## 1 Introduction  
The remarkable growth and outcomes of IoT technology are fueled by the continuous support by academia and industry. It is for this fact that the evolution of micro-technology [1], mobile networking [2], machine learning [3, 4], and advancement in IoT [5] is of an expanding nature. The assessment done by Gartner in [6] provides the road map for the maturity of more than 2000 technologies. The technologies are grouped into 119 distinct areas including digital workplace, smart machines, 3D printing, enterprise mobile security [7, 8, 9], and connected homes [10, 11, 12]. IoT and wearable user interfaces, which are both based on machine learning, are likely to not experience inflation. Similarly, Gartner predicts that by 2025, 50% of industries would be using industry cloud platforms to accelerate their businesses.  
The technologies based on IoT do not reside inside PCs and computers only. Ranging from a small light-dependent resistor (LDR), home appliances, traffic signals, air traffic control, weather systems, and sensory networks for pressure, humidity, and temperature, to the control system of a space shuttle's propulsion, all are considered in this autonomous machine-governed system. This concludes that the system of IoT comprises four basic sectors, which can be actuators, sensors, network, and computers. These sectors must take part in facilitating the user in development, as well as in sustaining human lives.  
IoT transforms passive, data-driven devices, i.e., things that make exclusive decisions, into a ubiquitously communicating and in-phase system for making concurrent single decisions in a feedback mechanism. Thus, the more it sounds easy to use, the more it complicates the situation for its designers to loop all the quantities and things with one another. The heterogeneous nature of IoT does not support a standard model for its mode of connectivity. Proper handshaking and making it continuous for uninterrupted data analytics and decision-making also requires more and more system renovation in IoT each time a new thing is considered.  
The paper highlights the support of IP protocol stack by IoT, wirelessly identifiable things [13], edge computing [14], persistence computing and ambient intelligence, recognition-interaction of portable devices [15] and their continuous handshaking, small-talk on faultless connection between people and things, a smart city's components, self-healing properties in IoT, and the framework for smart cities with user perspective.  
The organization of the paper is as follows. Section 2 encompasses the introductory concept of connected cities with respect to its market and technologies, data acquisition, device interfacing, connectivity and integration, data analytics, applications and software employed, and core services providers. Section 3 explains the importance of the physical and media access control layer in IoT. Section 4 includes the most widely used MAC layer IoT protocols in detail. Section 5 lists the networking protocols that are extensively used in IoT for the development of smart cities, along with their roles and limitations. Section 6 thoroughly explains IPv6-based encapsulation schemes for network layer. The IoT application layer protocols are thoroughly explained in Section 7 with the list of features that each application protocol provides. The discussion and open issues in the field of IoT with respect to the development of smart cities and concluding remarks are listed in Sections 8 and 9, respectively.