I. Introduction
The number of IoT devices increases rapidly. As reported by Cisco, there will be over 50 billion devices connected to the Internet by 2020, and there will be over 500 zettabytes of data produced by 2019 [1]. However, because IoT devices are suffering from a lack of computation power and storage, many IoT computations are outsourced to strong server ends. These strong server ends are mostly deployed in the cloud, which is considered a solution to deliver services to end users and provide applications with elastic resources at low cost [2]. As we can see, cloud computing is becoming the over-arching Internet approach for information storage, retrieval and management, and IoT devices become the major outlets of service applications. This means that the key task for the next networks generation is the successful integration of cloud computing and IoT devices. However, with cloud computing, this faces several fundamental challenges: