Made available in DSpace on 2015-03-05T14:01:21Z (GMT). No. of bitstreams: 0 Previous issue date: 31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Trabalhos recentes na literatura mencionam a importância de aplicações par-a-par, principalmente BitTorrent, em particular se apoiando em estudos divulgados por provedores de Internet. Apesar da importância dos dados levantados pelos provedores, tais estudos são limitados tanto em abrangência como em profundidade e, em certos casos, não há clareza quanto à metodologia empregada. Este trabalho apresenta TorrentU, uma arquitetura escalável e flexível para observação do universo de redes BitTorrent. O objetivo do TorrentU é ajudar a elucidar uma série de questões que tem sido levantadas quanto ao volume e teor de compartilhamento de arquivos em redes BitTorrent. / Recently, academic investigations mention the importance of peer-to-peer applications, mainly BitTorrent, focusing on studies published by internet providers as a source of information. Despite the importance of these collected data from internet providers, the studies behind this technique are limited in coverage, deepness, and, in some cases, do not show clarity in the method applied for retrieving the data. This work presents TorrentU, an scalable and flexible architecture for the observation of the BitTorrent universe. The main goal is to help on finding answers to a wide range of questions that has been raised regarding volume and types of files and content in BitTorrent networks.

<p>Peer-to-Peer networking technology is evolving rapidly. P2P networks overcome the limitations of client/server networks where each computer shares resources of other computer. There are different types of P2P networks depending upon their functionalities. Peer to peer networks provide long list of features like: selection of nearby peers, redundant storage, effi-cient search/location of data items, data performance or guarantees etc. It is important to see that how P2P can work with wireless ad hoc networks and why it is important. What are im-portant issues which come across by using P2P and wireless ad hoc networks together. How TCP/IP stack can be affected. How the whole system looks like in which P2P techniques are used with wireless ad hoc routing protocols to perform different tasks and services.</p>

Peer-to-Peer networking technology is evolving rapidly. P2P networks overcome the limitations of client/server networks where each computer shares resources of other computer. There are different types of P2P networks depending upon their functionalities. Peer to peer networks provide long list of features like: selection of nearby peers, redundant storage, effi-cient search/location of data items, data performance or guarantees etc. It is important to see that how P2P can work with wireless ad hoc networks and why it is important. What are im-portant issues which come across by using P2P and wireless ad hoc networks together. How TCP/IP stack can be affected. How the whole system looks like in which P2P techniques are used with wireless ad hoc routing protocols to perform different tasks and services.

P2P search system usually be integrated to many systems in wired network. As the result of technology development, wireless networks are more and more popular. Many system in wired networks are be implemented in wireless network environment, too. In virtue of diverseness between wired and wireless networks, there are some modify for characteristic of wireless network. In this paper, we demonstrate KAdHoc, a peer-to-peer search system for Mobile Ad Hoc Network (MANET).There are problems when P2P systems being used in MANET such as physical locality, power exhaustion and nodes information outdated when nodes move. KAdHoc consider these problems and design a mechanism for P2P search system in MANET. The simulation result show that KAdHoc has fewer lookup time and has high success rate and low total traffic even in High Node density. KAdHoc even has higher success rate in higher node velocity.

The problem of copyright infringement has always been a focus of concern of copyright owners and law enforcement units. P2P (peer-to-peer) software is one of the major ways to acquire unauthorized files on campus. In the 96th academic year, The Ministry of Education proclaimed the prohibition against P2P software using, issuing governmental documents to request every university to restrain students from using P2P software and to promote related measures. As an effect analysis to the P2P software restrain this time, this study had conducted an investigation and an analysis according to the above background, trying to find the perceptions of the students under the contol, and to explain how these perceptions impact the behavior intention on. This study is revealing that though anti-P2P campaigns generally influence every perception like subjective norm, perceived risk, moral judgment, knowledge of copyright (the mediating variables) of the students, there is only an evident effect of moral judgment on behavior intention. As for the effects of other perceptions, they are not prominent. The study¡¦s result can provide schools with not only some practical suggestions concerning how to plan restrain strategies, but also a resource of references to develop campus piracy model for following researchers.

