International Journal of Scientific & Technology Research Volume 1, Issue 4, MAY 2012
Traffic Generator Based Performance Evaluation of Proactive and Reactive Protocols of Mobile Ad-Hoc Networks Megha Rastogi, Kamal Kant Ahirwar, Abhay Bansal Abstract-The Mobile Ad-Hoc Networks are associated with the communication channels being set up between the nodes for short duration of time. Since the duration is generally small hence maximum throughput is required in order to utilize the entire communication period. Nodes which are part of this network behave both as the host and the router for the other communicating nodes. There are several approaches in the Ad-Hoc environment, of which dynamic topology is the best one. In order to communicate well the routing algorithm needed to be the best in all the conditions and the traffic environment. A lot of research work has been done on CBR type of traffic but variable bit rate traffic, web based traffic and multimedia traffic is not researched much till date. This paper focuses on these routing protocols as well as the different traffic generators and their overall performance under different scenarios. Better the adaptability of the routing algorithms better would the performance Index Terms— AODV, DSR, Manet routing protocol, Performance evaluation, Traffic generators, Packet delivery ratio, performance comparison
1 INTRODUCTION There are two distinct approaches that are widely known for enabling wireless communication between two mobile hosts. The first approach let the existing cellular network infrastructure carry both data as well as voice in the normal traditional way. The major problem lies with this approach is that of hand offs. The second approach is more practical to form an ad-hoc network among all mobile users wanted to communicate with each other at a particular moment. This implies that all users comprising the ad-hoc network must be capable of forwarding data packets to ensure the delivery of packets from source to destination. Ad-hoc networks are preferred as compared to traditional cellular systems because of several advantages. These advantages are as under: On demand setting up of infrastructure High fault tolerance power unimpeded connectivity Efficient routing is the current demand of a Mobile Ad-Hoc Network over which extensive research is going on for the past several years. Since in a MANET, routing should be done very efficiently in order to route data packets to their correct destination routing plays very crucial role. A routing protocol operates in the following two ways:
1. Route detection: In this phase, route is first determined. 2. Data Forwarding: In this phase, data is forwarded from source to destination over the above identified route. The route discovery phase is the most challenging function of a routing protocol in a Mobile Ad-Hoc Network. However, data forwarding phase is abstractly uncomplicated when variety of protocols and routing tables are there to utilize. Ad-hoc routing protocols can be classified according to different criteria. A protocol may fall under more than one class of distinction on the basis of the mechanism being employed by the routing protocol. Routing protocols for Ad-hoc networking can be classified into four broad categories .These are (i) Based on routing mechanism employed: proactive or table-driven, reactive or on-demand and hybrid protocols. (ii) Based on the basis of temporal information: Past Temporal and Future Temporal. (iii) Based on topology chosen for routing : Flat Topology, Hierarchical Topology (iv) Based on the Resources being utilized: Power Aware Routing and Geographical Information Assisted Routing. The MANETs reactive and proactive routing protocols we are going to focus in this paper are as follows:
----------------------------------------------------Megha Rastogi is currently pursuing masters degree program in computer science engineering in Amity University, India, PH9911497137. E-mail: email@example.com Kamal Kant Ahirwar is currently pursuing doctoral degree program in mobile computing engineering in Amity University, India, PH-9718281158. E-mail: firstname.lastname@example.org Dr. Abhay Bansal is currently working as Head Of The I.T. Department in Amity University and PhD is his recent achievement.
Ad hoc On-Demand Distance Vector (AODV) Dynamic Source Routing (DSR) Destination Sequenced Distance Vector (DSDV)
2.1 Ad hoc On-Demand Distance Vector (AODV) AODV is a reactive protocol hence the route to destination is only being established when demanded. The paths which are founded are independent upon the usage of the paths by the nodes to communicate the data. This protocol avoids the count-to-infinity problem associated with distance-vector routing protocols using the route update methodology as 118
International Journal of Scientific & Technology Research Volume 1, Issue 4, MAY 2012 implemented in DSDV. This routing protocol is capable of both multicast and unicast routing. As discussed, being the reactive protocol the routes are determined only on demand. Simple Hello messages are communicated in-order to detect and manage the neighboring nodes. During the transmission of the HELLO message the active nodes periodically broadcasts the messages so that the neighboring nodes responds accordingly. Since the HELLO message is a periodic transmission like beacons, if the node does not react to the message the communication to that node is seemed as broken or the link break is there. When the data is needed to be transmitted to a destination which is not known prior then the RREQ (Route Request) are broadcasted. To every intermediate node which responds to the RREQ the link is created , if it does not then the link is not created and the node is not an intermediate node from source to destination. The connecting node responds with RREP (Route Reply) message which is unicast in hop-by-hop fashion to source. As the RREP propagates through the network, each intermediary node creates a path to the destination. When source receives the RREP the node is added to the route as the intermediate node. If the multiple RREP are received then the minimum number of hop RREP is chosen. As the data is flowing from the source to destination the routes are managed along with the routing tables. If the data link break is detected then RRER (Route Error) message is sent , in this situation the sources reroutes the discovery of the route if necessary.
