O protocolo BitTorrent é uma das aplicações P2P mais bem sucedidas da Internet, sendo largamente estudada pela comunidade de pesquisa. Contudo, o estudo da dinâmica de uma rede BitTorrent de larga escala apresenta diversos desafios, tais como a dificuldade em realizar capturas da rede ou montar experimentos para medição. O método utilizado para superar estes desafios é a simulação, porém não há uma ferramenta adequada disponível para a comunidade de pesquisa. Por conta disso, a maioria dos trabalhos que utilizam simulação desenvolvem os seus próprios simuladores, resultando em trabalhos que não podem ser repetidos ou verificados. Neste trabalho, é apresentado o simulador de BitTorrent EbitSim, que permite a alteração dos mecanismos utilizados, a configuração dos parâmetros do sistema e a definição da topologia utilizada. O simulador foi desenvolvido utilizando o arcabouço OMNeT++, que fornece um conjunto de ferramentas que facilitam a configuração de variados cenários e dos parâmetros do modelo. Além disso, o arcabouço INET foi utilizado para modelar as camadas inferiores de rede. O desenvolvimento do modelo do BitTorrent foi baseado na especificação oficial, e contou com o auxilio de trabalhos relacionados e discussões com desenvolvedores de clientes BitTorrent. O EbitSim foi validado por meio de comparações com resultados obtidos a partir de uma implementação real de uma rede BitTorrent, realizada em um ambiente de testes controlado. Foi demonstrado que o EbitSim apresenta resultados compatíveis com uma rede BitTorrent real. / The BitTorrent protocol is one of the most successful P2P applications, being largely studied by the research community. Nevertheless, studying the dynamics of a large BitTorrent network presents several challenges, such as difficulty in acquiring network traces or building measurement experiments. The simulation method is capable of overcoming these challenges, but there is not an adequate simulation tool available for the research community. This thesis presents the EbitSim BitTorrent Simulator, which is capable of modifying the utilized mechanisms, configuring the systems parameters and defining the topology used in the simulations. The simulator was developed using the OMNeT++ framework, which provides a set of tools that facilitates the configuration of diversified scenarios and the parameters of the model. In addition, the INET framework was utilized to accurately model the lower network levels. We developed the BitTorrent model based on the official specification, with the aid of related works and discussions with developers of BitTorrent client programs. The EbitSim Simulator was validated by performing comparisons with results obtained from a real implementation of a BitTorrent network, deployed in a controlled testbed. We show that the EbitSim Simulator generates results compatible with a real BitTorrent network.

Companies that sell digital products such as software and movies transfer large amounts of data to its customers. In order to send this amount of data using FTP or HTTP and still maintain a high speed transfer rate it is required that the company have a large number of servers and a huge bandwidth. Servers and bandwidth costs money which means they have great costs on the distribution of their products. In order to reduce distribution costs, P2P technology can be used and the most powerful technology to transmit popular files is called BitTorrent.BitTorrent requires users to share their bandwidth. Nowadays, BitTorrent is frequently used to transfer products that are free of charge; one example is the Linux distribution Ubuntu. In these BitTorrent systems different incentives exist to motivate the users to share their bandwidth. If a company uses BitTorrent to save money and put the distribution cost on their customers, does the customers motivation to share their bandwidth disappear?To give the reader a clear picture of the subject, literature on how BitTorrent works and its different concepts have been acquired and processed. In addition to literature, a survey has been carried out in which BitTorrent users were asked about their willingness to share their bandwidth and what motivates them most in a possible commercial BitTorrent system.The result of this study shows that a marked increase in the propensity to share bandwidth appears as additional incentives are implemented to a BitTorrent system. These incentives may be of financial or functional value. Economic incentives proved to be the most requested implementation. / Företag som säljer digitala produkter så som mjukvara och film skickar stora mängder data till dess kunder. För att kunna överföra dessa mängder med FTP eller HTTP i hög hastighet till kunderna krävs det att företaget har ett stort antal servrar och enorm bandbredd. Servrar och bandbredd kostar pengar vilket betyder att företagen har stora kostnader på distribution av deras produkter. För att minska distributionskostnader kan P2P-teknik användas och den kraftfullaste tekniken för att överföra populära filer heter BitTorrent.BitTorrent kräver att användare delar