Ms Kaushika Patel, Prof J M Rathod Kaushika Patel is Research Scholar at CHARUSAT and Assistant Professor at B V M Engineering College, Vallabh Vidya Nagar-388120, Gujarat, India (phone: +91 9428479191; e-mail: kdpatel@ bvmengineering.ac.in). J M Rathod is Associate Professor at B V M Engineering College, Vallabh Vidya Nagar-388120, Gujarat, India (phone: +91 9428902849; e-mail: jmrathod@ bvmengineering.ac.in). ABSTRACT This paper is oriented towards performance of various existing reliable transport layer protocol implementations over Vehicular Ad-hoc Network. This includes the comprehensive survey of different Transmission Control Protocol (TCP) implementations using traffic and mobility models developed for Vehicular Ad-hoc Network (VANET). VANET considers car as moving node so the topology of it changes repeatedly. In VANET, vehicular to vehicular (V2V) and vehicular to infrastructure (V2I) communication are possible. Transmission control protocol provides end-to-end, reliable and congestion controlled connections over the Internet. It is required to understand congestion control algorithm for TCP, as it is heart of TCP. Out of all TCP implementations, TCP WestwoodNR has dynamic adjustment of congestion window and has control of congestion window with the help of end-to-end estimation of bandwidth. TCP WestwoodNR continuously estimates the available end-to-end bandwidth based on rate of Acknowledgement reception. Efforts are made to evaluate different mobility models for TCPs on VANET and as part of it different mobility models were implemented and evaluated. Routing protocols plays vital role in performance of any network, hence three of the most commonly used routing protocols DSR, DSDV and AODV were evaluated. In case of random drops due to bit error rate, which are frequent in case of wireless networks, WestwoodNR’s bandwidth estimation algorithm gives best results amongst all. Keywords: Vehicular Adhoc Network, TCP WestwoodNR, Network Simulator 2, BonnMotion, MANET, cwnd, RTT, Mobile Adhoc Network. 1. INTRODUCTION Vehicular Ad-hoc Network is a type of wireless network which uses running cars as nodes to create a network. This is one classification for mobile Ad-hoc network [1]. This makes any participating car as node and transmits the data from car to car and also car to infrastructure communication. Reliability and end-to-end delay are two most important factors in VANET’s security applications. Here Links existing is expected to be short lived because of high speed mobility. VANETs are similar to mobile ad hoc networks in the sense that nodes are self organized and self managed. The information is in a disseminated fashion without any authority or server which is dictating communication. Generally this type of network involves in to nodes themselves as the servers and/or clients, thereby exchanging and sharing the data like two peers. In this case the nodes are more or less mobile, so it makes data transmission and reception less reliable. The Institute of Electrical and Electronics Engineers (IEEE) draft for 802.11p has provided information for the mode of information interchange between the vehicles. The employment and testing of any VANETs is excessively costly and time intensive task, so VANET Simulators encourage one to perform any present reality activities under Differing circumstances without including high cost and colossal measure of time involved. Scientists across the world have created distinctive simulators for demonstrating vehicles. Simulation of VANET is entirely divergent from Mobile Adhoc Networks because any road or the vehicular transfer is characterized by the constrained road topology, direction of vehicles in addition to varying speed, multiple path fading, traffic congestion, change in network topology, traffic lights and driver’s activities etc [2]. (a)WLAN cellular (b) Ad hoc (c) Hybrid Figure 1. Three categories of VANET architecture [3] As shown in Fig. 1, the architecture of VANET is distributed in three categories: pure cellular/WLAN, pure ad hoc, and hybrid. In pure cellular/WLAN architecture, the network uses cellular gateways and WLAN access points to connect to the Internet and facilitate vehicular applications. Vehicles communicate with the Internet when in motion by either a cellular access point or a wireless access point. Evaluation of best suitable scenario for Vehicular Ad hoc Network International Journal of Computer Science and Information Security (IJCSIS), Vol. 14, No. 7, July 2016 518 https://sites.google.com/site/ijcsis/ ISSN 1947-5500