Mobile adhoc network routing protocols

Mobile Ad Hoc Network Routing Protocols

CHAPTER 1

INTRODUCTION

Wireless communication is an emerging and upcoming technology that will allow users to

access information and services electronically, irrespective of their geographic location.

There are solutions to these demands, one being wireless local area network (based on IEEE

802.11 standard). However, there is increasing demand for connectivity in situations/places

where there is no base station / infrastructure available. This is where ad hoc network came

into existence. Wireless networks can be classified into infrastructure networks and

infrastructure less networks or mobile ad hoc networks (MANETs). MANETs are

autonomously self-organized and self-configuring networks without infrastructure support. In

such networks, since node mobility is very high the network may experiences frequent and

unpredictable topology changes. Mobility and the absence of any fixed infrastructure make

MANETs very attractive for time-critical applications. Ad hoc network applications include

students using laptop to participate in an interactive lecture, business associates sharing in

Recently, Mobile Ad Hoc networks became a hot research topic among researchers due to

theirflexibility and independence of network infrastructures such as base stations. The

infrastructure less and the dynamic nature of these networks demand new set of networking

strategies to be implemented in order to provide efficient end-to-end communication.

MANETs can be deployed quickly at a very low cost and can be easily managed. In the

future, there is no doubt that we will have more and more ad-hoc networks, in which routing

is one of the critical issue. Need of a routing algorithm arises whenever a packet needs to be

transmitted to a node via number of different nodes. Several routing protocols exist for wired

networks, which can be classified as using either the distance vector or the link-state

algorithm. These algorithms were designed for use in wired networks where topology

changes are infrequent. They are also computation intensive, making them difficult to use

with limited resources. Due to these problems, new routing algorithms are designed keeping

in mind the characteristics of MANETs. An ad-hoc routing protocol must be able to decide

the best path between the nodes having unidirectional links, minimize the routing overhead to

enable proper routing, minimize the time required to converge after the topology changes and

maximize the bandwidth utilization. Therefore, developing support for routing is one of the

key research areas in MANETs.Until now, many researchers performed valuable research

with reference to routing in MANETs. This article is the first to present a qualitative

1Dept of ECE,SJBIT,Bangalore


comparison between the three typical representatives of routing protocols designed for

MANETs- DSDV, DSR & AODV. The rest of the article discusses the related work with a

focus on comparative study of the routing protocols and presents the classification of existing

routing protocols. Working of some of these protocols is described with a glimpse of their

advantages and limitations. It presents a comparative study of these protocols.

In Link State routing algorithm, each node periodically notifies its current status of links to

all routers in the network. Whenever a link state change occurs, the respective notifications

will be flooded throughout the whole network. After receiving the notifications, all routers re-

compute their routes according to the fresh topology information. In this way, a router gets to

know at least a partial picture of the whole network. In Link State routing, different metrics

can be chosen, such like number of hops, link speed and traffic congestion. Shortest (or

lowest cost) paths are calculated using Dijkstra’s algorithm. Routing Information Protocol

(RIP) is an Internet routing protocol based on Link State routing algorithm.

In wired networks, Distance Vector and Link State routing algorithms perform well because

of the predictable network properties, such as static link quality and network topology.

However, the dynamic features of mobile ad hoc networks deteriorate their effectiveness. In

mobile ad hoc networks, when using a Distance Vector routing or Link State based routing

protocol designed for wired networks, frequent topology changes will greatly increase the

control overhead. Without remedy, the overhead may overuse scarce bandwidth of mobile ad

hoc networks. Additionally, Distance Vector and Link State routing algorithms will cause

routing information inconsistency and route loops when used for dynamic networks.

As in wired networks, multicast is also appealing for mobile ad hoc networks. Multicast is an

appropriate communication scheme for many mobile applications and can save bandwidth

resource of wireless channels. Additionally, the inherent broadcast property of wireless

channels can be exploited to improve multicast performance in mobile ad hoc networks.

Compared to unicast routing schemes, designing multicast routing protocols for mobile ad

hoc networks is more difficult. The node mobility makes keeping track of the multicast group

membership more complicated and expensive than in wired networks. Also, a distribution

tree suffers from frequent reconstruction because of node movements. Therefore, multicast

routing schemes for mobile ad hoc networks must include mechanisms to cope with the

difficulties incurred by node mobility and topology changes.



FIG 1.1-WIRELESS COMMUNICATION

Ad Hoc Networks are useful in areas that have no fixed infrastructure and hence need

alternative ways to deliver services. Ad Hoc Networks work by having mobile devices

connect to each other in the transmission range through automatic configuration, i.e., setting

up an ad hoc network that is very flexible. In other words there is no intervention of any

controller that goes ahead and gathers data from all nodes and organizes it. All data gathering

and cross-node data transfer is taken care of by the nodes themselves.

Ad Hoc Networks are a major goal towards the evolution of 4G (Fourth generation) devices.

In the nodes of the Ad Hoc Networks, computing power and network connectivity are

embedded in virtually every device to bring computation to users, no matter where they are,

or under what circumstances they work. These devices personalize themselves to find the

information or software they need. The strife is to make use of alltechnologies available

without making any major change to the user’s behaviour. There is also work going on to

make the seamless integration of various networks possible, i.e., integration of LAN, WAN,

PAN and Ad Hoc Networks. But there is still a lot of work to be done to make this

completely possible. Node mobility in an ad hoc network causes frequent changes of the

network topology.



CHAPTER 2

LITERATURE SURVEY

2.1 ADVANTAGES OF AD HOC NETWORKS

The major advantage of the Ad Hoc Networks is that it does not need any base station

as is required in regular mobile networks. They can form a network in any place as required

immediately which make them indispensable in battlefield and disaster relief situations. They

are useful in areas that have no fixed network for internet coverage. Here they can be used to

provide coverage. They can be used in areas where the available network has been destroyed.

2.2 ISSUES FACED BY AD HOC NETWORKS

Security is a very major concern in the development of Ad Hoc Networks. The

boundaries of the network are not well defined and hence it is possible for any node to go out

of the network. It is also possible for an Ad Hoc Network having a large number of nodes to

split into two networks. It is less reliable than wired media due to the inherent problem faced

by any wireless network.

Due to the formation of Ad Hoc Networks by various devices that need not be having the

same capacity it is possible that each device may have different capacity, functionality and

protocols. Hence it is necessary to find a solution where all there varied devices can operate

together. They also have asymmetric propagation metrics. Capacity constraints faced by these

networks in the form of transmission range, wireless bandwidth is another concern.

This is taken care of to an extent by the use of Spread Spectrum techniques. Errors and

breakdown could also happen in these networks and it is imperative to have a solution or a

backup plan for these exigencies. Ad Hoc Networks also face a problem called the Hidden-

terminal and exposed-terminal phenomena.

In Hidden terminal situation as shown in figure 2.1, A and C are outside the transmission

range of each other and cannot detect each other’s transmissions, but B is in the transmission

range of both. As shown below a collision may occur, for example, when the station A and

station C start transmitting towards the same receiver, station B. This should be avoided.



Fig 2.1: Hidden Terminal Situation

In Exposed terminal situation as shown in figure 2.2, A transmission range covers B and C.

Hence when A transmits to B, C thinks that it cannot transmit when actually it could transmit

to D. This is a waste of resource which should also be avoided.

Fig 2.2: Exposed station Problem

Route changes will occur due to router mobility, i.e., as the node themselves act as routers

and certain nodes can leave the network in between.

Energy consumption and saving is a major are of interest. Advances in battery technology

have not been at par with the development of Ad Hoc technology. Most existing solutions for

saving energy in ad hoc networks revolve around the reduction of power used by the device.

At the MAC level and above, this is often done by selectively sending the device into a sleep

mode, or by using a transmitter with variable output power (and proportionate input power

draw) and selecting routes that require many short hops, instead of a few longer hops.

Beaconing is used by the nodes to let the other nodes know of its presence. The beaconing

interval has to be short enough to let the other nodes know that the node is in the network yet

long enough so as to save power.