med sig av sin bandbredd. I dag används BitTorrent ofta för att överföra produkter som är gratis, ett exempel är Linuxdistributionen Ubuntu. I dessa BitTorrent-system motiveras användarna att bidra med sin bandbredd för att ge tillbaka någonting till gemenskapen. För att spara pengar kan företaget sprida ut kostnader för distribution till kunderna. Vad händer med kundens motivation att dela med sig av sin bandbredd i detta fall?Litteratur om hur BitTorrent fungerar och dess olika begrepp har samlats in och bearbetats. Utöver tidigare litteratur har en enkätundersökning genomförts där BitTorrent-användare tillfrågats om deras relation till att bidra med bandbredd och vad som motiverar dem mest i ett eventuellt kommersiellt BitTorrent-system.Resultatet av undersökningen visar att en tydlig ökning av benägenhet att dela med sig av bandbredd infinner sig då ytterligare incitament tillförs i BitTorrent-system. Dessa incitament kan vara ekonomiska eller funktionella värden. Ekonomiska incitament visade sig dock vara de mest efterfrågade.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-31T13:30:39Z No. of bitstreams: 1 thiagoamaralguarnieri.pdf: 3369955 bytes, checksum: fd0e7e452cd11ad12220a57269ca1004 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-31T13:44:37Z (GMT) No. of bitstreams: 1 thiagoamaralguarnieri.pdf: 3369955 bytes, checksum: fd0e7e452cd11ad12220a57269ca1004 (MD5) / Made available in DSpace on 2017-05-31T13:44:37Z (GMT). No. of bitstreams: 1 thiagoamaralguarnieri.pdf: 3369955 bytes, checksum: fd0e7e452cd11ad12220a57269ca1004 (MD5) Previous issue date: 2014-08-22 / As aplicações peer-to-peer (P2P) estão presentes na Internet há mais de uma década. Seu sucesso, reconhecido em aplicações de compartilhamento de arquivo, tem se expandido para redes sociais, transmissão de vídeo, entre outras. Entretanto, o custo do tráfego das aplicações P2P é maior que o de sistemas cliente/servidor, pelo fato de os peers estarem dispersos geograficamente. Assim, muitos provedores reduzem a prioridade de pacotes P2P em seus roteadores, diminuindo o desempenho dessas aplicações. Observa-se ainda, a ocorrência de freeriders, que são peers que não destinam satifatoriamente recursos para as redes de disseminação em que participam (swarm). Muitas abordagens foram propostas para reduzir tráfego entre sistemas autônomos e freeriding, especialmente através do estabelecimento de relações de maior duração entre peers. Nessesentido,pesquisasdemonstramqueocontextosocialpodeauxiliarnoaumento de parcerias de longa duração e de regionalização de tráfego. Com base nesse contexto, este trabalho avalia a influência de uma rede social, o Facebook, na disseminação de dados em redes Bittorrent, tanto em suas características estáticas quanto na evolução de sua topologia ao longo do tempo. Para isso foram coletados mais de 16.600 swarms, divididos em tradicionais - disseminados via sites de indexação - e sociais, que são disseminados via Facebook. A análise estática tem como foco os seguintes fatores: (I) características gerais dos swarms (II) melhorias em disseminação de dados (i.e. saúde de swarms), (III) a localidade dos peers da rede P2P. Além disso é apresentado um estudo da evolução temporal de swarms segundo a duração das relações entre peers e métricas de centralidade. Os resultados demonstram que a disseminação social provoca uma sensível redução de freeriding e maior localização de peers, indicando novos caminhos que apontam para o equilíbrio entre vazão de dados e custo de transmissão. / Peer-to-peer applications are very important on Internet since last decade. Its success as a file-sharing application is unquestionable and has been repeated on applications such cloud computing, social network and video broadcasting. However, it is notorious that the traffic generated by peer-to-peer is not AS friendly: peers on a P2P system are usually geographically sparse, making more expensive the data traffic. Because of it, some content providers perform traffic shaping on their network, reducing P2P packet priority and, by consequence, its performance. Yet, other important problem on P2P systems is the freeriding behavior, where a peer doesn’t contribute to the system with its resources. Today, there are many proposed approaches to reduce inter-AS traffic and freeriding by finding a way to provide long term relationship between peers. With the present success of social networks, some proposals intend to investigate if social contexts can alleviate the impact of freeriding and inter-AS traffic. Through measurements performed in a Bittorrent real-world swarm data-set, we present a characterization that intends to investigate the influences of swarm social dissemination on Facebook in peer relationship and also performance metrics, location, and freeriding reduction. Results achieved by us shows that using social dissemination provides a notable improvement on solving the freeriding problem and peer geographic dispersion. So, a protocol that uses a geographic or social aware peer selection can have better performance on social disseminated swarms.

