Grid computing is a virtualized distributed computing environment aimed at enabling the sharing of geographically distributed resources. Grid resources have traditionally consisted of dedicated supercomputers, clusters, or storage units. With the present ubiquitous network connections and the growing computational and storage capabilities of modem everyday-use computers, more resources such as PCs, devices (e.g., PDAs and sensors), applications, and services are on grid networks. Grid is expected to evolve from a computing and data management facility to a pervasive, world-wide resource-sharing infrastructure. To fully utilize the wide range of grid resources, effective resource discovery mechanisms are required. However, resource discovery in a global-scale grid is challenging due to the considerable diversity, large number, dynamic behavior, and geographical distribution of the resources. The resource discovery technology required to achieve the ambitious global grid vision is still in its infancy, and existing applications have difficulties in achieving both rich searchability and good scalability. In this thesis, we investigate the resource discovery problem for open-networked global-scale grids. In particular, we propose a distributed semantics-based discovery framework. We show how this framework can be used to address the discovery problem in such grids and improve three aspects of performance: expressiveness, scalability, and efficiency. Expressiveness is the first characteristic that a grid resource-searching mechanism should have. Most existing search systems use simple keyword-based lookups, which limit the searchability of the system. Our framework improves search expressiveness from two directions: First, it uses a semantic metadata scheme to provide users with a rich and flexible representation mechanism, to enable effective descriptions of desired resource properties and query requirements. Second, we employ ontological domain knowledge to assist in the search process. The system is thus able to understand the semantics of query requests according to their meanings in a specific domain; this procedure helps the system to locate only semantically related results. The more expressive the resource description and query request, however, the more difficult it is to design a scalable and efficient search mechanism. We ensure scalability by reconfiguring the network with respect to shared ontologies. This reconfiguration partitions the large unorganized search space into multiple well-organized semantically related sub-spaces that we call semantic virtual organizations. Semantic virtual organizations help to discriminatively distribute resource information and queries to related nodes, thus reducing the search space and improving scalability. To further improve the efficiency of searching the virtual organizations, we propose two semantics-based resource-integrating and searching systems: GONID and OntoSum. These two systems address searching problems for applications based on different network topologies: structured and unstructured peer-to-peer overlay networks. Queries in the search systems are processed in a transparent way, so that users accessing the data can be insulated from the fact that the information is distributed across different sources and represented with different formats. In both systems, ontological knowledge is decomposed into different coarse-grained elements, and then these elements are indexed with different schemes to fit the requirements of different applications. Resource metadata reasoning, integrating, and searching are based on the index. A complex query can be evaluated by performing relational operations such as select, project, and join on combinations of the indexing elements. We evaluate the performance of our system with extensive simulation experiments, the results of which confirm the effectiveness of the design. In addition, we implement a prototype that incorporates our ontology-based virtual organization formation and semantics-based query mechanisms. Our deployment of the prototype verifies the system's feasibility and its applicability to real-world applications. / Science, Faculty of / Computer Science, Department of / Graduate

It was known for a long time that OpenStack has issues with scalability. Peer-to-Peer systems, on the other hand, have proven to scale well without significant reduction of performance. The objectives of this thesis are to study the challenges associated with P2P-enhanced clouds and present solutions for overcoming them. As a case study, we take the architecture of the P2P-enhanced OpenStack implemented at Ericsson that uses the CYCLON P2Pprotocol. We study the OpenStack architecture and P2P technologies and finally propose solutions and provide possibilities in addressing the challenges that are faced by P2P-enhanced OpenStack clouds. We emphasize mainly on a decentralized identity service and management of Virtual machine images. This work also investigates the characterization of P2P architectures for their use in P2P-enhanced OpenStack clouds. The results section shows that the proposed solution enables the existing P2P system to scale beyond what was originally possible. We also show that the P2P-enhanced system performs better than the standard OpenStack. / <p>Ericsson Cloud Research supported this work through the guidance of Dr. Fetahi Wuhib, Dr. Joao Monteiro Soares and Vinay Yadav, Experienced Researchers, Ericsson Cloud Research, Kista, Stockholm.</p>

Software piracy In this thesis I explore the current state of software piracy in the Czech Republic, which proves to be quite demanding due to its illegal nature and the lack of statistical data. I also take a look at the current legal protection which is awarded to the authors of computer software. Even with new trends in software piracy I conclude, that the current protection is satisfactory. I also explain how international treaties and european legislation influence czech laws.

