion controlled protocols like TCP. In this study we focus on a receiver-based loss differentiation approach to mitigating the problems, and more specifically on two different loss notification schemes. The fully receiver-based 3-dupack scheme uses additional dupacks to implicitly influence the retransmission behavior of the sender. The second TCP option scheme uses a TCP option to explicitly convey a corruption notification. Although these schemes look relatively simple at first glance, when examining the details several issues exist which are highlighted and discussed. A performance evaluation based on a FreeBSD kernel implementation show that the TCP option scheme works well in all tested cases and provides a considerable throughput improvement. The 3-dupack scheme also provide performance gains in most cases, but the improvements varies more between different test cases, with some cases showing no improvement over regular TCP.

  • 43.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT.
    Brunstrom, Anna
    Impact of Partial Reliability on Web Image Transport Performance2002In: Proceedings PromoteIT 2002, 2002Chapter in book (Other academic)
  • 44.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Asplund, Katarina
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Application and Transport Layer Flexibility - A User-influenced Web Browsing SystemManuscript (preprint) (Other academic)
  • 45.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    A Robust JPEG Coder for a Partially Reliable Transport Service2000Conference paper (Refereed)
  • 46.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    An Experimental Performance Evaluation of a Partially Reliable Web Application2002Conference paper (Refereed)
  • 47.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    An Experimental Study on the Performance and Fairness of Loss Differentiation for TCP2004In: ICETE 3, , INSTICC Press, 2004, p. -419Conference paper (Refereed)
    Abstract [en]

    This paper investigates the performance and fairness of receiver-based loss differentiation for TCP. Experimentshave been performed with a FreeBSD kernel implementation. As expected, the results verify theeffectiveness of receiver-based loss differentiation when corruption losses are present. However, if the the corruptinglink is shared with users that do not employ loss differentiation, the performance gain typically comesat the expense of increased unfairness. The results show that a single loss differentiating user may in somecases reduce the bandwidth of users without loss differentiation with up to 35 percent, but there are also cases where loss differentiation has limited fairness implications. The results further show that if a user employs multiple TCP connections over the corrupting link the negative effects of corruption losses are reduced. This is true even if all connections employ regular TCP. Hence, multiple connections at the application level can to some extent be used as a simple mechanism to limit the impact of corruption losses.

  • 48.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Checksum-based Loss Differentiation2002Conference paper (Refereed)
    Abstract [en]

    In a wireless environment the common transport protocol assumption that all packet losses are due to congestion no longer holds true. If the transport protocols react identically to both congestion and noncongestion related losses, performance will degrade. To avoid this performance problem, transport protocols must be able to differentiate between losses that are due to congestion and losses that are due to wireless link errors. Suitable congestion avoidance behavior can then be applied as appropriate. This paper overviews previous work on loss differentiation, and proposes a checksumbased scheme. The proposed scheme reuses the checksums already available at various layers in the receiver endhost protocol stack. It is an endtoend solution for the case where the lossy link is the last hop. Header decoding, data integrity and other issues related to the implementation of our cecksumbased scheme are also discussed

  • 49.
    Garcia, Johan
    et al.
    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).
    Clustering-based separation of media transfers in DPI-classified cellular video and VoIP traffic2018Conference paper (Refereed)
    Abstract [en]

    Identifying VoIP and video traffic is often useful in the context of managing a cellular network, and to perform such traffic classification deep packet inspection (DPI) approaches are often used. Commercial DPI classifiers do not necessarily differentiate between, for example, YouTube traffic that arises from browsing inside the YouTube app, and traffic arising from the actual viewing of a YouTube video. Here we apply unsupervised clustering methods on such cellular DPI-labeled VoIP and video traffic to identify the characteristic behavior of the two sub-groups of media-transfer and non media-transfer flows. The analysis is based on a measurement campaign performed inside the core network of a commercial cellular operator, collecting data for more than two billion packets in 40+ million flows. A specially instrumented commercial DPI appliance allows the simultaneous collection of per packet information in addition to the DPI classification output. We show that the majority of flows falls into clusters that are easily identifiable as belonging to one of the traffic sub-groups, and that a surprising majority of DPIlabeled VoIP and video traffic is non-media related.

  • 50.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Effects of Loss Notification and Loss Differentiation on DCCP and TCP Performance2004Conference paper (Refereed)
    Abstract [en]

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

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

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

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