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Arquitetura de IPTV com suporte à apresentação deslocada no tempo baseada em distribuição peer-to-peer.; IPTV architecture with time-shift support based on peer-to-peer distribution.

Gallo, Diego Sanchez
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/03/2009 Português
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Com o aumento da concorrência sofrido pelas operadoras de telecomunicações frente à entrada de diversas empresas de outros ramos no mercado de comunicação, como, por exemplo, os Provedores de Serviço de Internet (ISPs - Internet Service Providers) através da oferta de serviços de voz sobre IP, tais operadoras viram-se obrigadas a diversificar sua oferta de serviços para gerar novas fontes de receita. Por possuírem ampla infra-estrutura instalada, as operadoras de telecomunicações passaram a oferecer, também, serviço de TV aos usuários, através de suas redes (convergentes) de telefonia e dados já existentes, o chamado IPTV. O objetivo deste trabalho foi possibilitar, neste cenário, que estas empresas consigam oferecer, além dos serviços convencionais de TV (e.g., transmissões lineares dos conteúdos nos canais de TV), serviços diferenciados empregando-se a mesma infra-estrutura. O foco deste trabalho é a oferta do serviço de apresentação deslocada no tempo dos conteúdos transmitidos linearmente nos canais de TV, sem a necessidade de configuração prévia por parte do usuário. Desta maneira, dá-se maior flexibilidade ao usuário, possibilitando-o assistir aos conteúdos que lhe interessam, no horário mais conveniente...

Um modelo arquitetural para captura e uso de informações de contexto em sistemas de anotações de vídeo; An architectural model to capture and use context information in video annotation systems

Fagá Júnior, Roberto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/06/2010 Português
Relevância na Pesquisa
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Diversos pesquisadores vêm investigando métodos e técnicas para tornar possível às pessoas anotarem vídeos de modo transparente. A anotação pode ser realizada com a fala, com o uso de tinta digital ou algum outro meio que possa ser capturado enquanto a pessoa assiste ao vídeo. Tais anotações podem ser compartilhadas com outras pessoas, que podem estar assistindo ao mesmo vídeo em um mesmo instante ou em momentos diferentes, sendo interessante ainda que as anotações possam ser realizadas por várias pessoas de modo colaborativo. O paradigma Watch-and-Comment (WaC) propõe a captura transparente de anotações multimodais de usuários enquanto os mesmos assistem e comentam um vídeo. Como resultado desse processo, é gerado um vídeo digital interativo integrando o conteúdo original às anotações realizadas. Esta dissertação tem por objetivo explorar conceitos de computação ubíqua, redes sociais, redes peer-to-peer e TV interativa na proposta de um modelo arquitetural de ciência de informações de contexto para aplicações definidas segundo o paradigma WaC. O modelo explora a integração de um serviço ao paradigma, que auxilie ou forneça alternativas para que aplicações, do momento da captura ao acesso das anotações...

Limiting fake accounts in large-scale distributed systems through adaptive identity management; Gerenciamento adaptativo de identidades em sistemas distribuídos de larga escala

Cordeiro, Weverton Luis da Costa
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
Português
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Online systems such as Facebook, Twitter, Digg, and BitTorrent communities (among various others) offer a lightweight process for obtaining identities (e.g., confirming a valid e-mail address; the actual requirements may vary depending on the system), so that users can easily join them. Such convenience comes with a price, however: with minimum effort, an attacker can obtain a horde of fake accounts (Sybil attack), and use them to either perform malicious activities (that might harm legitimate users) or obtain unfair benefits. It is extremely challenging (if not impossible) to devise a single identity management solution at the same time able to support a variety of end-users using heterogeneous devices, and suitable for a multitude of environments (e.g., large-scale distributed systems, Internet-of-Things, and Future Internet). As a consequence, the research community has focused on the design of system-specific identity management solutions, in scenarios having a well-defined set of purposes, requirements, and constraints. In this thesis, we approach the issue of fake accounts in large-scale, distributed systems. More specifically, we target systems based on the peer-to-peer paradigm and that can accommodate lightweight, long-term identity management schemes (e.g....

