Inferring the quality of streaming video applications is important for Internet service providers, but the fact that most video streams are encrypted makes it difficult to do so. We develop models that infer quality metrics (\ie, startup delay and resolution) for encrypted streaming video services. Our paper builds on previous work, but extends it in several ways. First, the models work in deployment settings where the video sessions and segments must be identified from a mix of traffic and the time precision of the collected traffic statistics is more coarse (\eg, due to aggregation). Second, we develop a single composite model that works for a range of different services (\ie, Netflix, YouTube, Amazon, and Twitch), as opposed to just a single service. Third, unlike many previous models, our models perform predictions at finer granularity (\eg, the precise startup delay instead of just detecting short versus long delays) allowing to draw better conclusions on the ongoing streaming quality. Fourth, we demonstrate the models are practical through a 16-month deployment in 66 homes and provide new insights about the relationships between Internet "speed'' and the quality of the corresponding video streams, for a variety of services; we find that higher speeds provide only minimal improvements to startup delay and resolution.

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ResumoEste trabalho propõe uma adaptação da metodologia da Fragilidade Ambiental para a determinação da Fragilidade Emergente. Discute-se a necessidade de métodos de mensuração dos impactos causados pela agricultura que levem em conta diferentes práticas agrícolas e formas de manejo dos recursos naturais. Essa análise metodológica é realizada a partir de um estudo de caso no município de Colombo-PR, Região Metropolitana de Curitiba. Este município situa-se em uma área de mananciais e sobre um aquífero e pela presença da produção convencional e intensiva de hortaliças e de algumas culturas anuais. Foram elaboradas cartas de Fragilidade Ambiental (Potencial e Emergente) e avaliados os impactos da agricultura sobre a qualidade e disponibilidade dos recursos hídricos na área de estudo. Foram gerados novos parâmetros de diferenciação das práticas agrícolas e seus respectivos impactos ambientais. Os dados mostraram que, na medida em que são reconhecidas e analisadas com mais precisão as diferentes formas de uso agrícola do solo, os resultados em termos de fragilidade emergente também variam. No caso de Colombo, os dados mostram que a capacidade de proteção do solo é maior quando utilizada a metodologia proposta, mas reafirma que a agricultura praticada nas áreas de produção de hortaliças implica num elevado grau de vulnerabilidade do solo e, por decorrência, das águas. Conclui-se ainda que o procedimento metodológico apresentado é importante para que se rompa com uma visão equivocada que generaliza os impactos ambientais causados pela agricultura e se valorize iniciativas de uso de técnicas agrícolas de caráter mais conservacionista. Palavras AbstRActThis paper proposes an adaptation of the methodology of Environmental Fragility in order to detect Emergent Fragility. We discuss the needs for methods for measuring the impact of agriculture which take different agricultural practices and ways of using natural resources into account. This methodological analysis is carried out through a case study of the municipality of Colombo, Paraná, in Curitiba Metropolitan Region. This municipality is situated in an area of water springs and above an aquifer. It can be characterized by the presence of conventional and intensive vegetable production as well as the cultivation of several annual crops. We elaborated several charts on Environmental Fragility (Potential and Emergent) and evaluated the impact that agriculture has had on the quality and availability of water resources in the area we studied. We went on to generate new parameters for distinguishing agricultural practices and their respective environmental impacts. Data have shown that, to the extent that different forms of agricultural use of soil are recognized and analyzed with greater precision, prospects for emergent fragility also vary. In the case of Colombo, data show that the capacity for soil protection is greater when our proposed methodology is implemented, yet it restates the notion that agriculture that is practiced in areas where vegetables are grown implies ...

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