The IoT architecture is defined as a collection of smart elements like sensors, actuators, and cloud systems. The main intention of the design of IoT architecture is how to collect, analyze, and transmits the data. The IoT architecture comprises various protocols and layers to meet the application-specific requirements of IoT. For independent IoT applications, there are different architectures developed. The most common layers of IoT architecture are perception, transport, processing, and application layers. The perception layer comprises intelligent IoT devices such as sensors, actuators, and the transport layer transmits the collected information from perception to other cloud servers or edge devices. The processing layer utilizes the IoT platforms to consolidate and handles the data streams. The application layer delivers solutions related to analytics, device controls, and reporting. However, the key building of IoT is smart devices, networks and gateways, IoT platforms, and applications.
   Most of the basic IoT architectures are not well suitable for all IoT applications due to the lack of consideration on security and privacy concerns, reliability, and scalability issues. A unifying architecture still needs to be developed for IoT applications. For instance, IoT architecture for health care integrates the IoT features into medical devices, and it has to improve the quality of the services to the patients without compromising the communication security. A smart home IoT architecture should have the ability to control any device in the home via smartphone or laptop. Likewise, industry IoT architecture monitors air quality, temperature, and sends an alarm in case of emergencies.