CHAPTER 3

3.1 DESIGN AND IMPLEMENTATION

A number of routing protocols have been proposed and implemented for MANETs in

order to enhance the bandwidth utilization, minimum energy consumption, higher

throughputs, less overheads per packet, and others. Different routing protocols have used

different metrics to determine an optimal path between the sender and the recipient. All these

protocols have theirown advantages and disadvantages.

Any MANET routing protocol exhibits two types of properties:

• Qualitative such as loop freedom, security, demand based routing, distributed

operation,multi-path routing etc.

• Quantitative such as throughput, delay, route discovery time, packets delivery ratio,

jitter etc.

3.2 CLASSIFICATION OF ROUTING PROTOCOLS

The inadequate and limited resources in MANETs have made designing of an

efficient and reliable routing strategy a very challenging task. An intelligent routing

algorithm is required toefficiently use these limited resources while at the same time being

adaptable to the changing network conditions such as network size, traffic density, nodes

mobility, network topology and broken routes. Numerous routing protocols have been

proposed and developed for ad hoc networks. Such protocols must deal with the limited

resources available with these networks, which include high power consumption, low

bandwidth and high mobility. Existing routing protocols can be classified in many ways, but

most of these are done depending on routing strategy and network structure. According to the

routing strategy, routing protocols can be categorized as Table-driven, On-demand driven and

Hybrid while depending on the network structure they are classified as flat routing,

hierarchical routing andgeographic position assisted routing.



3.1 MANET ROUTING PROTOCOL

3.2.1 Table-driven Routing Protocols (Proactive)

Proactive protocols are also known as “table-driven” routing protocols. In this

protocol, each and every node maintains complete information about the network topology by

continuouslyevaluating routes to all the nodes. Hence, they maintain consistent and up-to-

date routing information. These protocols are known as proactive since they maintain the

routing before it is needed. Each and every node in the network maintains routing

information about how to reach every other node in the network. The route information in

proactive routing is maintained in the routing tables and is updated as and when the network

topology changes. This causes more overhead in the routing table leading to consumption of

more bandwidth. There are various existing proactive routing protocols. The areas in which

they differ are the number of necessary routing tables and the methods by which changes in

the network topology are broadcast. Some of the existing proactive protocols are Destination-

Sequenced Distance Vector (DSDV), Global State Routing (GSR), and Fisheye State Routing

(FSR).

3.2.2 On-demand Routing Protocols (Reactive)

A different approach from table-driven routing is on-demand routing.In this protocol

route is discovered whenever it is needed Nodes initiate route discovery on demand basis.

Source node sees its route cache for the available route from source to destination if the route

is not available then it initiates route discovery process. The on- demand routing protocols

have two major components.



Route discovery: In this phase source node initiates route discovery on demand basis.

Source nodes consults its route cache for the available route from source to destination

otherwise if the route is not present it initiates route discovery. The source node, in the

packet, includes the destination address of the node as well address of the intermediate nodes

to the destination.

Route maintenance: Due to dynamic topology of the network cases of the route failure

between the nodes arises due to link breakage etc., so route maintenance is done. Reactive

protocols have acknowledgement mechanism due to which route maintenance is possible

Reactive protocols add latency to the network due to the route discovery mechanism. Each

intermediate node involved in the route discovery process adds latency. These protocols

decrease the routing overhead but at the cost of increased latency in the network. Hence these

protocols are suitable in the situations where low routing overhead is required. There are

various well known reactive routing protocols present in MANET for example DSR, AODV,

TORA and LMR.

In this approach, a routing path is discovered only when the need arises. These are

called reactive since it is not necessary to maintain routing information at the nodes if there is

no communication. When needed, a route discovery operation in turn invokes a route-

determination procedure. The discovery procedure terminates either when a route has been

found or no route available after examination of all the route permutations. The primary

advantage of reactive routing is that the wireless medium is not subject to the routing

overhead for the routes that may never be used. Although reactive protocols do not have the

fixed overhead (required in maintaining continuous updated routing tables), they may have

significant route discovery delay. Some of the existing reactive protocols are Ad hoc On-

Demand Distance Vector (AODV), Dynamic Source Routing (DSR), Associativity Based

Routing (ABR), Signal stability based adaptive Routing (SSR).



