Evaluation Of Routing Protocols In MANETs Computer Science Essay

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A mobile ad hoc network (MANET) is a network of mobile nodes connected by wireless links. It is a collection of decentralized, autonomous nodes, terminal or wireless stations that are located in such a manner that the interconnections between stations may change on regular basis. Each mobile node acts as a host and router. The communication between the mobile nodes is carried out without any centralized control. A routing protocol is used to facilitate communication among the active stations on the network, for discovering routes between nodes. A routing protocol plays an important role for the overall performance of MANETs. A variety of routing protocols for MANETs have been developed by network researchers and designers primarily to improve the performance of MANETs with respect to correct and efficient route establishment between a pair of stations for message delivery. Examples of commonly used MANET routing protocols include optimized link state routing protocol (OLSR), ad-hoc on-demand distance vector (AODV), dynamic source routing (DSR), and temporary ordered routing algorithm (TORA). A good understanding of the effect of each of these routing protocols on a typical IEEE 802.11 network will assist an efficient design and deployment of appropriate MANETs.

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This research aims to study the impact of routing protocols on MANETs by evaluating the quality of services. This dissertation shows comparative evaluation within mobile ad hoc networks routing protocols from reactive, proactive and hybrid categories.

Chapter 1

Introduction

A wireless ad hoc network is a multi hop network that is a collection of mobile or sometimes stationary nodes connected with bandwidth constrained wireless links i.e. every node should have wireless interfaces and thus have their own transmission ranges, forming a decentralized ad hoc network. Laptop computer or Smartphone can be the example of the nodes in a mobile ad hoc network. A node can enter or leave the network whenever it is required. There is no central administration for that, each node forwards packets according to a routing protocol. A routing protocol is a principle or standard that controls how nodes come to agree in the way to route packets (using multi-hops) between computing devices in MANETs. A node in an ad hoc network is a host as well as a router. An ad hoc network is capable of adjusting itself in the change of routing topology in time. If any route is disturbed by the link failure or something, the station calls a route discovery function to find out an alternative route and forward the packet in the way of that route. To find out the way, a packet should be forwarded.

Figure 1.1: A Typical Ad hoc Network

In the figure 1.1, a typical ad hoc network with three participating nodes is shown, where node 1 cannot send packets directly to the node 3 because they are not in the same transmission range. Node 1 first sends the packet to node 2 and node 2 acts as a router, forwards the packet to node 3 as they are on the same transmission range. There is no central administration and according to the figure 1.1, it is a clear that change of node mobility changes the routes. Thus sending a packet from node 1 to node 3 is done with the help o routing protocol. In recent years a variety of MANET routing protocols have been developed. Examples of routing protocols are, Optimized Link State Routing Protocol (OLSR), Dynamic Source Routing Protocol (DSR), Ad hoc On Demand Distance Vector Routing (AODV), Wireless Routing Protocol (WRP) and Temporally Ordered Routing Algorithm (TORA).

Mobile ad hoc networks (MANETs) are being extensively deployed currently since they provide features that conventional networks find impossible or difficult to emulate. The ideal applications include settings that deal with mobile nodes; these include home networks, disaster operations, search and rescue operations and military operations. Furthermore, new application are rapidly developing for MANETs [1] and are also finding new entry in commercial usage like the vehicle ad hoc network used in taxi service operation [2].The nature of MANETs also brings about drawbacks in regards to communication link formation. The uncontrollable nodes causing uncertainty of when nodes disappear and reappear from the network communication range, causing highly variable message delays. These factors have an impact on routing protocol performance. Moreover as the potentials usage of MANET applications grow, it has raised critical concerns over identifying the routing protocol that best works in a given situation. Factors like mobility of nodes, the network size and packet size need to be considered in determining which routing protocol to be deployed in a situation.