As the success of P2P file sharing systems such as BitTorrent and eMule, P2P has become a promising technology to provide video streaming services over the Internet. The P2P technology is shown to be capable of significantly reducing the transmission overhead of video server. However, due to the dynamic nature of peers, a P2P streaming system suffers from bursty packet loss caused by peer departures. Furthermore, as the packet being forwarded peer by peer, the situation becomes worse and worse. This problem is recognized as packet loss accumulation problem. To overcome bursty packet loss and eliminate packet loss accumulation problems caused by peer departures in P2P streaming systems, a multi-source structure combining with a distributed FEC scheme for P2P streaming systems is proposed. In the proposed structure, each peer connects to multiple parents according to the pre-specified FEC packets ensemble and each parent forwards partial streaming packets to the peer. If one or few parents fail, other parents can still provide most of remaining part of streaming packets that can be used to recover the missing packets by using packet level FEC scheme. To evaluate the performance of P2P streaming systems using the proposed multi-source structure, we first propose a Continuous-Time Markov Chain to model the arrival/departure behavior of parents in P2P systems. Based on the Markov Chain, we further derived equations to calculate packet loss probabilities for both single-source and multi-source P2P systems. The mathematical analyses show how the packet loss accumulation occurs in P2P systems and how the proposed multi-source structure eliminates packet loss accumulation problem. In addition, simulations are conducted using NS2 to evaluate the proposed multi-source structure. Simulation results verify that the proposed multi-source structure combining with an appropriate FEC protection is capable of overcoming burst packet loss and eliminating packet loss accumulation problems. The simulation results also show that the proposed multi-source structure performs better than the single-source and the PROMISE/CollectCast P2P systems in terms of packet loss, end-to-end delay, and PSNR. A prototype system is implemented to conduct a real experiment over the Internet to validate the effectiveness of the proposed scheme.

Cooperative services--a term which includes any system that relies on the resources and participation of its clients to function--have proven to be a popular, naturally scalable means to disseminate content, distribute computational workloads, or provide network connectivity. However, because these services critically depend on participants that are not controlled by a single administrative domain, these services must be designed to function in environments where no participant--because of failure or selfishness--will necessarily follow the specified protocol. This thesis addresses the challenge of establishing and maintaining cooperation in cooperative services by (1) advancing our understanding of the limits to what our services can guarantee in the presence of failure, (2) demonstrating the critical role that correct participants can play in the incentives provided by the service, and (3) proposing a new notion of equilibrium that, unlike traditional notions, provides both rigorous yet practical guarantees in the presence of collusion. Furthermore, we demonstrate that our ideas can be applied to practice by designing and implementing Seer, a system that provides a scalable, reliable, and robust method for disseminating content even if participants may fail arbitrarily or deviate selfishly as a coalition. / text

Peer-to-Peer(P2P) systems have emerged as a promising paradigm to structure large scale distributed systems. They provide a robust, scalable and decentralized way to share and publish data.The unstructured P2P systems have gained much popularity in recent years for their wide applicability and simplicity. However efficient resource discovery remains a fundamental challenge for unstructured P2P networks due to the lack of a network structure. To effectively harness the power of unstructured P2P systems, the challenges in distributed knowledge management and information search need to be overcome. Current attempts to solve the problems pertaining to knowledge management and search have focused on simple term based routing indices and keyword search queries. Many P2P resource discovery applications will require more complex query functionality, as users will publish semantically rich data and need efficiently content location algorithms that find target content at moderate cost. Therefore, effective knowledge and data management techniques and search tools for information retrieval are imperative and lasting. In my dissertation, I present a suite of protocols that assist in efficient content location and knowledge management in unstructured Peer-to-Peer overlays. The basis of these schemes is their ability to learn from past peer interactions and increasing their performance with time.My work aims to provide effective and bandwidth-efficient searching and data sharing in unstructured P2P environments. A suite of algorithms which provide peers in unstructured P2P overlays with the state necessary in order to efficiently locate, disseminate and replicate objects is presented. Also, Existing approaches to federated search are adapted and new methods are developed for semantic knowledge representation, resource selection, and knowledge evolution for efficient search in dynamic and distributed P2P network environments. Furthermore,autonomous and decentralized algorithms that reorganizes an unstructured network topology into a one with desired search-enhancing properties are proposed in a network evolution model to facilitate effective and efficient semantic search in dynamic environments.

