Le pair-à-pair (P2P) offre de bonnes solutions pour de nombreuses applications distribuées, comme le partage de grandes quantités de données et/ou le support de collaboration dans les réseaux sociaux. Il apparaît donc comme un puissant paradigme pour développer des applications distribuées évolutives, comme le montre le nombre croissant de nouveaux projets basés sur cette technologie. Construire des applications P2P fiables est difficile, car elles doivent être déployées sur un grand nombre de noeuds, qui peuvent être autonomes, refuser de répondre à certaines demandes, et même quitter le système de manière inattendue. Cette volatilité des noeuds est un comportement commun dans les systèmes P2P et peut être interprétée comme une faute lors des tests. Dans cette thèse, nous proposons un cadre et une méthodologie pour tester et valider des applications P2P. Ce cadre s'appuie sur le contrôle individuel des noeuds, permettant de contrôler précisément la volatilité des noeuds au cours de leur exécution. Nous proposons également trois différentes approches de contrôle d'exécution de scénarios de test dans les systèmes distribués. La première approche étend le coordonnateur centralisé classique pour gérer la volatilité des pairs. Les deux autres approches permettent d'éviter le coordinateur central afin de faire passer à l'échelle l'exécution des cas de tests. Nous avons validé le cadre et la méthodologie à travers la mise en oeuvre et l'expérimentation sur des applications P2P open-source bien connues (FreePastry et OpenChord). Les expérimentations ont permis de tester le comportement des systèmes sur différentes conditions de volatilité, et de détecter des problèmes d'implémentation complexes.

ISPs are concerned about providing and maintaining the level of security of its End User's communications. A communication is initiated by the End User with a name, and goes on by exchanging packets between two IP addresses. In this thesis, we focused our attention on two main points: (1) providing a secure Naming service, and (2) making IPsec communication resilient to IP address modification, addition or lost of an interface. We designed MOBIKE-X for that purpose and propose it as a standard at the IETF

The wide-spread coverage and ubiquitous presence of mobile networks has propelled the usage and adoption of mobile phones to an unprecedented level around the globe. The computing capabilities of these mobile phones have improved considerably, supporting a vast range of third party applications. Simultaneously, Peer-to-Peer (P2P) overlay networks have experienced a tremendous growth in terms of usage as well as popularity in recent years particularly in fixed wired networks. In particular, Distributed Hash Table (DHT) based Structured P2P overlay networks offer major advantages to users of mobile devices and networks such as scalable, fault tolerant and self-managing infrastructure which does not exhibit single points of failure. Integrating P2P overlays on the mobile network seems a logical progression; considering the popularities of both technologies. However, it imposes several challenges that need to be handled, such as the limited hardware capabilities of mobile phones and churn (i.e. the frequent join and leave of nodes within a network) intensive mobile networks offering limited yet expensive bandwidth availability. This thesis investigates the feasibility of extending P2P to mobile networks so that users can take advantage of both these technologies: P2P and mobile networks. This thesis utilises OverSim, a P2P simulator, to experiment with the performance of various P2P overlays, considering high churn and bandwidth consumption which are the two most crucial constraints of mobile networks. The experiment results show that Kademlia and EpiChord are the two most appropriate P2P overlays that could be implemented in mobile networks. Furthermore, Network Address Translation (NAT) is a major barrier to the adoption of P2P overlays in mobile networks. Integrating NAT traversal approaches with P2P overlays is a crucial step for P2P overlays to operate successfully on mobile networks. This thesis presents a general approach of NAT traversal for ring based overlays without the use of a single dedicated server which is then implemented in OverSim. Several experiments have been performed under NATs to determine the suitability of the chosen P2P overlays under NATed environments. The results show that the performance of these overlays is comparable in terms of successful lookups in both NATed and non-NATed environments; with Kademlia and EpiChord exhibiting the best performance. The presence of NATs and also the level of churn in a network influence the routing techniques used in P2P overlays. Recursive routing is more resilient to IP connectivity restrictions posed by NATs but not very robust in high churn environments, whereas iterative routing is more suitable to high churn networks, but difficult to use in NATed environments. Kademlia supports both these routing schemes whereas EpiChord only supports the iterating routing. This undermines the usefulness of EpiChord in NATed environments. In order to harness the advantages of both routing schemes, this thesis presents an adaptive routing scheme, called Churn Aware Routing Protocol (ChARP), combining recursive and iterative lookups where nodes can switch between recursive and iterative routing depending on their lifetimes. The proposed approach has been implemented in OverSim and several experiments have been carried out. The experiment results indicate an improved performance which in turn validates the applicability and suitability of ChARP in NATed environments.

