liu.seSearch for publications in DiVA
Change search
Refine search result
1234 1 - 50 of 153
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Aaro, Gustav
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Roos, Daniel
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Toolset for Run-time Dataset Collection of Deep-scene Information2020In: Symposium on Modelling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS), Springer, 2020, p. 224-236Conference paper (Refereed)
    Abstract [en]

    Virtual reality (VR) provides many exciting new application opportunities, but also present new challenges. In contrast to 360° videos that only allow a user to select its viewing direction, in fully immersive VR, users can also move around and interact with objects in the virtual world. To most effectively deliver such services it is therefore important to understand how users move around in relation to such objects. In this paper, we present a methodology and software tool for generating run-time datasets capturing a user’s interactions with such 3D environments, evaluate and compare different object identification methods that we implement within the tool, and use datasets collected with the tool to demonstrate example uses. The tool was developed in Unity, easily integrates with existing Unity applications through the use of periodic calls that extracts information about the environment using different ray-casting methods. The software tool and example datasets are made available with this paper. 

  • 2.
    Abdel-Halim, Adam
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Danielsson, Max
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Arlitt, Martin
    Univ Calgary, Canada.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Temporal Analysis of X.509 Revocations and their Statuses2022In: 7TH IEEE EUROPEAN SYMPOSIUM ON SECURITY AND PRIVACY WORKSHOPS (EUROS&PW 2022), IEEE , 2022, p. 258-265Conference paper (Refereed)
    Abstract [en]

    Despite the X509 public key infrastructure (PKI) being essential for ensuring the trust we place in our communication with web servers, the revocation of the trust placed in individual X509 certificates is neither transparent nor well-studied, leaving many unanswered questions. In this paper, we present a temporal analysis of 36 million certificates, whose revocation statuses we followed for 120 days since first being issued. We characterize the revocation rates of different certificate authorities (CAs) and how the rates change over the lifetime of the certificates. We identify and discuss several instances where the status changes from "revoked" to "good", "unauthorized" or "unknown", respectively, before the certificates expiry. This complements prior work that has observed such inconsistencies in some CAs behavior after expiry but also highlight a potentially more severe problem. Our results highlight heterogeneous revocation practices among the CAs.

  • 3.
    Almquist, Mathias
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Almquist, Viktor
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Krishnamoorthi, Vengatanathan
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek
    Univ Saskatchewan, Canada.
    The Prefetch Aggressiveness Tradeof in 360 degrees Video Streaming2018In: PROCEEDINGS OF THE 9TH ACM MULTIMEDIA SYSTEMS CONFERENCE (MMSYS18), ASSOC COMPUTING MACHINERY , 2018, p. 258-269Conference paper (Refereed)
    Abstract [en]

    With 360 degrees video, only a limited fraction of the full view is displayed at each point in time. This has prompted the design of streaming delivery techniques that allow alternative playback qualities to be delivered for each candidate viewing direction. However, while prefetching based on the users expected viewing direction is best done close to playback deadlines, large buffers are needed to protect against shortfalls in future available bandwidth. This results in conflicting goals and an important prefetch aggressiveness tradeoff problem regarding how far ahead in time from the current playpoint prefetching should be done. This paper presents the first characterization of this tradeoff. The main contributions include an empirical characterization of head movement behavior based on data from viewing sessions of four different categories of 360 degrees video, an optimization-based comparison of the prefetch aggressiveness tradeoffs seen for these video categories, and a data-driven discussion of further optimizations, which include a novel system design that allows both tradeoff objectives to be targeted simultaneously. By qualitatively and quantitatively analyzing the above tradeoffs, we provide insights into how to best design tomorrows delivery systems for 360 degrees videos, allowing content providers to reduce bandwidth costs and improve users playback experiences.

  • 4.
    Arestrom, Erik
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Early Online Classification of Encrypted Traffic Streams using Multi-fractal Features2019In: IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (IEEE INFOCOM 2019 WKSHPS), IEEE , 2019, p. 84-89Conference paper (Refereed)
    Abstract [en]

    Timely and accurate flow classification is important for identifying flows with different service requirements, optimized network management, and for helping network operators simultaneously operate networks at higher utilization while providing end users good quality of experience (QoE). With most services starting to use end-to-end encryption (HTTPS and QUIC), traditional Deep Packet Inspection (DPI) and port-based approaches are no longer applicable. Furthermore, most flow-level-based approaches ignore the complex non-linear characteristics of internet traffic (e.g., self similarity). To address this challenge, in this paper, we present and evaluate a classification framework that combines multi-fractal feature extraction based on time series data (which captures these non-linear characteristics), principal component analysis (PCA) based feature selection, and man-in-the-middle (MITM) based flow labeling. Our detailed evaluation shows that the method is able to quickly and effectively classify traffic belonging to the six most popular traffic types (video streaming, web browsing, social networking, audio communication, text communication, and bulk download) and to distinguish between video-on-demand (VoD) and live streaming sessions delivered from the same services. Our results show that good accuracy can be achieved with only information about the timing of the packets within a flow.

  • 5. Arlitt, Martin
    et al.
    Carlsson, Niklas
    University of Calgary.
    Leveraging Organizational Etiquette to Improve Internet Security2010In: Proc. IEEE International Conference on Computer Communication Networks (ICCCN ’10), IEEE , 2010, p. 1-6Conference paper (Refereed)
  • 6.
    Arlitt, Martin
    et al.
    HP Labs.
    Carlsson, Niklas
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, Database and information techniques.
    Gill, Phillipa
    University of Toronto.
    Mahanti, Aniket
    University of Calgary.
    Williamson, Carey
    University of Calgary.
    Characterizing Intelligence Gathering and Control on an Edge Network2011In: ACM Transactions on Internet Technology, ISSN 1533-5399, E-ISSN 1557-6051, Vol. 11, no 1Article in journal (Refereed)
    Abstract [en]

    here is a continuous struggle for control of resources at every organization that is connected to the Internet. The local organization wishes to use its resources to achieve strategic goals. Some external entities seek direct control of these resources, for purposes such as spamming or launching denial-of-service attacks. Other external entities seek indirect control of assets (e. g., users, finances), but provide services in exchange for them. less thanbrgreater than less thanbrgreater thanUsing a year-long trace from an edge network, we examine what various external organizations know about one organization. We compare the types of information exposed by or to external organizations using either active (reconnaissance) or passive (surveillance) techniques. We also explore the direct and indirect control external entities have on local IT resources.