Suporte a colaboração em redes P2P; Collaborative support in P2P networks

Dalton Lopes Martins
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/12/2004 Português
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O suporte à colaboração e as redes P2P (peer-to-peer) tem sido dois assuntos que, por muitos momentos, se cruzam no estudo e na pesquisa do uso das novas tecnologias em ambientes colaborativos de aprendizado. O presente estudo trata das motivações sociais e técnicas para o uso das redes P2P como um suporte ao trabalho colaborativo entre grupos. Inicialmente, realizamos um estudo das características de uso e da mudança de paradigmas de trabalho em rede que o P2P nos fornece. Como base de aplicação prática deste trabalho, também apresentamos um estudo de protocolos e sistemas computacionais já existentes que tratam, de alguma forma, da questão da colaboração através de redes P2P. Por final, com base no estudo apresentado, elaboramos a especificação e a implementação de um sistema de colaboração, o SemiCode, de forma a validar algumas das idéias desenvolvidas neste trabalho, além de apresentarmos algumas soluções onde o P2P pode atuar em conjunto com sistemas cliente-servidor; The support to the collaboration and P2P network are two related subjects in the study and research involving new technologies for collaboratives learning environments. The present study deals with social motivations and techniques for the use of P2P nets as a support to the collaborative work. Initially...

Student Paper: Shared Situational Awareness Environment for Tactical Level Humanitarian Emergency Operations

Barge, Hezekiah, Jr.; Davis, Mark S.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Artigo de Revista Científica
Português
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1999 Command and Control Research and Technology Symposium (CCRTS), June 29 - July 1, 1999, U.S. Naval War College, Rhode Island; The Naval Postgraduate School (NPS) is exploring key factors that affect how teams, particularly distributed teams, develop shared situational awareness (SSA) in a Complex Humanitarian Emergency (CHE) environment. This research develops the foundation for deploying the following: Network-Centric Human-Agents in CHE habitats, an integrated environment of mobile operators, deployable wireless networks, sensors, collaborative tools, and multiagent systems. We experimentally explored how to integrate a deployable wireless network with peer-to-peer (P2P) collaborative tools and situational awareness agents. This was done to establish shared awareness of the events that were taking place during the CHE operation. The major findings include the following: a better understanding of the critical role of peer-to-peer communication, network performance monitoring, and innovative agent-based architecture for maintaining seamless access to the remote data bases and expert sources.

Methods to enhance content distribution for very large scale online communities

Tirado Martín, Juan Manuel
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado Formato: application/pdf
Português
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The Internet has experienced an exponential growth in the last years, and its number of users far from decay keeps on growing. Popular Web 2.0 services such as Facebook, YouTube or Twitter among others sum millions of users and employ vast infrastructures deployed worldwide. The size of these infrastructures is getting huge in order to support such a massive number of users. This increment of the infrastructure size has brought new problems regarding scalability, power consumption, cooling, hardware lifetime, underutilization, investment recovery, etc. Owning this kind of infrastructures is not always affordable nor convenient. This could be a major handicap for starting projects with a humble budget whose success is based on reaching a large audience. However, current technologies might permit to deploy vast infrastructures reducing their cost. We refer to peer-to-peer networks and cloud computing. Peer-to-peer systems permit users to yield their own resources to distributed infrastructures. These systems have demonstrated to be a valuable choice capable of distributing vast amounts of data to large audiences with a minimal starting infrastructure. Nevertheless, aspects such as content availability cannot be controlled in these systems...

Towards effective control of P2P traffic aggregates in network infrastructures

Sousa, Pedro
Fonte: Croatian Communications and Information Society (CCIS) Publicador: Croatian Communications and Information Society (CCIS)
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
Relevância na Pesquisa
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Nowadays, many P2P applications proliferate in the Internet. The attractiveness of many of these systems relies on the collaborative approach used to exchange large resources without the dependence and associated constraints of centralized approaches where a single server is responsible to handle all the requests from the clients. As consequence, some P2P systems are also interesting and cost-effective approaches to be adopted by content-providers and other Internet players. However, there are several coexistence problems between P2P applications and In- ternet Service Providers (ISPs) due to the unforeseeable behavior of P2P traffic aggregates in ISP infrastructures. In this context, this work proposes a collaborative P2P/ISP system able to underpin the development of novel Traffic Engi- neering (TE) mechanisms contributing for a better coexistence between P2P applications and ISPs. Using the devised system, two TE methods are described being able to estimate and control the impact of P2P traffic aggregates on the ISP network links. One of the TE methods allows that ISP administrators are able to foresee the expected impact that a given P2P swarm will have in the underlying network infrastructure. The other TE method enables the definition of ISP friendly P2P topologies...

