Made available in DSpace on 2015-03-05T13:58:27Z (GMT). No. of bitstreams: 0 Previous issue date: 16 / Bolsa para curso e programa de Pós Graduação / BitTorrent é a tecnologia de compartilhamento de arquivos mais popular atualmente na Internet e responsável por fração significativa do tráfego nela existente. Considerando sua importância e adoção em larga escala, a arquitetura BitTorrent precisa ser robusta e resistente a pares maliciosos. Esta dissertação constitui a primeira investigação em termos de vulnerabilidades do BitTorrent, apresentando quatro contribuições principais: (a) auxilia no entendimento do BitTorrent; (b) identifica vulnerabilidades e descreve ataques e contramedidas possíveis à arquitetura; (c) descreve um modelo de simulação discreto, que permite mapear o comportamento do protocolo BitTorrent; e (d) avalia, via simulação, o impacto de dois dos ataques identificados, Mentira de Peças e Eclipse. Os resultados mostram que BitTorrent é suscetível a ataques em que pares maliciosos mentem a posse de peças e tornam-nas mais raras, fazendo com que downloads em geral sejam atrasados em até 50%. Em ataques Eclipse, com uma proporção em torno de / BitTorrent is the most popular file sharing technology and associated with a significant fraction of the Internet traffic. Considering its importance and large scale adoption, the BitTorrent architecture should be robust and resistant to malicious peers. This dissertation is the first investigation in terms of vulnerabilities against BitTorrent architecture, providing four important contributions: (a) it helps to increase the understanding of the BitTorrent protocol; (b) it identifies vulnerabilities and describes feasible attacks and countermeasures to the BitTorrent architecture; (c) it presents a discrete event simulation model which maps the behaviour of the protocol; and (d) it evaluates, through simulation, the impact of two proposed attacks, namely Piece Lying and Eclipse. Results show what BitTorrent is vulnerable to cheating peers that lie about having pieces, in order to make them rarer, causing an increase of about 50% in downloading times. Eclipse attacks can cause even more damage, as analysis

Suite à la diffusion des applications P2P et en particulier du video P2P, le trafic P2P représente déjà une portion importante de la totalité du trafic sur Internet. Dans ce contexte cette thèse propose des nouveaux outils pour mesurer, identifier et contrôler le trafic P2P. Concernant la classification de trafic, vue l'inefficacité des techniques traditionnelles, nous proposons un nouveau classificateur comportemental, Abacus, spécifique pour les applications P2P-TV. Nos expériences prouvent que Abacus, bien qu'il soit basé sur la simple mesure du numéro des paquets et octets échanges par un hôte, fourni une solution légère et efficace pour l'identification des applications P2P. En suite, nous évaluons l'impact de la réduction des données, due à l'utilisation très commune de Netflow et de l'échantillonnage à niveau paquet, sur la classification de trafic. Nous montrons que Abacus peut être adapté à utiliser ce type des données, et que même si l'échantillonnage de paquets cause une dégradation importante de la qualité des mesurés, cependant la classification reste possible si l'apprentissage du classificateur est fait avec des données eux même échantillonnées. En fin, nous étudions un nouveau type de protocole de transport pour les applications P2P, LEDBAT, proposé et utilisé par la version officielle de BitTorrent. Ce protocole, basé sur le délai, veut implémenter un transport a basse priorité. Nous montrons que LEDBAT atteinte son objectif, mais qu'il souffre d'un problème d'équité entre flux du même type: nous identifions la cause de ce problème et proposons des solutions efficaces, qui rétablissent l'équité.

Cette thèse présente deux axes de recherche que j'ai menés entre 2004 et 2011. Le premier axe est sur la compréhension sur protocole BitTorrrent. Il recouvre des travaux expérimentaux et de mesures montrant l'efficacité de BitTorrent et expliquant les variations de performances observées dans la littérature et interprétées à tort comme un problème de BitTorrent. Une caractéristique de ces travaux est l'utilisation d'expérimentations à grande échelle (par exemple 10 000 pairs BitTorrent que l'on expérimente dans un environnement contrôlé) et de mesures à grande échelle (par exemple, 148 millions d'adresses IP mesurées sur 3 mois). Le deuxième axe est sur l'étude de la protection de la vie privée sur Internet. Ces travaux montrent que l'on peut surveiller sans infrastructure dédiée (c'est-à-dire d'une seule machine) la quasi-intégralité des utilisateurs de BitTorrent. On montre également qu'en exploitant les communications pair-à-pair dans Skype on peut lier une identité sociale (nom, prénom, adresse email, etc.) à une activité sur Internet (par exemple, une liste de contenus téléchargés avec BitTorrent). On peut également suivre la mobilité des utilisateurs de Skype et on montre que cette mobilité est réelle pour un utilisateur standard. Pour finir, on montre qu'un réseau garantissant l'anonymat, comme Tor, n'offre pas une protection satisfaisante.

