at network layer for routing message packets between vehicles. To conduct this study two traditionally used transport layer protocols, namely, TCP and UDP, ...
International Journal of Computer Applications (0975 – 8887) Volume 36– No.6, December 2011
Performance Evaluation of TCP and UDP Protocols in VANET Scenarios using NCTUns-6.0 Simulation Tool Kusum Dalal
Prachi Chaudhary
Dr. Pawan Dahiya
Assistant Professor ECE Deptt., B.M.I.E.T., Sonepat, Haryana-131001.
Assistant Professor ECE Deptt., D.C.R.U.S.T, Murthal, Haryana-131039.
Assistant Professor ECE Deptt., D.C.R.U.S.T, Murthal, Haryana-131039.
ABSTRACT The paper presents an insight into the VANETs (Vehicular Adhoc NETworks) technology. The main objective of this study is to investigate the performance of transport layer protocols in different VANET environments. AODV routing protocol is used at network layer for routing message packets between vehicles. To conduct this study two traditionally used transport layer protocols, namely, TCP and UDP, have been selected for making performance evaluations on basis of three performance metrics, namely, throughput, number of packet drop and number of collision packets. In order to make this study more comprehensive, three set of mobility scenarios are considered and evaluations are conducted with the help of a very advanced and efficient simulation tool – “NCTUns-6.0 simulator”.
General Terms Transport protocols, VANET scenarios.
Keywords VANET, TCP, UDP, AODV, NCTUns-6.0 simulator.
vehicular network is restricted and is frequently changing. VANETs provide a tremendous potential for low latencies which means communication delay for message or packet transmission is quite low and hence helps in increasing the performance of system by allowing the network connection to remain active even if vehicles are moving at fast speeds and in dynamic topologies. In VANETs each vehicle acts as a transceiver by simultaneously receiving and transmitting data packets. Basically, VANET is not an individual technology rather it integrates number of technologies like GPS, GPRS etc. in order to achieve a single goal of providing user safety and comfort and presenting a highly intelligent transportation system. The communication among vehicles and between vehicles and RSUs is achieved using a dedicated short range communication (DSRC) wireless standard or more recently developed Wireless Access in Vehicular Environments (WAVE) standard [3]. The data packets are transmitted among vehicles and between vehicles and RSUs using TCP/UDP/IP network transmission mode. A VANET overview is as shown in figure 1.
1. INTRODUCTION According to the Global Status Report on Road Safety released by WHO (World Health Organization), the direct economic costs of global road accidents have been estimated at US $ 518 Billion, with an estimation of around US $65 Billion in low income countries [1]. The situation in India verify these figures as almost 13 people die every hour in road accidents in India according to the latest report of the National Crime Records Bureau [2]. All these terrifying facts reveal just one thing that road safety is a very critical field of research arena. One of the solutions devised is VANETs (Vehicular Adhoc NETworks) which is related to adhoc networking among vehicles and between vehicle and road side equipments. VANET is such a field of research which has a direct impact on human life. Thus, a very ardent approach is required towards this field. A lot of work has been conducted so far but looking at the increasing trend of road accidents, it seems that much more effort is required. VANETs can be considered as a special case of MANETs (Mobile Adhoc NETworks) except that in VANETs the nodes present are basically vehicles which strictly follow the traffic rules and have highly complex and dynamic topology. The mobility of vehicles on road is restricted by factors like driving behavior of the driver as well as surrounding people, traffic jams, traffic signals, road-side mishap, unseen obstacles, free passage of emergency vehicles etc., thus the mobility patterns in
Fig 1: VANET Scenario [4] In this paper, the performance of two traditionally used transport layer protocols are evaluated in detail, using simulation case study in different VANET scenarios and their use in real-time applications is verified. VANET scenarios used in this paper are closely related to real-life traffic mobility conditions. The protocols evaluated are the two most widely used transport layer protocols, namely, TCP and UDP. NCTUns-6.0 simulation tool is used in this study for evaluating the performances.