Made available in DSpace on 2014-06-12T15:53:32Z (GMT). No. of bitstreams: 2 arquivo1922_1.pdf: 1019141 bytes, checksum: fd41612907761997292dae2b897da5b2 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2009 / As redes ad hoc sem fio ou MANETs são conhecidas pela sua flexibilidade e independência de uma infraestrutura para coordenação de nós. A quantidade de aplicações apoiadas nesta arquitetura tem aumentado vertiginosamente nos últimos anos dado que operações de resgate, aplicações de conferências e de compartilhamento de arquivos encontraram nestas redes um ambiente favorável ao seu desenvolvimento. Estas aplicações emergentes executadas no topo das MANETs funcionam em uma lógica peer-to-peer, uma vez que os peers da rede executam a mesma função e repassam informações seguindo algoritmos de roteamento no nível aplicação. Além disso, uma MANET compartilha vários pontos em comum com uma rede P2P, entre eles a descentraliza ção e a flexibilidade mediante a entrada e sa´&#305;da de nós. Desta forma, entende-se que as aplicações desenvolvidas para MANETs podem ser inspiradas nos protocolos P2P utilizados com sucesso na Internet. Entretanto, as MANETs possuem uma natureza bastante diversa da Internet, uma vez que oferecem novos desafios, como a mobilidade dos nós e as limitações na largura de banda. Estes fatores levam ao fraco desempenho das aplicações P2P nesta arquitetura, em comparação ao desempenho das mesmas na Internet. Assim, melhorias destes protocolos destinadas ao ambiente sem fio se fazem necessárias. Esta dissertação propõe um Sistema de Disseminação para otimização do protocolo BitTorrent no ambiente de MANETs. O sistema proposto consiste em estratégias espec íficas para disseminação de conteúdo e em uma interface que permite que algumas mensagens de PIECE do BitTorrent sejam entregues no modo broadcast, tirando proveito da natureza difusora do meio de comunicação sem fio. O desempenho do BitTorrent tradicional e de sua versão melhorada com o Sistema

Made available in DSpace on 2014-06-12T15:56:38Z (GMT). No. of bitstreams: 2 arquivo2959_1.pdf: 5622692 bytes, checksum: 03f9776f9c2fee455957a3c73eddfd9b (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Com o desenvolvimento tecnológico e a diminuição de preços dos computadores pessoais as empresas passaram a investir na compra de equipamentos, buscando automatizar processos, interligarem setores, criando assim uma atmosfera favorável a captura de dados para análise estratégica e políticas de expansão e investimento [2]. Tal fato gerou uma grande quantidade de recursos que podem ser considerados ociosos dentro das empresas. Por outro lado, surgiu um novo problema, a informação pode se perder devido a erros de operação do usuário, falhas de software e/ou hardware. Neste contexto, a plataforma p2p mostra-se eficiente na implementação de um sistema de backup, por fazer usufruto desta capacidade ociosa para o armazenamento de dados. A dificuldade de implementação de um software P2P que faça backup esta no fato que as mesmas podem ficar indisponíveis, fazendo com que o restore dos dados não possa acontecer quando o usuário necessitar do mesmo, visto que partes do backup podem estar espalhadas. O principal objetivo deste trabalho é apresentar uma proposta de um algoritmo que permita medir a confiabilidade da disponibilidade do restore de um backup efetuado em uma rede P2P bem como a arquitetura de software, na qual, estão definidos os componentes que medem as taxas de falhas das máquinas que compõe a rede e realizam a distribuição do backup com base no calculo estatístico da disponibilidade do restore, fazendo com que eventuais falhas não afetem o funcionamento ideal da restauração dos arquivos perdidos