## 1 Introduction  
Heterogeneous networks allow users to communicate with each other despite having various infrastructures and communication manners that have contrasting properties and characteristics. IoT is one of the largest heterogeneous networks that allows distinct devices to communicate with each other, making an extensive network of various devices. The internet of things (IoT) and the Internet of Everything are now recognized as inevitable concepts in communication technology. It has gained rapid and vast attention from a wide range of applications, services, and industries. It is a global network of machines interconnected with each other and capable of interacting with the real world. In 2014, Gartner predicted that IoT will reach 25 billion units by 2020, up from 0.9 billion in 2009 [1]. In 2021, according to Statista, there were 21.6 interconnected devices around the globe, and it is expected to reach 30.9 billion units in 2025 [2]. IoT provides access to information anytime and anywhere; however, this results in excess traffic. The basic abstract model of IoT is presented in Figure 1[3]. This model describes the lower layer, referred to as the sensing layer, responsible for collecting data from different applications and services. These collected data are transferred to IoT servers through different paths in a communication network referred to as the network layer. IoT servers provide different services and IoT applications as well. This last upper layer is known as the application layer. This model describes the basic architecture of IoT and its principal layers. Smart cities, intelligent transportation systems, smart farming, and smart homes are all concepts that have become a reality due to IoT. Despite all the enormous advancements by IoT in numerous applications, it is still in the development stage. Challenges like security, standard architecture, scalability, management, and heterogeneity still exist, and the research community is dealing with challenges to make IoT more efficient. Hence, a great amount of research is being carried out to improve its technicalities and overcome its issues. [PERSON] et al. [4] discussed open and key challenges and issues in IoT. The authors categorized research areas in IoT. Standardization is one of the main research areas in IoT due to the diversity of technology. Currently, there is no single standardization available for IoT despite many standardization bodies being involved to develop such standards. An open standard is an important facilitator for the development of IoT systems because of its availability to the public. IoT architectures should design in such a way that they provide scalability, interoperability, heterogeneity, and openness. IoT is the complete integration of systems from hardware to software. Hence, the researchers divided architecture into four categories: general architecture, hardware/network architecture, software architecture, and process architecture. The general architecture is a conceptual model for applications, businesses, and services for IoT and operating with other services. Hardware/network architecture enables heterogeneity among different hardware devices and communication protocols and methods. Software architecture provides a common set of services for data collection and processing. IoT application software frameworks are required to provide easy interface with sensors and communication between different devices. Interoperability in IoT systems between different devices is one of the key issues. At all layers of IoT, this interoperability causes a problem, and a layered framework standardization architecture is used to cater to this problem. IoT is developed on various existing communication technologies, and communicating between these different technologies is a complex task. Figure 1: IoT abstract model. [PERSON] et al. [5] discussed the open challenges in IoT regarding service management. IoT has more diversity in hardware, software, services, and protocols. This diversity raises issues.