Internet of Things refers to the connection of real-world things around us with the internet. The reason behind this IoT technology is to provide ubiquitous computing that is monitoring and control of anything, anytime at anywhere. To build successful IoT applications we are in need of certain layer-wise communication knowledge about the technology. Starting from the OSI physical layer till application layer the book describes each layer with its necessary applications. The topics covered in this book are based on the curricula of engineering and science students who are in development as well as in research stage. Several real-time case studies are the added feature of this book for better understanding.