  • 7.
    Arlitt, Martin
    et al.
    HP Labs.
    Carlsson, NiklasLinköping University, Department of Computer and Information Science, Database and information techniques.Hedge, NidhiTechnicolor.Wierman, AdamCalifornia Institute of Technology.
    ACM SIGMETRICS Performance Evaluation ReviewVolume 40 Issue 3, December 2012.: Special issue on the 2012 GreenMetrics workshop2013Conference proceedings (editor) (Refereed)
  • 8. Arlitt, Martin
    et al.
    Carlsson, NiklasRolia, Jerry
    GreenMetrics '09 Workshop Seattle, WA, June 2009.: in conjunction with ACM SIGMETRICS/Performance '09  (Proceedings appeared in ACM Performance Evaluation Review (PER), Special Issue on the 2009 GreenMetrics Workshop, 37, 4 (Mar. 2010).)2009Conference proceedings (editor) (Other academic)
  • 9. Arlitt, Martin
    et al.
    Carlsson, NiklasRolia, Jerry
    GreenMetrics '10 Workshop: In conjunction with ACM SIGMETRICS, New York, NY, June 2010. (Proceedings appeared in ACM Performance Evaluation Review (PER), Special Issue on the 2010 GreenMetrics Workshop, 38, 3 (Dec. 2010).) 2010Conference proceedings (editor) (Other academic)
  • 10. Arlitt, Martin
    et al.
    Carlsson, NiklasRolia, Jerry
    Proceedings of the Third GreenMetrics '11 Workshop, in conjunction with (and sponsored by) ACM SIGMETRICS.: ACM Performance Evaluation Review (PER), Special Issue on the 2011 GreenMetrics Workshop.  Volume 39, Issue 3, December 2011.2011Conference proceedings (editor) (Refereed)
  • 11.
    Arlitt, Martin
    et al.
    HP Labs; University of Calgary, Canada.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Williamson, Carey
    University of Calgary, Canada.
    Rolia, Jerry
    HP Labs.
    Passive Crowd-based Monitoring of World Wide Web Infrastructure and its Performance2012In: Proc. IEEE International Conference on Communications (ICC 2012), IEEE , 2012, p. 2689-2694Conference paper (Refereed)
    Abstract [en]

    The World Wide Web and the services it provides are continually evolving. Even for a single time instant, it is a complex task to methodologically determine the infrastructure over which these services are provided and the corresponding effect on user perceived performance. For such tasks, researchers typically rely on active measurements or large numbers of volunteer users. In this paper, we consider an alternative approach, which we refer to as passive crowd-based monitoring. More specifically, we use passively collected proxy logs from a global enterprise to observe differences in the quality of service (QoS) experienced by users on different continents. We also show how this technique can measure properties of the underlying infrastructures of different Web content providers. While some of these properties have been observed using active measurements, we are the first to show that many of these properties (such as location of servers) can be obtained using passive measurements of actual user activity. Passive crowd-based monitoring has the advantages that it does not add any overhead on Web infrastructure, it does not require any specific software on the clients, but still captures the performance and infrastructure observed by actual Web usage.

  • 12.
    Arvanitaki, Antonia
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Mohapatra, Parthajit
    Indian Institute of Technology, Tirupati, India.
    Secrecy in Congestion-Aware Broadcast Channels2021In: Proc. Wireless Days Conference (WD) 2021, Institute of Electrical and Electronics Engineers (IEEE), 2021Conference paper (Refereed)
    Abstract [en]

    Congestion-aware scheduling in the case of traditional downlink cellular communication has neglected the heterogeneity in terms of secrecy among different clients. In this paper, we study a two-user congestion-aware broadcast channel with heterogeneous traffic and different security requirements. The traffic with security requirements is intended for a legitimate user and it has bursty nature. The incoming packets are stored in a queue at the source. Furthermore, there is a second traffic flow intended for another user, it is delay tolerant and does not have secrecy constraints. The receiver which needs to be served with confidential data has full-duplex capabilities, and it can send a jamming signal to hinder eavesdropping of its data at the other user. We consider two randomized policies for selecting which packets to transmit, one is congestion-aware by taking into consideration the queue size, whereas the other one is non-congestion-aware. We analyse the throughput and the delay performance under two decoding schemes at the receivers and provide insights into their relative security performance and into how congestion control at the queue holding confidential information can help decrease the average delay per packet. We show that the two policies have the same secrecy performance for large random access probabilities. The derived results also take account of the self-interference caused at the receiver for whom confidential data is intended due to its full-duplex operation while jamming the communication at the other user.

  • 13.
    Arvanitaki, Antonia
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Mohapatra, Parthajit
    Indian Inst Technol, India.
    Burdakov, Oleg
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Performance analysis of congestion-aware secure broadcast channels2021In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2021, no 1, article id 178Article in journal (Refereed)
    Abstract [en]

    Congestion-aware scheduling in case of downlink cellular communication has ignored the distribution of diverse content to different clients with heterogeneous secrecy requirements. Other possible application areas that encounter the preceding issue are secure offloading in mobile-edge computing, and vehicular communication. In this paper, we extend the work in Arvanitaki et al. (SN Comput Sci 1(1):53, 2019) by taking into consideration congestion and random access. Specifically, we study a two-user congestion-aware broadcast channel with heterogeneous traffic and different security requirements. We consider two randomized policies for selecting which packets to transmit, one is congestion-aware by taking into consideration the queue size, whereas the other one is congestion-agnostic. We analyse the throughput and the delay performance under two decoding schemes at the receivers, and provide insights into their relative security performance and into how congestion control at the queue holding confidential information can help decrease the average delay per packet. We show that the congestion-aware policy provides better delay, throughput, and secrecy performance for large arrival packet probabilities at the queue holding the confidential information. The derived results also take account of the self-interference caused at the receiver for whom confidential data is intended due to its full-duplex operation while jamming the communication at the other user. Finally, for two decoding schemes, we formulate our problems in terms of multi-objective optimization, which allows for finding a trade-off between the average packet delay for packets intended for the legitimate user and the throughput for the other user under congestion-aware policy.

    Download full text (pdf)
    fulltext
  • 14.
    Arvanitaki, Antonia
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Mohapatra, Parthajit
    Indian Inst Technol Tirupati, India.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Delay Performance of a Two-User Broadcast Channel with Security Constraints2018In: 2018 GLOBAL INFORMATION INFRASTRUCTURE AND NETWORKING SYMPOSIUM (GIIS), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    In this paper we consider the two-user broadcast channel with security constraints. We assume that one of the receivers has a secrecy constraint; i.e., its packets need to be kept secret from the other receiver. The receiver with secrecy constraint has full-duplex capability to transmit a jamming signal to increase its secrecy. We derive the average delay per packet and provide simulation and numerical results, where we compare different performance metrics for the cases when the legitimate receiver performs successive decoding and when both receivers treat interference as noise.