TABLE 3.1 PARAMETRIC COMPARISION

3.3 ROUTING PROTOCOLS

3.3.1 Destination-Sequence Distance Vector (DSDV) routing protocol

The DSDV protocol described in is a table-driven protocol based on the classical Bellman-

Ford algorithm. Each node in the network maintains a routing table that contains a list of all

the possible destinations within the network. Each entry in the table contains the destination

address, the shortest metric to that destination in terms if hop count, the next hop address and

a sequence number generated by the destination node. The route with the greater sequence

numbers is preferred. Sequence numbers are used to distinguish stale routes from fresh ones,

thereby avoiding the routing loops. Routing table updates are periodically transmitted

throughout the network in order to maintain updated information in the table and its



consistency. The route updates can be either time-driven or event-driven. Every node

periodically transmits routing information to its immediate neighbours. Instead of

transmitting the entire routing table, a node can also propagate its changed routing table since

the last update. To reduce the large amount of network traffic that such updates can create,

route updates can employ two possible types of packets. The first is known as a full dump.

This type of packet carries complete routing information and can require multiple network

protocol data units (NPDUs). During periods of infrequent movement, these packets are

transmitted occasionally. Smaller incremental packets are used to transmit only that

information which has changed since the last full dump.

FIG 3.2 ROUTING

Advantages:

Guarantees loop free paths.

Sequence number ensures the freshness of routing information available in the routing

table.

DSDV avoids extra traffic by using incremental updates instead of full dump updates.

DSDV maintains only the best path or shortest path to every destination. Hence,

amount of space in routing table is reduced.



Limitations:

Large amount of overhead due to the requirement of periodic update messages, which

makes them un-effective in large networks.

It doesn’t support multi path routing.

Wastage of bandwidth due to needless advertising of routing information even if there

is no change in the network topology.

3.3.2 Wireless Routing Protocol (WRP)

WRP belongs to the general class of path-finding algorithms defined as the set of

distributed shortest path algorithms that calculate the paths using information regarding the

length and second-to-last hop of the shortest path to eachdestination. WRP reduces the

number of cases in which a temporary routing loop can occur. For the purpose of routing,

each node maintains four things: 1. A distance table 2. A routing table 3.A link-cost table 4.

A message retransmission list (MRL). WRP uses periodic update message transmissions to

the neighbours of a node. The nodes in the response list of update message (which is formed

using MRL) should send acknowledgments. If there is no change from the last update, the

nodes in the response list should send an idle Hello message to ensure connectivity. A node

can decide whether to update its routing table after receiving an update message from a

neighbour and always it looks for a better path using the new information. If a node gets a

better path, it relays back that information to the original nodes so that they can update their

tables. After receiving the acknowledgment, the original node updates its MRL. Thus, each

time the consistency of the routing information is checked by each node in this protocol,

which helps to eliminate routing loops and always tries to find out the best solution for

routing in the network.



FIG 3.3 WIRELESS ROUTING PROTOCOL (WRP)

3.3.3Cluster Gateway Switch Routing Protocol (CGSR)

CGSR considers a clustered mobile wireless network instead of a „„flat‟‟ network.

For structuring the network into separate but interrelated groups, cluster heads are elected

using a cluster head selection algorithm. By forming several clusters, this protocol achieves a

distributed processing mechanism in the network. However, one drawback of this protocol is

that, frequent change or selection of cluster heads might be resource hungry and it might

affect the routing performance. CGSR uses DSDV protocol as the underlying routing scheme

and, hence, it has the same overhead as DSDV. However, it modifies DSDV by using a

hierarchical cluster-head-to-gateway routing approach to route traffic from source to

destination. Gateway nodes are nodes that are within the communication ranges of two or

more cluster heads. A packet sent by a node is first sent to its cluster head, and then the

packet is sent from the cluster head to a gateway to another cluster head, and so on until the

cluster head of the destination node is reached. The packet is then transmitted to the

destination from its own cluster head destination. WRP reduces the number of cases in which

a temporary routing loop can occur. For the purpose of routing, each node maintains four

things: 1. A distance table 2. A routing table 3.A link-cost table 4. A message retransmission



list (MRL). WRP uses periodic update message transmissions to the neighbours of a node.

The nodes in the response list of update message (which is formed using MRL) should send

acknowledgments. If there is no change from the last update, the nodes in the response list

should send an idle Hello message to ensure connectivity. A node can decide whether to

update its routing table after receiving an update message from a neighbour and always it

looks for a better path using the new information. If a node gets a better path, it relays back

that information to the original nodes so that they can update their tables. After receiving the

acknowledgment, the original node updates its MRL. Thus, each time the consistency of the

routing information is checked by each node in this protocol, which helps to eliminate routing

loops and always tries to find out the best solution for routing in the network.

FIG 3.4- Cluster Gateway Switch Routing Protocol (CGSR)

3.3.4 Dynamic Source Routing (DSR)

DSR, a reactive unicast protocol is based on source routing algorithm. In source

routing, each data packet contains complete routing information to reach its destination.

There are two major phases in DSR: route discovery and route maintenance.

When a source node wants to send a packet, it first searches for an entry in its route cache. If

the route is available, the source node includes the routing information inside the data packet

before sending it. Otherwise, the source node initiates a route discovery operation by

broadcasting route request (RREQ) packets. Each RREQ packet is uniquely identified by the

source address and the request id (a unique number). On receipt it the RREQ packet, an

intermediary node checks its route cache. If the node doesn’t have routing information for the

requested destination, it appends its own address to the route record field of the route request

packet. Then, the request packet is forwarded to its neighbours. A node processes route



request packets only if it has not seen the packet before and its address is not presented in the

route record field. If the route request packet reaches the destination or an intermediate node

has routing information to the destination, a route reply packet is generated. When the route

reply packet is generated by the destination, it comprises addresses of nodes that have been

traversed by the route request packet. Otherwise, theroute reply packet comprises the

addresses of nodes the route request packet has traversedconcatenated with the route in the

intermediate node’s route cache.

FIG 3.5- Dynamic Source Routing (DSR)

Advantages:

Reduction of route discovery overheads with the use of route cache.

Supports multi path routing.

Does not require any periodic beaconing or hello message exchanges.

Limitations:

DSR is not very effective in large networks, as the amount of overhead carried in the

Packet will continue to increase as the network diameter increases.

Because of source routing, packet size keeps on increasing with route length.

Being a reactive protocol, DSR suffers from high route discovery latency.



3.3.5 Ad-Hoc On-Demand Distance Vector (AODV) Routing protocol

As a reactive protocol, AODV only needs to maintain the routing information about

the active paths. Every node keeps a next-hop routing table, which includes only those

destinations to which it currently has a route. A route entry in the routing table expires if it

has not been used for a pre-specified expiration time. Moreover, AODV adapts the

destination sequence number technique used by DSDV.

In AODV, when a source node wants to send packets to the destination, it initiates a

routediscovery operation if no route is available. In the route discovery operation, the

sourcebroadcasts route request (RREQ) packets. A RREQ includes addresses of the source

and the destination, the broadcast ID, which is used as its identifier, the last seen sequence

number of the destination as well as the source node’s sequence number. Sequence numbers

ensure loop-free and up-to-date routes. In AODV, each node maintains a cache to keep track

of RREQs it has received. The cache also stores the path back to each RREQ originator.

When the destination or a node that has a route to the destination receives the RREQ, it

checks the destination sequence numbers it currently knows and the one specified in the

RREQ. In response to RREQ, a route reply (RREP) packet is created and forwarded back to

the source only if the destination sequence number is equal to or greater than the one

specified in RREQ. This in turn guarantees the freshness of the routing information.

Upon receiving the RREP packet, each intermediate node along the route updates its next-hop

table entries with respect to the destination node. The redundant RREP packets or RREP

packets with lower destination sequence number will be dropped.

