# Performance Evaluation of Mobile RPL-Based IoT Networks under Hello Flood Attack
## 3 Background  
### RPL Overview  
The RPL protocol was designed to tackle the unique challenges posed by Low-Power and Lossy Networks (LLNs) in the vast realm of the Internet of Things (IoT). With the continuous growth of IoT, the demand for efficient communication among devices with limited resources becomes even more critical. One of its primary goals is energy efficiency, aiming to optimize the consumption of energy within LLNs. RPL, with its focus on efficient energy utilization and reliability in LLNs, addresses the challenges posed by devices with limited resources. It incorporates mechanisms for robust and adaptive routing, adapting to changing network conditions, and overcoming challenges presented by intermittent links and device failures [2]. Moreover, RPL is designed to be scalable, accommodating networks of varying sizes and dynamically adjusting to the addition or removal of nodes. Its versatility extends to supporting diverse applications within LLNs, ranging from home automation and smart cities to industrial control systems. This multifaceted approach underscores RPL's significance as a comprehensive and flexible solution for the complexities of LLNs across various applications. Furthermore, RPL employs Destination-Oriented Directed Acyclic Graphs (DODAGs) rooted at a singular destination, referred to as the sink, operating within the IP networking layer through the 6 LoWPAN protocol stack. This approach involves constructing a network of logical channels leading to the sink, utilizing actual network connections. Node ranking within the DODAG is a result of evaluating various metrics, such as link reliability, latency, throughput, and constraints like nodes' energy, link color, and throughput. The selection of parents on paths towards the DODAG root is thus framed as a multi-objective optimization problem. The designated Objective Function (OF) guides RPL nodes in choosing and optimizing routing paths within a DODAG, transforming metrics and constraints into ranks. RPL utilizes three primary ICMPv6 control messages for constructing and managing the network topology and routing data. The DODAG Information Object (DIO) message serves as a cornerstone, fostering DODAG creation, maintenance, and the establishment of upward routes from nodes to the root. This message encapsulates vital configuration parameters, including the sender node's rank, RPL instance ID, DODAG ID, version number, RPL mode of operation, and other essential maintenance parameters. Furthermore, DIO messages are strategically issued in response to a DODAG Information Solicitation (DIS) message, contributing to the dynamic adaptability of the network. In tandem, the DODAG Information Solicitation (DIS) message functions as an upward ICMP control message, which is critical for nodes aspiring to join an existing network. When a new node seeks to integrate into the network, it deploys DIS to ask nearby nodes for a DIO message, facilitating a seamless emboading process. In instances where a node does not receive a DIO message within a designated time frame, it autonomously transmits a DIS message, ensuring the continued progression of network establishment [3]. Additionally, the Destination Advertisement Object (DAO) message is instrumental in constructing downward routes within the network. Each node, in the process of building downward routes, advertises to its parent the selection of nodes in its sub-DODAG that prefer it as their parent. This collaborative information exchange is vital for the creation and maintenance of upward routes, facilitated by DIO and DIS messages. Notably, the DAO receiving node retains the option to dispatch a DAO acknowledgement message, a practice not implemented in RPL Contiki. Convergence marks the culmination of this process when each node attains a path to the root, and periodic communication among nodes ensures the network's ongoing stability and maintenance.