  • 15.
    Arvanitaki, Antonia
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Mohapatra, Parthajit
    Indian Institute of Technology, Tirupati, India.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Delay Performance of a Two-User Broadcast Channel with Security Constraints2020In: SN Computer Science, ISSN 2661-8907, Vol. 1, no 1, article id 53Article in journal (Refereed)
    Abstract [en]

    In this paper, we consider the two-user broadcast channel with security constraints. We assume that a source broadcasts packets to two receivers, and that one of them has secrecy constraints, i.e., its packets need to be kept secret from the other receiver. The receiver with secrecy constraint has full-duplex capability, allowing it to transmit a jamming signal to increase its secrecy. We derive the average delay per packet and provide simulations and numerical results, where we compare different performance metrics for the cases when both receivers treat interference as noise, when the legitimate receiver performs successive decoding, and when the eavesdropper performs successive decoding. The results show that successive decoding provides better average packet delay for the legitimate user. Furthermore, we define a new metric that characterizes the reduction on the success probability for the legitimate user that is caused by the secrecy constraint. The results show that secrecy poses a significant amount of packet delay for the legitimate receiver when either receiver performs successive decoding. We also formulate an optimization problem, wherein the throughput of the eavesdropper is maximized under delay and secrecy rate constraints at the legitimate receiver. We provide numerical results for the optimization problem, where we show the trade-off between the transmission power for the jamming and the throughput of the non-legitimate receiver. The results provide insights into how channel ordering and encoding differences can be exploited to improve performance under different interference conditions.

  • 16.
    Bertmar, Sofia
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Gerhardsen, Johanna
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Ekblad, Alice
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Höglund, Anna
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Mineur, Julia
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Oknegard Enavall, Isabell
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Minh Ha, Le
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Who's Most Targeted and Does My New Adblocker Really Help: A Profile-based Evaluation of Personalized Advertising2021In: Proc. ACM CCS Workshop on Privacy in the Electronic Society (ACM WPES @CCS), ACM Digital Library, 2021Conference paper (Refereed)
    Abstract [en]

    There is limited prior work studying how the ad personalization experienced by different users is impacted by the use of adblockers, geographic location, the user's persona, or what browser they use. To address this void, this paper presents a novel profile-based evaluation of the personalization experienced by carefully crafted user profiles. Our evaluation framework impersonates different users and captures how the personalization changes over time, how it changes when adding or removing an extension, and perhaps most importantly how the results differ depending on the profile's persona (e.g., interest, occupation, age, gender), geographic location (US East, US West, UK), what browser extension they use (none, AdBlock, AdBlock Plus, Ghostery, CatBlock), what browser they use (Chrome, Firefox), and whether they are logged in to their Google account. By comparing and contrasting observed differences we provide insights that help explain why some user groups may feel more targeted than others and why some people may feel even more targeted after having turned on their adblocker.  

  • 17.
    Borghol, Youmna
    et al.
    NICTA, Australia; University of New South Wales, Sydney, NSW, Australia.
    Ardon, Sebastien
    NICTA, Alexandria, NSW, Australia .
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Eager, Derek
    University of Saskatchewan, Canada.
    Mahanti, Anirban
    NICTA, Alexandria, NSW, Australia .
    The Untold Story of the Clones: Content-agnostic Factors that Impact YouTube Video Popularity2012In: Proc. ACM SIGKDD Conference on Knowledge Discovery and Data Mining (KDD) 2012, Association for Computing Machinery (ACM), 2012, p. 1186-1194Conference paper (Refereed)
    Abstract [en]

    Video dissemination through sites such as YouTube can have widespread impacts on opinions, thoughts, and cultures. Not all videos will reach the same popularity and have the same impact. Popularity differences arise not only because of differences in video content, but also because of other "content-agnostic" factors. The latter factors are of considerable interest but it has been difficult to accurately study them. For example, videos uploaded by users with large social networks may tend to be more popular because they tend to have more interesting content, not because social network size has a substantial direct impact on popularity.

    In this paper, we develop and apply a methodology that is able to accurately assess, both qualitatively and quantitatively, the impacts of various content-agnostic factors on video popularity. When controlling for video content, we observe a strong linear "rich-get-richer" behavior, with the total number of previous views as the most important factor except for very young videos. The second most important factor is found to be video age. We analyze a number of phenomena that may contribute to rich-get-richer, including the first-mover advantage, and search bias towards popular videos. For young videos we find that factors other than the total number of previous views, such as uploader characteristics and number of keywords, become relatively more important. Our findings also confirm that inaccurate conclusions can be reached when not controlling for content.

  • 18.
    Borghol, Youmna
    et al.
    NICTA, Alexandria, Australia.
    Ardon, Sebastien
    NICTA, Alexandria, Australia.
    Carlsson, Niklas
    University of Calgary, Canada.
    Mahanti, Anirban
    NICTA, Alexandria, Australia.
    Toward Efficient On-demand Streaming with BitTorrent2010In: NETWORKING 2010: 9th International IFIP TC 6 Networking Conference, Chennai, India, May 11-15, 2010. Proceedings / [ed] Mark Crovella, Laura Marie Feeney, Dan Rubenstein, S. V. Raghavan, Springer , 2010, p. 53-66Chapter in book (Refereed)
    Abstract [en]

    This paper considers the problem of adapting the BitTorrent protocol for on-demand streaming. BitTorrent is a popular peer-to-peer file sharing protocol that efficiently accommodates a large number of requests for file downloads. Two components of the protocol, namely the Rarest-First piece selection policy and the Tit-for-Tat algorithm for peer selection, are acknowledged to contribute toward the protocol's efficiency with respect to time to download files and its resilience to freeriders. Rarest-First piece selection, however, does not augur well for on-demand streaming. In this paper, we present a new adaptive Window-based piece selection policy that achieves a balance between the system scalability provided by the Rarest-First algorithm and the necessity of In-Order pieces for seamless media playback. We also show that this simple modification to the piece selection policy allows the system to be efficient with respect to utilization of available upload capacity of participating peers, and does not break the Tit-for-Tat incentive scheme which provides resilience to freeriders.

  • 19.
    Borghol, Youmna
    et al.
    NICTA, Australia.
    Mitra, Siddharth
    Indian Institute Technology Delhi.
    Ardon, Sebastien
    NICTA, Australia.
    Carlsson, Niklas
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, Database and information techniques.
    Eager, Derek
    University of Saskatchewan.
    Mahanti, Anirban
    NICTA, Australia.
    Characterizing and modelling popularity of user-generated videos2011In: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, Vol. 68, no 11, p. 1037-1055Article in journal (Refereed)
    Abstract [en]

    This paper develops a framework for studying the popularity dynamics of user-generated videos, presents a characterization of the popularity dynamics, and proposes a model that captures the key properties of these dynamics. We illustrate the biases that may be introduced in the analysis for some choices of the sampling technique used for collecting data; however, sampling from recently-uploaded videos provides a dataset that is seemingly unbiased. Using a dataset that tracks the views to a sample of recently-uploaded YouTube videos over the first eight months of their lifetime, we study the popularity dynamics. We find that the relative popularities of the videos within our dataset are highly non-stationary, owing primarily to large differences in the required time since upload until peak popularity is finally achieved, and secondly to popularity oscillation. We propose a model that can accurately capture the popularity dynamics of collections of recently-uploaded videos as they age, including key measures such as hot set churn statistics, and the evolution of the viewing rate and total views distributions over time.

