268 research outputs found

    GRIDKIT: Pluggable overlay networks for Grid computing

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    A `second generation' approach to the provision of Grid middleware is now emerging which is built on service-oriented architecture and web services standards and technologies. However, advanced Grid applications have significant demands that are not addressed by present-day web services platforms. As one prime example, current platforms do not support the rich diversity of communication `interaction types' that are demanded by advanced applications (e.g. publish-subscribe, media streaming, peer-to-peer interaction). In the paper we describe the Gridkit middleware which augments the basic service-oriented architecture to address this particular deficiency. We particularly focus on the communications infrastructure support required to support multiple interaction types in a unified, principled and extensible manner-which we present in terms of the novel concept of pluggable overlay networks

    A lightweight distributed super peer election algorithm for unstructured dynamic P2P systems

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    Dissertação apresentada na Faculdade de CiĂȘncias e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia ElectrotĂ©cnica e de ComputadoresNowadays with the current growth of information exchange, and the increasing mobility of devices, it becomes essential to use technology to monitor this development. For that P2P networks are used, the exchange of information between agencies is facilitated, these now being applied in mobile networks, including MANETs, where they have special features such as the fact that they are semi-centralized, where it takes peers more ability to make a greater role in the network. But those peer with more capacity, which are used in the optimization of various parameters of these systems, such as optimization\to research, are difficult to identify due to the fact that the network does not have a fixed topology, be constantly changing, (we like to go online and offline, to change position, etc.) and not to allow the exchange of large messages. To this end, this thesis proposes a distributed election algorithm of us greater capacity among several possible goals, enhance research in the network. This includes distinguishing characteristics, such as election without global knowledge network, minimal exchange of messages, distributed decision made without dependence on us and the possibility of influencing the election outcome as the special needs of the network

    Data Storage and Dissemination in Pervasive Edge Computing Environments

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    Nowadays, smart mobile devices generate huge amounts of data in all sorts of gatherings. Much of that data has localized and ephemeral interest, but can be of great use if shared among co-located devices. However, mobile devices often experience poor connectivity, leading to availability issues if application storage and logic are fully delegated to a remote cloud infrastructure. In turn, the edge computing paradigm pushes computations and storage beyond the data center, closer to end-user devices where data is generated and consumed. Hence, enabling the execution of certain components of edge-enabled systems directly and cooperatively on edge devices. This thesis focuses on the design and evaluation of resilient and efficient data storage and dissemination solutions for pervasive edge computing environments, operating with or without access to the network infrastructure. In line with this dichotomy, our goal can be divided into two specific scenarios. The first one is related to the absence of network infrastructure and the provision of a transient data storage and dissemination system for networks of co-located mobile devices. The second one relates with the existence of network infrastructure access and the corresponding edge computing capabilities. First, the thesis presents time-aware reactive storage (TARS), a reactive data storage and dissemination model with intrinsic time-awareness, that exploits synergies between the storage substrate and the publish/subscribe paradigm, and allows queries within a specific time scope. Next, it describes in more detail: i) Thyme, a data storage and dis- semination system for wireless edge environments, implementing TARS; ii) Parsley, a flexible and resilient group-based distributed hash table with preemptive peer relocation and a dynamic data sharding mechanism; and iii) Thyme GardenBed, a framework for data storage and dissemination across multi-region edge networks, that makes use of both device-to-device and edge interactions. The developed solutions present low overheads, while providing adequate response times for interactive usage and low energy consumption, proving to be practical in a variety of situations. They also display good load balancing and fault tolerance properties.Resumo Hoje em dia, os dispositivos mĂłveis inteligentes geram grandes quantidades de dados em todos os tipos de aglomeraçÔes de pessoas. Muitos desses dados tĂȘm interesse loca- lizado e efĂȘmero, mas podem ser de grande utilidade se partilhados entre dispositivos co-localizados. No entanto, os dispositivos mĂłveis muitas vezes experienciam fraca co- nectividade, levando a problemas de disponibilidade se o armazenamento e a lĂłgica das aplicaçÔes forem totalmente delegados numa infraestrutura remota na nuvem. Por sua vez, o paradigma de computação na periferia da rede leva as computaçÔes e o armazena- mento para alĂ©m dos centros de dados, para mais perto dos dispositivos dos utilizadores finais onde os dados sĂŁo gerados e consumidos. Assim, permitindo a execução de certos componentes de sistemas direta e cooperativamente em dispositivos na periferia da rede. Esta tese foca-se no desenho e avaliação de soluçÔes resilientes e eficientes para arma- zenamento e disseminação de dados em ambientes pervasivos de computação na periferia da rede, operando com ou sem acesso Ă  infraestrutura de rede. Em linha com esta dico- tomia, o nosso objetivo pode ser dividido em dois cenĂĄrios especĂ­ficos. O primeiro estĂĄ relacionado com a ausĂȘncia de infraestrutura de rede e o fornecimento de um sistema efĂȘmero de armazenamento e disseminação de dados para redes de dispositivos mĂłveis co-localizados. O segundo diz respeito Ă  existĂȘncia de acesso Ă  infraestrutura de rede e aos recursos de computação na periferia da rede correspondentes. Primeiramente, a tese apresenta armazenamento reativo ciente do tempo (ARCT), um modelo reativo de armazenamento e disseminação de dados com percepção intrĂ­nseca do tempo, que explora sinergias entre o substrato de armazenamento e o paradigma pu- blicação/subscrição, e permite consultas num escopo de tempo especĂ­fico. De seguida, descreve em mais detalhe: i) Thyme, um sistema de armazenamento e disseminação de dados para ambientes sem fios na periferia da rede, que implementa ARCT; ii) Pars- ley, uma tabela de dispersĂŁo distribuĂ­da flexĂ­vel e resiliente baseada em grupos, com realocação preventiva de nĂłs e um mecanismo de particionamento dinĂąmico de dados; e iii) Thyme GardenBed, um sistema para armazenamento e disseminação de dados em redes multi-regionais na periferia da rede, que faz uso de interaçÔes entre dispositivos e com a periferia da rede. As soluçÔes desenvolvidas apresentam baixos custos, proporcionando tempos de res- posta adequados para uso interativo e baixo consumo de energia, demonstrando serem prĂĄticas nas mais diversas situaçÔes. Estas soluçÔes tambĂ©m exibem boas propriedades de balanceamento de carga e tolerĂąncia a faltas

    A Taxonomy and Review of Lightweight Blockchain Solutions for Internet of Things Networks

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    Internet of things networks have spread to most digital applications in the past years. Examples of these networks include smart home networks, wireless sensor networks, Internet of Flying Things, and many others. One of the main difficulties that confront these networks is the security of their information and communications. A large number of solutions have been proposed to safeguard these networks from various types of cyberattacks. Among these solutions is the blockchain, which gained popularity in the last few years due to its strong security characteristics, such as immutability, cryptography, and distributed consensus. However, implementing the blockchain framework within the devices of these networks is very challenging, due to the limited resources of these devices and the resource-demanding requirements of the blockchain. For this reason, a large number of researchers proposed various types of lightweight blockchain solutions for resource-constrained networks. The "lightweight" aspect can be related to the blockchain architecture, device authentication, cryptography model, consensus algorithm, or storage method. In this paper, we present a taxonomy of the lightweight blockchain solutions that have been proposed in the literature and discuss the different methods that have been applied so far in each "lightweight" category. Our review highlights the missing points in existing systems and paves the way to building a complete lightweight blockchain solution for resource-constrained networks.Comment: 64 pages, 11 figures

    Overlay networks for smart grids

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    Blockchain-based Security Framework for Critical Industry 4.0 Cyber-physical System

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    There has been an intense concern for security alternatives because of the recent rise of cyber attacks, mainly targeting critical systems such as industry, medical, or energy ecosystem. Though the latest industry infrastructures largely depend on AI-driven maintenance, the prediction based on corrupted data undoubtedly results in loss of life and capital. Admittedly, an inadequate data-protection mechanism can readily challenge the security and reliability of the network. The shortcomings of the conventional cloud or trusted certificate-driven techniques have motivated us to exhibit a unique Blockchain-based framework for a secure and efficient industry 4.0 system. The demonstrated framework obviates the long-established certificate authority after enhancing the consortium Blockchain that reduces the data processing delay, and increases cost-effective throughput. Nonetheless, the distributed industry 4.0 security model entails cooperative trust than depending on a single party, which in essence indulges the costs and threat of the single point of failure. Therefore, multi-signature technique of the proposed framework accomplishes the multi-party authentication, which confirms its applicability for the real-time and collaborative cyber-physical system.Comment: 07 Pages, 4 Figures, IEEE Communication Magazin
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