1.1 Research objective

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There are many different type of routing protocols, with competing features, developed for MANETs. These protocols have varying qualities for different wireless routing aspects. It is due to the reason that the choice of a correct routing protocol is critical. The aim of this research is to investigate the impact of routing protocols on MANETs. Simulation methodology is used in the investigation. In this dissertation the following research questions are answered: what impact do different routing protocols have on a MANET performance and how can the impact be quantified? In particular, what effect proactive (OLSR), reactive (AODV) and hybrid (TORA) routing protocols have on MANETs.A detailed description of the practical investigation is outlined in Chapter 3.

1.2 Dissertation structure

Chapter 2 present background material. In Chapter 2, a literature on MANET routing protocols is presented. Chapter 3 describes the experimental designs and investigation carried out. Chapter 4 describes results and comparative analysis. Chapter 5 summarized the dissertation.

Chapter 2

Mobile Ad Hoc Network Routing Protocols

This chapter provides a review of literature on MANET routing protocols. The dynamic nature of MANETs makes them ideal candidates for a number of applications. These networks are quick to deploy and require minimal configuration thus making them suitable for emergencies such as natural disasters. MANETs are also used to extend service coverage in cost effective ways. As technology advances in the development of devices such as Wi-Fi capable laptops, mobile phones and other portable devices, MANETs are increasingly becoming popular.

By definition MANET routing protocols are mechanisms to transfer information in data packets from a source to a destination in a network. Generally, two activities take place in routing protocols which enables communication to occur between two nodes. First is to determine optimal routing paths and the transferring of packets through the network but still using low computing power. Second, to achieve these activities, each routing protocol uses different metrics to evaluate the best path that data packets should use when sending packets in a network. To accomplish effective performance the nature of routing algorithms, design and performance issues require careful consideration.

This chapter is divided into seven sections. Section 2.1 outlines the term routing. The routing types are presented in Section 2.2 and MANETs routing protocols in Section 2.3 and Section 2.4 summarised this chapter.

2.1 Routing

Routing means to choose a path. Routing in MANET means to choose a right and suitable path from source to destination. Routing terminology is used in different kinds of networks such as in telephony technology, electronic data networks and in the internet network. Routing protocols in mobile ad hoc network means that the mobile nodes will search for a route or path to connect to each other and share the data packets. Protocols are the set of rules through which two or more devices (mobile nodes, computers or electronic devices, smartphones) can communicate to each other. In mobile ad hoc networks the routing is mostly done with the help of routing tables. These tables are kept in the memory cache of these mobile nodes. When routing process is going on, it route the data packets in different mechanisms. The first is unicast, in which the source directly sends the data packets to the destination. The sec is multicast, in this the source node sends data packet to the specified multiple nodes in the network. The third is broadcast; it means the source node sends messages to all the near and far nodes in the network.

2.2 Routing Types

Routing has two basic types, which are as under.

Static routing: is done by the administrator manually to forward the data packets in the network and it is permanent. No any administrator can change this setting [3]. These static routers are configured by the administrator, which means there is no need to make routing tables by the router itself.

Dynamic Routing is automatically done by the choice of router. It can route the traffic on any route depend on the routing table. Dynamic routing allows the routers to know about the networks and the interesting thing is to add this information in their routing tables. This is shown in the below figure 2.1. In dynamic routing the routers exchange the routing information if there is some change in the topology [4]. Exchanging information between these dynamic routers learn to know about the new routes and networks. Dynamic routing is more flexible than static routing. In dynamic routing it have the capability to overcome the overload traffic. Dynamic routing uses different paths to forward the data packets. Dynamic routing is better than static routing.

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Figure 2.1: Dynamic Routing Exchange

2.3 Routing Protocols for MANETs

There are many ways to classify protocols for MANETs depending on how the protocols handle the packet to deliver from source to destination. The protocols for MANETs are classified as follows.

2.3.1 Proactive Routing Protocols

This type of protocols is called table driven protocol. In the routing, the route is predefined. Packets are transferred to that predefined route.Control messages are transmitted with periodically intervals. Even if there is no data flow still control messages are transmitted. Because of these control messages proactive routing protocols are not bandwidth efficient. In this scheme, packet forwarding is faster but routing overhead is greater because one has to define all of the routes before transferring the packets. Proactive protocols have lower latency because all routes are maintained at all the times. Examples of proactive are DSDV (Destination Sequenced Distance Vector), OLSR (Optimized Link State Routing).

2.3.1.2 OLSR (Optimized Link State Routing Protocol)

The OLSR protocol is an optimised pure state link algorithm. It is designed to reduce retransmission duplicates and with a proactive nature the routes are always available when needed. It uses hop by hop mechanics when forwarding packets. To accommodate this, the nodes exchange topological information periodically using Multi Point Rely (MPR) nodes. MPR is a distinctive feature over other protocols. Other features of OLSR include Neighbouring Sensing, Hello and Topological Control (TC) message. Figure 2.2 shows MPR and how messages are forward. In OLSR, MPRs selected nodes are the only nodes that forwards control traffic hence reducing the size of the control message from flooding the network therefore minimising the overheads. MPRs periodically advertise their link state information to each other nodes. MPR also forms a route from a given source to destination. A hello message is periodically broadcast by each node for link sensing, neighbour detection and MPR selection process. A neighbouring detection is a process where two nodes link, sense, and considers each other as a neighbour only if a link is established symmetrically. A link can be considered a bi or unidirectional. A hello message sent by a node contains its address and all the address for its neighbours. Each node can obtain topological information up to 2 hops from a hello message.

Figure 2.2: OLSR MPR Node

The MPR selection process that uses 1 and 1 hop symmetrical information to recalculate the MPR set. MPR recalculation occurs when a change in 1 or 2 hop neighbourhood's topology has been detected. When receiving the update information, each node recalculates and updates the route to each known destination. TC message is used to broadcast topological information throughout the network however, only MPR nodes are used to forward the TC messages to nodes in its routing table.

2.3.2 Reactive Routing Protocols

These types of protocols are called On Demand Routing Protocol. In the routing, the routes are not predefined. A node calls for route discovery to find out a new route when needed. This route discovery mechanism is based on flooding algorithm which employs on the technique, a node just broadcasts the packet to all of its neighbors and intermediate nodes just forward the packet to their neighbors. This is a repetitive technique until reaches to destination, reactive techniques have smaller routing overheads but higher latency because a route from node A to node B will be found only when A wants to send to B.Examples of Reactive are DSR (Dynamic Source Routing), AODV(Adhoc On demand Distance Vector Routing).

2.3.2.1 AODV (Ad hoc On Demand Distance Vector Routing Protocol)

AODV provides a good compromise between proactive and reactive routing protocols. AODV uses a distributed approach which means that a source node is not required to maintain a complete sequence of intermediate nodes to reach the destination. It is also an improvement from DSR by addressing the issue of high messaging overhead and large header packets in maintaining routing tables at nodes, so that packets do not have to store much routing information in the headers. AODV uses a routing table in each node and keeps one to two fresh routes. The incorporated features of AODV include features of DSDV, like the use of hop by hop routing, periodic beacon messaging and sequence numbering. A periodic beacon message is used to identify neighbouring nodes. The sequence numbering guarantees a loop free routing and fresh route to destination. AODV has the advantage of minimizing routing table size and broadcast process as routes are created on demand. The two mechanisms; route discovery and route maintenance of AODV are like those of DSR.

In Route discovery, if a node wants to send a packet to a destination like DSR, it initiates RREQ throughout the network. A RREQ message contains the source node address, source sequence number, destination sequence number, destination address, hop count and broadcast ID. The combination of source broadcast ID and source address is to uniquely identify a route request message. Any node with a valid route to the destination also needs to have the destination responding by sending a route reply message. A link failure or invalid or expired route will trigger route maintenance. During route discovery there are two pointers set at intermediate nodes between source and destination. Forward pointers, as illustrated in Figure 2.6, are pointers set for route request and packets to propagate from source to destination while back pointers relay reply messages from destination to source. During route request, if the route is found in the table list, the route request message will not be saved but forward to other nodes.