  • 20.
    Brecht, Tim
    et al.
    University of Waterloo, Canada.
    Carlsson, NiklasLinköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.Vernblom, MikaelLinköping Hockey Club.Lambrix, PatrickLinköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Proceedings of the Linköping Hockey Analytics Conference LINHAC 2023 Research Track2023Conference proceedings (editor) (Refereed)
    Abstract [en]

    LINHAC 2023 took place June 7-9, 2023, and was organized by Linköping University (Patrick Lambrix and Niklas Carlsson) and Linköping Hockey Club (Mikael Vernblom). LINHAC brought together professionals and academics with an interest in hockey analytics. It featured the latest research in hockey analytics in academia and companies, discussions with analysts and coaches, industry sessions with the latest hockey analytics products, and an analytics competition for students.

  • 21.
    Bruhner, Carl Magnus
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Hasselquist, David
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering. Sectra Communications, Sweden.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Bridging the Privacy Gap: Enhanced User Consent Mechanisms on the Web2023In: Proc. NDSS Workshop on Measurements, Attacks, and Defenses for the Web (MADWeb @NDSS), 2023Conference paper (Refereed)
    Abstract [en]

    In the age of the General Data Protection Regula-tion (GDPR) and the California Consumer Privacy Act (CCPA),privacy and consent control have become even more apparent forevery-day web users. Privacy banners in all shapes and sizes askfor permission through more or less challenging designs and makeprivacy control more of a struggle than they help users’ privacy.In this paper, we present a novel solution expanding the AdvancedData Protection Control (ADPC) mechanism to bridge currentgaps in user data and privacy control. Our solution moves theconsent control to the browser interface to give users a seamlessand hassle-free experience, while at the same time offering contentproviders a way to be legally compliant with legislation. Throughan extensive review, we evaluate previous works and identifycurrent gaps in user data control. We then present a blueprintfor future implementation and suggest features to support privacycontrol online for users globally. Given browser support, thesolution provides a tangible path to effectively achieve legallycompliant privacy and consent control in a user-oriented mannerthat could allow them to again browse the web seamlessly.

  • 22.
    Bruhner, Carl Magnus
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Linnarsson, Oscar
    Linköping University.
    Nemec, Matus
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Arlitt, Martin
    Univ Calgary, Canada.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Changing of the Guards: Certificate and Public Key Management on the Internet2022In: Passive and active measurement (PAM 2022) / [ed] Hohlfeld, O., Moura, G., Pelsser, C, 2022, Vol. 13210, p. 50-80Conference paper (Refereed)
    Abstract [en]

    Certificates are the foundation of secure communication over the internet. However, not all certificates are created and managed in a consistent manner and the certificate authorities (CAs) issuing certificates achieve different levels of trust. Furthermore, user trust in public keys, certificates, and CAs can quickly change. Combined with the expectation of 24/7 encrypted access to websites, this quickly evolving landscape has made careful certificate management both an important and challenging problem. In this paper, we first present a novel server-side characterization of the certificate replacement (CR) relationships in the wild, including the reuse of public keys. Our data-driven CR analysis captures management biases, highlights a lack of industry standards for replacement policies, and features successful example cases and trends. Based on the characterization results we then propose an efficient solution to an important revocation problem that currently leaves web users vulnerable long after a certificate has been revoked.

    Download full text (pdf)
    fulltext
  • 23.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Broadening the Audience: Popularity Dynamics and Scalable Content Delivery2012In: Advances in secure and networked information systems: the ADIT perspective ; Festschrift in honor of professor Nahid Shahmehri / [ed] Patrick Lambrix, Linköping: Linköping University Electronic Press, 2012, p. 139-144Chapter in book (Other academic)
    Abstract [en]

    The Internet is playing an increasingly important role in today’s society and people are beginning to expect instantaneous access to information and content wherever they are. As content delivery is consuming a majority of the Internet bandwidth and its share of bandwidth is increasing by the hour, we need scalable and efficient techniques that can support these user demands and efficiently deliver the content to the users. When designing such techniques it is important to note that not all content is the same or will reach the same popularity. Scalable techniques must handle an increasingly diverse catalogue of contents, both with regards to diversity of content (as service are becoming increasingly personalized, for example) and with regards to their individual popularity. The importance of understanding content popularity dynamics is further motivated by popular contents widespread impact on opinions, thoughts, and cultures. This article will briefly discuss some of our recent work on capturing content popularity dynamics and designing scalable content delivery techniques

    Download full text (pdf)
    fulltext
  • 24.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Optimized eeeBond: Energy Efficiency with non-Proportional Router Network Interfaces2016In: PROCEEDINGS OF THE 2016 ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE'16), ACM Digital Library, 2016, p. 215-223Conference paper (Refereed)
    Abstract [en]

    The recent Energy Efficient Ethernet (EEE) standard and the eBond protocol provide two orthogonal approaches that allow significant energy savings on routers. In this paper we present the modeling and performance evaluation of these two protocols and a hybrid protocol. We first present eeeBond, pronounced ``triple-e bond'', which combines the eBond capability to switch between multiple redundant interfaces with EEE's active/idle toggling capability implemented in each interface. Second, we present an analytic model of the protocol performance, and derive closed-form expressions for the optimized parameter settings of both eBond and eeeBond. Third, we present a performance evaluation that characterizes the relative performance gains possible with the optimized protocols, as well as a trace-based evaluation that validates the insights from the analytic model. Our results show that there are significant advantages to combine eBond and EEE. The eBond capability provides good savings when interfaces only offer small energy savings when in short-term sleep states, and the EEE capability is important as short-term sleep savings improve.

    Download full text (pdf)
    fulltext
  • 25.
    Carlsson, Niklas
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, Database and information techniques.
    Arlitt, Martin
    Towards More Effective Utilization of Computer Systems2011In: Proc. ACM/SPEC International Conference on Performance Engineering (ICPE ’10), Karlsruhe, Germany, March 2011., ACM , 2011, p. 235-246Conference paper (Refereed)
  • 26.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Cohen, Edith
    Google Res, CA 94043 USA.
    Robert, Philippe
    INRIA, France.
    POMACS V5, N3, December 2021 Editorial2021In: PROCEEDINGS OF THE ACM ON MEASUREMENT AND ANALYSIS OF COMPUTING SYSTEMS, ISSN 2476-1249, Vol. 5, no 3, article id 29Article in journal (Other academic)
    Abstract [en]

    n/a

  • 27.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Cohen, Edith
    Google Res, MA USA.
    Robert, Philippe
    INRIA, France.
    POMACS V6, N1, March 2022 Editorial2022In: PROCEEDINGS OF THE ACM ON MEASUREMENT AND ANALYSIS OF COMPUTING SYSTEMS, ISSN 2476-1249, Vol. 6, no 1, article id 1Article in journal (Other academic)
    Abstract [en]

    n/a

  • 28.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Cohen, Edith
    Google Res, CA USA.
    Robert, Philippe
    INRIA, France.
    POMACS V6, N2, June 2022 Editorial2022In: PROCEEDINGS OF THE ACM ON MEASUREMENT AND ANALYSIS OF COMPUTING SYSTEMS, ISSN 2476-1249, Vol. 6, no 2, article id 24Article in journal (Other academic)
    Abstract [en]

    n/a

  • 29.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Dan, Gyorgy
    KTH Royal Institute of Technology, Stockholm.
    Eager, Derek
    University of Saskatchewan, Canada.
    Mahanti, Anirban
    NICTA, Sydney, Australia,.
    Tradeoffs in Cloud and Peer-assisted Content Delivery Systems2012In: Peer-to-Peer Computing (P2P), 2012: , IEEE , 2012, p. 249-260Conference paper (Refereed)
    Abstract [en]