Web 2.0 has significantly transformed the way how modern society works now-a-days. In today‘s Web, information not only flows top down from the web sites to the readers; but also flows bottom up contributed by mass user. Hugely popular Web 2.0 applications like Wikis, social applications (e.g. Facebook, MySpace), media sharing applications (e.g. YouTube, Flickr), blogging and numerous others generate lots of user generated contents and make heavy use of the underlying storage. Data storage system is the heart of these applications as all user activities are translated to read and write requests and directed to the database for further action. Hence focus is on the storage that serves data to support the applications and its reliable and efficient design is instrumental for applications to perform in line with expectations. Large scale storage systems are being used by popular social networking services like Facebook, MySpace where millions of users‘ data have been stored and fully accessed by these companies. However from users‘ point of view there has been justified concern about user data ownership and lack of control over personal data. For example, on more than one occasions Facebook have exercised its control over users‘ data without respecting users‘ rights to ownership of their own content and manipulated data for its own business interest without users‘ knowledge or consent. The thesis proposes, designs and implements a large scale, robust and fault-tolerant key-value data storage prototype that is peer-to-peer based and intends to back away from the client-server paradigm with a view to relieving the companies from data storage and management responsibilities and letting users control their own personal data. Several read and write APIs (similar to Yahoo!‘s P NUTS but different in terms of underlying design and the environment they are targeted for) with various data consistency guarantees are provided from which a wide range of web applications would be able to choose the APIs according to their data consistency, performance and availability requirements. An analytical comparison is also made against the PNUTS system that targets a more stable environment. For evaluation, simulation has been carried out to test the system availability, scalability and fault-tolerance in a dynamic environment. The results are then analyzed and conclusion is drawn that the system is scalable, available and shows acceptable performance.

Endocrine-disrupting chemicals (EDCs) are known to cause endocrine disruption (ED), developmental neurotoxicity (DNT), infertility and impaired embryo development. EDCs do therefore impose a threat to humans, wildlife and the environment. The present study investigated the effects of the reference compounds dihydrotestosterone, estradiol, benzo(a)pyrene, rosiglitazone, as well as the EDCs bisphenol F and perfluorooctanesulfonic acid at various concentrations on zebrafish embryos. The scientific questions of the study were to investigate how these environmental pollutants impact the development of zebrafish, what their molecular mechanisms are and what the link between ED and DNT is. Zebrafish embryos were exposed for 5 days to the compounds and various parameters on development were collected at different time points. The expression of 41 genes (qPCR) related to ED and DNT, and the levels of 23 steroids (LC-MS/MS) were determined. Gene correlations were determined with Pearson’s correlation test and paired t-tests were used to determine significantly altered gene activities. The significant gene expression changes were further related to the pathways of steroids in order to connect how gene activity impacted steroid levels. Exposure to estradiol, dihydrotestosterone and bisphenol F induced cyp19a1b expression which can affect personality traits. Perfluorooctanesulfonic acid interferes with thyroid hormone transport by binding to TTR causing profound effects on neurodevelopmental processes and cognitive functions. The compounds influenced genes that can disrupt endocrine systems which can cause neurodevelopmental impairments.

No description available.

