## 2 Related Work
### Communication in Vehicular Networks
In [31], the authors deal with the problem of broadcast storms using a barrier time mechanism, where a super-node delays data delivery in a cluster-based solution in order to control flooding instead of immediate retransmission. Nevertheless, their aim is to extend the messages network-wide to the majority of clusters. The distributed data dissemination protocol DV-cast is presented in [32]. Fully connected, fully disconnected, and sparsely connected networks are observed in addition to the changes in topology at the same time. Broadcast suppression and store-carry-forward approaches are applied if connected or disconnected networks are detected, respectively. The geographical position, heading, and local or distant neighbors are identified through hello packets. An epidemic routing is used in sparse scenarios. The authors in [33] propose location services for mobile nodes in order to locate and deliver data with reduced overheads. Described as semi-flooding, the nodes periodically broadcast their current position with a time stamp and maintain neighbor tables to be updated with received data. Two-dimensional and uni-dimensional scenarios as urban and highway scenarios are considered with uniform distribution densities. Problems such as topology changes or disconnected networks are not treated. Head of clusters are computed according to the prey location behavior of whales in the work of [34]. The heuristic determines the optimal cluster formation, since the problem is NP-Hard. The revealed benefits of clustered-based solutions are reduced delay, scalability, no hidden node problems, and topology stability, among others. However, the vehicles must match the optimal speed and acceleration, while the iterative evolutive-like algorithm for cluster conformation must be run on every agent. Open problems such as security in heterogeneous networks, non-standardization in car makers and local regulations, scalability, priority, and compatibility in future communication frameworks are explored in [35]. The authors also classify routing protocols in VANETs as follows:  
* Topology-based protocols: Routing tables are created from the topology in the network. The same routes are maintained proactively or reactively, i.e., routes are calculated before being required or on-demand when required, respectively, or are locally proactive and externally reactive in hybrid scenarios. * Position-based protocols: Information regarding position and geographic location is required for every node. Data are sent at once from the source to the destination in the non-DTN mode; meanwhile, in DTNs, data are communicated when connectivity happens. In hybrid modes, data run through both non-delay-tolerant networks (non-DTNs) and delay-tolerant networks (DTNs). * Broadcast-based protocols: Packets are forwarded in multiple hops and delivered intentionally to all nodes in the network. * Cluster-based protocols: Groups of vehicles are formed (clusters) where receivers forward data to designated heads responsible for delivering data to every node in the cluster. This approach is used to deal with blind flooding; however, the objective is to forward packets to all nodes in the network, similar to a broadcast, and thus it is questionable whether this can be described as routing. * Geo-cast protocols: Destinations are computed by means of geographical locations. [PERSON] et al. (2016) define routing as follows:...'the network-wide process that determines the end-to-end paths that packets take from source to destination'... Note that it is unclear if broadcast and cluster-based message dissemination approaches might be considered as routing given their controlled or uncontrolled forwarding to every feasible node in the network, as opposed to the other approaches that determine paths according to their path discovery algorithms.