The Internet of Things (IoT) is envisioned to connect things of the physical world and the cyber world to make humans ever smart by greatly improving their efficiency, safety, health, and comforts, as well as solving numerous challenges related with the environment, energy, urbanization, industry, logistic, transportation, to name a few. Consequently, the IoT has been an important topic of study in the International Telecommunications Union (ITU) for several years in different Study Groups. The new ITU-T Study Group 20 has just been established in June 2015 for further promoting coordinated progress of global IoT technologies, services and applications. In this paper, we review the IoT related activities being pursued in ITU by presenting the IoT reference model. We then describe a number of key requirements the IoT infrastructure should satisfy to make it economically and technologically deployable for useful services and applications. We present some prospective technologies, such as software-defined networking, information-centric networking, and ID-based communication, while pointing out to the related technologies that are worth further study in ITU.