The era of selective neurotoxins arose predominately in the 1960s with the discovery of the norepinephrine (NE) isomer 6-hydroxydopamine (6-OHDA), which selectively destroyed noradrenergic sympathetic nerves in rats. A series of similarly selective neurotoxins were later discovered, having high affinity for the transporter site on nerves and thus being accumulated and able to disrupt vital intraneuronal processes, to lead to cell death. The Trojan Horse botulinum neurotoxins (BoNT) and tetanus toxin bind to glycoproteins on the neuronal plasma membrane, then these stealth neurotoxins are taken inside respective cholinergic or glycinergic nerves, producing months-long functional inactivation but without overtly destroying those nerves. The mitochondrial complex I inhibitor rotenone, while lacking total specificity, still destroys dopaminergic nerves with some selectivity; and importantly, results in the neural accumulation of synuclein-to model Parkinson’s disease (PD) in animals. Other neurotoxins target specific subtypes of glutamate receptors and produce excitotoxicity in nerves with that receptor population. The dopamine D2 receptor agonist quinpirole, termed a selective neurotoxin, produces a behavioral state replicating some of the notable features of schizophrenia, but without overtly destroying nerves. These processes, mechanisms or treatment-outcomes account for the means by which neurotoxins are classified as such, and represent some of the means by which neurotoxins as a group are able to destroy or functionally inactivate nerves; or replicate an altered neurological state. Selective neurotoxins have proven to be important in gaining insight into biochemical processes and mechanisms responsible for survival or demise of a nerve. Selective neurotoxins are useful also for animal modeling of human neural disorders such as PD, Alzheimer disease, attention-deficit hyperactivity disorder (ADHD), Lesch-Nyhan disease, tardive dyskinesia, schizophrenia and others. The importance of neurotoxins in neuroscience will continue to be ever more important as even newer neurotoxins are discovered.

Le routage dans Internet est basé sur des tables dites de routage, formées de blocs d’adresses IP. Cependant, la construction et la maintenance de telles tables de routage nécessitent l’utilisation de protocoles complexes qui ne passent pas à l’échelle en termes de mémoire et d’utilisation CPU. De plus, l’expérience montre que le plan d’adressage IP est insuffisant, car la sémantique d’une adresse IP est à la fois un identificateur et un localisateur. Dans nos travaux, nous proposons un système de réseau recouvrant pair-à-pair libre de toute contrainte topologique et utilisant des coordonnées virtuelles prises dans le plan hyperbolique nommé CLOAK (Covering Layer Of Abstract Knowledge en anglais). Les schémas de routages locaux basés sur des coordonnées virtuelles extraites du plan hyperbolique ont suscité un intérêt considérable ces dernières années. Dans cette thèse, nous proposons une nouvelle approche pour saisir le potentiel de la géométrie hyperbolique. L’objectif est de construire un système extensible et fiable pour créer et gérer des réseaux recouvrants dans Internet. Le système est implémenté comme une infrastructure pair-à-pair structuré basé sur les protocoles de la couche transport entre les pairs. Quant à l’organisation des données dans l’espace virtuel, nous employons la réplication pour améliorer la disponibilité et l’accessibilité des objets de l’overlay potentiellement instable. Nous avons implémenté et évalué différentes méthodes de réplication (réplication radiale, réplication circulaire).A l’aide de simulations, nous évaluons notre proposition à travers un certain nombre de métriques et nous montrons que les réseaux recouvrants pair-à-pair basés sur la géométrie hyperbolique ont de bonnes performances par rapport aux autres DHT existantes tout en introduisant flexibilité et robustesse dans les réseaux recouvrants dynamiques. / Internet routing is based on forwarding tables populated by blocks of IP addresses. However, the construction and maintenance of such tables require the use of complex routing protocols that are typically not scalable in terms of memory and CPU usage. Moreover, experience shows that the IP addressing plane is insufficient due to the semantic of an IPaddress being both an identifier and a locator. In this paper, we propose a P2P overlay system of freed topology and using virtual coordinates taken from the hyperbolic plane named CLOAK(Covering Layer Of Abstract Knowledge en anglais). Local knowledge routing schemes based on virtual coordinates taken from the hyperbolic plane have attracted considerable interest in recent years. In this thesis we propose a new approach for seizing the power of the hyperbolic geometry. We aim at building a scalable and reliable system for creating and managing overlay networks over the Internet. The system is implemented as a structured peer-to-peer infrastructure based on the transport layer connections between the peers. Concerning data organisation in the virtual space, we use replication strategy for improve overlay objects disponibilty and accessibility in context potentially unstable. We have implemented and evaluated various replication methods (radial replication, circular replication). Using simulations, we assess our proposal across a certain number of metric and show that overlay Peer-to-Peer network based on the hyperbolic geometry have good performances in comparison with other existent DHT while introducing suppleness and robustness in the dynamic overlay network.