Tagging with DHARMA, a DHT-based Approach for Resource Mapping through Approximation

Aiello, Luca Maria; Milanesio, Marco; Ruffo, Giancarlo; Schifanella, Rossano
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/01/2011 Português
Relevância na Pesquisa
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We introduce collaborative tagging and faceted search on structured P2P systems. Since a trivial and brute force mapping of an entire folksonomy over a DHT-based system may reduce scalability, we propose an approximated graph maintenance approach. Evaluations on real data coming from Last.fm prove that such strategies reduce vocabulary noise (i.e., representation's overfitting phenomena) and hotspots issues.; Comment: 8 pages, 8 figures

Survey on Distributed Data Mining in P2P Networks

T, Rekha Sunny; Thampi, Sabu M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/05/2012 Português
Relevância na Pesquisa
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The exponential increase of availability of digital data and the necessity to process it in business and scientific fields has literally forced upon us the need to analyze and mine useful knowledge from it. Traditionally data mining has used a data warehousing model of gathering all data into a central site, and then running an algorithm upon that data. Such a centralized approach is fundamentally inappropriate due to many reasons like huge amount of data, infeasibility to centralize data stored at multiple sites, bandwidth limitation and privacy concerns. To solve these problems, Distributed Data Mining (DDM) has emerged as a hot research area. Careful attention in the usage of distributed resources of data, computing, communication, and human factors in a near optimal fashion are paid by distributed data mining. DDM is gaining attention in peer-to-peer (P2P) systems which are emerging as a choice of solution for applications such as file sharing, collaborative movie and song scoring, electronic commerce, and surveillance using sensor networks. The main intension of this draft paper is to provide an overview of DDM and P2P Data Mining. The paper discusses the need for DDM, taxonomy of DDM architectures, various DDM approaches, DDM related works in P2P systems and issues and challenges in P2P data mining.; Comment: 23 pages 3 figures

Let Your CyberAlter Ego Share Information and Manage Spam

Kong, Joseph S.; Boykin, P. Oscar; Rezaei, Behnam A.; Sarshar, Nima; Roychowdhury, Vwani P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Almost all of us have multiple cyberspace identities, and these {\em cyber}alter egos are networked together to form a vast cyberspace social network. This network is distinct from the world-wide-web (WWW), which is being queried and mined to the tune of billions of dollars everyday, and until recently, has gone largely unexplored. Empirically, the cyberspace social networks have been found to possess many of the same complex features that characterize its real counterparts, including scale-free degree distributions, low diameter, and extensive connectivity. We show that these topological features make the latent networks particularly suitable for explorations and management via local-only messaging protocols. {\em Cyber}alter egos can communicate via their direct links (i.e., using only their own address books) and set up a highly decentralized and scalable message passing network that can allow large-scale sharing of information and data. As one particular example of such collaborative systems, we provide a design of a spam filtering system, and our large-scale simulations show that the system achieves a spam detection rate close to 100%, while the false positive rate is kept around zero. This system has several advantages over other recent proposals (i) It uses an already existing network...

Collaborative Applications over Peer-to-Peer Systems - Challenges and Solutions

Bandara, H. M. N. Dilum; Jayasumana, Anura P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Emerging collaborative Peer-to-Peer (P2P) systems require discovery and utilization of diverse, multi-attribute, distributed, and dynamic groups of resources to achieve greater tasks beyond conventional file and processor cycle sharing. Collaborations involving application specific resources and dynamic quality of service goals are stressing current P2P architectures. Salient features and desirable characteristics of collaborative P2P systems are highlighted. Resource advertising, selecting, matching, and binding, the critical phases in these systems, and their associated challenges are reviewed using examples from distributed collaborative adaptive sensing systems, cloud computing, and mobile social networks. State-of-the-art resource discovery/aggregation solutions are compared with respect to their architecture, lookup overhead, load balancing, etc., to determine their ability to meet the goals and challenges of each critical phase. Incentives, trust, privacy, and security issues are also discussed, as they will ultimately determine the success of a collaborative P2P system. Open issues and research opportunities that are essential to achieve the true potential of collaborative P2P systems are discussed.; Comment: Keywords - Collaborative applications...