P2P Grid computing seeks the convergence of Grid and P2P technologies. Deploying a P2P Grid middleware on a set of computers enables an organization to automatically barter computing time with other Internet-connected organizations. Such P2P exchanges of computing time enable individual Peers, i.e. organizations, to transparently aggregate large amounts of computational power with minimal infrastructure requirements or administrative cost. Challenges arise from the requirement for scalability and robustness. Individual worker nodes are unreliable, as P2P Grids operate on unmanaged desktop computers. A specificity of P2P Grids is that each Peer can reclaim at any time the computational power of worker nodes supplied to other Peers, leading to bursts of execution preemption. These are the major contributions of our dissertation: * Firstly, we propose a new P2P Grid architecture, the Lightweight Bartering Grid (LBG). Through systematic cooperation between Grid nodes, the reliability of execution of computational requests is greater than the sum of the reliabilities of worker nodes. * Secondly, we propose a highly scalable data transfer architecture. It is based both on the BitTorrent P2P file sharing protocol and on the removal of the temporal cost of downloading redundant copies of input data files. * Thirdly, besides a middleware implementation of LBG, we also provide an implementation of a discrete-event simulator. Its originality resides in the weaving of the simulator code into the bartering code of the middleware, which is made possible through the virtualization of Grid nodes. This enables reproducible testing and accurate performance evaluation of the bartering policies because the Peers of a simulated Grid make the same bartering decisions as Peers deployed on real computers. The LBG architecture exhibits the following remarkable features: * The scheduling model supports the queueing of external requests and the architecture enables a flexible study of bartering policies. * The architecture is open, flexible, lightweight and facilitates software engineering. It enables the easy development, testing, evaluation and deployment of combinations of scheduling policies. * The architecture is fully P2P.

Problem: Record companies are facing a downturn in sales of music. This is seen as consequence of the growth of distribution of music through Internet by file sharing networks such as BitTorrent networks. On one side there are record companies who feel threatened of the illegal file sharing, and on the other side file sharing BitTorrent networks has increased dramatically in number of users since they first approached. Some record companies have responded by taking hostile actions towards the BitTorrent networks and their users with lawsuits and penalties for illegal file sharing. Other record companies and artists have joined forces with BitTorrent networks and see them as an advantage. Purpose: The purpose of this paper is to explore and analyze if, and how record companies can collaborate with the BitTorrent networks. Method: A hermeneutic inductive approach is used, in combination with qualitative interviews with both record companies and BitTorrent networks. Conclusions: It is argued that record companies can find a way in communicating and cooperating with BitTorrent networks. Instead of adopting hostile approaches and trying to restrict the technologies adopted by end users, companies should open themselves up and accept the current changes initiated and developed by BitTorrent networks. Thus, it was concluded that companies have to concentrate around collaborating with BitTorrent networks rather than fiercely protecting old business models. By opening up to the users, record companies will adopt open innovations approach that is characterized by combining external and internal ideas, as well internal and external paths to market, thus obtaining future technological developments. As for the BitTorrent networks, by going from outlaw to crowdsourcing mode, the networks’ creative solutions can be further harnessed by record companies. Finally, strengthening relationships between customers and music artists can be considered as beneficial for both record companies and BitTorrent networks. Thus, giving opportunities for customers to win special items, tickets for concerts, watch sound check, eat dinner backstage with the group, take pictures, get autographs, watch the show from the side of the stage, etc. can lead to valuable relationship in a long run.