    With the proliferation of cloud services, cloud-based systems can become a cost-effective means of on-line content delivery. In order to make best use of the available cloud bandwidth and storage resources, content distributors need to have a good understanding of the tradeoffs between various system design choices. In this work we consider a peer-assisted content delivery system that aims to provide guaranteed average download rate to its customers. We show that bandwidth demand peaks for contents with moderate popularity, and identify these contents as candidates for cloud-based service. We then consider dynamic content bundling and cross-swarm seeding, which were recently proposed to improve download performance, and evaluate their impact on the optimal choice of cloud service use. We find that much of the benefits from peer seeding can be achieved with careful torrent inflation, and that hybrid policies that combine bundling and peer seeding often reduce the delivery costs by 20% relative to only using seeding. Furthermore, all these peer-assisted policies reduce the number of files that would need to be pushed to the cloud. Finally, we show that careful system design is needed if locality is an important criterion when choosing cloud-based service provisioning.

  • 30.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Dan, György
    KTH Royal Institute of Technology, Sweden.
    Arlitt, Martin
    NICTA, Australia.
    Mahanti, Anirban
    HP Labs, USA.
    A Longitudinal Characterization of Local and Global BitTorrent Workload Dynamics2012In: Passive and Active Measurement: 13th International Conference, PAM 2012, Vienna, Austria, March 12-14th, 2012. Proceedings / [ed] Nina Taft; Fabio Ricciato, Springer Berlin/Heidelberg, 2012, p. 252-262Conference paper (Refereed)
    Abstract [en]

    This book constitutes the refereed proceedings of the 13th International Conference on Passive and Active Measurement, PAM 2012, held in Vienna, Austria, in March 2012. <br>The 25 revised full papers presented were carefully reviewed and selected from 83 submissions. The papers were arranged into eight sessions traffic evolution and analysis, large scale monitoring, evaluation methodology, malicious behavior, new measurement initiatives, reassessing tools and methods, perspectives on internet structure and services, and application protocols.

  • 31.
    Carlsson, Niklas
    et al.
    University of Calgary.
    Eager, Derek
    Content Delivery using Replicated Digital Fountains2010In: Proc. IEEE/ACM International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS ’10), IEEE , 2010, p. 338-348Conference paper (Refereed)
  • 32.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek
    University of Saskatchewan, Canada.
    Cross-user Similarities in Viewing Behavior for 360°Video and Caching Implications2023In: ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP), ISSN 1551-6857, E-ISSN 1551-6865, Vol. 19, no 5, article id 152Article in journal (Refereed)
    Abstract [en]

    The demand and usage of 360°video services are expected to increase. However, despite these services being highly bandwidth intensive, not much is known about the potential value that basic bandwidth saving techniques such as server or edge-network on-demand caching (e.g., in a CDN) could have when used for delivery of such services. This problem is both important and complicated as client-side solutions have been developed that split the full 360°view into multiple tiles, and adapt the quality of the downloaded tiles based on the user’s expected viewing direction and bandwidth conditions. This paper presents new trace-based analysis methods that incorporate users’ viewports (the area of the full 360°view the user actually sees), a first characterization of the cross-user similarities of the users’ viewports, and a trace-based analysis of the potential bandwidth savings that caching-based techniques may offer under different conditions. Our analysis takes into account differences in the time granularity over which viewport overlaps can be beneficial for resource saving techniques, compares and contrasts differences between video categories, and accounts for uncertainties in the network conditions and the prediction of the future viewing direction when prefetching. The results provide substantial insight into the conditions under which overlap can be considerable and caching effective, and inform the design of new caching system policies tailored for 360°video.

  • 33.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek
    University of Saskatchewan, Canada.
    Ephemeral Content Popularity at the Edge and Implications for On-Demand Caching2017In: IEEE Transactions on Parallel and Distributed Systems, ISSN 1045-9219, E-ISSN 1558-2183, Vol. 28, no 6, p. 1621-1634Article in journal (Refereed)
    Abstract [en]

    The ephemeral content popularity seen with many content delivery applications can make indiscriminate on-demand caching in edge networks highly inefficient, since many of the content items that are added to the cache will not be requested again from that network. In this paper, we address the problem of designing and evaluating more selective edge-network caching policies. The need for such policies is demonstrated through an analysis of a dataset recording YouTube video requests from users on an edge network over a 20-month period. We then develop a novel workload modelling approach for such applications and apply it to study the performance of alternative edge caching policies, including indiscriminate caching and cache on kth request for different k. The latter policies are found able to greatly reduce the fraction of the requested items that are inserted into the cache, at the cost of only modest increases in cache miss rate. Finally, we quantify and explore the potential room for improvement from use of other possible predictors of further requests. We find that although room for substantial improvement exists when comparing performance to that of a perfect "oracle" policy, such improvements are unlikely to be achievable in practice.

    Download full text (pdf)
    fulltext
  • 34.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek
    Univ Saskatchewan, Canada.
    Had You Looked Where Im Looking? Cross-user Similarities in Viewing Behavior for 360 degrees Video and Caching Implications2020In: PROCEEDINGS OF THE ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE20), ASSOC COMPUTING MACHINERY , 2020, p. 130-137Conference paper (Refereed)
    Abstract [en]

    The demand and usage of 360 degrees video services are expected to increase. However, despite these services being highly bandwidth intensive, not much is known about the potential value that basic bandwidth saving techniques such as server or edge-network on-demand caching (e.g., in a CDN) could have when used for delivery of such services. This problem is both important and complicated as client-side solutions have been developed that split the full 360 degrees view into multiple tiles, and adapt the quality of the downloaded tiles based on the users expected viewing direction and bandwidth conditions. To better understand the potential bandwidth savings that caching-based techniques may offer for this context, this paper presents the first characterization of the similarities in the viewing directions of users watching the same 360 degrees video, the overlap in viewports of these users (the area of the full 360 degrees view they actually see), and the potential cache hit rates for different video categories and network conditions. The results provide substantial insight into the conditions under which overlap can be considerable and caching effective, and can inform the design of new caching system policies tailored for 360 degrees video.

