Sistema de monitorização baseado em fog computing

Mestrado em Engenharia de Computadores e TelemáticaThis thesis is a contribution of an architectural solution, describing a system that represents an extra layer of computing power, placed between the cloud and sensor networks, acting both as a mediator whose central task is to manage, monitor and collect data from geographically-located groups of sensor nodes and as a communication hub to the cloud with which data is exchanged in a compact and minimalist fashion. The latter is accomplished by designing nodes as autonomous entities, able to organise themselves in smaller groups, within the system. Additionally, these entities possess inherent mechanisms which aim to accomplish fault tolerance within groups of nodes, maintaining the status quo of the overall system while performing in an ubiquitous environment, continuously embracing contextual changes. The overall solution was tested in a proof of concept where we conceived three test cases that helped us validate it.Este documento apresenta uma arquitectura como solução para o desenvolvimento de uma camada extra de poder computacional entre os serviços na núvem e a Internet das Coisas, denominada de computação no nevoeiro. Esta camada é responsável pela gestão e recolha de dados provenientes de conjuntos de sensores, geograficamente distribuídos, em níveis inferiores. Assim, o nevoeiro permite servir como ponto de agregação comunicando directamente com a núvem, minimizando a quantidade de tráfego na rede. A solução descreve a camada de nevoeiro como um conjunto de grupos de nós que se agrupam e organizam como um todo, autonomamente. Existem ainda mecanismos auxiliares que permitem a existência de um certo grau de tolerância a falhas de forma a manter o status quo do sistema em ambientes ubíquos, lidando com as constantes alterações de contexto. A solução foi testada e validada através de uma prova de conceito onde foram realizados três casos de teste, concebidos de forma a abranger todos os componentes da mesma

Hybrid overlay structure based on random walks

Application-level multicast on structured overlays often suffer several drawbacks: 1) The regularity of the architecture makes it difficult to adapt to topology changes; 2) the uniformity of the protocol generally does not consider node heterogeneity. It would be ideal to combine the scalability of these overlays with the flexibility of an unstructured topology. In this paper, we propose a locality-aware hybrid overlay that combines the scalability and interface of a structured network with the connection flexibility of an unstructured network. Nodes self-organize into structured clusters based on network locality, while connections between clusters are created adaptively through random walks. Simulations show that this structure is efficient in both delay and bandwidth. The network also supports the scalable fast rendezvous interface provided by structured overlays, resulting in fast membership operations.