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  • 1.
    Arad, Cosmin
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Message-Passing Concurrency for Scalable, Stateful, Reconfigurable Middleware2012In: Middleware 2012: ACM/IFIP/USENIX 13th International Middleware Conference, Montreal, QC, Canada, December 3-7, 2012. Proceedings / [ed] Priya Narasimhan and Peter Triantafillou, Springer Berlin/Heidelberg, 2012, p. 208-228Conference paper (Refereed)
    Abstract [en]

    Message-passing concurrency (MPC) is increasingly being used to build systems software that scales well on multi-core hardware. Functional programming implementations of MPC, such as Erlang, have also leveraged their stateless nature to build middleware that is not just scalable, but also dynamically reconfigurable. However, many middleware platforms lend themselves more naturally to a stateful programming model, supporting session and application state. A limitation of existing programming models and frameworks that support dynamic reconfiguration for stateful middleware, such as component frameworks, is that they are not designed for MPC.

    In this paper, we present Kompics, a component model and programming framework, that supports the construction and composition of dynamically reconfigurable middleware using stateful, concurrent, message-passing components. An added benefit of our approach is that by decoupling our component execution model, we can run the same code in both simulation and production environments. We present the architectural patterns and abstractions that Kompics facilitates and we evaluate them using a case study of a non-trivial key-value store that we built using Kompics. We show how our model enables the systematic development and testing of scalable, dynamically reconfigurable middleware.

  • 2.
    Baig, Roger
    et al.
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Escrich, Pau
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Freitag, Felix
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain .
    Meseguer, Roc
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Moll, Agusti
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Navarro, Leandro
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Pietrosemoli, Ermanno
    The Abdus Salam International Centre for Theoretical Physics (ICTP). Trieste, Italy.
    Pueyo, Roger
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Zennaro, Marco
    The Abdus Salam International Centre for Theoretical Physics (ICTP). Trieste, Italy.
    Deploying Clouds in the Guifi Community Network2015In: Proceedings of the 2015 IFIP/IEEE International Symposium on Integrated Network Management, IM 2015, IEEE , 2015, p. 1020-1025Conference paper (Refereed)
    Abstract [en]

    This paper describes an operational geographically distributed and heterogeneous cloudinfrastructure with services and applications deployed in the Guifi community network. The presentedcloud is a particular case of a community cloud, developed according to the specific needs and conditions of community networks. We describe the concept of this community cloud, explain our technical choices for building it, and our experience with the deployment of this cloud. We review our solutions and experience on offering the different service models of cloud computing (IaaS, PaaS and SaaS) in community networks. The deployed cloud infrastructure aims to provide stable and attractive cloud services in order to encourage community network user to use, keep and extend it with new services and applications.

  • 3. Bessani, A.
    et al.
    Brandt, J.
    Bux, M.
    Cogo, V.
    Dimitrova, L.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Gholami, Ali
    KTH.
    Hakimzadeh, Kamal
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Hummel, M.
    Ismail, Mahmoud
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC. KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Leser, U.
    Litton, J. -E
    Martinez, R.
    Niazi, Salman
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Reichel, J.
    Zimmermann, K.
    BiobankCloud: A platform for the secure storage, sharing, and processing of large biomedical data sets2016In: 1st International Workshop on Data Management and Analytics for Medicine and Healthcare, DMAH 2015 and Workshop on Big-Graphs Online Querying, Big-O(Q) 2015 held in conjunction with 41st International Conference on Very Large Data Bases, VLDB 2015, Springer, 2016, p. 89-105Conference paper (Refereed)
    Abstract [en]

