# CERP: Cooperative and Efficient Routing Protocol for Wireless Sensor Networks
## 2 RPL Routing Mechanism Overview  
Numerous embedded devices with constrained power, memory, and computing capabilities are joined through various connections, such as IEEE 802.15.4, to form WSNs [1]. The IETF ROLL working group created an IPv6 RPL to help with battery life. It may be utilized in data-collecting networks while using very little power. Here, we provide an analysis of the RPL routing mechanism to expose its limitations, for which nu merous research works have been conducted. Moreover, we summarize the abbreviations used throughout this paper in Table 1.  
Routing in RPL is performed using the destination-oriented directed acyclic graphs (DODAGs) idea, making it a distance vector routing protocol [11]. This is accomplished by constructing and updating a decentralized data structure whilst the WSN is in operation. The RPL method constructs this kind of distributed routing table to direct data packets throughout the network [12]. A root node is one that has no child nodes or outbound connections. The low power and lossy network is connected to the Internet and other external networks through \"roots\". Using three predetermined messages, the root node chooses the optimal way based on predefined parameters (such as hop count, energy cost, dependability, latency, etc.) as shown in Figure 1:  
* Destination information object (DIO): sent from the DODAG's root to its child nodes in order to perform certain operations. * Destination advertisement object (DAO): broadcasts information about a destination node up the distributed outage distribution graph (DODAG) to update the routing tables of parent nodes. * DODAG information solicitation (DIS): in the case of grounding and floating DODAGs, it can help locate them. It is the DIO's job to respond to a DIS transmission. Depending on the specific use case, we categorize RPL functionality into one of three distinct modes [13] as follows: 1. **Collect protocol**: Data from all the other nodes are gathered via the collect protocol and then sent to the root node. As for the route, all one have to do is follow the DODAG. 2. **Distribute protocol**: With the help of the distribute protocol, information may be sent from the hub to individual nodes. The path is determined by using the name and origin place provided in the DAO message. 3. **Peer-to-peer protocol**: Data may be sent from one node to another via the P2P protocol, with the most often used route being through the parents or the root node. In this paper, our focus is primarily placed on the collect mode, as our objective is to communicate detected leaks to the cluster head (CH) to facilitate apt responses. The initiation of constructing the RPL destination-oriented directed acyclic graph (DODAG) to back the collect protocol is spearheaded by the root node. DIO messages are multicast, reaching all accessible nodes. Each node's rank value must be ascertained utilizing an objective function (OF), in alignment with RPL standards [14; 15]. The OF specifies the process whereby RPL nodes rank input metrics, and hence how routes in a DODAG should be chosen and optimized [16]. Its primary function is to compute rankings according to predefined routing metrics including latency, throughput, and connectivity, as \begin{table}
\begin{tabular}{l l} \hline \hline
**Abbreviation** & **Full Form** \\ \hline BEP & Bit error probability \\ CH & Cluster head \\ DAO & Destination advertisement object \\ DIO & Destination information object \\ DIS & DODAG information solicitation \\ DODAG & Destination-oriented directed acyclic Graphs \\ IETF & Internet Engineering Task Force \\ OF & Objective function \\ RPL & Routing Protocol for Low Power and Lossy Networks \\ RSSI & Received signal strength indication \\ SDR & Selective digital relaying \\ SNR & Relaying (SDR) \\ WSNs & Wireless sensor networks \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Abbreviations. well as to define routing limits and optimization goals. As a result, developing the effective OF remains a topic of inquiry.