  • 35.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek
    Univ Saskatchewan, Canada.
    Optimized Dynamic Cache Instantiation2020In: 2020 IFIP NETWORKING CONFERENCE AND WORKSHOPS (NETWORKING), IEEE , 2020, p. 145-153Conference paper (Refereed)
    Abstract [en]

    By caching content at geographically distributed servers, content delivery applications can achieve scalability and reduce wide-area network traffic. However, each deployed cache has an associated cost. As the request rate from a region varies (e.g., according to a daily cycle), there may be periods when the request rate is high enough to justify this cost, and other periods when it is not. Cloud computing offers a solution to problems of this kind, by supporting the dynamic allocation and release of resources. In this paper, we analyze the potential benefits from dynamically instantiating caches using resources from cloud service providers. We develop novel analytic caching models that accommodate time-varying request rates, transient behavior as a cache fills following instantiation, and selective cache insertion policies. Using these models, within the context of a simple cost model, we then develop bounds and compare policies with optimized parameter selections to obtain insights into key cost/performance tradeoffs. We find that dynamic cache instantiation can provide substantial cost reductions, that potential reductions strongly dependent on the object popularity skew, and that selective cache insertion can be even more beneficial in this context than with conventional edge caches.

  • 36.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek
    Univ Saskatchewan, Canada.
    Worst-case bounds and optimized cache on Mth request cache insertion policies under elastic conditions2018In: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, Vol. 127, p. 70-92Article in journal (Refereed)
    Abstract [en]

    Cloud services and other shared third-party infrastructures allow individual content providers to easily scale their services based on current resource demands. In this paper, we consider an individual content provider that wants to minimize its delivery costs under the assumptions that the storage and bandwidth resources it requires are elastic, the content provider only pays for the resources that it consumes, and costs are proportional to the resource usage. Within this context, we (i) derive worst-case bounds for the optimal cost and competitive cost ratios of different classes of cache on Mth request cache insertion policies, (ii) derive explicit average cost expressions and bounds under arbitrary inter request distributions, (iii) derive explicit average cost expressions and bounds for short tailed (deterministic, Erlang, and exponential) and heavy-tailed (Pareto) inter-request distributions, and (iv) present numeric and trace-based evaluations that reveal insights into the relative cost performance of the policies. Our results show that a window-based cache on 2nd request policy using a single threshold optimized to minimize worst-case costs provides good average performance across the different distributions and the full parameter ranges of each considered distribution, making it an attractive choice for a wide range of practical conditions where request rates of individual file objects typically are not known and can change quickly. (C) 2018 Elsevier B.V. All rights reserved.

  • 37.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Eager, Derek
    University of Saskatchewan, Canada.
    Gopinathan, Ajay
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Li, Zongpeng
    University of Calgary, Canada.
    Caching and optimized request routing in cloud-based content delivery systems2014In: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, Vol. 79, p. 38-55Article in journal (Refereed)
    Abstract [en]

    Geographically distributed cloud platforms enable an attractive approach to large-scale content delivery. Storage at various sites can be dynamically acquired from (and released back to) the cloud provider so as to support content caching, according to the current demands for the content from the different geographic regions.  When storage is sufficiently expensive that not all content should be cached at all sites, two issues must be addressed: how should requests for content be routed to the cloud provider sites, and what policy should be used for caching content using the elastic storage resources obtained from the cloud provider.  Existing approaches are typically designed for non-elastic storage and little is known about the optimal policies when minimizing the delivery costs for distributed elastic storage.

    In this paper, we propose an approach in which elastic storage resources are exploited using a simple dynamic caching policy, while request routing is updated periodically according to the solution of an optimization model.  Use of pull-based dynamic caching, rather than push-based placement, provides robustness to unpredicted changes in request rates.  We show that this robustness is provided at low cost \textendash{} even with fixed request rates, use of the dynamic caching policy typically yields content delivery cost within 10\% of that with the optimal static placement.  We compare request routing according to our optimization model to simpler baseline routing policies, and find that the baseline policies can yield greatly increased delivery cost relative to optimized routing.  Finally, we present a lower-cost approximate solution algorithm for our routing optimization problem that yields content delivery cost within 2.5\% of the optimal solution.

  • 38.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek
    University of Saskatchewan, Canada.
    Krishnamoorthi, Vengatanathan
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Polishchuk, Tatiana
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Optimized Adaptive Streaming of Multi-video Stream Bundles2017In: IEEE transactions on multimedia, ISSN 1520-9210, E-ISSN 1941-0077, Vol. 19, no 7, p. 1637-1653Article in journal (Refereed)
    Abstract [en]

    In contrast to traditional video, multi-view video streaming allows viewers to interactively switch among multiple perspectives provided by different cameras. One approach to achieve such a service is to encode the video from all of the cameras into a single stream, but this has the disadvantage that only a portion of the received video data will be used, namely that required for the selected view at each point in time. In this paper, we introduce the concept of a multi-video stream bundle that consists of multiple parallel video streams that are synchronized in time, each providing the video from a different camera capturing the same event or movie. For delivery we leverage the adaptive features and time-based chunking of HTTP-based adaptive streaming, but now employing adaptation in both content and rate. Users are able to change their viewpoint on-demand and the client player adapts the rate at which data are retrieved from each stream based on the users current view, the probabilities of switching to other views, and the users current bandwidth conditions. A crucial component of such a system is the prefetching policy. For this we present an optimization model as well as a simpler heuristic that can balance the playback quality and the probability of playback interruptions. After analytically and numerically characterizing the optimal solution, we present a prototype implementation and sample results. Our prefetching and buffer management solution is shown to provide close to seamless playback switching when there is sufficient bandwidth to prefetch the parallel streams.

    Download full text (pdf)
    fulltext
  • 39.
    Carlsson, Niklas
    et al.
    University of Saskatchewan, Canada .
    Eager, Derek L.
    University of Saskatchewan, Canada .
    Modeling Priority-based Incentive Policies for Peer-assisted Content Delivery Systems2008In: NETWORKING 2008 Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet: 7th International IFIP-TC6 Networking Conference Singapore, May 5-9, 2008, Proceedings / [ed] Amitabha Das, Hung Keng Pung, Francis BuSung Lee and Lawrence WaiChoong Wong, Springer Berlin/Heidelberg, 2008, p. 421-432Chapter in book (Refereed)
    Abstract [en]

    Content delivery providers can improve their service scalability and offload their servers by making use of content transfers among their clients. To provide peers with incentive to transfer data to other peers, protocols such as BitTorrent typically employ a tit-for-tat policy in which peers give upload preference to peers that provide the highest upload rate to them. However, the tit-for-tat policy does not provide any incentive for a peer to stay in the system beyond completion of its download.

    This paper presents a simple fixed-point analytic model of a priority-based incentive mechanism which provides peers with strong incentive to contribute upload bandwidth beyond their own download completion. Priority is obtained based on a peer's prior contribution to the system. Using a two-class model, we show that priority-based policies can significantly improve average download times, and that there exists a significant region of the parameter space in which both high-priority and low-priority peers experience improved performance compared to with the pure tit-for-tat approach. Our results are supported using event-based simulations.