2.2 Dynamic Source Routing (DSR) It is a reactive protocol used in Wireless Mesh Networks. It is similar to the AODV in the route being discovered and made on-demand. But it relies on source routing in place of routing tables being managed in the AODV at every intermediate node. To determine the source it requires address to be accumulated at every node between the source and destination. This information being accumulated is processed by route discovering packets. The processed paths are used to route the packets. To use the source routing, each packet being transmitted contains the address of every other node the packet is going to traverse. This might result in more overhead in case of paths having longer traversals or address like IPv6. In-order to avoid source routing the DSR also provides a flowid option which forward packets on hop-by-hop basis. Being the source routing protocol the information are maintained at the nodes and being constantly updated. It operates in two phases: Route Discovery and Route Maintenance. The RREP message is only generated if the message reaches the destined node; the RREQ is inserted in the RREP. This allows the nodes to discover and maintain the routes found ondemand basis. In DSR the overhead is automatically scaled down and up depending upon the changes in the routes being established. This protocol allows the multiple routes and enables each sender to select and control the route being used. Use of SOFT STATE routing helps in maintaining and updating the routes in the frequent changing environment. It works pretty well up to 200 nodes in the network and designed to work well with high mobility rates of nodes. 2.3 Destination Sequenced Distance Vector (DSDV) This routing protocol is table-driven routing protocol for ad-hoc mobile networks which uses Bellman-Ford Algorithm for shortest path route finding. Itâ€™s main contribution being to solve the routing loop problem. Each of the nodes in the
routing table contains the sequence number given even number if the link is present from one node to another else an odd number is used to present no link between the nodes. The number being generated by the destination and the intermediate node needs to update the source with this number. This routing information is distributed less frequently to the incremental updates being updated more frequently.
3 PROBLEM FORMULATION A fundamental problem associated with the Ad-Hoc Networks is how to route data packets among mobile nodes proficiently devoid of predetermined topology or centralized administration , which is the main purpose of ad hoc routing protocols. Because of the ever changing topology of the Mobile networks, routing the data packets correctly between sourcedestination pair becomes a very challenging task. Moreover, availability of the limited resources, bandwidth and energy add extra burden on the routing process. In the literature survey conducted so far, it is observed that most of the research work revolves around CBR traffic pattern whereas practically most of the traffic on the Internet consists of the TCP and variable bit rate type traffic. It is therefore required to study and investigate the performance of different MANET routing protocols using different types of traffic generators. In this paper, we will assess the performance of Reactive protocols (AODV and DSR) and Proactive protocols (DSDV) of mobile ad-hoc network for different traffic generators. The performance of these routing protocols is analyzed with respect to two performance parameters, throughput and packet delivery ratio (PDR %).
4 TRAFFIC GENERATORS A Traffic Generator models the traffic which behaves in a predefine structure and schedule manner. It sends the demand to transmit the traffic payload regardless of the state of the agent being attached at a specific time and interval. The following traffic generators are taken into consideration for the analysis:
4.1 File Transfer Protocol (FTP) A FTP traffic generator creates the payload depending upon the bandwidth of the connection. It uses the entire bandwidth for the transmission. 4.2 Constant Bit Rate (CBR) CBR traffic Generator creates the payload which is fixed in size and the generation of packet interval is fixed. 4.3 Variable Bit Rate (Exponential) Exponential Traffic Generator creates the payloads similar to the CBR but it have the interval of ON/OFF states in which, the ON states the traffic being generated and the OFF states the traffic being not generated in the specified time interval. The ON/OFF states of the traffic generator are exponentially distributed. 4.4 Pareto (Poisson) Pareto is the traffic generator with similar feature of the exponential Traffic Generator but the ON/OFF states or the periods are dependent upon the Pareto Distribution.
