CLOSER: A Collaborative Locality-aware Overlay SERvice

Current Peer-to-Peer (P2P) file sharing systems make use of a considerable percentage of Internet Service Providers (ISPs) bandwidth. This paper presents the Collaborative Locality-aware Overlay SERvice (CLOSER), an architecture that aims at lessening the usage of expensive international links by exploiting traffic locality (i.e., a resource is downloaded from the inside of the ISP whenever possible). The paper proves the effectiveness of CLOSER by analysis and simulation, also comparing this architecture with existing solutions for traffic locality in P2P systems. While savings on international links can be attractive for ISPs, it is necessary to offer some features that can be of interest for users to favor a wide adoption of the application. For this reason, CLOSER also introduces a privacy module that may arouse the users' interest and encourage them to switch to the new architectur

Content Distribution in P2P Systems

The report provides a literature review of the state-of-the-art for content distribution. The report's contributions are of threefold. First, it gives more insight into traditional Content Distribution Networks (CDN), their requirements and open issues. Second, it discusses Peer-to-Peer (P2P) systems as a cheap and scalable alternative for CDN and extracts their design challenges. Finally, it evaluates the existing P2P systems dedicated for content distribution according to the identied requirements and challenges

Incentive-driven QoS in peer-to-peer overlays

A well known problem in peer-to-peer overlays is that no single entity has control over the software, hardware and configuration of peers. Thus, each peer can selfishly adapt its behaviour to maximise its benefit from the overlay. This thesis is concerned with the modelling and design of incentive mechanisms for QoS-overlays: resource allocation protocols that provide strategic peers with participation incentives, while at the same time optimising the performance of the peer-to-peer distribution overlay. The contributions of this thesis are as follows. First, we present PledgeRoute, a novel contribution accounting system that can be used, along with a set of reciprocity policies, as an incentive mechanism to encourage peers to contribute resources even when users are not actively consuming overlay services. This mechanism uses a decentralised credit network, is resilient to sybil attacks, and allows peers to achieve time and space deferred contribution reciprocity. Then, we present a novel, QoS-aware resource allocation model based on Vickrey auctions that uses PledgeRoute as a substrate. It acts as an incentive mechanism by providing efficient overlay construction, while at the same time allocating increasing service quality to those peers that contribute more to the network. The model is then applied to lagsensitive chunk swarming, and some of its properties are explored for different peer delay distributions. When considering QoS overlays deployed over the best-effort Internet, the quality received by a client cannot be adjudicated completely to either its serving peer or the intervening network between them. By drawing parallels between this situation and well-known hidden action situations in microeconomics, we propose a novel scheme to ensure adherence to advertised QoS levels. We then apply it to delay-sensitive chunk distribution overlays and present the optimal contract payments required, along with a method for QoS contract enforcement through reciprocative strategies. We also present a probabilistic model for application-layer delay as a function of the prevailing network conditions. Finally, we address the incentives of managed overlays, and the prediction of their behaviour. We propose two novel models of multihoming managed overlay incentives in which overlays can freely allocate their traffic flows between different ISPs. One is obtained by optimising an overlay utility function with desired properties, while the other is designed for data-driven least-squares fitting of the cross elasticity of demand. This last model is then used to solve for ISP profit maximisation

Development of an adaptable multicast overlay network

Dissertação de mestrado em Informatics EngineeringMulticast is a group communication paradigm created in order to reduce, as much as possible, the amount of data generated to the network. However, limited deployment of IP Multicast protocols has motivated an interest in alternative approaches which implement a similar process of Multicast at an application-level (using solely end-systems and not the routers). In this context, different methodologies are presented, entitled Application-Layer Multicast or Overlay Multicast, which may vary in the way they operate. This dissertation’s objective is to develop and experiment a prototype of an overlay multicast system. This system should be easily configurable and adaptable in order to assume different strategies when establishing the multicast distribution tree. It is also expected to explore and integrate collaborative mechanisms between the overlay network and the Internet Service Providers (ISP). With the presented context, the first step to take is an investigation on the state of the art, where technologies relevant to this work will be presented. After this initial step, the developed system’s architecture will be described, one which enables different ways of building and maintaining the multicast distribution tree. The envisioned system can operate independently, integrating mechanisms where the distribution tree relies solely on peer decisions, which will be firstly addressed. Then, this work will move on to collaborative mechanisms between the overlay’s management (the central node) and the Internet Service Providers. Based on the proposed system architecture, several mechanisms are explored, not only focusing on alternative ways to build distribution trees, but also mechanisms allowing for some traffic engineering objectives involving the Internet Service Providers. Using the CORE network emulator, all the proposed mechanisms are tested, and results are analyzed to corroborate the system’s correct operation.O multicast é um paradigma de comunicação em grupo que tem como objetivo reduzir, tanto quanto possível, a quantidade de tráfego gerada para a rede. No entanto, a implantação limitada de protocolos IP Multicast tem motivado o interesse em abordagens alternativas que implementam processos de distribuição Multicast na camada aplicacional (ou seja, usando apenas os sistemas/aplicações finais e não os routers). Neste contexto, surgem as soluções denominadas por Application-Layer Multicast ou Overlay Multicast, podendo estas apresentar algumas variantes na sua operação. Nesta dissertação, tem-se como objetivo o desenvolvimento e experimentação de um protótipo de um sistema de Overlay Multicast. Este sistema deverá ser capaz de ser facilmente (re)configurado para assumir diferentes estratégias no estabelecimento da árvore de distribuição Multicast, e integrar mecanismos de colaboração entre a rede Overlay e os Internet Service Providers. No contexto apresentado, o primeiro passo consiste na investigação do estado da arte, onde tecnologias relevantes ao atual trabalho serão apresentadas. Após este passo inicial, a arquitectura do sistema será apresentada, uma arquitectura que considera diferentes maneiras de construir e manter a árvore de distribuição multicast. O sistema proposto pode operar de forma independente, contemplando mecanismos onde a árvore de distribuição depende apenas das decisões dos vários peers, sendo que estes serão os primeiros mecanismos a serem apresentados. De seguida, o sistema direcciona-se para mecanismos colaborativos entre a gestão da rede overlay e o ISP, de maneira a incluir conhecimento acerca da topologia da rede que nenhuma outra entidade seria capaz de providenciar. Com base na arquitectura do sistema proposto, vários mecanismos são explorados, não só mecanismos que se concentram em formas alternativas de construir a árvore de distribuição, mas também mecanismos que permitem cumprir os objetivos de engenharia de tráfico dos ISPs. Por fim, utilizando o emulador de redes CORE, todas as soluções serão testadas, e os seus resultados analisados por forma a validar a correta operação de todo o sistema

Development of a system compliant with the Application-Layer Traffic Optimization Protocol

Dissertação de mestrado integrado em Engenharia InformáticaWith the ever-increasing Internet usage that is following the start of the new decade, the need to optimize this world-scale network of computers becomes a big priority in the technological sphere that has the number of users rising, as are the Quality of Service (QoS) demands by applications in domains such as media streaming or virtual reality. In the face of rising traffic and stricter application demands, a better understand ing of how Internet Service Providers (ISPs) should manage their assets is needed. An important concern regards to how applications utilize the underlying network infras tructure over which they reside. Most of these applications act with little regard for ISP preferences, as exemplified by their lack of care in achieving traffic locality during their operation, which would be a preferable feature for network administrators, and that could also improve application performance. However, even a best-effort attempt by applications to cooperate will hardly succeed if ISP policies aren’t clearly commu nicated to them. Therefore, a system to bridge layer interests has much potential in helping achieve a mutually beneficial scenario. The main focus of this thesis is the Application-Layer Traffic Optimization (ALTO) work ing group, which was formed by the Internet Engineering Task Force (IETF) to explore standardizations for network information retrieval. This group specified a request response protocol where authoritative entities provide resources containing network status information and administrative preferences. Sharing of infrastructural insight is done with the intent of enabling a cooperative environment, between the network overlay and underlay, during application operations, to obtain better infrastructural re sourcefulness and the consequential minimization of the associated operational costs. This work gives an overview of the historical network tussle between applications and service providers, presents the ALTO working group’s project as a solution, im plements an extended system built upon their ideas, and finally verifies the developed system’s efficiency, in a simulation, when compared to classical alternatives.Com o acrescido uso da Internet que acompanha o início da nova década, a necessidade de otimizar esta rede global de computadores passa a ser uma grande prioridade na esfera tecnológica que vê o seu número de utilizadores a aumentar, assim como a exigência, por parte das aplicações, de novos padrões de Qualidade de Serviço (QoS), como visto em domínios de transmissão de conteúdo multimédia em tempo real e em experiências de realidade virtual. Face ao aumento de tráfego e aos padrões de exigência aplicacional mais restritos, é necessário melhor compreender como os fornecedores de serviços Internet (ISPs) devem gerir os seus recursos. Um ponto fulcral é como aplicações utilizam os seus recursos da rede, onde muitas destas não têm consideração pelas preferências dos ISPs, como exemplificado pela sua falta de esforço em localizar tráfego, onde o contrário seria preferível por administradores de rede e teria potencial para melhorar o desempenho aplicacional. Uma tentativa de melhor esforço, por parte das aplicações, em resolver este problema, não será bem-sucedida se as preferências administrativas não forem claramente comunicadas. Portanto, um sistema que sirva de ponte de comunicação entre camadas pode potenciar um cenário mutuamente benéfico. O foco principal desta tese é o grupo de trabalho Application-Layer Traffic Optimization (ALTO), que foi formado pelo Internet Engineering Task Force (IETF) para explorar estandardizações para recolha de informação da rede. Este grupo especificou um protocolo onde entidades autoritárias disponibilizam recursos com informação de estado de rede, e preferências administrativas. A partilha de conhecimento infraestrutural é feita para possibilitar um ambiente cooperativo entre redes overlay e underlay, para uma mais eficiente utilização de recursos e a consequente minimização de custos operacionais. É pretendido dar uma visão da histórica disputa entre aplicações e ISPs, assim como apresentar o projeto do grupo de trabalho ALTO como solução, implementar e melhorar sobre as suas ideias, e finalmente verificar a eficiência do sistema numa simulação, quando comparado com alternativas clássicas