  • 40.
    Carlsson, Niklas
    et al.
    University of Saskatchewan.
    Eager, Derek L.
    University of Saskatchewan.
    Non-Euclidian Geographic Routing in Wireless Networks2007In: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, ISSN 1570-8705, Vol. 5, no 7, p. 1173-1193Article in journal (Refereed)
    Abstract [en]

    Greedy geographic routing is attractive for large multi-hop wireless networks because of its simple and distributed operation. However, it may easily result in dead ends or hotspots when routing in a network with obstacles (regions without sufficient connectivity to forward messages). In this paper we propose a distributed routing algorithm that combines greedy geographic routing with two non-Euclidean distance metrics, chosen so as to provide load balanced routing around obstacles and hotspots. The first metric, Local Shortest Path, is used to achieve high probability of progress, while the second metric, Weighted Distance Gain, is used to select a desirable node among those that provide progress. The proposed Load Balanced Local Shortest Path (LBLSP) routing algorithm provides loop freedom, guarantees delivery when a path exists, is able to efficiently route around obstacles, and provides good load balancing.

  • 41.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek L.
    University of Sakatchewan, Canada.
    Optimized Dynamic Cache Instantiation and Accurate LRU Approximations under Time-varying Request Volume2023In: IEEE Transactions on Cloud Computing, ISSN 2168-7161, Vol. 11, no 1, p. 779-797Article in journal (Refereed)
    Abstract [en]

    Content-delivery applications can achieve scalability and reduce wide-area network traffic using geographically distributed caches. However, each deployed cache has an associated cost, and under time-varying request rates (e.g., a daily cycle) there may be long periods when the request rate from the local region is not high enough to justify this cost. Cloud computing offers a solution to problems of this kind, by supporting dynamic allocation and release of resources. In this paper, we analyze the potential benefits from dynamically instantiating caches using resources from cloud service providers. We develop novel analytic caching models that accommodate time-varying request rates, transient behavior as a cache fills following instantiation, and selective cache insertion policies. Within the context of a simple cost model, we then develop bounds and compare policies with optimized parameter selections to obtain insights into key cost/performance tradeoffs. We find that dynamic cache instantiation can provide substantial cost reductions, that potential reductions strongly dependent on the object popularity skew, and that selective cache insertion can be even more beneficial in this context than with conventional edge caches. Finally, our contributions also include accurate and easy-to-compute approximations that are shown applicable to LRU caches under time-varying workloads.

  • 42.
    Carlsson, Niklas
    et al.
    University of Saskatchewan, Canada.
    Eager, Derek L.
    University of Saskatchewan, Canada.
    Peer-assisted On-demand Streaming of Stored Media using BitTorrent-like Protocols2007In: NETWORKING 2007. Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet: 6th International IFIP-TC6 Networking Conference, Atlanta, GA, USA, May 14-18, 2007. Proceedings / [ed] Ian F. Akyildiz, Raghupathy Sivakumar, Eylem Ekici, Jaudelice Cavalcantede Oliveira and Janise McNair, Springer Berlin/Heidelberg, 2007, p. 570-581Chapter in book (Refereed)
    Abstract [en]

    With BitTorrent-like protocols a client may download a file from a large and changing set of peers, using connections of heterogeneous and time-varying bandwidths. This flexibility is achieved by breaking the file into many small pieces, each of which may be downloaded from different peers. This paper considers an approach to peer-assisted on-demand delivery of stored media that is based on the relatively simple and flexible BitTorrent-like approach, but which is able to achieve a form of “streaming” delivery, in the sense that playback can begin well before the entire media file is received. Achieving this goal requires: (1) a piece selection strategy that effectively mediates the conflict between the goals of high piece diversity, and the in-order requirements of media file playback, and (2) an on-line rule for deciding when playback can safely commence. We present and evaluate using simulation candidate protocols including both of these components.

  • 43.
    Carlsson, Niklas
    et al.
    University of Calgary.
    Eager, Derek L.
    University of Calgary.
    Server Selection in Large-scale Video-on-Demand Systems2010In: ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP), ISSN 1551-6857, E-ISSN 1551-6865, ISSN 1551-6857, Vol. 6, no 1, p. 1:1-1:26Article in journal (Refereed)
    Abstract [en]

     

    Video on demand, particularly with user-generated content, is emerging as one of the most bandwidth-intensive applications on the Internet. Owing to content control and other issues, some video-on-demand systems attempt to prevent downloading and peer-to-peer content delivery. Instead, such systems rely on server replication, such as via third-party content distribution networks, to support video streaming (or pseudostreaming) to their clients. A major issue with such systems is the cost of the required server resources.

    By synchronizing the video streams for clients that make closely spaced requests for the same video from the same server, server costs (such as for retrieval of the video data from disk) can be amortized over multiple requests. A fundamental trade-off then arises, however, with respect to server selection. Network delivery cost is minimized by selecting the nearest server, while server cost is minimized by directing closely spaced requests for the same video to a common server.

    This article compares classes of server selection policies within the context of a simple system model. We conclude that: (i) server selection using dynamic system state information (rather than only proximities and average loads) can yield large improvements in performance, (ii) deferring server selection for a request as late as possible (i.e., until just before streaming is to begin) can yield additional large improvements, and (iii) within the class of policies using dynamic state information and deferred selection, policies using only “local” (rather than global) request information are able to achieve most of the potential performance gains.

     

  • 44.
    Carlsson, Niklas
    et al.
    University of Calgary, Canada.
    Eager, Derek L.
    University of Saskatchewan, Canada.
    Mahanti, Anirban
    NICTA. Sydney, Australia.
    Peer-assisted On-demand Video Streaming with Selfish Peers2009In: NETWORKING 2009: 8th International IFIP-TC 6 Networking Conference, Aachen, Germany, May 11-15, 2009. Proceedings / [ed] Luigi Fratta, Henning Schulzrinne, Yutaka Takahashi and Otto Spaniol, Springer Berlin/Heidelberg, 2009, p. 586-599Chapter in book (Refereed)
    Abstract [en]

    Systems delivering stored video content using a peer-assisted approach are able to serve large numbers of concurrent requests by utilizing upload bandwidth from their clients to assist in delivery. In systems providing download service, BitTorrent-like protocols may be used in which “tit-for-tat” policies provide incentive for clients to contribute upload bandwidth. For on-demand streaming delivery, however, in which clients begin playback well before download is complete, all prior proposed protocols rely on peers at later video play points uploading data to peers at earlier play points that do not have data to share in return. This paper considers the problem of devising peer-assisted protocols for streaming systems that, similar to download systems, provide effective “tit-for-tat” incentives for clients to contribute upload bandwidth. We propose policies that provide such incentives, while also providing short start-up delays, and delivery of (almost) all video frames by their respective playback deadlines.

