IoT reference model

Just like the OSI reference model for the internet, IoT architecture is defined through six layers: four horizontal layers and two vertical layers. The two vertical layers are Management and Security and they're spread over all four horizontal layers, as seen in the following diagram:

The Device Layer: At the bottom of the stack, we have the device layer, also called the perception layer. This layer contains the physical things needed to sense or control the physical world and acquire data (that is, by perceiving the physical world). Existing hardware, such as sensors, RFID, and actuators, constitutes the perception layer. 

The Network Layer: This layer provides the networking support and transfer of data over either wired or wireless network. The layer securely transmits the information from the devices in the device layer to the information processing system. Both transmission Medium and Technology are part of the networking layer. Examples include 3G, UMTS, ZigBee, Bluetooth, Wi-Fi, and so on.

The Service Layer: This layer is responsible for service management. It receives information from the network layer, stores it into the database, processes that information, and can make an automatic decision based on the results. 

The Application Layer: This layer manages the applications dependent upon the information processed in the service layer. There's a wide range of applications that can be implemented by IoT: smart cities, smart farming, and smart homes, to name a few.