Durant ces dernières années, les délais de transmission sur Internet ont augmenté de manière considérable, causant une détérioration de performances des applications interactives. La cause de ces augmentations de délais est l’excès de mémoire tampon à l’intérieur du réseau, appelé "bufferbloat". Les efforts de recherche dans cette direction vont vers des techniques de gestion des files d’attente actives et des techniques de contrôle de congestion de bout-à-bout. Dans ce contexte, nous avons examiné LEDBAT, un protocole introduit par BitTorrent qui se base sur le délai au niveau transport, et conçu pour transférer grandes quantités de données sans affecter les délais expérimentés par d’autres applications ou utilisateurs. Nous avons analysé la performance de niveau de transport de LEDBAT avec de mesures expérimentales, de simulations et de modèles analytiques, en comparant ses performances au standard TCP ou à d’autre protocoles de failbe priorité. Nous avons ensuite identifié un problème d’iniquité, et nous avons proposé fLEDBAT, qui ré-introduit l’équité intra-protocole. Dans un deuxième temps, nous avons étudié l’impact du protocole LEDBAT sur la performance de BitTorrent. Par des simulations et des expérimentations sur réseaux réelles, nous avons analysé les effets de LEDBAT sur le remplissage des tampons des noeuds d’accès. Les performances de BitTorrent ont été évaluées en termes de temps d’exécution, qui reflète la qualité de l’expérience utilisateur. Dans les deux cas, les résultats ont montré que LEDBAT diminue le temps de traitement par rapport à TCP et réduit de manière significative l’utilisation de tampons, ce qui se traduit par une baisse des délais. / In the last years, Internet delays are considerably growing, causing a performance deterioration of interactive applications. This phenomenon is getting worse with the increasing popularity of bandwidth-intensive applications, as video streaming, remote backup and P2P systems. The cause of these delays has been identified with the excess buffering inside the network, called “bufferbloat”. Research efforts in this direction head toward active queue management techniques and end-to-end congestion control. In this context, we investigated LEDBAT, a low-priority delay-based transport protocol introduced by BitTorrent. This protocol is designed to transfer large amount of data without affecting the delay experienced by other applications or users. First we analysed transport-level performance of LEDBAT using experimental measurement, simulation and analytical model. Specifically, we evaluated LEDBAT as is, comparing its performance to standard TCP or to other low priority protocols. We then identified a later-comer advantage and we proposed fLEDBAT, which re-introduces intra-protocol fairness maintaining the original LEDBAT objectives. Finally we studied the impact of the LEDBAT protocol on BitTorrent performance. Through simulations and real network experiments, we analysed how BitTorrent impacts on the buffer occupancy of the access node. BitTorrent performance was evaluated in terms of completion time, the main metric to assess the user quality of experience. Results showed that LEDBAT decreases the completion time with respect to standard TCP and significantly reduces the buffer occupancy, that translates in lower delays experienced by competing interactive applications.

Smartphones now account for the majority of all cell phones in use today [23]. Ubiquitous Internet access is a valuable feature offered by these devices and the vast majority of smartphone applications make use of the Internet in one way or another. However, the bandwidth offered by these cellular networks is often much lower than we typically experience on our standard home networks, leading to a less-than-optimal user experience. This makes it very challenging and frustrating to access certain types of web content such as video streaming, large file downloads, loading large webpages, etc. Given that most modern smartphones are multi-homed and are capable of ac- cessing multiple networks simultaneously, this thesis attempts to utilize all available network interfaces in order to achieve the aggregated bandwidth of each to improve the overall network performance of the phone. To do so, I implement a bandwidth aggregation system for iOS that combines the bandwidths of multiple devices located within close proximity of each other. Deployed on up to three devices, speedups of up to 1.82x were achieved for downloading a single, 10mb file. Webpage loading saw speedups of up to 1.55x.

No description available.

Este trabalho apresenta a avaliação de diferentes algoritmos de roteamento utilizados na camada lógica ponto a ponto (P2P) adotada por um Metaescalonador que provê Qualidade de Serviços (QoS) na Computação em Nuvem. Experimentos mostram a superioridade de três algoritmos de roteamento P2P (BCR, Chord e Pastry) em relação à utilização de Round Robin, analisando-se o tempo de resposta e a variabilidade entre os resultados obtidos em diferentes testes. Os experimentos consideram, além dos algoritmos de roteamento, a influência do número de usuários e do tipo de serviço requisitado e como esses fatores interagem entre si. É apresentado ainda um estudo sobre a melhor métrica a ser adotada para representar as informações da rede. As métricas consideradas foram latência e número de saltos. Os resultados obtidos permitem determinar, com base nos objetivos especificados, qual o impacto dos sistemas P2P utilizados pelo metaescalonador na busca e descoberta de serviços em relação à forma como a qualidade de serviços é abordada / This work presents an evaluation of different routing algorithms that are employed in a logical layer peer-to-peer (P2P) that are adopted by a Metascheduler that provides quality of services (QoS) in Cloud Computing. The experiments show the superiority of three P2P routing algorithms (BCR, Chord, Pastry) in relation to Round Robin utilization, analysing the response times and the variation between the results obtained results in different tests. The experiments consider, besides the routing algorithms, the influence of the number of the users and the type of requested services and how these factors interact between themselves. Besides of this, it is presented a study about the better metric to be adopted to represent the network information. The considered metrics were the latency and number of hops. The obtained results allow to determine, based on specific objectives, the impact of the utilization of P2P systems by the metascheduler in the search and discovery of services in relation to the way that the QoS is performed

