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Internet of Things (IoT), getting popular day by day, thanks to the every object that has been made intelligent and started communicated among themselves with ease. These objects are equipped with sensors and capable of connecting and exchanging the application data over the Internet. While the application data is getting exchanged among these intelligent objects smoothly, there are various concerns with these intelligent objects like they are constrained when it comes to resources like memory, processing capability, power consumption etc. In this regard many attempts are made to enhance or to optimize existing messaging protocols so that we can get best out of these objects. Along with this there are some serious issues need to be addressed to achieve the growth of IoT systems globally, to name a few are security, standardization, privacy, government regulations and politics and civic engagement.
In this article, we present the previous research contributions in the area of optimization related work in application layer protocols in IoT, especially Message Queuing Telemetry Transport (MQTT) Protocol and Constrained Application Protocol (CoAP) by the help of detail bibliometric analysis. For this analysis, we have referred to the Scopus database and for pictorial depiction of the data we have used the tools like VOSviewer, iMapBuilder. We have selected last 10 years duration for this analysis considering the significant evolvement in the IoT and its allied areas. In this period, a total of 1106 research articles are published by various researchers. We have observed the significant rise in the research in IoT related areas in last 4 years, where the total of 862 articles are published & in the year of 2019, it was having the maximum count of 287 articles published. The detailed analysis study revealed that a maximum of published articles are conference papers followed by journal articles and book chapters. According to the analysis, India is the torch bearer in the IoT related research areas & is followed by countries like South Korea and Italy.