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Different architectures have been proposed by different researchers for IoT, out of which the most popular architecture is three-layer architecture as shown in Figure 1.1. As per its name, this architecture has three layers, namely, i) Perception Layer, ii) Network Layer, and iii) Application Layer. This architecture basically provides the basic idea of the IoT that is further divided into five-layer architecture [2, 5, 20].

The Perception Layer is also known as a physical layer that consists of sensors and actuators. Sensors sense information from the surrounding environment and actuators actuate, i.e., perform some actions based on its sensing from the environment. So, actuators are mechanisms that control the system and accordingly act in the environment. So, basically, this layer provides/acts as input to the IoT architecture.

The Network Layer acts as an intermediate layer that provides communication between perception layer and network layer using communication devices such as routers and gateways. The basic task of this layer is to connect smart devices and its related servers. As an intermediary layer, it also transmits and processes the input data of sensing devices received from the perception layer.

The Application Layer defines various applications in which IoT is deployed. This layer performs application specific tasks and delivers service accordingly. The specific application may be smart farms, smart homes, smart cities, etc.

Figure 1.1 Three-layer IoT architecture.

Furthermore, this three-layer architecture converts into five-layer architecture. In this architecture, the perception layer and application remains and acts the same but the intermediate network layer is again divided into three sub layers such as Transport Layer, Processing Layer, and Business Layer. In this five-layer architecture, the transport layer transmits sensor data from perception layer to processing layer. Processing layer acts as a middleware layer and it can store, analyze, and process data that was received from the transport layer. To do such a task on data, this layer basically deals with many other data management technologies such as Big Data computing to process, cloud computing to store, and database management system to manage the data. The Business Layer acts on the top of the application layer and manages the entire IoT system. It consists of all application-related information such as profit model of business to that application, user privacy to the specific application, and other such business application-related information. Based on this architecture, the merits and demerits of IoT are as follows.