1,720,965 research outputs found
Closing the gap between the Web and Peer to Peer
No full textDuring the course of Q4 of the 2012-2013 academic year, we have worked on the project of a Peer-to-Peer web browser. After a two week orientation phase, a six week programming phase and nally another two week reporting phase we deliver our product. The final result of this endeavor is an integrated web browser in the Tribler platform, which supports automatic retrieval and distribution of resources encountered on the web page.Parallel and Distributed Systems groupDepartment of Software and Computer TechnologyElectrical Engineering, Mathematics and Computer Scienc
Merging the best of HTTP and P2P
No full textThe World Wide Web is growing fast. Web content is growing as well. To cope with this trend, server infrastructures must be able to serve a huge amount of traffic. When this cannot happen, service denial is the consequence. Small content publishers are the most affected by this phenomenon. At the same time, BitTorrent is leading the file sharing world, generating a big part of the network traffic. Therefore combining HTTP and BitTorrent is a candidate solution for dealing with phenomena like flashcrowds. But how to merge the HTTP and BitTorrent protocols? How to leverage the P2P network when the only input is the web content URL? This document proposes an approach to support HTTP with the BitTorrent protocol. The architecture of HTTP2P, a tool capable of hybrid download, is described in its details. It is shown that the main problem to face when creating such an hybrid is preventing content pollution attacks. The solution to this problem is the Pollution Prevention algorithm presented in this work. The experiment results show that the achieved performance when combining HTTP and BitTorrent is the best of both protocols: slow start-up delay, improved download speed and server load reduction.Distributed systemsElectrical Engineering, Mathematics and Computer Scienc
CoopViz: Real Time Visualization of BitTorrent Swarm Dynamics
No full textMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Splash: Data synchronization in unmanaged, untrusted peer-to-peer networks
No full textPeer-to-peer networks rely on gossip algorithms to spread information about the peer activity and the network status. State-of-the-art gossip algorithms are not sufficient to spread the information widely, as the size and the complexity of the unmanaged networks grow. They suffer from high bandwidth utilization and lack mechanisms to verify the validity of the transferred information. We set the following questions for research: How can we achieve high coverage ratio for all the peers in the network while using as little bandwidth as possible? How can such a mechanism scale to millions of nodes? How can we reduce the effects of high churn rates? And finally, how we secure that the data transmitted are genuine? We develop Splash, a data synchronization algorithm with emphasis on high data coverage and efficient bandwidth usage. Our solution is based on Bloom filters and allows both partial and full synchronizations while avoiding the transmission of duplicate information. We propose two schemes to synchronize current and historical data between peers, over unmanaged and untrusted peer-to-peer networks. We use a SyncLog to keep the state of the synchronization algorithm to a minimum. For scalability we categorize data based on their origin, as local or global, and we investigate the use of different synchronization policies. Finally we discuss mechanisms that validate data to prevent the spread to invalid information. Through a series of experiments we present the effectiveness of this solution in networks with different sizes and churn effects. In simulation Splash achieves 95% data coverage for all the peers in the network, which is 5 times more compared to BarterCast. Additionally Splash uses 107 times less bandwidth compared to BarterCast to achieve the same data coverage.gComputer EngineeringParallel and Distributed SystemsElectrical Engineering, Mathematics and Computer Scienc
BitTorrent file sharing using Tor-like hidden services
No full textThe Internet is a large public network of networks and computers. When no countermeasures are taken, all information and activities taking place on the public Internet are subject to traffic analysis, threatening personal freedom and privacy. The first measure to take is securing all transferred information by applying encryption on it, which makes it at least very hard to tap the contents of the transferred information. But encryption does not add any value when it comes to anonymity. Although the contents of the message are not known (because it is encrypted), it is still possible to track down where a message comes from, and where it is going to by analyzing the network infrastructure. Governments or Internet providers may apply censorship or block any kind of network traffic coming or going from somewhere. This is where hidden services come in. The idea of hidden services was described by the authors of Tor (The onion router). The hidden services protocol hides the location of both the sender and receiver by transferring and encrypting messages over multiple hops, without revealing the true identity or contents of the messages in transit. This thesis proposes a design for implementing Tor-like hidden services in a decentralized peer-to-peer system, enabling the possibility of downloading and seeding anonymously. A proof-of-concept will be implemented into Tribler, a BitTorrent client developed at Delft University of Technology. Tribler already supports anonymous downloading using encryption over circuits with multiple hops, but to make hidden services work, an end-to-end encrypted circuit between both the seeder and downloader needs to be established. This is not as easy as it seems, because the seeder and downloader do not know each other. The implementation details of hidden services are part of this work, as well as experiments on the performance of the system. Furthermore, a number of issues related to transforming the original idea of hidden services into a fully distributed context are solved.CSPDSElectrical Engineering, Mathematics and Computer Scienc
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Libswift-PPSPP Information Centric Router: SHA1 Accelerator
No full textPeer to peer content streaming is the next generation content delivery method, making obsolete the client-server communication model which is not sustainable in the current Internet environment. One effort to standardize this new protocol is represented by the Libswift-PPSPP (Peer to Peer Streaming Peer Protocol) Information Centric Network (ICN). In this thesis we lay the foundation for developing a Libswift ICN router using FPGA technology. We start by describing the protocol, provide a set of requirements for the generic router and identify a subset that we will implement. Using the NetFPGA development platform, we build a hash (SHA1) computation accelerator, which is one of the fundamental building blocks for the Libswift ICN router. Our measurements show that the prototype outperforms a general purpose CPU in hash calculation. The measured speedup is of 1.54 and the area overhead is small considering the complete system. Possible optimizations are discussed and the impact of those optimizations is compared with our working implementation. We conclude with a brief description of further work needed to obtain a complete Libswift-PPSPP ICN Router.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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