    Biobanks store and catalog human biological material that is increasingly being digitized using next-generation sequencing (NGS). There is, however, a computational bottleneck, as existing software systems are not scalable and secure enough to store and process the incoming wave of genomic data from NGS machines. In the BiobankCloud project, we are building a Hadoop-based platform for the secure storage, sharing, and parallel processing of genomic data. We extended Hadoop to include support for multi-tenant studies, reduced storage requirements with erasure coding, and added support for extensible and consistent metadata. On top of Hadoop, we built a scalable scientific workflow engine featuring a proper workflow definition language focusing on simple integration and chaining of existing tools, adaptive scheduling on Apache Yarn, and support for iterative dataflows. Our platform also supports the secure sharing of data across different, distributed Hadoop clusters. The software is easily installed and comes with a user-friendly web interface for running, managing, and accessing data sets behind a secure 2-factor authentication. Initial tests have shown that the engine scales well to dozens of nodes. The entire system is open-source and includes pre-defined workflows for popular tasks in biomedical data analysis, such as variant identification, differential transcriptome analysis using RNA-Seq, and analysis of miRNA-Seq and ChIP-Seq data.

  • 4. Biskupski, Bartosz
    et al.
    Dowling, Jim
    Swedish Institute of Computer Science.
    Sacha, Jan
    Properties and Mechanisms of Self-Organizing MANET and P2P Systems2007In: ACM Transactions on Autonomous and Adaptive Systems, ISSN 1556-4665, Vol. 2, no 1Article in journal (Refereed)
    Abstract [en]

    Despite the recent appearance of self-organizing distributed systems for Mobile Ad Hoc Networks (MANETs) and Peer-to-Peer (P2P) networks, specific theoretical aspects of both their properties and the mechanisms used to establish those properties have been largely overlooked. This has left many researchers confused as to what constitutes a self-organizing distributed system and without a vocabulary with which to discuss aspects of these systems. This article introduces an agent-based model of self-organizing MANET and P2P systems and shows how it is realised in three existing network systems. The model is based on concepts such as partial views, evaluation functions, system utility, feedback and decay. We review the three network systems, AntHocNet, SAMPLE, and Freenet, and show how they can achieve high scalability, robustness and adaptability to unpredictable changes in their environment, by using self-organizing mechanisms similar to those found in nature. They are designed to improve their operation in a dynamic, heterogeneous environment, enabling them to often demonstrate superior performance to state of the art distributed systems. This article is also addressed at researchers interested in gaining a general understanding of different mechanisms and properties of self-organization in distributed systems.

  • 5. Bux, M.
    et al.
    Brandt, J.
    Lipka, C.
    Hakimzadeh, Kamal
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Leser, U.
    SAASFEE: Scalable scientific workflow execution engine2015In: Proceedings of the VLDB Endowment, ISSN 2150-8097, E-ISSN 2150-8097, Vol. 8, no 12, p. 1892-1895Article in journal (Refereed)
    Abstract [en]

    Across many fields of science, primary data sets like sensor read-outs, time series, and genomic sequences are analyzed by complex chains of specialized tools and scripts exchanging intermediate results in domain-specific file formats. Scientific work ow management systems (SWfMSs) support the development and execution of these tool chains by providing work ow specification languages, graphical editors, fault-tolerant execution engines, etc. However, many SWfMSs are not prepared to handle large data sets because of inadequate support for distributed computing. On the other hand, most SWfMSs that do support distributed computing only allow static task execution orders. We present SAASFEE, a SWfMS which runs arbitrarily complex work ows on Hadoop YARN. Work ows are specified in Cuneiform, a functional work ow language focusing on parallelization and easy integration of existing software. Cuneiform work ows are executed on Hi-WAY, a higher-level scheduler for running work ows on YARN. Distinct features of SAASFEE are the ability to execute iterative work ows, an adaptive task scheduler, re-executable provenance traces, and compatibility to selected other work ow systems. In the demonstration, we present all components of SAASFEE using real-life work ows from the field of genomics.

  • 6.
    Dowling, Jim
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Developing a Distributed Electronic Health-Record Store for India2008In: ERCIM News, ISSN 0926-4981, E-ISSN 1564-0094, no 75, p. 56-57Article, review/survey (Other (popular science, discussion, etc.))
    Abstract [en]

    The DIGHT project is addressing the problem of building a scalable and highly available information store for the Electronic Health Records (EHRs) of the over one billion citizens of India.

    There has been much recent interest in information services that offer to manage an individual's healthcare records in electronic form, with systems such as Microsoft HealthVault and Google Health receiving widespread media attention. These systems are, however, proprietary and fears have been expressed over how the information stored in them will be used. In relation to these developments, countries with nationalized healthcare systems are also investigating the construction of healthcare information systems that store Electronic Health Records (EHRs) for their citizens.

  • 7.
    Dowling, Jim
    et al.
    Swedish Inst Comp Sci, Kista.
    Sacha, Jan
    Swedish Inst Comp Sci, Kista.
    Haridi, Seif
    Swedish Inst Comp Sci, Kista.
    Improving ICE service selection in a P2P system using the gradient topology2007In: First IEEE International Conference on Self-Adaptive and Self-Organizing Systems, 2007, p. 285-288Conference paper (Refereed)
    Abstract [en]

    Internet Connectivity Establishment (ICE) is becoming increasingly important for P2P systems on the open Internet, as it enables NAT-bound peers to provide accessible services. A problem for P2P systems that provide ICE services is how peers discover good quality ICE servers for NAT traversal, that is, the TURN and STUN servers that provide relaying and hole-punching services, respectively. Skype provides a P2P-based solution to this problem, where super-peers provide ICE services. However experimental analysis of Skype indicates that peers perform a random walk of super-peers to find one with an acceptable round-trip latency. In this paper, we discuss a self organizing approach to discovering good quality ICE servers in a P2P system based the walk Topology. The walk Topology uses information about each peer’s ability to provide ICE services (open IP address, available bandwidth and expected session times) to construct a topology where the “better” peers for providing ICE services cluster in the center of the topology; this adaptation of the super-peer search space reduces the problem of finding a good quality ICE server from a random walk to a gradient ascent search.

  • 8. Dowling, Jim
    et al.
    Taïani, F.
    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics): Preface2013In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, p. VII-VIIIArticle in journal (Refereed)
  • 9.
    Gholami, Ali
    et al.
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC. KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    A security framework for population-scale genomics analysis2015In: Proceedings of the 2015 International Conference on High Performance Computing and Simulation, HPCS 2015, IEEE conference proceedings, 2015, p. 106-114Conference paper (Refereed)
    Abstract [en]

    Biobanks store genomic material from identifiable individuals. Recently many population-based studies have started sequencing genomic data from biobank samples and cross-linking the genomic data with clinical data, with the goal of discovering new insights into disease and clinical treatments. However, the use of genomic data for research has far-reaching implications for privacy and the relations between individuals and society. In some jurisdictions, primarily in Europe, new laws are being or have been introduced to legislate for the protection of sensitive data relating to individuals, and biobank-specific laws have even been designed to legislate for the handling of genomic data and the clear definition of roles and responsibilities for the owners and processors of genomic data. This paper considers the security questions raised by these developments. We introduce a new threat model that enables the design of cloud-based systems for handling genomic data according to privacy legislation. We also describe the design and implementation of a security framework using our threat model for BiobankCloud, a platform that supports the secure storage and processing of genomic data in cloud computing environments.

  • 10. Hakimzadeh, Kamal
    et al.
    Peiro Sajjad, Hooman
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Scaling HDFS with a Strongly Consistent Relational Model for Metadata2014In: Distributed Applications and Interoperable Systems, 2014, p. 38-51Conference paper (Refereed)
    Abstract [en]

    The Hadoop Distributed File System (HDFS) scales to store tens of petabytes of data despite the fact that the entire file system's metadata must fit on the heap of a single Java virtual machine. The size of HDFS' metadata is limited to under 100 GB in production, as garbage collection events in bigger clusters result in heartbeats timing out to the metadata server (NameNode). In this paper, we address the problem of how to migrate the HDFS' metadata to a relational model, so that we can support larger amounts of storage on a shared-nothing, in-memory, distributed database. Our main contribution is that we show how to provide at least as strong consistency semantics as HDFS while adding support for a multiple-writer, multiple-reader concurrency model. We guarantee freedom from deadlocks by logically organizing inodes (and their constituent blocks and replicas) into a hierarchy and having all metadata operations agree on a global order for acquiring both explicit locks and implicit locks on subtrees in the hierarchy. We use transactions with pessimistic concurrency control to ensure the safety and progress of metadata operations. Finally, we show how to improve performance of our solution by introducing a snapshotting mechanism at NameNodes that minimizes the number of roundtrips to the database.

  • 11.
    Haridi, Seif
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Arad, Cosmin
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Developing, simulating, and deploying peer-to-peer systems using the Kompics component model2009In: Proceedings of the 4th International Conference on COMmunication System softWAre and MiddlewaRE / [ed] ACM 2009, 2009Conference paper (Refereed)
    Abstract [en]

    Currently, the development of overlay network systems typically produces two software artifacts: a simulator to model key protocols and a production system for a WAN environment. However, this methodology requires the maintenance of two implementations, as well as adding both development overhead and the potential for errors, through divergence in the different code bases. This paper describes how our message-passing component model, called Kompics, is used to build overlay network systems using a P2P component framework, where the same implementation can be simulated or deployed in a production environment. Kompics enables two different modes of simulation: deterministic simulation for reproducible debugging, and emulation mode for stress-testing systems. We used our P2P component framework to build and evaluate overlay systems, and we show how our model lowers the programming barrier for simulating and deploying overlay network systems.

  • 12.
    Ismail, Mahmoud
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Gebremeskel, Ermias
    Kakantousis, Theofilos
    Berthou, Gautier
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS. RISE SICS, Sweden.
    Hopsworks: Improving User Experience and Development on Hadoop with Scalable, Strongly Consistent Metadata2017In: 2017 IEEE 37TH INTERNATIONAL CONFERENCE ON DISTRIBUTED COMPUTING SYSTEMS (ICDCS 2017) / [ed] Lee, K Liu, L, IEEE COMPUTER SOC , 2017, p. 2525-2528Conference paper (Refereed)
    Abstract [en]

    Hadoop is a popular system for storing, managing, and processing large volumes of data, but it has bare-bones internal support for metadata, as metadata is a bottleneck and less means more scalability. The result is a scalable platform with rudimentary access control that is neither user-nor developer friendly. Also, metadata services that are built on Hadoop, such as SQL-on-Hadoop, access control, data provenance, and data governance are necessarily implemented as eventually consistent services, resulting in increased development effort and more brittle software. In this paper, we present a new project-based multi-tenancy model for Hadoop, built on a new distribution of Hadoop that provides a distributed database backend for the Hadoop Distributed Filesystem's (HDFS) metadata layer. We extend Hadoop's metadata model to introduce projects, datasets, and project-users as new core concepts that enable a user-friendly, UI-driven Hadoop experience. As our metadata service is backed by a transactional database, developers can easily extend metadata by adding new tables and ensure the strong consistency of extended metadata using both transactions and foreign keys.

  • 13.
    Ismail, Mahmoud
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Niazi, Salman
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Ronstrom, M.
    Haridi, S.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Scaling HDFS to more than 1 million operations per second with HopsFS2017In: Proceedings - 2017 17th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing, CCGRID 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 683-688Conference paper (Refereed)
    Abstract [en]

    HopsFS is an open-source, next generation distribution of the Apache Hadoop Distributed File System(HDFS) that replaces the main scalability bottleneck in HDFS, single node in-memory metadata service, with a no-sharedstate distributed system built on a NewSQL database. By removing the metadata bottleneck in Apache HDFS, HopsFS enables significantly larger cluster sizes, more than an order of magnitude higher throughput, and significantly lower clientlatencies for large clusters. In this paper, we detail the techniques and optimizations that enable HopsFS to surpass 1 million file system operations per second-at least 16 times higher throughput than HDFS. In particular, we discuss how we exploit recent high performance features from NewSQL databases, such as application defined partitioning, partition-pruned index scans, and distribution aware transactions. Together with more traditional techniques, such as batching and write-Ahead caches, we show how many incremental optimizations have enabled a revolution in distributed hierarchical file system performance.

  • 14.
    Kroll, Lars
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Static Type Checking for the Kompics Component Model: Kola – The Kompics Language2016In: First Workshop on Programming Models and Languages for Distributed Computing, ACM Digital Library, 2016, p. 2-1Conference paper (Refereed)
    Abstract [en]

    Distributed systems are becoming an increasingly important part of systems and applications software and it is widely accepted that writing correct distributed systems is challenging. Message-passing concurrency models are the dominant programming paradigm and, even in statically typed languages, programming frameworks typically only have limited type checking support for messages, channels, and ports or mailboxes. In this paper, we present Kola, a language-level implementation of Kompics, a component model with message-passing concurrency. Kola comes with its own compiler and some special language constructs which extend Java's type system as necessary to enforce static type checking on messages, channels, and ports. We show that Kola improves the readability of Kompics code and removes opportunities to introduce bugs, at the cost of little compile time overhead and no runtime overhead.

  • 15.
    Niazi, Salman
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Ismail, Mahmoud
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Berthou, Gautier
    Leader Election Using NewSQL Database Systems2015In: Distributed Applications and Interoperable Systems: 15th IFIP WG 6.1 International Conference, DAIS 2015, Held as Part of the 10th International Federated Conference on Distributed Computing Techniques, DisCoTec 2015, Grenoble, France, June 2-4, 2015, Proceedings / [ed] Alysson Bessani and Sara Bouchenak, France: Springer, 2015, p. 158-172Conference paper (Refereed)
    Abstract [en]

    Leader election protocols are a fundamental building blockfor replicated distributed services. They ease the design of leader-basedcoordination protocols that tolerate failures. In partially synchronoussystems, designing a leader election algorithm, that does not permit mul-tiple leaders while the system is unstable, is a complex task. As a resultmany production systems use third-party distributed coordination ser-vices, such as ZooKeeper and Chubby, to provide a reliable leader electionservice. However, adding a third-party service such as ZooKeeper to adistributed system incurs additional operational costs and complexity.ZooKeeper instances must be kept running on at least three machinesto ensure its high availability. In this paper, we present a novel leaderelection protocol using NewSQL databases for partially synchronous sys-tems, that ensures at most one leader at any given time. The leaderelection protocol uses the database as distributed shared memory. Ourwork enables distributed systems that already use NewSQL databasesto save the operational overhead of managing an additional third-partyservice for leader election. Our main contribution is the design, imple-mentation and validation of a practical leader election algorithm, basedon NewSQL databases, that has performance comparable to a leaderelection implementation using a state-of-the-art distributed coordinationservice, ZooKeeper

  • 16.
    Niazi, Salman
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Ismail, Mahmoud
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Grohsschmiedt, Steffen
    Ronström, Mikael
    HopsFS: Scaling Hierarchical File System Metadata Using NewSQL Databases2017In: 15th USENIX Conference on File and Storage Technologies, FAST 2017, Santa Clara, CA, USA, February 27 - March 2, 2017, USENIX Association , 2017, p. 89-103Conference paper (Refereed)
    Abstract [en]

    Recent improvements in both the performance and scalability of shared-nothing, transactional, in-memory NewSQL databases have reopened the research question of whether distributed metadata for hierarchical file systems can be managed using commodity databases. In this paper, we introduce HopsFS, a next generation distribution of the Hadoop Distributed File System (HDFS) that replaces HDFS’ single node in-memory metadata service, with a distributed metadata service built on a NewSQL database. By removing the metadata bottleneck, HopsFS enables an order of magnitude larger and higher throughput clusters compared to HDFS. Metadata capacity has been increased to at least 37 times HDFS’ capacity, and in experiments based on a workload trace from Spotify, we show that HopsFS supports 16 to 37 times the throughput of Apache HDFS. HopsFS also has lower latency for many concurrent clients, and no downtime during failover. Finally, as metadata is now stored in a commodity database, it can be safely extended and easily exported to external systems for online analysis and free-text search.