Optimization in a Self-Stabilizing Service Discovery Framework for Large Scale Systems

Caron, Eddy; Chuffart, Florent; Lamani, Anissa; Petit, Franck
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/07/2012 Português
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Ability to find and get services is a key requirement in the development of large-scale distributed sys- tems. We consider dynamic and unstable environments, namely Peer-to-Peer (P2P) systems. In previous work, we designed a service discovery solution called Distributed Lexicographic Placement Table (DLPT), based on a hierar- chical overlay structure. A self-stabilizing version was given using the Propagation of Information with Feedback (PIF) paradigm. In this paper, we introduce the self-stabilizing COPIF (for Collaborative PIF) scheme. An algo- rithm is provided with its correctness proof. We use this approach to improve a distributed P2P framework designed for the services discovery. Significantly efficient experimental results are presented.; Comment: (2012)

Greening File Distribution: Centralized or Distributed?

Verma, Kshitiz; Rizzo, Gianluca; Anta, Antonio Fernández; Rumín, Rubén Cuevas; Azcorra, Arturo
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/11/2011 Português
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Despite file-distribution applications are responsible for a major portion of the current Internet traffic, so far little effort has been dedicated to study file distribution from the point of view of energy efficiency. In this paper, we present a first approach at the problem of energy efficiency for file distribution. Specifically, we first demonstrate that the general problem of minimizing energy consumption in file distribution in heterogeneous settings is NP-hard. For homogeneous settings, we derive tight lower bounds on energy consumption, and we design a family of algorithms that achieve these bounds. Our results prove that collaborative p2p schemes achieve up to 50% energy savings with respect to the best available centralized file distribution scheme. Through simulation, we demonstrate that in more realistic cases (e.g., considering network congestion, and link variability across hosts) we validate this observation, since our collaborative algorithms always achieve significant energy savings with respect to the power consumption of centralized file distribution systems.

Peer to Peer Optimistic Collaborative Editing on XML-like trees

Lugiez, Denis; Martin, Stéphane
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/01/2009 Português
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Collaborative editing consists in editing a common document shared by several independent sites. This may give rise to conficts when two different users perform simultaneous uncompatible operations. Centralized systems solve this problem by using locks that prevent some modifications to occur and leave the resolution of confict to users. On the contrary, peer to peer (P2P) editing doesn't allow locks and the optimistic approach uses a Integration Transformation IT that reconciliates the conficting operations and ensures convergence (all copies are identical on each site). Two properties TP1 and TP2, relating the set of allowed operations Op and the transformation IT, have been shown to ensure the correctness of the process. The choice of the set Op is crucial to define an integration operation that satisfies TP1 and TP2. Many existing algorithms don't satisfy these properties and are indeed incorrect i.e. convergence is not guaranteed. No algorithm enjoying both properties is known for strings and little work has been done for XML trees in a pure P2P framework (that doesn't use time-stamps for instance). We focus on editing unranked unordered labeled trees, so-called XML-like trees that are considered for instance in the Harmony pro ject. We show that no transformation satisfying TP1 and TP2 can exist for a first set of operations but we show that TP1 and TP2 hold for a richer set of operations. We show how to combine our approach with any convergent editing process on strings (not necessarily based on integration transformation) to get a convergent process.

Flow-based reputation: more than just ranking

Simone, Antonino; Skoric, Boris; Zannone, Nicola
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/01/2012 Português
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The last years have seen a growing interest in collaborative systems like electronic marketplaces and P2P file sharing systems where people are intended to interact with other people. Those systems, however, are subject to security and operational risks because of their open and distributed nature. Reputation systems provide a mechanism to reduce such risks by building trust relationships among entities and identifying malicious entities. A popular reputation model is the so called flow-based model. Most existing reputation systems based on such a model provide only a ranking, without absolute reputation values; this makes it difficult to determine whether entities are actually trustworthy or untrustworthy. In addition, those systems ignore a significant part of the available information; as a consequence, reputation values may not be accurate. In this paper, we present a flow-based reputation metric that gives absolute values instead of merely a ranking. Our metric makes use of all the available information. We study, both analytically and numerically, the properties of the proposed metric and the effect of attacks on reputation values.