  • 45.
    Carlsson, Niklas
    et al.
    University of Saskatchewan.
    Eager, Derek L.
    University of Saskatchewan.
    Vernon, Mary K.
    University of Wisconsin-Madison.
    Multicast Protocols for Scalable On-demand Download2006In: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, ISSN 0166-5316, Vol. 63, no 9/10, p. 864-891Article in journal (Refereed)
    Abstract [en]

    Previous scalable protocols for downloading large, popular files from a single server include batching and cyclic multicast. With batching, clients wait to begin receiving a requested file until the beginning of its next multicast transmission, which collectively serves all of the waiting clients that have accumulated up to that point. With cyclic multicast, the file data is cyclically transmitted on a multicast channel. Clients can begin listening to the channel at an arbitrary point in time, and continue listening until all of the file data has been received.This paper first develops lower hounds on the average and maximum client delay for completely downloading a file, as functions of the average server bandwidth used to serve requests for that file, for systems with homogeneous clients. The results show that neither cyclic multicast nor batching consistently yields performance close to optimal. New hybrid download protocols are proposed that achieve within 15% of the optimal maximum delay and 20% of the optimal average delay in homogeneous systems.For heterogeneous systems in which clients have widely varying achievable reception rates, an additional design question concerns the use of high rate transmissions, which can decrease delay for clients that can receive at such rates, in addition to low rate transmissions that can be received by all clients. A new scalable download protocol for such systems is proposed, and its performance is compared to that of alternative protocols as well as to new lower bounds on maximum client delay. The new protocol achieves within 25% of the optimal maximum client delay in all scenarios considered.

  • 46.
    Carlsson, Niklas
    et al.
    University of Saskatchewan.
    Eager, Derek L.
    Vernon, Mary K.
    Multicast Protocols for Scalable On-demand Download2004In: Proc. ACM SIGMETRICS/Performance ’04, New York, NY, June 2004, ACM , 2004, p. 428-429Conference paper (Refereed)
  • 47.
    Carlsson, Niklas
    et al.
    University of Calgary, Canada.
    Eager, Derek
    University of Saskatchewan, Canada.
    Mahanti, Anirban
    NICTA. Sydney, Australia.
    Using Torrent Inflation to Efficiently Serve the Long Tail in Peer-assisted Content Delivery Systems2010In: NETWORKING 2010: 9th International IFIP TC 6 Networking Conference, Chennai, India, May 11-15, 2010. Proceedings / [ed] Mark Crovella, Laura Marie Feeney, Dan Rubenstein and S. V. Raghavan, Springer Berlin/Heidelberg, 2010, p. 1-14Chapter in book (Refereed)
    Abstract [en]

    A peer-assisted content delivery system uses the upload bandwidth of its clients to assist in delivery of popular content. In peer-assisted systems using a BitTorrent-like protocol, a content delivery server seeds the offered files, and active torrents form when multiple clients make closely-spaced requests for the same content. Scalability is achieved in the sense of being able to accommodate arbitrarily high request rates for individual files. Scalability with respect to the number of files, however, may be much more difficult to achieve, owing to a “long tail” of lukewarm or cold files for which the server may need to assume most or all of the delivery cost. This paper first addresses the question of how best to allocate server resources among multiple active torrents. We then propose new content delivery policies that use some of the available upload bandwidth from currently downloading clients to “inflate” torrents for files that would otherwise require substantial server bandwidth. Our performance results show that use of torrent inflation can substantially reduce download times, by more than 50% in some cases.

  • 48.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Li, Xiaolin Andy
    University of Florida, USA.
    Singhal, Mukesh
    University of California, Merced, USA.
    Wang, Mea
    University of Calgary, Canada.
    Guest Editorial - Cloud and Big Data2014In: Journal of Communications, ISSN 1796-2021, E-ISSN 2374-4367, Vol. 9, no 4, p. i-iiiArticle in journal (Refereed)
    Abstract [en]

    In the current digital age, massive amounts of data are generated in many different ways and forms. The data may be collected from everything from personal web logs to purposefully placed sensors. Today, companies and researchers use this data for everything from targeted personalized ads based on social data to solving important scientific problems that may help future generations of word citizens. Regardless if measured in monetary profit or other measures, the value of this data has proven valuable for many purposes and has led us into the Big Data era. Due to the large volume of data, Big Data requires significant storage, processing, and bandwidth resources. To date, the Cloud provides the largest collection of disk storage, CPU power, and network bandwidth, which makes it a natural choice for housing the Big Data.

  • 49.
    Carlsson, Niklas
    et al.
    University of Saskatchewan.
    Mahanti, Anirban
    IIT Delhi, India.
    Li, Zongpeng
    University of Calgary.
    Eager, Derek L.
    University of Saskatchewan.
    Optimized Periodic Broadcast of Non-linear Media2008In: IEEE transactions on multimedia, ISSN 1520-9210, E-ISSN 1941-0077, ISSN 1520-9210, Vol. 10, no 5, p. 871-884Article in journal (Refereed)
    Abstract [en]

    Conventional video consists of a single sequence of video frames. During a client's playback period, frames are viewed sequentially from some specified starting point. The fixed frame ordering of conventional video enables efficient scheduled broadcast delivery, as well as efficient near on-demand delivery to large numbers of concurrent clients through use of periodic broadcast protocols in which the video file is segmented and transmitted on multiple channels. This paper considers the problem of devising scalable protocols for near on-demand delivery of “nonlinear” media files whose content may have a tree or graph, rather than linear, structure. Such media allows personalization of the media playback according to individual client preferences. We formulate a mathematical model for determination of the optimal periodic broadcast protocol for nonlinear media with piecewise-linear structures. Our objective function allows differing weights to be placed on the startup delays required for differing paths through the media. Studying a number of simple nonlinear structures we provide insight into the characteristics of the optimal solution. For cases in which the cost of solving the optimization model is prohibitive, we propose and evaluate an efficient approximation algorithm.

  • 50.
    Carlsson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Williamson, Carey
    University of Calgary, Canada.
    Hirt, Andreas
    University of Calgary, Canada.
    Jacobson, Micheal
    University of Calgary, Canada.
    Performance Modeling of Anonymity Protocols2012In: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, Vol. 69, no 12, p. 643-661Article in journal (Refereed)
    Abstract [en]

    Anonymous network communication protocols provide privacy for Internet-based communication. In this paper, we focus on the performance and scalability of anonymityprotocols. In particular, we develop performance models for two anonymityprotocols from the prior literature (Buses and Taxis), as well as our own newly proposed protocol (Motorcycles). Using a combination of experimental implementation, simulation, and analysis, we show that: (1) the message latency of the Buses protocol is O(N2), scaling quadratically with the number of participants; (2) the message latency of the Taxis protocol is O(N), scaling linearly with the number of participants; and (3) the message latency of the Motorcycles protocol is O(log2N), scaling logarithmically with the number of participants. Motorcycles can provide scalable anonymous network communication, without compromising the strength of anonymity provided by Buses or Taxis.

1234 1 - 50 of 153
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf