## 2 Background and Related Work  
VANETs exhibit notable distinctions when compared to traditional wireless networking methodologies. The high degree of mobility that its nodes exhibit is what makes VANETs unique. The conventional network routing protocol is not directly applicable to VANETs. In recent years, researchers have put forth a range of routing protocols. However, the routing mechanism in an SDN-based VANET is similar to that in conventional VANETs, but it necessitates certain modifications to align with the SDN architecture. Significant contributions have been made in recent scholarly publications in the area of routing in SD-VANETs. One of the most popular location-based routing protocols used in VANETs is GPSR [23]. It uses a greedy forwarding strategy that relies only on the information of nearby nodes in the network's architectural context. When greedy forwarding is not feasible, the algorithm compensates by redirecting the packet around the periphery of the region that is beyond the immediate area. GPSR outperforms shortest path and ad hoc routing protocols in terms of scalability. GPSR needs to store information about the immediate network structure, which enables it to handle a growing number of network destinations without difficulty. The GPS efficiently utilizes local topology information to rapidly identify accurate new routes within the rapid-changing mobility topology. The GPSR protocol depends on the fact that forwarding choices in geographic routing relies exclusively on information about the neighbor. Despite the several advantages of GPSR and its use of local information for routing decisions, it also has notable limitations. In sparse network conditions, where nodes are few and far away from each other, GPSR may struggle to find a suitable next hop, leading to routing inefficiencies. A recent study [24] presents a novel location-based routing protocol, OPBR, for VANETs that combines opportunistic and location-based approaches. This protocol considers variables such as the quality of the links, the density of the nodes, and the location of the nodes to determine the route. A greedy forwarding mechanism is utilized by the system, and ideal candidate nodes are selected through a combination of opportunistic and location-based strategies. In addition to this, it identifies the nodes that have reached the end of their allotted time in the routing process and removes them from the running order. While OPBR protocols offer advantages like efficiency in dynamic networks, reduced overhead, and scalability, they also face challenges such as dependence on accurate location data, performance issues in sparse networks, potential delays, risks of routing loops, and the lack of inherent support for varying QoS requirements. Some researchers have also investigated routing in SD-VANETs. In their study, the authors of [25] introduced an innovative packet routing scheme for SD-VANETs. This scheme incorporates a flow instantiation operation based on source routing. The routing problem was transformed into an integer linear programming problem. A novel approach involving incremental packet allocation was proposed as a solution to address the routing problem, with the aim of reducing time complexity. Although the scheme reduced the time complexity of routing, the VANET architecture lacks flexibility that makes large-scale service and protocol deployment difficult. In a scholarly article, the authors of [26] presented a routing framework that utilizes SDN to facilitate message propagation within VANETs. The routing protocol that was proposed computes routing paths that are globally optimized, thereby reducing the routing overhead. In a recent study, the authors of [27] introduced a novel routing protocol that operates based on the principles of spray and pray multiple-copy routing. The spray technique was employed for the purpose of elimination, while pray was utilized to mitigate the delay in packet delivery.