Internet of Things (IoT) is smartly changing various existing research areas into new themes including smart-health, smart-home, smart-industry and smart-transport. Relying on the basis of ‘Smart-Transport’, Internet of Vehicles (IoV) is evolving as a new theme of research and development from Vehicular Adhoc Networks (VANETs). This paper presents a comprehensive framework of IoV with emphasis on layered architecture, protocol stack, network model, challenges and future aspects. Specifically, following the background on evolution of VANETs and motivation on IoV, an overview of IoV is presented as a heterogeneous vehicular networks. The IoV includes five types of vehicular communications; namely, Vehicle-to-Vehicle, Vehicle-to-Roadside, Vehicle-to-Infrastructure of cellular networks, Vehicle-to-Personal devices and Vehicle-to-Sensors. A five layered architecture of IoV is proposed considering functionalities and representations of each layer. A protocol stack for the layered architecture is structured considering management, operational and security planes. A network model of IoV is proposed based on the three network elements including cloud, connection and client. The benefits of the design and development of IoV are highlighted by performing a qualitative comparison between IoV and VANETs. Finally, the challenges ahead for realizing IoV are discussed and future aspects of IoV are envisioned.