<p>Existing VoD solutions often rely on unicast to distribute content, which leads to a higher load on the VoD server as more nodes become interested in the content. In such case, P2P is an alternative way of distributing content since it makes better use of available resources in the network. In this report, several P2P structures are evaluated from an operators point of view. We believe BitTorrent is the most adequate protocol for a P2P solution in IPTV environments. Two BitTorrent clients have been implemented on an IP-STB as proof of concept to find out whether P2P is suited for IPTV environments. Several tests were conducted to evaluate the performance of both clients and to see if they were able to reach a sufficient throughput on the IP-STB. Based upon the tests and the overall impressions, we are convinced that this particular P2P protocol is well suited for IPTV environments. Hopefully, a client developed from scratch for the IP-STB will offer even greater characteristics.</p><p>Further, we have studied how to share recorded content among IP-STBs. Such a design would probably have many similarities to BitTorrent since a central node needs to keep track of content; the IP-STBs take care of the rest.</p><p>The report also brings up whether BitTorrent is suitable for streaming. We believe that the necessary changes required to obtain such functionality will disrupt the strengths of BitTorrent. Some alternative solutions are presented where BitTorrent has been extended with additional modules, such as a server.</p>

There is no doubt that BitTorrent nowadays is one of the most popular peer-to-peer (P2P) applications on the Internet, contributing to a significant portion of the total Internet traffic and being a basis for many other emerging services such as P2P Internet Protocol Television and Video on Demand. On the other hand, Network Address Translation (NAT) devices have become pervasive in almost all networking scenarios. Despite of the effort of NAT traversal, it is still very likely that applications, especially P2P ones, cannot receive incoming connection requests properly if they are behind NAT. Although this phenomenon has been widely observed in measurement work, so far there is no quantitative study in the literature examining the impact of NAT on P2P applications. In this work, we build analytical models to capture the performance of BitTorrent-like P2P systems in a steady state, in the presence of homogeneous and heterogeneous NAT peers. We also propose biased optimistic unchoke strategies, in order to improve the overall system performance and fairness metrics considerably. The analytical models have been validated by simulation results, which also reveal some interesting facts about the coexistence of NAT and public peers in P2P systems.

Trabalhos recentes na literatura indicam que o BitTorrent é o protocolo de com- partilhamento de arquivos com maior popularidade, sendo responsável por mais da metade do tráfego P2P em algumas localidades geográficas. Apesar de vários estudos sobre a dinâmica do “universo BitTorrent”, até recentemente não existia metodologia para observá-lo sistematicamente. Um estudo preliminar indicou a existência de múltiplas estratégias de monito- ramento, que diferem em termos de objetos observados, conjunto de parâmetros e custos associados, e se sobrepõem em termos de informações extraídas. Um se- gundo trabalho apresentou uma combinação dessas estratégias na forma de uma arquitetura de monitoramento flexível e escalável. Nesse contexto, o objetivo da presente dissertação é investigar como otimizar o conjunto de estratégias e seus parâmetros para monitorar eficientemente o universo de redes BitTorrent tendo em vista um dado conjunto de informações a ser observado e recursos computacionais disponíveis. Como solução é proposto um controle de monitoramento adaptativo, que emprega um modelo de programação para otimizar, a cada rodada, o monitoramento considerando o estado percebido da rede. Embora o foco deste trabalho seja redes BitTorrent, é proposto um modelo genérico, que pode ser aplicado a outras redes P2P, aumentando portanto a contribuição desta dissertação. Os resultados de uma avaliação analítica indicam que o modelo de programação proposto gera soluções ótimas. Além disso, experimentos realizados com instâncias desse modelo geradas aleatoriamente mostram que o mesmo tem potencial para ser aplicado em redes mais complexas que BitTorrent. / Recent studies in the literature have indicated that BitTorrent is the most pop- ular file sharing protocol, being responsible for more than half of the P2P traffic in some geographical locations. Despite the several studies about the dynamics of the “BitTorrent universe”, until recently there has been no methodology to systematically observe it. A preliminary study identified multiple monitoring strategies, which differ in terms of observed objects, set of parameters and associated costs, and overlap in terms of extracted information. A subsequent work has combined those strategies in a flexible, extensible BitTorrent monitoring architecture. In this context, the goal of the present dissertation is to investigate how to optimize the set of strategies and their parameters for efficiently monitoring the universe of BitTorrent networks, considering a given set of monitoring objectives and available computational resources. As a solution, an adaptive monitoring control is proposed, which employs a programming model to optimize the monitoring at each round, considering the perceived network state. Although the focus of this work is BitTorrent networks, we propose a generic model that can be applied to other P2P networks, thereby increasing the contribution of this dissertation. The results of an analytical evaluation indicate that the proposed programming model generates optimal solutions. Furthermore, experiments carried out with ran- domly generated instances of this model show that it has potential to be applied to more complex networks than BitTorrent.

