## 1 Introduction
### Related Works  
Since vehicular ad-hoc networks have a lack of a central controller and dynamically changing topology, distributed routing protocols are the most suitable for them. Many researchers have developed scalable and reliable dissemination protocols that spread the message as fast as possible among the vehicles by grouping (clustering) the vehicles based on topology, density, distance, speed, or location for suppressing the rebroadcasts to the extent possible without reducing the reachability. [PERSON] et al. [24] developed two protocols namely, V-TRADE (Vector based Tracking Detection), HV-TRADE (History and Vector based Tracking Detection) that are based on the location of the vehicles. They categorize the vehicles into five classes namely: (i) vehicles that are moving ahead of this vehicle on the same road in the same direction; (ii) vehicles that are coming behind this vehicle on the same road in the same direction; (iii) vehicles that are approaching towards this vehicle on the same road in the opposite direction; (iv) vehicles that are leaving away from this vehicle on the same road in the opposite direction; and (v) vehicles that are moving on other roads. The sender selects zero or more vehicles from each class as a forwarder of the message. In HV-TRADE, the history of the movement of the vehicles is also included in the classification process to provide better precision in the forwarder selection process. [PERSON] et al. [25] designed another protocol named ODAM-C (Optimized Dissemination of Alarm Messages-Capacitor) that selects the relay vehicle based on distance and location. Each vehicle maintains two lists L1 and L0. Upon receiving a packet if the packet is not present in both lists, the packet is placed in the L1 list, and a timer is set for that packet which is inversely proportional to the distance from the sender of the packet. After the timer expires, the packet is forwarded. If the packet received is already present in either L1 or L0, the angle between the current vehicle, original sender, and the current sender is calculated from their location information. If the angle is less than 90\({}^{\circ}\), it will stop the forward of that packet. Otherwise, if the packet is in L1, then stops its timer, deletes from L1, and inserts into L0 and a timer is set. Before the timer in L0 for that packet expires, if it receives duplicate packets, the timer is stopped; otherwise, on expiry of the timer, the packet is forwarded. In all these three protocols the message overhead is higher as each vehicle has to keep track of 1-hop neighborhood information and the packets they have received and forwarded. [PERSON] et al. designed a protocol named BODYF [14; 15], a Parameter-less Broadcasting Protocol over Dynamic Forest which constructs a source tree based on a Dynamicity Aware Graph Relabeling System (DAGRS,) model [26]. The next forwarders are the internal nodes of the tree topology formed using the DAGRS model. [PERSON] and [PERSON] [22] designed a protocol named DTA, with a hybrid approach--a combination of the topology-based and density-based conditions for selecting the vehicles to include in the connected dominating set (CDS). The vehicles with the highest 1-hop neighbor density will become a CDS member. The vehicles that do not have the highest density check for the following three topology-based conditions to overcome network partition. If a vehicle has at least two neighbors that are not directly connected to each other or if it has at least one neighbor that is not covered by its other neighbors, then it becomes a CDS member. If a vehicle has at least one neighbor that is not covered by a pair of gateway vehicles' neighbors where these two vehicles are neighbors of each other, then it becomes a gateway vehicle. Even though these topology-based conditions avoid network partition problem, they compromise on the optimality of CDS members and result in an unnecessary increase in the number of gateway vehicles.