Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-30T20:25:10Z No. of bitstreams: 1 franciscohenriquecerdeiraferreira.pdf: 1810078 bytes, checksum: b5d9796bdd636be5e4f0f3212220ad0a (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-06-01T11:36:20Z (GMT) No. of bitstreams: 1 franciscohenriquecerdeiraferreira.pdf: 1810078 bytes, checksum: b5d9796bdd636be5e4f0f3212220ad0a (MD5) / Made available in DSpace on 2017-06-01T11:36:20Z (GMT). No. of bitstreams: 1 franciscohenriquecerdeiraferreira.pdf: 1810078 bytes, checksum: b5d9796bdd636be5e4f0f3212220ad0a (MD5) Previous issue date: 2013-03-11 / Nos últimos anos, as aplicações P2P de transmissão de vídeo ao vivo despertaram um grande interesse na comunidade cientí ca. Essas aplicações geram um grande volume de dados que afetam diretamente o desempenho da rede. Apesar de existir um grande número de trabalhos dedicados a entender as aplicações P2P de transmissão de vídeo ao vivo, a maioria deles se baseia em uma visão estática desses sistemas. Estes trabalhos não se preocupam em entender a dinâmica do sistema, ou seja, como eles evoluem ao longo do tempo. Através de experimentos realizados na plataforma PlanetLab, este trabalho apresenta uma caracterização da aplicação SopCast, um dos mais importantes sistemas P2P de transmissão de vídeo ao vivo. O estudo é realizado levando-se em consideração a dinamicidade da topologia construída. Também é investigada a formação de comunidades na rede sobreposta e a correlação dessas comunidades com os Sistemas Autônomos da Internet (AS). Os resultados mostram que a formação de comunidades é bem de nida pela troca de tráfego e uma pequena porção de participantes desses grupos é responsável por sustentar toda a comunidade. Além disso, não existe indícios que os participantes se agrupam de acordo com seus Sistemas Autônomos. De fato, a probabilidade de uma comunidade ser formada com mais da metade de membros pertencentes a um mesmo AS é inferior a 10%. Finalmente, as caracterizações apresentadas fornecem informações importantes para o desenvolvimento de novas aplicações P2P de transmissão de vídeo ao vivo. Mais que isso, será possível algoritimos de formação de parcerias e grupos de tal forma que seja possível reduzir os custos de transmissão entre redes diferentes. / P2P live streaming systems have attracted a lot of attention from the research community in the last years. Such systems generate a large amount of data which impacts the network performance. Despite large number of works devoted to understand P2P live streaming applications, most of them rely on characterizing the static view of these systems. These works do not worry about either understanding the systems dynamics or analyzing how it evolves over time. Through experiments in PlanetLab platform, we present a characterization of the SopCast application, one of the most important P2P live streaming system. We focus on characterizing the dynamics of P2P overlay topology. We also investigated the community formation process in SopCast overlay and the correlation of these communities with the Autonomous Systems of the Internet (AS). Our results show that the formation of communities is well de ned by the exchange of tra c and a small portion of peers of these groups is responsible for supporting the entire community. Furthermore, there is a evidence that peeers are not grouped according to their Autonomous Systems. Indeed, the probability of a community be formed with more 50% of members belonging to the same AS is less than 10%. Finally, the characterizations we conduct provide important information to new P2P live streaming protocols and membership algorithms design. Moreover, the presented characterization may be useful to developers create algorithms that reduces the transmission cost on the P2P network.

Dans cette thèse, nous nous sommes intéressés aux protocoles pair-à-pair (P2P), qui représentent une solution prometteuse pour la diffusion et le partage de données à faible coût sur Internet. Nous avons mené, dans un premier temps, une étude comportementale de différents protocoles P2P pour le partage de fichier (distribution de contenus sans contrainte de temps) puis le live. Dans la première étude centréesur le partage de fichier, nous avons montré l’impact d’Hadopi sur le comportement des utilisateurs et discuté l’efficacité des protocoles en fonction du contenu et l’efficacité protocolaire, en se basant sur les choix des utilisateurs. BitTorrent s’est nettement démarqué au cours de cette étude, notamment pour les grands contenus. En ce qui concerne le live, nous nous sommes intéressés à la qualité de servicedu réseau de distribution live Sopcast, car plus de 60% des événements live diffusés en P2P le sont sur ce réseau. Notre analyse approfondie de ces deux modes de distribution nous a fait nous recentrer sur BitTorrent, qui est à la base de tous les protocoles P2P Live, et est efficace en partage de fichier et complètement open source. Dans la seconde partie de la thèse, nous avons proposé et implémenté dansun environnement contrôlé un nouveau protocole sur la base de BitTorrent avec des mécanismes protocolaires impliquant tous les pairs dans la gestion du réseau. Ces nouveaux mécanismes permettent d’augmenter l’efficacité du protocole via une meilleure diffusion, tant pour le live que le partage de fichier, de métadonnées (la pièce la plus rare) et via une méthode dite de push, par laquelle un client va envoyer du contenu aux pairs les plus dans le besoin / In this study, we focused on peer-to-peer protocols (P2P), which represent a promising solution for data dissemination and content delivery at low-cost in the Internet. We performed, initially, a behavioral study of various P2P protocols for file sharing (content distribution without time constraint) and live streaming. Concerning file sharing, we have shown the impact of Hadopi on users’ behavior and discussed the effectiveness of protocols according to content type, based on users’ choice. BitTorrent appeared as the most efficient approach during our study, especially when it comes to large content. As for streaming, we studied the quality of service of Sopcast, a live distribution network that accounts for more than 60% of P2P broadcast live events. Our in-depth analysis of these two distributionmodes led us to focus on the BitTorrent protocol because of its proven efficiency in file sharing and the fact that it is open source. In the second part of the thesis, we proposed and implemented a new protocol based on BitTorrent, in a controlled environment. The modifications that we proposed allow to increase the efficiency of the protocol through improved dissemination of metadata (the rarest piece), both for live and file sharing. An enhanced version is introduced with a push method, where nodes that lag behind receive an extra service so as to improve the overall performance