If a link break occurs in an active route, the node broadcasts a route error (RERR) packet to

its neighbours, which in turn propagates the RERR packet towards the source node. Then, the

affected source can re-initiate a route discovery operation to find a route to the desired

destination.



FIG 3.6- Ad-Hoc on-Demand Distance Vector (AODV) Routing protocol

Advantages:

AODV can handle highly dynamic MANETs.

Less amount of storage space as compared to other reactive routing protocols, since

routinginformation which is not in use expires after a pre-specified expiration time.

Supports multicasting.

Limitations:

AODV lacks an efficient route maintenance technique. The routing information is

alwaysobtained on demand.

Similar to DSR, AODV also suffers from high route discovery latency.

More number of control overheads due to many route reply messages for single

routerequest.

3.3.6 THE TEMPORALLY ORDERED ROUTING

ALGORITHM(TORA)

The Temporally Ordered Routing Algorithm (TORA) [18,19] is a reactive routing

algorithm based on the concept of link reversal. TORA improves the partial link reversal

method by detecting partitions and stopping non-productive link reversals. TORA can be

used for highly dynamic mobile ad hoc networks.

In TORA, the network topology is regarded as a directed graph. A Directional Acyclical

Graph (DAG) is accomplished for the network by assigning each node I a height metric hi. A

link directional from i to j means hi >hj. In TORA, the height of a node is defined as a

quintuple, which includes the A Survey of Mobile Ad Hoc Network Routing Protocols



logical time of a link failure, the unique ID of the node that defines the new reference level, a

reflection indicator bit, a propagation ordering parameter and an unique ID of the node. The

first three elements collectively represent the reference level. The last two values define an

offset with respect to the reference level. Like water flowing, a packet goes from upstream to

downstream according the height difference between nodes. DAG provides TORA the

capability that many nodes can send packets to a given destination and guarantees that all

routes are loop-free.

TORA has three basic operations: route creation, route maintenance and route erasure. A

route creation operation starts with setting the height (propagation ordering parameter in the

quintuple) of the destination to 0 and heights of all other nodes to NULL (i.e., undefined).

The source broadcasts a QRY packet containing the destination’s ID. A node with a non-

NULL height responds by broadcasting a UPD packet containing the height of its own. On

receiving a UPD packet, a node sets its height to one more than that of the UPD generator. A

node with higher height is considered as upstream and the node with lower height is

considered as downstream. In this way, a directed acyclic graph is constructed from the

source to the destination and multiple paths route may exist.

The DAG in TORA may be disconnected because of node mobility. So, route maintenance

operation is an important part of TORA. TORA has the unique feature that control messages

are localized into a small set of nodes near the occurrence of topology changes. After a node

loses its last downstream link, it generates a new reference level and broadcasts the reference

to its neighbours. Therefore, links are reversed to reflect the topology change and adapt to the

new reference level. The erase operation in TORA floods CLR packets through the network

and erase invalid routes.

3.7 Comparison of DSR, AODV and TORA

As reactive routing protocols for mobile ad hoc networks, DSR, AODV and TORA are

proposed to reduce the control traffic overhead and improve scalability. In the appendix, their

main differences are listed.

DSR exploits source routing and routing information caching. A data packet in DSR carries

the routing information needed in its route record field. DSR uses flooding in the route

discovery phase. AODV adopts the similar route discovery mechanism used in DSR, but

stores the next hop routing information in the routing tables at nodes along active routes.



Therefore, AODV has less traffic overhead and is more scalable because of the size limitation

of route record field in DSR data packets.

Both DSR and TORA support unidirectional links and multiple routing paths, but AODV

doesn’t. In contrast to DSR and TORA, nodes using AODV periodically exchange hello

messages with their neighbours to monitor link disconnections. This incurs extra control

traffic overhead. In TORA, utilizing the "link reversal" algorithm, DAG constructs routing

paths from multiple sources to one destination and supports multiple routes and multicast

[37]. In AODV and DSR, a node notifies the source to re-initiate a new route discovery

operation when a routing path disconnection is detected. In TORA, a node re-constructs DAG

when it lost all downstream links. Both AODV and DSR use flooding to inform nodes that

are affected by a link failure. However, TORA localizes the effect in a set of node near the

occurrence of the link failure.