La plupart de nos activités quotidiennes sont aujourd'hui rythmées et régies par Internet, qu'il s'agisse de partage de fichiers, d'interaction sur les réseaux sociaux, de banques et de cours en ligne, ou encore de publication de blogs. En ce qui concerne le partage de fichiers, l'une des activités les plus pratiquées sur Internet, diverses solutions ont déjà été proposées, créées et implantées, pour constituer des réseaux de partage de fichiers aux performances et objectifs parfois très différents. Cette société du numérique permet le profilage des utilisateurs. Chaque information envoyée ou reçue sur Internet va ainsi traverser une série de noeuds intermédiaires jusqu'à atteindre sa destination. Un observateur pourra ainsi déterminer la provenance et la destination des paquets et de ce fait surveiller et profiler les activités des utilisateurs en identifiant le serveur auquel ils se connectent ou la durée de leur session. Parallèlement, les communications anonymes se sont développées afin de permettre aux utilisateurs d'utiliser Internet sans que leur identité ne soit nécessairement révélée.Notre contribution se veut double. Nous nous intéressons tout d'abord aux environnements de partage de fichiers hybrides en nous focalisant sur des réseaux réels largement déployés. Nous visons, au travers de cette étude, deux objectifs. Le premier consiste en l'amélioration du système d'indexation de contenu au sein de l'environnement de partage de fichiers BitTorrent. Il s'agit, plus précisément, de renforcer le système BitTorrent par le biais d'une indexation de son contenu dans la table de hachage distribuée Kad. Notre second but est d'améliorer les conditions d'accès au contenu ainsi que sa disponibilité au sein de l'environnement I2P de partage de fichiers. Nous permettons aux utilisateurs d'I2P d'accéder anonymement au contenu public de BitTorrent et nous aboutissons ainsi à un environment de partage de fichiers totalement anonyme, indexation et distribution du contenu comprises. Nous centrons ensuite notre analyse sur une meilleure compréhension des environnements anonymes par le biais d'une surveillance à grande échelle. Nous définissons les caractéristiques du réseau I2P, en visant l'intégralité de l'environnement anonyme et son large champ d'activités et de services anonymes. Nous analysons les différents aspects du réseau, comme le nombre des utilisateurs, leurs caractéristiques ainsi que le nombre de services anonymes disponibles. Au travers des mesures et évaluations réalisées à long terme sur le réseau, couplées à différentes analyses de corrélation, nous avons réussi à identifier et caractériser un petit groupe d'individus exécutant un service anonyme spécifique comme, par exemple, les habitants d'une même ville utilisant une application anonyme de partage de fichiers / Most of our daily activities are carried out over the Internet, from file-sharing and social networking to home banking, online-teaching and online-blogging. Considering file-sharing as one of Internet top activities, different architectures have been proposed, designed and implemented, leading to a wide set of file-sharing networks with different performances and goals. This digital society enables as well users' profiling. As Internet users surf the World Wide Web, every sent or received packet passes through several intermediate nodes until they reach their intended destination. So, an observer will be able to determine where a packet comes from and where it goes to, to monitor and to profile users' online activities by identifying to which server they are connected or how long their sessions last. Meanwhile, anonymous communications have been significantly developed to allow users to carry out their online activities without necessarily revealing their real identity. Our contribution is twofold. On the one hand, we consider hybrid file-sharing environments, with a special focus on widely deployed real-world networks and targeting two defined goals. The first goal is to improve content indexation in the BitTorrent file-sharing environment, enabling BitTorrent content to be indexed in the Kad distributed has table and leading to a more robust BitTorrent system. The second goal is to improve content availability in the I2P file-sharing environment. We allow I2P users to anonymously access public BitTorrent content and we obtain a fully anonymous file-sharing environment, including anonymous content indexation and anonymous content distribution. On the other hand, we focus on the understanding of anonymous environments through extensive monitoring. We characterise the I2P network, targeting the entire anonymous environment and its anonymous services. We consider different aspects of the network, such as the number of users, their characteristics as well as the number of anonymous services available. Through long-term measurements on the network and along with different correlation analyses, we are able to characterise a small group of users using a specific anonymous service, such as the users from a particular city performing anonymous file-sharing

This master's thesis deals with analysis and implementation of methods for BitTorrent monitoring focusing on the Mainline DHT protocol. The aim of the thesis was to create a system, that will be looking for BitTorrent peers that participe in the illegal file distribution. Another task of the system was to collect and analyze data for counting size of the BitTorrent network. That was achieved by taking over of existing method. The system was designed and implemented as a module for monitoring of cybernetic crime. It also defines an interface for storing and sharing data, that provides data evaluation, easy data manipulation and serves for possible future extensions.

BitTorrent is a peer-to-peer protocol useful for distributing large files over the Internet. Many organizations use BitTorrent to distribute their software in order to reduce client download time and reduce the load on their servers. While there is a lot of legitimate content available via BitTorrent, some organizations ban BitTorrent usage due to concerns over copyright infringement and the amount of bandwidth that peers can consume. A BitTorrent proxy will allow organizations to control those risks and allow its members to use the BitTorrent protocol for approved uses. It will allow the organization to control the files that are downloaded and the total bandwidth that can be used, and it will eliminate redundant downloads by acting as a cache.

Hoje em dia, distribuições de grandes volumes de dados por redes TCP/IP corporativas trazem problemas como a alta utilização da rede e de servidores, longos períodos para conclusão e maior sensibilidade a falhas na infraestrutura de rede. Estes problemas podem ser reduzidos com utilização de redes par-a-par (P2P). O objetivo desta dissertação é analisar o desempenho do protocolo BitTorrent padrão em redes corporativas e também realizar a análise após uma modificação no comportamento padrão do protocolo BitTorrent. Nesta modificação, o rastreador identifica o endereço IP do par que está solicitando a lista de endereços IP do enxame e envia somente aqueles pertencentes à mesma rede local e ao semeador original, com o objetivo de reduzir o tráfego em redes de longa distância. Em cenários corporativos típicos, as simulações mostraram que a alteração é capaz de reduzir o consumo médio de banda e o tempo médio dos downloads, quando comparados ao BitTorrent padrão, além de conferir maior robustez à distribuição em casos de falhas em enlaces de longa distância. As simulações mostraram também que em ambientes mais complexos, com muitos clientes, e onde a restrição de banda em enlaces de longa distância provoca congestionamento e descartes, o desempenho do protocolo BitTorrent padrão pode ser semelhante a uma distribuição em arquitetura cliente-servidor. Neste último caso, a modificação proposta mostrou resultados consistentes de melhoria do desempenho da distribuição. / Nowadays, distributions of large volumes of data over enterprise TCP/IP networks bring problems such as high network and server utilizations, long periods for completion, and greater sensitivity to flaws in network infrastructure. These problems can be reduced with the use of Peer-to-Peer networks (P2P). The aim of this work is to analyze the performance of the standard BitTorrent protocol in corporate networks and also perform the analysis after a change in the default behavior of the BitTorrent protocol. In this modification, the tracker identifies the peer IP address requesting the list of IP addresses of the swarm and sends only those belonging to the same LAN and to the original seeder, with the aim of reducing traffic on WAN links. In typical enterprise scenarios, the simulations showed that the change is able to reduce the average bandwidth consumption and the average time of downloads compared with standard BitTorrent, and give greater robustness to the distribution in case of failure of WAN links. The simulations also showed that in more complex network environments, with many clients, and where the bandwidth restriction on long distance links causes congestion and packet drops, the performance of standard BitTorrent protocol can be similar than a distribution in client-server architecture. In the latter case, the proposed change showed consistent results in improving distribution performance.