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International Journal of Computer Applications (0975 – 8887) Volume 36– No.6, December 2011
2. RELATED WORK Many researchers have done qualitative and quantitative analysis of TCP and UDP Protocols in various scenarios. Some of them are mentioned below as under: • Bruno R. et. al. [5] compared TCP and UDP performances in an IEEE 802.11 WLAN scenario on basis of throughput. • Hongtao Wang et. al. [6] compared the performance of PRSCTP, TCP and UDP for MPEG-4 video traffic over mobile networks. • Rind A.R. et. al. [7] compared the performance of TCP & UDP over wired cum wireless LAN is conducted using DSDV routing and Network Simulator-2 in terms of throughput. • Petrovic M. et al. [8] compared the performance of TCP and UDP using IEEE 802.11 adhoc network and two topologies, string and mesh.
3. TRANSPORT LAYER PROTOCOLS Transport Layer is used for providing end-to-end communication in a peer-to-peer application service. The two most well-known transport protocols used are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). The key difference between TCP and UDP protocol is the guarantee of reliable communication. TCP is used for connection-oriented transmissions as it provides the acknowledgement and retransmission facilities. TCP uses three additional packets for establishing the connection between peers and then sends the actual data. This results in a packet header size of 20-30 bytes. Besides this, TCP offers the advantage of an ordered delivery of data packets and also provide for error correction capability. TCP is usually used for non-time critical applications due to its comparatively slow speed.
3. Number of Collision Packet: It shows the number of packets that were discarded due to collision among them. Lower collision rate shows higher protocol performance.
4.3 Simulation Setup The following parameters are selected for the presented work: IEEE 802.11b (adhoc mode) standard is used for each node. 1400 bytes of TCP and UDP packets are respectively used. 15dbm Transmission power used for each node operation. AODV protocol for routing of both TCP and UDP packets. 20, 30 and 50 nodes are used for individual scenarios with 50, 36 and 18 m/s max. speed in the respective cases.
4.4 Simulation Scenario In this paper, three simulation scenarios are considered which are mainly prevalent in city-like environments with variable number of nodes (vehicles) and variable speeds. As congestion on road increases, the maximum speed a vehicle can attain, correspondingly decreases as is highlighted in table 1. Table 1. Parameters of Simulation Scenarios Grid Scenario
No. of nodes
Max. Speed of nodes
2*2 grid
20
50 m/s
3*3 grid
30
36 m/s
5*5 grid
50
18 m/s
With UDP, messages or datagrams are sent without establishing any prior communications. No acknowledgement facility is inherited in UDP and it is one of the reasons for unreliable communication service with UDP in which some datagrams may get lost or may come in out-of-order fashion. This, on other hand, reduces the overhead with the packet header size of just 8 bytes. UDP has comparatively fast speed and is thus used for games or applications that require fast transmission of data.
4. SIMULATION TOOL USED 4.1 NCTUns-6.0 Tool
Fig 1: 2*2 Grid City Scenario with 20 nodes & max. speed of 50 m/s.
In the presented work a hybrid simulator NCTUns-6.0(National Chiao Tung University network simulator) is used whose core technology is based on the novel kernel re-entering methodology invented by Prof. S.Y. Wang. The various features of VANET supported by NCTUns-6.0 makes it an obvious choice.
4.2 Performance Metrics For this study three performance metrics are selected as under: 1. Throughput: It gives the total number of received packets at the destination out of total transmitted packets [9]. It is calculated in bytes/sec or data packets per second. 2. Number of Packet Drop: It shows total number of data packets that could not reach destination successfully. The reason for packet drop may arise due to congestion, faulty hardware and queue overflow etc. Lower packet drop rate shows higher protocol performance.
Fig 2: 3*3 Grid City Scenario with 30 nodes and max. speed of 36 m/s. 7
International Journal of Computer Applications (0975 – 8887) Volume 36– No.6, December 2011 As seen from fig. 4 and 5, the performance of both protocols is optimum in 2*2 grid city scenario .This is due to the fact that, as traffic density increases more number of packets collide and net throughput decreases. Overall throughput is much high with UDP connection as compared to TCP, but, UDP throughput is highly unstable indicating its unreliable approach.
Fig 3: 5*5 Grid City Scenario with 50 nodes and max. speed of 18 m/s.
4.5 Simulation Results The graphs below show the performance of both TCP and UDP protocols individually in all three VANET scenarios discussed above. Overall six graphs are drawn based on following three performance metrics:
Fig 6: Packet Drop Performance of TCP Protocol for 3 scenarios
1. Throughput 2. Packet Drop Rate 3. Collision Rate The inferences drawn from each graph are also listed to provide a more vivid picture of the comparison.