Även om delning av resurser har funnit sedan urminnes tider har delningsekonomi vuxit fram under det senaste årtiondet, där företagens nya uppbyggnad skapar komplikationer. Detta bland annat då det inte finns en entydig definition av vad delningsekonomi faktiskt innebär, likväl som det fortfarande är debatt kring hur delningsekonomiska företag bör förhålla sig till den traditionella marknaden. Studien syftar därmed att tydliggöra konkurrens inom delningsekonomi på den svenska marknaden utifrån delningsekonomiska aktörers perspektiv. Kvalitativa intervjuer har utförts med fem bolag på den svenska transportmarknaden, där intervjuerna baseras på fyra ämnesområden: marknad &amp; konkurrens, prissättning, förtroende och kommunikation &amp; marknadsföring. Resultaten har analyserats, där analysen och slutsatsen har sammanfattat likheter och skillnader i företagsuppbyggnader och företagens uppfattning av marknaden. Återkommande upplevelse från aktörerna är att delningsekonomi är nytt vilket märks av på marknaden. Konsumentbeteende uppfattas samtidigt ännu inte vara väletablerat, likväl som att det svenska regelverket till fullo inte är anpassat efter delningsekonomins snabba utveckling. Ytterligare gemensamma faktorer framkommer vara enkelhet vid pris och teknik, användande av betygssystem och att ett personligare angreppssätt både ökar förtroendet och är positivt vid marknadsföring. Även en större företagsstorlek tycks vara en konkurrensfördel.

Made available in DSpace on 2017-07-21T14:19:33Z (GMT). No. of bitstreams: 1 Luiz Rafael Schmitke.pdf: 1854453 bytes, checksum: c7e3cc9cb3865213cd2b9f59a4cf211c (MD5) Previous issue date: 2012-06-30 / Agriculture is an activity where the weather has more impact, influencing techniques and crops employed. Much of the agricultural productivity is affected by climatic conditions that are created by natural factors and are not likely to control. Although you can’t control the weather, we can predict it, or even simulate their conditions to try minimize its impact on agriculture. To be able to make these predictions and simulations are necessary data collected from weather stations that can be conventional or automatic and must be without gaps or abnormal data. Most of these errors are caused by signal interference, disconnection, oxidation of cables and spatio-temporal variation of climate which consequently end up generating those problems at the climates bases. Thus, this research work has as main objective to create a model capable of correcting gaps in climate databases, observing that not to correct abnormal observations or replace statistical methods for the same purpose. Therefore a model was created to correct the gaps in weather data between stations using the P2P architecture. With this model, an application was created to test its performance to correct the gaps. Also to perform the tests were used bases in the cities of Ponta Grossa, Fernandes Pinheiro and Telêmaco Borba provided by Instituto Tecnológico SIMEPAR, and bases of the cities of Castro, Carambeí, Pirai do Sul and Tibagi provided by Fundação ABC, which are collected daily on automatic stations. As a result it was observed that the performance of P2P correction model was satisfactory when compared to the simulator used in the tests, with lower results only in February, which corresponds to the period of summer, to the autumn, winter and spring the model P2P was better than simulated. Although it was found that the number of stations participating in the network at the time of correcting influences the results, and the higher it is, the better the results obtained with the correcting. / A agricultura é uma das atividades onde o clima tem mais impacto, influenciando as técnicas e os cultivos empregados. Grande parte da produtividade agrícola se deve as condições climáticas que são criadas por fatores naturais e não são passíveis de controle. Embora não seja possível controlar o clima, pode-se prevê-lo ou até simular suas condições para tentar minimizar seu impacto na agricultura. Para que seja possível realizar estas previsões e simulações são necessários dados coletados em estações climáticas que podem ser convencionais ou automáticas e que precisam estar sem dados anormais ou lacunas. Grande parte desses erros se deve a interferência no sinal, desconexão, oxidação de cabos e a variação espaço-temporal do clima que por consequência acabam gerando aqueles problemas nas bases climáticas. Desta forma, este trabalho de pesquisa tem como objetivo principal criar um modelo capaz de corrigir as lacunas existentes nas bases de dados climáticas, salientando-se que não visa à correção de observações anormais e nem a substituição dos métodos estatísticos para o mesmo fim. Para tanto foi criado um modelo de correção das lacunas em dados climáticos entre as estações utilizando a arquitetura P2P. Com este modelo, foi criada uma aplicação para testar seu desempenho em corrigir as lacunas encontradas. Também para a realização dos testes foram utilizadas bases das cidades de Ponta Grossa, Fernades Pinheiro e Telêmaco Borba, fornecidas pelo Instituto Tecnológico SIMEPAR, e bases das cidades de Castro, Carambeí, Tibagi e Pirai do Sul fornecidas pela Fundação ABC, sendo estes dados, diários e coletados em estações automáticas. Como resultados foi possível observar que o desempenho do modelo de correção P2P foi satisfatório quando comparado ao simulador utilizado nos testes, apresentando resultados inferiores somente no mês de fevereiro, que corresponde ao período de verão, para as estações de outono, inverno e primavera o modelo P2P foi melhor que o simulado. Ainda foi verificado que a quantidade de estações que participa da rede na hora da correção influencia os resultados, sendo que quanto maior ela for, melhores são os resultados obtidos com a correção. Palavras-chave: Redes P2P, Correção, Dados Climáticos.

Dans cette nouvelle ère du numérique, l'accès à l'information est entré désormais dans une autre dimension. Nous assistons à la dominance d'un modèle fondé sur les opportunités offertes par un accès mondialisé à l'Internet et à son application phare : le "World Wide Web". Les services se sont multipliés. Les terminaux se sont diversifiés. Les technologies de transport se sont améliorées. Les attentes se sont élevées. Dans cette spirale que nous nous abstenons de qualifier, les opérateurs se trouvent désormais confrontés à une croissance soutenue du trafic dans leurs réseaux, en grande partie due au transport de flux vidéo. Les fournisseurs de services sur Internet se trouvent aussi concernés par la problématique de la qualité de service dont dépend la satisfaction de leurs utilisateurs. Pour l'ensemble des acteurs, ces nouvelles tendances présentent à la fois des défis et des opportunités. Les défis se concentrent dans la problématique de gestion de la demande croissante du trafic tout en maintenant une qualité d'expérience appropriée pour les utilisateurs. Les opportunités proviendront de l'adéquation entre une demande croissante des services Web en termes de qualité de services et des ressources qui devront supporter la distribution de ces services. Il est crucial pour chaque acteur de bien se positionner dans la chaîne de valeur pour gérer cette adéquation. Le rôle que prendra le réseau support, simple ensemble de tuyaux surdimensionnés, ou bien réseau intelligent offrant des fonctions avancées de contrôle illustre parfaitement cet enjeu. Ces deux alternatives sont respectivement connues sous les termes "dumb-pipe" ou "smart network". Dans cette thèse, nous considérons une nouvelle approche, qui se veut simple, efficace et adaptée pour faire face à ces défis. Les opérateurs réseaux et les fournisseurs de services sont mutuellement gagnants dans l'amélioration du transport de données dans les réseaux tout en continuant à opérer leur propre infrastructure. Cette démarche coopérative est le point de départ de nos travaux qui visent à définir un cadre, une architecture et des techniques appropriées qui amèneront ces acteurs à collaborer en vue de gérer conjointement cette problématique. Cette collaboration est nécessaire car chaque acteur quoique prisonnier de ses contraintes peut les transformer en relations contractuelles dans un processus client fournisseur pour l'optimisation de la gestion du trafic. / In this new digital world, driven by the dominance of a model based on the opportunities offered by global access to the Internet and its killer app: the World Wide Web, access to information is becoming a matter of a good experience and responsiveness. We are witnessing the Web services are of increasing popularity. New types of terminals are proposed. Communications technologies are improved. Users expectations are becoming higher. In such a context, network operators are facing serious challenges arising from the management of a massive traffic growth, largely driven by the increasing amount of video streams while internet services providers are also concerned by the issue of providing an adequate quality of experience to their end-users. For both actors, these dual trends present both challenges and opportunities. The challenges arise from the issues of managing the growing demand for traffic while maintaining appropriate quality of experience for users. Opportunities come from a smart management of the increasing demands of Web services in terms of quality of services and of the resources that will support the delivery of these services. It is then crucial for each actor to be well-positioned in the value chain to take part in this process. The role that will be played by the networks, as a basic set of oversized pipes, or as an intelligent network providing advanced management facilities, perfectly illustrates this issue. These two alternatives are respectively known as the "dumb-pipe" or "smart networks". In this thesis, we consider a new approach, which is simple, effective and adapted to meet these challenges. Network operators and service providers can mutually benefit from improving the data delivery in the networks while continuing to fully control their infrastructures. This collaborative approach is the starting bloc of our work aiming at defining a framework, an architecture and appropriate procedures to bring these actors to work together to manage this problem. This collaboration is particularly necessary because each actor, though prisoner of its constraints and capacities, can turn them into a contractual relation with the other in a client-supplier process for the optimization of traffic management.