Redes BitTorrent (BT) atualmente representam o método Par-a-Par (P2P) de compartilhamento de arquivos pela Internet mais utilizado. Relatórios de monitoramento recentes revelam que as cópias de conteúdo sendo compartilhadas são, em grande maioria, ilegais e que filmes são os tipos de mídia mais populares. Iniciativas de pesquisa que tentaram entender a dinâmica da produção e do compartilhamento de conteúdo em redes BT não conseguiram prover informações precisas acerca da disseminação de cópias ilegais. No presente trabalho realizamos um extenso estudo experimental para caracterizar o comportamento de produtores, publicadores, provedores e consumidores de arquivos violando direitos autorais. O estudo conduzido é baseado em dados coletados durante sete meses de monitoração de enxames compartilhando filmes por meio de uma das comunidades públicas mais populares de BT. Os dados foram obtidos via emprego de uma arquitetura de monitoração do \universo" BitTorrent, o que permitiu popular uma base com informações acerca de mais de 55.000 torrents, 1.000 rastreadores e 1,9 milhões de IPs. Nossa análise não somente mostra que um pequeno grupo de usuários ativos _e responsável pela maior parte do compartilhamento de cópias ilegais, como desvenda relacionamentos existentes entre esses atores e caracteriza os padrões de consumo respeitados pelos usuários interessados nesse tipo de conteúdo. / BitTorrent (BT) networks are nowadays the most employed method of Peerto- Peer (P2P) le sharing in the Internet. Recent monitoring reports reveal that content copies being shared are mostly illegal and movies are the most popular media type. Research e orts carried out to understand the dynamics of content production and sharing in BT networks have been unable to provide precise information regarding the dissemination of illegal copies. In this work we perform an extensive experimental study in order to characterize the behavior of producers, publishers, providers and consumers of copyright-infringing les. This study is based on seven months of traces obtained by monitoring swarms sharing movies via one of the most popular BT public communities. Traces were obtained with an extension of a BitTorrent \universe" observation architecture, which allowed the collection of a database with information about more than 55,000 torrents, 1,000 trackers and 1.9 million IPs. Our analysis not only shows that a small group of active users is responsible for the majority of disseminated illegal copies, as it unravels existing relationships among these actors and characterizes consuming patterns respected by users interested in this particular set of contents.

Submitted by Pós-Com Pós-Com (pos-com@ufba.br) on 2015-01-15T13:19:47Z No. of bitstreams: 1 Lineu Vilanova Miranda de Oliveira.pdf: 920093 bytes, checksum: 748c04b4ac70bb037ebec152043c610f (MD5) / Approved for entry into archive by Vania Magalhaes (magal@ufba.br) on 2018-02-06T11:32:00Z (GMT) No. of bitstreams: 1 Lineu Vilanova Miranda de Oliveira.pdf: 920093 bytes, checksum: 748c04b4ac70bb037ebec152043c610f (MD5) / Made available in DSpace on 2018-02-06T11:32:00Z (GMT). No. of bitstreams: 1 Lineu Vilanova Miranda de Oliveira.pdf: 920093 bytes, checksum: 748c04b4ac70bb037ebec152043c610f (MD5) / Capes / O fenômeno do compartilhamento de arquivos vêm crescendo desde o início dos anos 2000. A partir de 2004, com a expansão do compartilhamento de filmes através de sistemas p2p, representantes dos grandes estúdios de Hollywood decidiram adotar uma estratégia semelhante àquela adotada pela indústria fonográfica, levando-os a processar centenas de usuários finais. Essa atitude agressiva acabou empurrando muitos dos usuários mais ativos de sistemas p2p para comunidades subterrâneas de compartilhamento como as comunidades privadas BitTorrent. Este trabalho apresenta um relato descritivo de uma comunidade privada BitTorrent dedicada ao compartihamento de filmes na internet. A construção do relato descritivo baseou-se em premissas da teoria ator-rede, mais especificamente em três princípios de incerteza discutidos por Bruno Latour em Reassembling The Social (2005). O relato descritivo pretendeu reunir o maior número possível de atores envolvidos na manutenção da Aliança Cinéfila. / The file sharing phenomenon has been growing since the beginning of 2000. After 2004, with the expansion of movie file sharing on p2p networks, the movie industry decided to adopt the same strategy that had been used by the recording industry and began suing hundreds of end users. This aggressive approach pushed many of the most active users to underground file sharing communities. This work presents a descriptive account of a private BitTorrent community that is dedicated to the file sharing of certain types of movies. The construction of the descriptive account was based in some of actor-network theory premises, more specifically, on the three sources of uncertainties discussed by Bruno Latour in Reassembling The Social (2005). The descriptive account was an attempt to assemble most of the actors involved in the maintenance of Aliança Cinéfila.