The Internet Engineering Task Force (IETF) has published RFC 6550, which defines the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL). RPL is designed to provide routing mechanisms for networks with constrained nodes, such as those with limited processing power, memory, and energy. These networks often have high loss rates, low data rates, and unstable links. RPL supports various traffic flows, including multipoint-to-point, point-to-multipoint, and point-to-point traffic. RPL operates by constructing and maintaining Directed Acyclic Graphs (DAGs) that represent the network topology. Each DAG is rooted at a destination and is used to route traffic towards that destination. RPL allows for multiple DAGs within a single instance, each with its own objective function (OF) for optimizing routing. The OF determines how nodes select parents and how ranks are calculated to avoid loops and ensure efficient routing. RPL includes mechanisms for loop detection and avoidance, such as data-path validation and rank-based comparisons. It also supports security features, including message confidentiality and integrity, with different security modes for unsecured, preinstalled, and authenticated networks. RPL uses DIO (DODAG Information Object) and DAO (Destination Advertisement Object) messages to maintain and update routing information. RPL is designed to be flexible and adaptable to various LLN applications, including building automation, home automation, industrial, and urban scenarios. It supports both storing and non-storing modes for downward traffic, with the latter using source routing to prevent loops. RPL also includes mechanisms for managing routing adjacency, maintaining routing tables, and ensuring consistency in routing information. The protocol is structured to allow for efficient and autonomous operation within LLNs, with minimal configuration requirements. It uses Trickle for optimized dissemination of routing information and supports a variety of link-layer technologies. RPL is intended to be used in conjunction with other protocols and standards, and it includes detailed specifications for its operation, security, and management. The document also outlines future considerations for extending RPL to support additional features and applications.The Internet Engineering Task Force (IETF) has published RFC 6550, which defines the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL). RPL is designed to provide routing mechanisms for networks with constrained nodes, such as those with limited processing power, memory, and energy. These networks often have high loss rates, low data rates, and unstable links. RPL supports various traffic flows, including multipoint-to-point, point-to-multipoint, and point-to-point traffic. RPL operates by constructing and maintaining Directed Acyclic Graphs (DAGs) that represent the network topology. Each DAG is rooted at a destination and is used to route traffic towards that destination. RPL allows for multiple DAGs within a single instance, each with its own objective function (OF) for optimizing routing. The OF determines how nodes select parents and how ranks are calculated to avoid loops and ensure efficient routing. RPL includes mechanisms for loop detection and avoidance, such as data-path validation and rank-based comparisons. It also supports security features, including message confidentiality and integrity, with different security modes for unsecured, preinstalled, and authenticated networks. RPL uses DIO (DODAG Information Object) and DAO (Destination Advertisement Object) messages to maintain and update routing information. RPL is designed to be flexible and adaptable to various LLN applications, including building automation, home automation, industrial, and urban scenarios. It supports both storing and non-storing modes for downward traffic, with the latter using source routing to prevent loops. RPL also includes mechanisms for managing routing adjacency, maintaining routing tables, and ensuring consistency in routing information. The protocol is structured to allow for efficient and autonomous operation within LLNs, with minimal configuration requirements. It uses Trickle for optimized dissemination of routing information and supports a variety of link-layer technologies. RPL is intended to be used in conjunction with other protocols and standards, and it includes detailed specifications for its operation, security, and management. The document also outlines future considerations for extending RPL to support additional features and applications.