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International Journal of Scientific & Technology Research Volume 1, Issue 4, MAY 2012
4.5 PackMime (HTTP 1.1) The traffic generator provides the traffic similar to the HTTP1.1 traffic. It controls the operation of two applications in PackMime HTTP, one is server other being the client. The Client-Server type of traffic is simulated and each of the traffic generators is connected to the FULL-TCP Agent only as it supports only full TCP agents.
5 PERFORMANCE METRICS There are two main factors over which the performance of the AODV, DSR and DSDV will be analyzed.
Figure1. Shows the performance of AODV, DSR and DSDV for CBR Traffic (20 nodes)
Packet Delivery Ratio Throughput
5.1 Packet Delivery Ratio Packet delivery ratio is obtained by dividing the total number of packets acknowledged by the destination through the total number of packets created or send by the application layer of the source node . It also rates the packet loss which confines the network from attaining the maximum throughput. The more accurate the delivery ratio, the more absolute and correct is the routing protocol. 5.2 Throughput Throughput is defined as the rate at which a network sends or receives data . It is a good channel capacity of network connections and rated in terms of bits per second (bit/s). Throughput =
Figure2. Shows the performance of AODV, DSR and DSDV for FTP Traffic (20 nodes) The performance of DSDV is better as compared to other two protocols with packet delivery ratio observed as 96% for FTP traffic
Where Pa is the packets received and Pf is the amount of forwarded packets over certain time interval.
6 SIMULATION ENVIRONMENT The Routing protocols AODV, DSR and DSDV are taken under the analysis for this paper. The Fedora OS is used to run the Simulating Software NS2 (Network Simulator 2) version 2.35 for the performance evaluation. The performance is observed at various pause time and intervals with total number of nodes taken as 20. In this situation 20 nodes will be simulated which move randomly in 2500m X 2500 m range.
7 SIMULATION RESULTS The performance of three routing protocols for different traffic generators are obtained as shown below:
Figure3. Shows the performance of AODV, DSR and DSDV for VBR Traffic (20 nodes) AODV out performs with packet delivery ratio as 96% for VBR traffic.
For CBR Traffic, all the three protocols show almost same performance with packet delivery ratio above 92%.
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International Journal of Scientific & Technology Research Volume 1, Issue 4, MAY 2012 Figure4. Shows the performance of AODV, DSR and DSDV for HTTP (Web based) Traffic (20 nodes) 
  
HTTP traffic constitutes approximately 95% of the total traffic in a Mobile Ad-Hoc Network. Therefore it deserves the best performance but unfortunately none of the routing protocols performs better for HTTP traffic.
Comparison of Multi-hop Wireless Ad Hoc Network Routing Protocols‖. Mobicom'98, Dallas Texas Josh Broch, David B. Johnsson, David A. Maltz, ―The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks‖. Charles E. Perkins, ―Ad Hoc on Demand Distance Vector (AODV) Routing‖. Trace Analyzer for NS-2 Theodore S. Rappaport, ―Wireless Communications: Principles and Practice”. New Jersey, Prentice Hall. ISBN 0-13-375536-3. Vikas Singla, Praveen Kakkar,‖ Traffic Pattern based performance comparison of Reactive and Proactive protocols of Mobile Ad-hoc Networks‖, ISSN- 0975 – 8887, Volume 5– No.10, August 2010. Vasudha Arora and C.Rama Krishna,‖ Performance evaluation of routing protocols for manets under different traffic conditions‖ 978-1-4244-6349-7, _c 2010 IEEE
Figure5. Shows the performance of AODV, DSR and DSDV for Multimedia Traffic (20 nodes) DSDV shows 95% of performance for the multimedia traffic using Pareto analysis.
8 CONCLUSION The Routing algorithms under the analysis have been simulated and their performance is being analyzed. Under the CBR, VBR and Exponential traffic source the entire routing algorithm performed well and produced over 90% throughput under different pause time. For the FTP traffic source the performance of the DSDV is better than the other two algorithms majorly due to the shortest path algorithm and FTP traffic scenario. Under HTTP traffic (Packmime) all the algorithms suffered as the packet interval being not fixed and variable packet size. Under Pareto traffic which is similar to the multimedia traffic with variable intervals and fixed packet sizes DSDV is better than the other two algorithms.
9 FUTURE SCOPE The future scope of the research is simulation of other modified routing algorithms so that the comparisons can be done on the larger scale. More number of nodes can be simulated so that network performance can be analyzed under stressful conditions on the routing algorithms.
REFERENCES  Josh Broch, David A. Maltz, David B. Johnson, Yih-
Hu and Jorjeta Jetcheva, ―A performance 121 IJSTR©2012 www.ijstr.org