Route maintenance is performed using three different messages: hello message, RERR message and route timeout message. A periodic hello message is to prevent forward and backward pointers form expiring. Route timeout messages are sent if there is no activity on a certain route for some time so that route pointers in immediate nodes will timeout (expired) therefore are deleted. An up-stream route error message is initiated when one of the links in the route fails hence the error packet is broadcast globally. Nodes affected, illustrated in Figure 2.6, are nodes 3 and 4; they immediately broadcast an update message to remove the affected route in their route cache and to other nodes that stored the failed route. Route maintenance is accomplished through the use of error packets and acknowledgement, when link is broken (transmission error) an error message is sent to other nodes. The nodes with the error routes are erased from route tables.

When a link failure occurs, the route repair is executed using local and global route repair. A local route repair is where the intermediate nodes tries to repair the route at first however, if there is no available routes in intermediate nodes, the message is then sent to the source where the source initiates a global route repair.

Without source routing, AODV relies on routing table entries to propagate a route reply (RREP) back to the source node and subsequently to a route data packets to the destination. The advantages of AODV are Loop free routing, optional multicast, reduced control overhead and a quick response to link breakage. The disadvantages are delay caused by route discovery process and the bidirectional connection needed in order to detect a unidirectional link.

2.3.3 Hybrid Routing Protocol

This type of protocols combines the advantages of proactive and reactive routing. The routing is initially established with some proactively prospected routes and then serves the demand from additionally activated nodes through reactive flooding. The choice for one or the other method requires predetermination for typical cases. The main disadvantages of such protocols are:

Advantage depends on amount of nodes activated.

Reaction to traffic demand depends on gradient of traffic volume.

Examples of hybrid routing protocols are HRPLS (Hybrid Routing Protocol for Large Scale Mobile Ad Hoc Networks with Mobile Backbones), HSLS (Hazy Sighted Link State routing protocol), TORA (Temporally-Ordered Routing Algorithm), ZRP (Zone Routing Protocol) and SSR (Scalable Source Routing).

2.3.3.4 TORA (Temporally-Ordered Routing Algorithm)

TORA is a fully distributed routing protocol in a multi hop network, i.e. there is no central administration and each router keeps information of its adjacent routers only. TORA has a minimum reaction in topological changes which depends on Internet MANET Encapsulation Protocol [5]. TORA has the characteristics of loop free and multipath routing, minimized communication overhead, scalability, composed of reactive and proactive routing and maintenance [6]. TORA uses first route finder algorithm to find routes.

To describe the operation of TORA, three main functions that TORA does are:

1. Route Creation

2. Route Maintenance

3. Route Erasing

TORA assigns directional links in an undirected network or a portion of the network with central focus to destination. In another word, building a Directed Acyclic Graph (DAG) is the target of TORA in route creation function. In the network, an associate height is given to each node and packets are traversed only from higher height node to smaller height node. When any node finds no route to the destination in its downstream, it generates QRY (Query) message to discover route. The QRY message traverses the network until it finds the destination or any node that has the path to destination. The node then broadcasts an UPD (Update) message to inform others about its height. The other nodes than update their own heights according to UPD. This process may cause a number of directed links or route from the QRY originator node. Any topological changes, TORA can react in re-establishment of a route within a finite time. All the links partitioned from the destination are assigned undirected and erased by a clear (CLR) message [5].TORA uses internet MANET encapsulation protocol (IMEP) for link status and neighbor connectivity sensing. IMEP provide reliable, in-order delivery of all routing control messages from a node to all of its neighbors, and notification to the routing protocol whenever a link neighbors is created or broken. Moreover, it is bandwidth efficient and highly adaptive and quick in route repair during link failure and providing multiple routes to destination node in wireless networks.

