Internet of things (IoT) and Internet of Mobile things (IoMT) are the extension of ubiquitous and pervasive computing which enables various types of devices to communicate to the Internet using TCP/IP protocol stack. Since the devices in IoT are characterized with low power, low memory and buffer, they struggle to communicate using the conventional TCP/IP. The RPL proposed by IETF has become the standard routing protocol for devices which are part of 6LoWPAN (IPV6 for Low power Wireless Personal Area Networks). Due to the constrained resources such as low bandwidth and unreliable link, the network often face problems such as congestion, dropped packets, high power consumption for data transmission, decreased throughput, decreased success rate of packet delivery and increased in overall delay. Several metrics, objective functions, methodologies and enhanced protocols have been proposed in the literature to mitigate the problems encountered by the RPL. The proposed approaches either falls under energy aware or congestion aware routing using RPL. Some of the approaches fall under hybrid which attempts to minimize the energy consumption as well as congestion. In this paper we provide a deep insight into various metrics, objective functions and methodologies proposed in the literature for alleviating congestion and minimizing energy consumption for RPL and present the advantages and overheads associated with each. At the end we provide our inference on the possible scope for extensions/enhancement of routing protocol efficiency under situations like high mobility rate with diverse device characteristics. © BEIESP.