Ce mémoire est une synthèse de nos travaux de recherche menés au sein des laboratoires d'Orange Labs (anciennement France Télécom R&D) pour répondre à une problématique identifiée par ledit opérateur et concernant les flux d'échanges en mode pair-à-pair (P2P). Communément assimilé à un échange de fichiers, le P2P a de nombreuses applications. Il correspond à une évolution du monde du logiciel, des réseaux et des équipements. Au-delà du partage, nous sommes confrontés à une puissance disponible de façon distribuée (en termes de CPU, bande passante, stockage, etc.). La montée en puissance du P2P exige de nouveaux systèmes pouvant satisfaire les besoins des usagers, mais aussi ceux des fournisseurs d'accès à Internet (FAI) et autres opérateurs de réseaux. Les premiers cherchent en permanence une bonne qualité de service (QoS) bien perceptible. Les seconds aspirent à l'optimisation de l'usage des ressources du réseau (notamment la bande-passante) et à la réduction des différents coûts d'opération et de maintenance (dont ceux découlant de leurs accords économiques inter-opérateurs). D'où l'intérêt de nos travaux de recherche qui visent à sensibiliser un réseau P2P au réseau IP sous-jacent, afin d'aboutir à un système de routage P2P efficace, en phase avec les politiques des réseaux d'infrastructures sous-jacents. Ces travaux se focalisent sur les systèmes P2P utilisant des tables de hachage distribuées (DHT), après les avoir étudiées et analysées. Ce mémoire commence par une analyse des principaux protocoles de découverte de ressources dynamiques dans les différentes architectures de réseaux P2P. Les exigences requises pour un routage P2P efficace sont par la suite établies. Il s'en suit une présentation des techniques de génération de l'information de proximité sous-jacente, ainsi que des techniques et principaux systèmes d'exploitation de cette information. Nos travaux de recherche ont abouti à la définition, la conception, la spécification et l'analyse individuelle et comparative de deux systèmes : CAP (Context-Aware P2P system) et NETPOPPS (NETwork Provider Oriented P2P System). Le premier système est sensible au contexte et introduit une sémantique dans les identifiants des pairs et des objets. Le second système est orienté opérateur de réseau, et adapte les flux P2P à la topologie sous-jacente et aux politiques de l'opérateur, tout en simplifiant la gestion des différents identifiants.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The increase in linear and non-linear loads experienced by Brazil in recent years has changed the way distribution networks are planned and Operated. In addition, the competitiveness of the market and the demand for the improvement in power quality indexes mean that current e orts are increasingly focused on areas such as voltage profile control and voltage harmonic distortion control. This work deals, exactly, with the Integrated control of voltage and harmonic voltage distortion (volt/thd) in distribution systems, within the scope of planning, through the insertion of passive harmonics filters and voltage regulators. To solve the problem in question, a multiobjective algorithm, the NSGA-II, is applied, since the presented problem can be treated as a combinatorial optimization problem. The power summation method is used as an alternative for the resolution of the load flow. While the current injection method is used as a calculation of the harmonic flow. The mathematical models of the network components were presented, taking into account the influence of frequency, in a detailed way. The proposed algorithm was applied in benchmark systems, a 34-bus and a 104-bus, the systems were simulated with and without the presence of the devices for comparison and validation of the results. / O aumento de cargas, lineares e não-lineares, vivenciado pelo Brasil nos últimos anos, tem alterado a maneira com as redes de distribuição são planejadas e operadas. Além disso, a competitividade do mercado e exigência pela melhoria nos índices de qualidade da energia fazem com que os esforços atuais sejam cada vez mais direcionados para áreas como o controle do perfil de tensão e o controle das distorções harmônicas de tensão. Esta dissertação trata, exatamente, do controle integrado de tensão e distorção harmônica de tensão (volt/dht) em sistemas de distribuição, no âmbito do planejamento, através da inserção de filtros harmônicos passivos e reguladores de tensão. Para resolver o problema em questão, um algoritmo multiobjetivo, o NSGA-II, é aplicado, uma vez que o problema apresentado é tratado como um problema de otimização combinatória. O método da soma de potências é utilizado como alternativa para a resolução do fluxo de carga. Enquanto que o método da injeção de correntes é utilizado como cálculo do fluxo de harmônicos. Os modelos matemáticos dos componentes da rede foram apresentados, levando-se em consideração a influência da frequência, de forma detalhada. O algoritmo proposto foi aplicado em sistemas teste de 34 e 104 barras e os sistemas foram simulados com e sem a presença dos dispositivos para efeito de comparação e validação dos resultados.