2.4 Summary

This chapter provides background information reviewing the literature on MANET routing protocols. A simulation methodology approach will be used to examine the impact on routing protocols on MANETs performance is presented in Chapter 3.

Chapter 3

Experimental Design and Investigation

In Chapter 2, a review of literature on routing protocols was presented. This chapter provides the design parameters, and the various metrics considered necessary for the performance evaluation of routing protocols. This chapter is divided into three sections. Section 3.1 outlines the performance metrics. Section 3.2 presents the software information used and Section 3.3 presents network modelling and scenarios. Section 3.4 summaries the chapter.

3.1 Performance metrics

A metric is a standard used for measuring the best possible, effective and efficient route to destination in a routing algorithm. It represents different characteristics of the overall network performance. The performance metrics used to measure the performance of routing protocols are; average throughput, end to end delay, routing load, network load, packet delivery ratio and retransmission attempts.

Throughput - is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node. The throughput is usually measured in bits per second (bit/s or bps), and sometimes in data packets per second or data packets per time slot. Throughput measures the effectiveness and efficiency of routing protocols usage (performance) over the network in delivering message from a source to a destination node. Factors that affect the throughput in MANETs are frequent topology changes, unreliable communication, limited bandwidth and energy. A high network throughput is required.

End to end delay â€" is the time taken for a packet to be transmitted across a network from source to destination node. It is commonly referred in RTSP.It is expressed in seconds. It includes all delays in the network such as buffer queues, transmission time, delay induced by routing activities and MAC control exchange.

Routing load - is the total number of routing packets transmitted over the network expressed in bits per second or packets per second delivered at destination. Every hop-wise transmission is counted as one transmission. Packet overhead constitutes the number of packets "transmitted" per data packet that is "delivered" at destination. It is also called as routing overhead. In other words, routing overhead is determined by the ratio of the amount of information needed to carry control traffic over information needed to carry data traffic.

Media Access Delay - is the media transfer delay for multimedia and real time traffics’ data packets from senders to receivers.

Throughput and end to end delay are the most important metrics to consider for best effort traffic whereas routing load evaluates the efficiency of routing protocols. These metrics are not totally independent of each other. A large overhead may result in great delays and lower throughputs, on the other hand a short delay cannot be generalised or imply higher throughput since delay is only measured in data packets that are successfully delivered .

3.2 Software Platform

Software used in evaluating the performance of routing protocols is OPNET modeler 14.5. OPNET is a network and application management software designed and distributed by OPNET Technologies Inc [7]. Among other things OPNET Technologies Inc, model communication devices, technologies, protocols, and architectures, and provide simulation of their performance in a dynamic virtual network environment [7].

OPNET Technologies through its R&D provides solutions that help in academic research in the following areas: Evaluation and enhancement of wireless technologies e.g., WIMAX, Wi-Fi, UMTS, evaluation and design of MANET protocols, analysis of optical network designs, enhancements in the core network technologies such as IPv6, MPLS, and power management schemes in sensor networks [7]. OPNET is a useful tool in research. Its use can be broken down in four major steps. The first step is modeling (creating network nodes). Then choose statistics, run simulations and finally view and analyze results.

3.3 Network modelling and scenario

In order to evaluate routing protocols i.e. OLSR, AODV and TORA the network size, node mobility and data traffic load is chosen. The standard 802.11b is the IEEE standard which is used.

The parameters used in assessing the performance of protocols are carefully designed as outline in Tables 3.1 to 3.3. A protocol is being stressed by varying several parameters at a time in all possible directions. Table 3.1 presents the general parameters configured in experiment. The experiment is conducted using a campus network of area space 700 x 700 square meters. The node size is 30. The nodes and server are spread randomly within a geographic area. Node speeds are configured using the Random Waypoint mobility model; traffic patterns are not directly investigated therefore the Random Waypoint (Record Trajectory) is not required. The node speeds used are 10 meters per second (m/s). The File Transfer Protocol (FTP) is the data type used in generating traffic. The data rate used by the mobile nodes is 11 Mbps. The packet lengths used to investigate traffic loads are 15000000 (heavy load), bytes. All simulations are carried out in 900 seconds of simulation time.