Hoje em dia, distribuições de grandes volumes de dados por redes TCP/IP corporativas trazem problemas como a alta utilização da rede e de servidores, longos períodos para conclusão e maior sensibilidade a falhas na infraestrutura de rede. Estes problemas podem ser reduzidos com utilização de redes par-a-par (P2P). O objetivo desta dissertação é analisar o desempenho do protocolo BitTorrent padrão em redes corporativas e também realizar a análise após uma modificação no comportamento padrão do protocolo BitTorrent. Nesta modificação, o rastreador identifica o endereço IP do par que está solicitando a lista de endereços IP do enxame e envia somente aqueles pertencentes à mesma rede local e ao semeador original, com o objetivo de reduzir o tráfego em redes de longa distância. Em cenários corporativos típicos, as simulações mostraram que a alteração é capaz de reduzir o consumo médio de banda e o tempo médio dos downloads, quando comparados ao BitTorrent padrão, além de conferir maior robustez à distribuição em casos de falhas em enlaces de longa distância. As simulações mostraram também que em ambientes mais complexos, com muitos clientes, e onde a restrição de banda em enlaces de longa distância provoca congestionamento e descartes, o desempenho do protocolo BitTorrent padrão pode ser semelhante a uma distribuição em arquitetura cliente-servidor. Neste último caso, a modificação proposta mostrou resultados consistentes de melhoria do desempenho da distribuição. / Nowadays, distributions of large volumes of data over enterprise TCP/IP networks bring problems such as high network and server utilizations, long periods for completion, and greater sensitivity to flaws in network infrastructure. These problems can be reduced with the use of Peer-to-Peer networks (P2P). The aim of this work is to analyze the performance of the standard BitTorrent protocol in corporate networks and also perform the analysis after a change in the default behavior of the BitTorrent protocol. In this modification, the tracker identifies the peer IP address requesting the list of IP addresses of the swarm and sends only those belonging to the same LAN and to the original seeder, with the aim of reducing traffic on WAN links. In typical enterprise scenarios, the simulations showed that the change is able to reduce the average bandwidth consumption and the average time of downloads compared with standard BitTorrent, and give greater robustness to the distribution in case of failure of WAN links. The simulations also showed that in more complex network environments, with many clients, and where the bandwidth restriction on long distance links causes congestion and packet drops, the performance of standard BitTorrent protocol can be similar than a distribution in client-server architecture. In the latter case, the proposed change showed consistent results in improving distribution performance.

<p>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>

In future telecommunication systems, we observe an increasing diversity of access networks. The separation of transport services and applications or services leads to multi-network services, i.e., a future service has to work transparently to the underlying network infrastructure. Multi-network services with edge-based intelligence, like P2P file sharing or the Skype VoIP service, impose new traffic control paradigms on the future Internet. Such services adapt the amount of consumed bandwidth to reach different goals. A selfish behavior tries to keep the QoE of a single user above a certain level. Skype, for instance, repeats voice samples depending on the perceived end-to-end loss. From the viewpoint of a single user, the replication of voice data overcomes the degradation caused by packet loss and enables to maintain a certain QoE. The cost for this achievement is a higher amount of consumed bandwidth. However, if the packet loss is caused by congestion in the network, this additionally required bandwidth even worsens the network situation. Altruistic behavior, on the other side, would reduce the bandwidth consumption in such a way that the pressure on the network is released and thus the overall network performance is improved. In this monograph, we analyzed the impact of the overlay, P2P, and QoE paradigms in future Internet applications and the interactions from the observing user behavior. The shift of intelligence toward the edge is accompanied by a change in the emerging user behavior and traffic profile, as well as a change from multi-service networks to multi-networks services. In addition, edge-based intelligence may lead to a higher dynamics in the network topology, since the applications are often controlled by an overlay network, which can rapidly change in size and structure as new nodes can leave or join the overlay network in an entirely distributed manner. As a result, we found that the performance evaluation of such services provides new challenges, since novel key performance factors have to be first identified, like pollution of P2P systems, and appropriate models of the