  • 17.
    Payberah, Amir H.
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Shuffling with a Croupier: Nat-Aware Peer-Sampling2012In: Proceedings of the 2012 32nd IEEE International Conference on Distributed Computing Systems (ICDCS 2012) / [ed] Lisa O'Conner, IEEE Computer Society, 2012, p. 102-111Conference paper (Refereed)
    Abstract [en]

    Despite much recent research on peer-to-peer (P2P) protocols for the Internet, there have been relatively few practical protocols designed to explicitly account for Network Address Translation gateways (NATs). Those P2P protocols that do handle NATs circumvent them using relaying and hole-punching techniques to route packets to nodes residing behind NATs. In this paper, we present Croupier, a peer sampling service (PSS) that provides uniform random samples of nodes in the presence of NATs in the network. It is the first NAT-aware PSS that works without the use of relaying or hole-punching. By removing the need for relaying and hole-punching, we decrease the complexity and overhead of our protocol as well as increase its robustness to churn and failure. We evaluated Croupier in simulation, and, in comparison with existing NAT-aware PSS', our results show similar randomness properties, but improved robustness in the presence of both high percentages of nodes behind NATs and massive node failures. Croupier also has substantially lower protocol overhead.

  • 18.
    Payberah, Amir H.
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Rahimian, Fatemeh
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Distributed optimization of P2P live streaming overlays2012In: Computing, ISSN 0010-485X, Vol. 94, no 8/10, p. 621-647Article in journal (Refereed)
    Abstract [en]

    Peer-to-peer live media streaming over the Internet is becoming increasingly more popular, though it is still a challenging problem. Nodes should receive the stream with respect to intrinsic timing constraints, while the overlay should adapt to the changes in the network and the nodes should be incentivized to contribute their resources. In this work, we meet these contradictory requirements simultaneously, by introducing a distributed market model to build an efficient overlay for live media streaming. Using our market model, we construct two different overlay topologies, tree-based and mesh-based, which are the two dominant approaches to the media distribution. First, we build an approximately minimal height multiple-tree data dissemination overlay, called Sepidar. Next, we extend our model, in GLive, to make it more robust in dynamic networks by replacing the tree structure with a mesh. We show in simulation that the mesh-based overlay outperforms the multiple-tree overlay. We compare the performance of our two systems with the state-of-the-art NewCoolstreaming, and observe that they provide better playback continuity and lower playback latency than that of NewCoolstreaming under a variety of experimental scenarios. Although our distributed market model can be run against a random sample of nodes, we improve its convergence time by executing it against a sample of nodes taken from the Gradient overlay. The evaluations show that the streaming overlays converge faster when our market model works on top of the Gradient overlay.

  • 19.
    Roverso, Roberto
    et al.
    Peerialism AB, Sweden .
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Jelasity, Mark
    University of Szeged.
    Through the Wormhole: Low Cost, Fresh Peer Sampling for the Internet2013In: 13th IEEE International Conference on Peer-to-Peer Computing, IEEE P2P 2013 - Proceedings, IEEE , 2013, p. 6688707-Conference paper (Refereed)
    Abstract [en]

    State of the art gossip protocols for the Internet are based on the assumption that connection establishment between peers comes at negligible cost. Our experience with commercially deployed P2P systems has shown that this cost is much higher than generally assumed. As such, peer sampling services often cannot provide fresh samples because the service would require too high a connection establishment rate. In this paper, we present the wormhole-based peer sampling service (WPSS). WPSS overcomes the limitations of existing protocols by executing short random walks over a stable topology and by using shortcuts (wormholes), thus limiting the rate of connection establishments and guaranteeing freshness of samples, respectively.We show that our approach can decrease the connection establishment rate by one order of magnitude compared to the state of the art while providing the same levels of freshness of samples. This, without sacrificing the desirable properties of a PSS for the Internet, such as robustness to churn and NAT-friendliness. We support our claims with a thorough measurement study in our deployed commercial system as well as in simulation.