The simulation parameters are shown in Tables 3.2 and 3.3. Most parameters use is default settings some of useful parameters for OLSR are listed in Table 3.2 likewise for AODV and TORA in Table 3.3 and Table 3.4

Parameters

Value

Channel Type

Wireless Channel

MAC Type

802.11 b

Date Rate

11 Mbs

Radio Propagation Model

Direct Sequence

AP Beacon Interval

0.02 Sec

Network Interface Type

Wireless Physical Layer

Buffer Size

102400000

Link Layer Type

Data Link Layer

Large Packet Processing

Fragment

Packet Reception Power Threshold

-95

Transmit Power

0.030

Wireless LAN

IEEE 802.11e capable

HCF for QoS support

Promoted.

Table 3.1 Wireless LAN Parameters

Parameters

Value

Hello Interval

2 Sec

TC Interval

5sec

Neighbor Hold Time

6 Sec

Topology Hold Time

15 Sec

Duplicate Message Hold Time

30 Sec

Willingness

Willingness Always

Addressing Mode

IPv4

Table 3.2 OLSR Parameters

Parameters

Value

Route Discovery Parameter

Gratuitous Reply

Active Route Timeout

30 Seconds

Hello Interval

uniform (10,10.1)

Allowed Hello Loss

10

TTL Parameter

2

Table 3.3 AODV Parameters

Parameters

Value

Beacon Periods

3 sec

Max Beacon Timer

9 sec

Max Tries

3 Attempts

Table 3.4 TORA Parameters

Figure 3.1 illustrates the OPNET simulation environment with a network size of 30 nodes. The network area used is 700 square meters. The objects in the environment are nodes, mobility, application, profile. The node objects are labelled according to the number of nodes present in the network. FTP Server is (destination) configured to support and service FTP traffics. Mobile Node 20, like other nodes apart from FTP Server, is configured to generate FTP traffic randomly, with the ability to route received packets to the destination. All nodes, including the destination node, are configured to use the same routing protocol. The mobility configuration object is used to configure the node speed.

Figure 3.1: Optimized Link State Routing Protocol Scenario

The application configuration object is used in configuring the types of application used, and the packet length. The profile application object is used to group applications configured in the application object into a profile. For example; an FTP profile is the profile created in the profile object and configured to support FTP application created in the application object. The FTP profile is then configured in all nodes except the destination node. This will enable nodes to generate traffics. The Rx group configuration object enables nodes to move within the 700 square meter area allocated. Traffics generated from any node that is outside the range will be discarded. The experiment is duplicated and routing protocols are changed. This is repeated for the remaining three protocols. All four experiments, each configured with a different routing protocol, are placed together in a scenario.

3.4 Summary

In this chapter a detailed experimental designs and parameters used are presented. The results gained from the experiments are investigated properly through proper validation and verification. In Chapter 4 evaluation and analysis of the findings are provided on the basis of performance metrics such as throughput, end to end delay and routing load.

Chapter 4

Results and Comparative Analysis

In this chapter, analysis of results from experiment is provided. The section 4.1 represents results from scenario and comparative analysis. Analysis is performed on the performance metrics throughput, end to end delay, routing load and media access delays. Global statistics for the entire network are collected and presented average values in the report. Section 4.2 represents the summary of chapter.

4.1 Experimental results

Throughput:

Throughput which is the number of routing packets received successfully by each routing protocol is shown in figure 4.1. When comparing the routing throughput packets received by each of the protocols, OLSR has the high throughput. Throughput is a measure of effectiveness of a routing protocol. OLSR receives about 3,500,000 routing packets at start of simulation time, then start to drop down continiously till the end of smiulation receiving around 1,000,000 data packets.

