FEATURES AND CHALLENGES OF VANET1.1 Features of VANET [2, 5]:Dynamic topology-One of the most important features of VANET is the dynamic topology. In this the nodes or vehicles move at high speed relative to each other. No Power Constraints and Adequate Storage – In VANET, we use vehicles as nodes instead of other devices so that vehicles have sufficient amount of energy and power including both processing and storage; so battery power and storage are not an issue in VANET. Frequent Network Disconnection: In VANET, vehicles move very frequently on roads, so in the network the link connectivity in VANET also changes frequently. The chances of grid disconnection are high when vehicle density is low. Mobility modeling and prediction: Due to the high dynamic topology, mobility modeling and prediction plays a very important role to design data dissemination in VANET. Different communication environments: VANET has two types of environments, such as highway environment and urban environment. In the highway traffic environment, communication is relatively simpler and more direct. But in the city traffic environment it becomes quite complex compared to the highway traffic environment. 1.2 Challenges of VANET [6, 7]: Hidden terminal problem - This problem can occur when two or more objects send packets, these packets are not within the direct transmission range of each other. Collision at the common receiver node. Error prone shared relationship - In VANET, during propagation the radio wave experiences various disturbances such as attenuation, multipath propagation and interference. Insecure medium - In VANET, due to the nature of transmission, communication is insecure. It is difficult for these networks to support different... middle of paper...warding. This protocol also adopts periodic transmission, i.e. used to reduce network fragmentation. In this protocol, a broken vehicle broadcasts a warning message to all vehicles in the group, and the neighbor who received the warning message analyzes its applicability based on its location by informing the risk area. The Robust Vehicular Routing Protocol (ROVER) [9] is geographic multicast protocol. In ROVER, control packets use broadcasting while data packets use unicasting mechanism. The main objective of this protocol is to transmit a message to all vehicles presented in the specified zone of relevance (ZOR). ZOR can be designated as a rectangle specified by its corner coordinates. In this, a message can be described using three terms called triplet (application, message, ZOR). If the vehicle re-enters its ZOR and receives a message, it accepts that message.