The days when the Internet was the only focus of the information society have already gone, and innovative network paradigms such as IoT, cloud computing, smartphone networks, social networks, and industrial networks are gaining popularity and establishing themselves as indispensable ingredients of the future smart universe. Among them, IoT is the most widespread one, envisioned to involve all things in the world. However, its potential will never be fully explored before the complete formation of cyberspace, where humans, computers, and smart objects are pervasively interconnected. Therefore, one of the most important development trends of IoT is its integration with existing network systems. In this tutorial, we provide a detailed analysis of this issue. In particular, the latest achievements, technical solutions, and influential ongoing projects are described, and possible visions and open challenges are also discussed.