Throughput.JPG

Figure 4.1: Throughput

End to End Delay:

Figure 4.2 shows that OLSR has lowest steady end to end delays which are about 0.003 seconds. Further on, the end to end delay start to rise and fall abruptly in AODV and TORA therefore ends up in less end to end delays in AODV as compare to TORA that is around on average 0.06 second TORA have higher delays because of network congestion. As created loop where the number of routing packets sent caused MAC layer collisions, and data, Hello and ACK packets were lost that resulted in assuming that links to neighbors was broken by IMEP. Therefore, TORA reacted to these link failures by sending more UPDATEs, in turn that created more congestion as failure to receive an ACK from retransmitted UPDATEs was considered as link failure indication. Overall, OLSR has lowest end to end delays with high throughput.

Delay.JPG

Figure 4.2: End to End Delay

Media Access Details:

Figure 4.3 shows media access delay which is very important for multimedia and real time traffic; furthermore it is vital for any application where data is processed online. Media access delays are low for OLSR that is around 0.05 second. However, the media access delay for AODV and TORA fluctuates more frequently but TORA fluctuates more frequently above and below its mean while AODV mainly around its mean, thus in both case fluctuation in TORA is higher and more frequent as compared to OLSR that remains steady to 0.01 second after 150 seconds of time over 900 seconds of simulation time.

Media Access Delay.JPG

Figure 4.3: Media Access Delay

Routing Load:

Figure 4.4 shows routing load which is very significant to show routing load over communications links. It is observed that the average routing load for OLSR is 3,000,000 bits per seconds. OLSR protocol shows increase in throughput even when the routing load is increasing over network.Whereas AODV have the highest routing load at the start of simulation which is 3,100,000 bits per second due to heavy traffic load. Routing load for TORA fluctuates more frequently, but TORA experiences less routing load as compare to AODV.With the exception of OLSR, AODV and TORA protocols show decreased quality of service due to the increase in routing load over the network.

Load.JPG

Figure 4.4: Routing Load

4.2 Summary

This chapter presented the simulation experiment results of a mobile ad hoc network with nodes size 30 and heavy traffic load. The results obtained show that mobility is one of the contributing factors affecting the routing protocol's performance. Network size is the other factor that also plays an important role in the overall performance. The last factor looked at is the traffic load. In the presence of node mobility routing protocols have mixed reactions.

Chapter 5

Summary and Conclusions

The mobile nodes mobility management is key area since mobility causes route change and frequent changes in network topology, therefore effective routing has to be performed immediately. This thesis makes contributions in two areas. Firstly, a comparison of performance of reactive ad hoc on demand distance vector protocol, proactive, optimized link state routing protocol and hybrid temporary ordered routing algorithm protocol in mobile ad hoc networks under ftp traffic is done. Secondly, comprehensive results of throughput, media access delay, end to end delay and routing load over mobile ad hoc networks of thirty mobile nodes moving about and communicating with each other have been presented. The simulation results were presented for a range of node mobility at varying time.

OLSR performs quite predictably, delivering virtually most data packets at node mobility. In [8] also shows that OLSR shows the best performance in terms of end-to-end delay. Since the network was unable to handle all of the traffic generated by the routing protocol and a significant fraction of data packets were dropped. As well as in [9] shows that the relative performance of TORA was decisively dependent on the network size, and average rate of topological changes; TORA can perform well in small network size but TORA’s performance decreases when network size increases to 30 nodes. On the other hand, AODV performed better than TORA in most performance metrics with response to frequent topology changes. Finally, the overall performance of OLSR was very good when mobile nodes movement was changing over varying time. OLSR has high control traffic as compared to TORA as it searches for routes to destination more frequently.

Despite the other routing protocols, OLSR protocol showed increase in throughput even when the routing load was increased. We have analyzed that all routing protocol successfully delivers data when subjected to different network stresses and topology changes. Moreover, mathematical analysis and simulation results both show that optimized link state routing protocol, from proactive protocol category, is a very effective, efficient route discovery protocol for MANETs.