Fig 7: Packet Drop Performance of UDP Protocol for 3 scenarios
Fig 4: Throughput Performance of TCP Protocol for 3 scenarios
Fig 5: Throughput Performance of UDP Protocol for all 3 scenarios
From fig. 6 and 7, it can be seen that less number of packets drop with TCP scenario, which allow for a reliable communication or transfer of message packets. In UDP transmission reliability is compromised as is evident from number of packets dropped while transmission. Due to less congestion in a 2*2 city scenario packet drop rate is comparatively less for this case.
Fig 8: Collision Rate Performance of TCP Protocol for 3 scenarios 8
International Journal of Computer Applications (0975 – 8887) Volume 36– No.6, December 2011 throughput. Thus both protocols show their best performances with moderate traffic density with moderate vehicle speed.
6. REFERENCES [1]
Tenth Five Year Plan Vol II page 963.
[2] World Report on Road Traffic Injury Prevention, page 5 WHO, 2004. [3] Sherrill Zeadally1, Ray Hunt2, Yuh-Shyan Chen3, Angela Irwin4, Aamir Hassan5, “Vehicular Ad Hoc Networks (VANETS): Status, Results, and Challenges”. [4] Vanet Simulator, Report for the Computer Security exam at the Politecnico di Torino Walter Dal Mut, Armand Sofack. Fig 9: Collision Rate Performance of UDP Protocol for 3 scenarios It can be seen from fig. 8 and 9, that, the rate of collision is much higher in UDP communication because burst of datagram are generated which are transmitted without any dedicated link and this result in collision of data packets. As for other two performance metrics, this performance metric evaluation indicates the efficiency of both protocols in a less dense VANET environment.
5. CONCLUSION On basis of three performance metrics, the performance graphs of TCP and UDP protocols are obtained using simulation results from NCTUns-6.0 simulator tool. It is observed that throughput with UDP protocol is much greater than TCP in all the three scenarios considered, whereas packet drop rate and collision rate is considerably less for TCP protocol. These observations are in conformance with the work done by other researchers as mentioned earlier. Further, inferences can be drawn from above observations that TCP protocol should be used where reliability is of chief concern such as in internet banking, www etc. and UDP should be used where high throughput with low latency is emphasized such as for broadcasting/multicasting purposes like in internet gaming, internet radio etc. where some packet loss can be afforded.
[5] Bruno, R.; Conti, M.; Gregori, E.; “Throughput Analysis of UDP and TCP Flows in IEEE 802.11b WLANs: A Simple Model and Its Validation”, Workshop on Techniques, Methodologies and Tools for Performance Evaluation of Complex Systems, 2005. (FIRB-Perf 2005), pp. 54 - 63, 19 Sept. 2005. [6] Hongtao Wang, Yuehui Jin, Wendong Wang, Jian Ma, Dongmei Zhang, “The performance comparison of PRSCTP, TCP and UDP for MPEG-4 multimedia traffic in mobile network”, International Conference on Communication Technology Proceedings, pp. 403 - 406 vol.19-11, April 2003 . [7] Rind, A.R.; Shahzad, K.; Qadir, M.A.; “Evaluation and comparison of TCP and UDP over Wired-cum-Wireless LAN”, IEEE Multitopic Conference, 2006, pp. 337 – 342, 23-24 Dec. 2006. [8] Petrovic, M.; Aboelaze, M.; “Performance of TCP/UDP under ad hoc IEEE802.11”, 10th International Conference on Telecommunications, 2003, pp. 700 - 708 vol.1, 23 Feb.-1 March 2003. [9] S.Y. Wang and H.T. Kung, “A Simple Methodology for Constructing Extensible and High-Fidelity TCP/IP Network Simulator”, IEEE INFOCOM’99, March 21-25, 1999, New York, USA.
Another point observed in this study is that, as the traffic density is increased from 20 to 30 nodes throughput increases and as density is further increased to 50 nodes throughput decreases slightly. This may be due to the fact that as density increases initially more intermediate nodes are available for packet transmission, but, as traffic density further increases it leads to more number of packet collisions which inturn decreases the
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