The growth of internet of things (IoT) devices and apps has caused disruptions in key sectors such as smart environment, healthcare, and mission-critical tool. Security of IoT devices, networks, and infrastructure is the biggest challenge. RPL, a routing protocol optimised for low-power and lossy networks, is applied by the IoT to offer seamless information transfer among the myriad of interconnected entities. So, the paper delves into the nuts and bolts of RPL, covering its protocol settings, trickle timer, and objective function, as well as the IoT’s architecture and applications. This article also provides a framework for categorising past research on the effects of RPL-IoT on energy consumption, transportation, service quality, traffic congestion, and safety. The future of energy efficiency, congestion, objective function, mobility, stability, security, collaborative intrusion detection systems, active learning, and Key Management are all considered in this analysis.