A Survey on Load Balancing Schemes in RPL based Internet of Things

Internet of Things technology is a collection of sensors and actuators which gathers data from physical environment that can be stored and processed to generate actuating information. Physical environment data such as temperature, pressure, humidity, pollution and any valuable parameters related to human body, machine, etc. have great value for automation, fault detection and timely remedy. Thus, IoT networks have given rise to Smart Cities, Smart Health, Smart Transport Logistics, Smart Production and Supply chain management, Smart Home and many more. For IoT deployments, ROLL-WG has standardized Routing Protocol for Low Power and Lossy Networks (RPL) for urban environment (RFC 5548), home automation (RFC 5826), industrial control (RFC 5673) and building automation (RFC 5867). RPL is a destination vector protocol for low power devices which is designed to address the needs of constrained IoT environment. In RPL, nodes organize themselves by forming a Destination Oriented Directed Acyclic Graph (DODAG) rooted towards the sink. RPL uses Objective Functions (ETX & Hop Count) to optimize path selection. Many newObjective Functions for IoT applications are suggested by researchers for path optimization. In most cases, RPL is efficient in providing fast network convergence. However, path optimization and network performance are affected by Load Balancing problem. In this article, we survey existing load balancing schemes in RPL based Internet of Things. We also list out load balancing metrics and challenges in RPL with reference to load imbalance.