  • 20. Sacha, Jan
    et al.
    Biskupski, Bartosz
    Dahlem, Dominik
    Cunningham, Raymond
    Meier, Rene
    Dowling, Jim
    Trinity College, Dublin, Ireland.
    Haahr, Mads
    Decentralising a service-oriented architecture2010In: Peer-to-Peer Networking and Applications, ISSN 1936-6442, E-ISSN 1936-6450, Vol. 3, no 4, p. 323-350Article in journal (Refereed)
    Abstract [en]

    Service-oriented computing is becoming an increasingly popular paradigm for modelling and building distributed systems in open and heterogeneous environments. However, proposed service-oriented architectures are typically based on centralised components, such as service registries or service brokers, that introduce reliability, management, and performance issues. This paper describes an approach to fully decentralise a service-oriented architecture using a self-organising peer-to-peer network maintained by service providers and consumers. The design is based on a gradient peer-to-peer topology, which allows the system to replicate a service registry using a limited number of the most stable and best performing peers. The paper evaluates the proposed approach through extensive simulation experiments and shows that the decentralised registry and the underlying peer-to-peer infrastructure scale to a large number of peers and can successfully manage high peer churn rates.

  • 21. Spjuth, Ola
    et al.
    Karlsson, Andreas
    Clements, Mark
    Humphreys, Keith
    Ivansson, Emma
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Eklund, Martin
    Jauhiainen, Alexandra
    Czene, Kamila
    Gronberg, Henrik
    Sparen, Par
    Wiklund, Fredrik
    Cheddad, Abbas
    Palsdottir, Porgerodur
    Rantalainen, Mattias
    Abrahamsson, Linda
    Laure, Erwin
    Litton, Jan-Eric
    Palmgren, Juni
    E-Science technologies in a workflow for personalized medicine using cancer screening as a case study2017In: JAMIA Journal of the American Medical Informatics Association, ISSN 1067-5027, E-ISSN 1527-974X, Vol. 24, no 5, p. 950-957Article in journal (Refereed)
    Abstract [en]

    Objective: We provide an e-Science perspective on the workflow from risk factor discovery and classification of disease to evaluation of personalized intervention programs. As case studies, we use personalized prostate and breast cancer screenings. Materials and Methods: We describe an e-Science initiative in Sweden, e-Science for Cancer Prevention and Control (eCPC), which supports biomarker discovery and offers decision support for personalized intervention strategies. The generic eCPC contribution is a workflow with 4 nodes applied iteratively, and the concept of e-Science signifies systematic use of tools from the mathematical, statistical, data, and computer sciences. Results: The eCPC workflow is illustrated through 2 case studies. For prostate cancer, an in-house personalized screening tool, the Stockholm-3 model (S3M), is presented as an alternative to prostate-specific antigen testing alone. S3M is evaluated in a trial setting and plans for rollout in the population are discussed. For breast cancer, new biomarkers based on breast density and molecular profiles are developed and the US multicenter Women Informed to Screen Depending on Measures (WISDOM) trial is referred to for evaluation. While current eCPC data management uses a traditional data warehouse model, we discuss eCPC-developed features of a coherent data integration platform. Discussion and Conclusion: E-Science tools are a key part of an evidence-based process for personalized medicine. This paper provides a structured workflow from data and models to evaluation of new personalized intervention strategies. The importance of multidisciplinary collaboration is emphasized. Importantly, the generic concepts of the suggested eCPC workflow are transferrable to other disease domains, although each disease will require tailored solutions.

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