Byzantine Fault Tolerance of Regenerating Codes

Oggier, Frédérique; Datta, Anwitaman
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/06/2011 Português
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Recent years have witnessed a slew of coding techniques custom designed for networked storage systems. Network coding inspired regenerating codes are the most prolifically studied among these new age storage centric codes. A lot of effort has been invested in understanding the fundamental achievable trade-offs of storage and bandwidth usage to maintain redundancy in presence of different models of failures, showcasing the efficacy of regenerating codes with respect to traditional erasure coding techniques. For practical usability in open and adversarial environments, as is typical in peer-to-peer systems, we need however not only resilience against erasures, but also from (adversarial) errors. In this paper, we study the resilience of generalized regenerating codes (supporting multi-repairs, using collaboration among newcomers) in the presence of two classes of Byzantine nodes, relatively benign selfish (non-cooperating) nodes, as well as under more active, malicious polluting nodes. We give upper bounds on the resilience capacity of regenerating codes, and show that the advantages of collaborative repair can turn to be detrimental in the presence of Byzantine nodes. We further exhibit that system mechanisms can be combined with regenerating codes to mitigate the effect of rogue nodes.; Comment: In The 11th IEEE International Conference on Peer-to-Peer Computing (P2P 2011)

The Case for a Collaborative Universal Peer-to-Peer Botnet Investigation Framework

Scanlon, Mark; Kechadi, M-Tahar
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/09/2014 Português
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28.214243%
Peer-to-Peer (P2P) botnets are becoming widely used as a low-overhead, efficient, self-maintaining, distributed alternative to the traditional client/server model across a broad range of cyberattacks. These cyberattacks can take the form of distributed denial of service attacks, authentication cracking, spamming, cyberwarfare or malware distribution targeting on financial systems. These attacks can also cross over into the physical world attacking critical infrastructure causing its disruption or destruction (power, communications, water, etc.). P2P technology lends itself well to being exploited for such malicious purposes due to the minimal setup, running and maintenance costs involved in executing a globally orchestrated attack, alongside the perceived additional layer of anonymity. In the ever-evolving space of botnet technology, reducing the time lag between discovering a newly developed or updated botnet system and gaining the ability to mitigate against it is paramount. Often, numerous investigative bodies duplicate their efforts in creating bespoke tools to combat particular threats. This paper outlines a framework capable of fast tracking the investigative process through collaboration between key stakeholders.; Comment: 9th International Conference on Cyber Warfare and Security (ICCWS-2014)

Test Targets 6.0: A Collaborative effort exploring the use of scientific methods for color imaging and process control

Chung, Robert; Sigg, Franz; Ploumidis, Dimitrios; Caruso, Doug; Riordan, Michael; Hsu, Michael; Freedman, Henry; Rees, Matthew
Fonte: RIT School of Media Print Publicador: RIT School of Media Print
Tipo: Periódico Formato: 9059917 bytes; application/pdf
Português
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Test Targets is a collection of scholarly papers contributed by faculty, students, and alumni of Rochester Institute of Technology. We realize the importance of having faculty set examples as authors for students to follow. We have a three-course sequence over a time span of a year to prepare students to publish their first articles when completing Tone and Color Analysis, Printing Process Control, and Advanced Color Management. In this instance, Test Targets 6.0 is a part of the course content in the Advanced Color Management course.; Introduction & Acknowledgments; Testing for Resolution and Contrast; Process Control for Metallic Color Printing Using Commonly Available Metrology in the Graphic Arts; Improving Printability on a Sheet-fed Offset Press With Continuous Dampening System Upgrade; The Effect of Profiling Target Variations on Colorimetric Accuracy of Printer Profiles; Implementation of PDF/X-3 in Production; Matching Electrophotographic Color Printing to Offset Lithography - Color Measurement Targets Perform Magic; Bridging Traditional and Digital Printing Standards; Pictorial Color Reference Images; ΔE*ab vs. ΔE*00; Handling Problem Images: Shadow/Highlight Adjustment; Bit Depth; Effect of Monochrome Image Reproduction; Grey Component Replacement; IT8.7/3 Target (basic); Pictorial Reference Images; Synthetic Targets; Total Area Coverage Chart (TAC); Monochrome Test Target; Color Sequence Target; GRACoL P2P Test Target; Grey Balance Chart; IT8.7/4 (Random) Test Target - CMYK Ink Sequence; IT8.7/4 (Random) Test Target - KCMY Ink Sequence; IT8.7/4 (Visual) Test Target; Press Run Organizer; About the Authors; “Test Targets is a peer-reviewed publication. The content reflects scholarship and is the property of the publisher and the author. To reprint any part of the publication...