emerging user behavior are required, e.g. taking into account user impatience. As common denominator of the presented studies in this work, we focus on a user-centric view when evaluating the performance of future Internet applications. For a subscriber of a certain application or service, the perceived quality expressed as QoE will be the major criterion of the user's satisfaction with the network and service providers. We selected three different case studies and characterized the application's performance from the end user's point of view. Those are (1) cooperation in mobile P2P file sharing networks, (2) modeling of online TV recording services, and (3) QoE of edge-based VoIP applications. The user-centric approach facilitates the development of new mechanisms to overcome problems arising from the changing user behavior. An example is the proposed CycPriM cooperation strategy, which copes with selfish user behavior in mobile P2P file sharing system. An adequate mechanism has also been shown to be efficient in a heterogeneous B3G network with mobile users conducting vertical handovers between different wireless access technologies. The consideration of the user behavior and the user perceived quality guides to an appropriate modeling of future Internet applications. In the case of the online TV recording service, this enables the comparison between different technical realizations of the system, e.g. using server clusters or P2P technology, to properly dimension the installed network elements and to assess the costs for service providers. Technologies like P2P help to overcome phenomena like flash crowds and improve scalability compared to server clusters, which may get overloaded in such situations. Nevertheless, P2P technology invokes additional challenges and different user behavior to that seen in traditional client/server systems. Beside the willingness to share files and the churn of users, peers may be malicious and offer fake contents to disturb the data dissemination. Finally, the understanding and the quantification of QoE with respect to QoS degradations permits designing sophisticated edge-based applications. To this end, we identified and formulated the IQX hypothesis as an exponential interdependency between QoE and QoS parameters, which we validated for different examples. The appropriate modeling of the emerging user behavior taking into account the user's perceived quality and its interactions with the overlay and P2P paradigm will finally help to design future Internet applications. / Applikationen im heutigen Internet werden immer mehr durch intelligente Endknoten bereitgestellt, deren Kommunikation in logischen, virtuellen Netzwerken, (Overlays) realisiert wird. Die verstärkte Diensterbringung durch solche Overlays, wie zum Beispiel bei Peer-to-Peer Dateitauschbörsen oder Telefonie über das Internet, wird durch einen Paradigmenwechsel von Multi-Service Networks zu Multi-Network Services beschrieben. Während in einem Multi-Service Network verschiedene Dienste innerhalb eines Netzes angeboten werden, beschreibt ein Multi-Network Service die Diensterbringung über verschiedene Netze und Netzzugangstechnologien, wie es im Internet der Fall ist. Dadurch kann die technische Güte des Telekommunikationsdienstes (Quality of Service, QoS) nicht mehr die alleinige Metrik für die Qualität eines Dienstes sein. Stattdessen ist die vom Nutzer erfahrene Dienstgüte (User Perceived Quality of Experience, QoE) zu betrachten. Diese QoE muss entsprechend modelliert werden, um die Performanz von heutigen oder auch zukünftigen Internetapplikationen zu beurteilen. Die Berücksichtigung der QoE beinhaltet unter anderem auch neuartige Verhaltensweisen der Teilnehmer, die ebenfalls modelliert werden müssen. Ein Beispiel ist der Dienstabbruch durch ungeduldige Nutzer beim Herunterladen von Filmen oder bei nicht ausreichender Qualität bei Internet-Telefonie. Durch die Verschiebung der Intelligenz von Applikationen in Richtung Endknoten entstehen neu aufkommende Verhaltensweisen der Teilnehmer und sich ändernde Charakteristika des Netzwerkverkehrs, die sie von klassischen Client-Server-Anwendungen unterscheiden. Beispiele hierfür sind egoistisches oder altruistisches Nutzerverhalten bei der Einbringung von Endnutzer-Ressourcen zur Diensterbringung oder auch bösartiges Nutzerverhalten bei der gezielten Störung eines Dienstes (Pollution). In beiden Fällen sind die zeitdynamischen Verhaltensmuster (Churn, Flash Crowds) zu berücksichtigen. Um die ausgedehnten Overlay. Netze zu planen und zu evaluieren, sind überdies auch neue Leistungsbewertungsmodelle notwendig, damit zum Beispiel die Simulation skaliert oder aber auch zeitdynamische Nutzerverhalten in analytischen Modellen abgebildet wird. Diese Doktorarbeit arbeitet diese Aspekte an drei Anwendungsbeispielen auf: Verteilernetz für Dateiinhalte (Content Distribution Network), Netzwerk-basierte Videorekorder (Online TV Recorder) und Sprachtelefonie über P2P (VoP2P). Die Ergebnisse und Untersuchungen dieser Arbeit gliedern sich entsprechend dieser Anwendungsbeispiele.