Internet of Things (IoT) is an emerging paradigm that transforms everyday devices (Things) into Internet-connected devices with sensing, processing, and actuation capabilities. These devices have limited storage and processing capacity, so they have been integrated with Cloud computing to overcome these limitations. Cloud computing offers various benefits such as offload data storage and processing burden at the Cloud side. Nevertheless, because Cloud is not an efficient solution for IoT latency-sensitive applications, Fog computing was introduced to address this limitation. Although Fog–Cloud IoT environments have begun to be adopted in the last few years, such environments have not been properly assessed in terms of their capacity to meet the growing demand of IoT devices. In this work, we present a Deterministic and Stochastic Petri Net (DSPN) approach for evaluating Fog–Cloud IoT environments composed of hundreds physical Things. Our approach allows evaluating the trade-offs of many performability metrics (e.g., utilization, response time, throughput, and availability) and, consequently, may help system designers to choose the most suitable Fog–Cloud IoT environment. We demonstrate the feasibility of our approach through a real-world case study. The results revealed that adopting a Fog device can improve availability. However, the performance is only improved in certain conditions like when the environment is not at full capacity.

中文翻译：

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雾云物联网环境中的性能和可用性权衡

物联网 (IoT) 是一种新兴范式，可将日常设备 (Things) 转变为具有传感、处理和驱动功能的互联网连接设备。这些设备的存储和处理能力有限，因此它们已与云计算集成以克服这些限制。云计算提供了各种好处，例如在云端卸载数据存储和处理负担。然而，由于云并不是物联网延迟敏感应用程序的有效解决方案，因此引入了雾计算来解决这一限制。尽管过去几年开始采用雾云物联网环境，但尚未对此类环境在满足物联网设备不断增长的需求的能力方面进行适当评估。在这项工作中，我们提出了一种确定性和随机 Petri 网 (DSPN) 方法来评估由数百个物理事物组成的雾云物联网环境。我们的方法允许评估许多性能指标（例如，利用率、响应时间、吞吐量和可用性）的权衡，因此可以帮助系统设计人员选择最合适的雾云物联网环境。我们通过实际案例研究证明了我们方法的可行性。结果表明，采用 Fog 设备可以提高可用性。但是，性能仅在某些条件下才会提高，例如环境未满负荷时。吞吐量和可用性），因此可以帮助系统设计人员选择最合适的雾云物联网环境。我们通过实际案例研究证明了我们方法的可行性。结果表明，采用 Fog 设备可以提高可用性。但是，性能仅在某些条件下才会提高，例如环境未满负荷时。吞吐量和可用性），因此可以帮助系统设计人员选择最合适的雾云物联网环境。我们通过实际案例研究证明了我们方法的可行性。结果表明，采用 Fog 设备可以提高可用性。但是，性能仅在某些条件下才会提高，例如环境未满负荷时。