AODV uses sequence numbers to avoid formation of route loops. Because DSR is based on

source routing, a loop can be avoided by checking addresses in route record field of data

packets. In TORA, each node in an active route has a unique height and packets are

forwarded from a node with higher height to a lower one. So, a loop-free property can be

guaranteed in TORA. However, TORA has an extra requirement that all nodes must have

synchronized clocks. In TORA, oscillations may occur when coordinating nodes currently

execute the same operation.

Performances of DSDV, TORA, DSR and AODV are compared in based on simulation. The

simulation results showed that DSDV performs well when node mobility rates and speed of

movements are low. When the number of source nodes is large, the performance of TORA

decreases. As shown in [9], both AODV and DSR perform well for different simulation

scenarios. DSR outperforms AODV because it has less routing overhead when nodes have

high mobility. A simulation-based comparison of two reactive mobile ad hoc network routing

protocols, the AODV and DSR, is reported. The general result was that DSR performs better

than AODV when number of nodes is small, lower load and /or mobility, and AODV

outperforms DSR in more demanding situations.



3.3.7 THE FISHEYE STATE ROUTING (FSR)

The Fisheye State Routing (FSR) is a proactive unicast routing protocol based on

Link State routing algorithm with effectively reduced overhead to maintain network topology

information. As indicated in its name, FSR utilizes a function similar to a fish eye. The eyes

of fishes catch the pixels near the focal with high detail, and the detail decreases as the

distance from the focal point increases. Similar to fish eyes, FSR maintains the accurate

distance and path quality information about the immediate neighbouring nodes, and with the

progressive detail as the distance increase.

In Link State routing algorithm used for wired networks, link state updates are generated and

flooded through the network whenever a node detects a topology change. In FSR, however,

nodes exchange link state information only with the neighbouring nodes to maintain up-to-

date topology information. Link state updates are exchanged periodically in FSR, and each

node keeps a full topology map of the network. To reduce the size of link state update

messages, the key improvement in FSR is to use different update periods for different entries

in the routing table. Link state updates corresponding to the nodes within a smaller scope are

propagated with higher frequency.

Using different link state exchange frequencies for nodes with different distances, FSR has

better scalability in large networks than traditional Link State routing due to the decreasing

traffic overhead. Nevertheless, FSR guarantees the route computation accuracy because when

the destination is near, the topology information is more accurate is.

FIG 3.7-THE FISHEYE STATE ROUTING (FSR)



3.4 COMPARISION OF WRP, DSDV and FSR

Control traffic overhead and loop-free property are two important issues when

applying proactive routing to mobile ad hoc networks. The proactive routing protocols used

for wired networks normally have predictable control traffic overhead because topology of

wired networks change rarely and most routing updates are periodically propagated.

However, periodic routing information updates are not enough for mobile ad hoc routing

protocols. The proactive routing in mobile ad hoc networks needs mechanisms that

dynamically collect network topology changes and send routing updates in an event-triggered

style.

Although belonging to the same routing category for mobile ad hoc networks, WRP, DSDV

and FSR have distinct features. Both WRP and DSDV exploited event-triggered updates to

maintain up-to-date and consistent routing information for mobile nodes. In contrast to using

event-triggered updates, the updates in FSR are exchanged between neighbouring nodes and

the update the frequency is adjusted according to the nodes’ distance effect. In this way,

routing update overhead is reduced and the far-reaching effect of Link State routing is

restricted.

Different mechanisms are used in WRP, DSDV and FSR for loop-free guarantee. WPR

records the predecessor and the successor along a path in its routing table and introduces

consistence-checking mechanism. In this way, WRP avoids the forming of temporary route

loops with the trade-off that each node needs to maintain more information and execute more

operations. In DSDV, a destination sequence number is introduced to avoid route loops. FSR

is a modification of traditional Link State routing and its loop-free property is inherited from

Link State routing algorithm.

WRP, DSDV and FSR have the same time and communication complexity. Whereas WRP

has a large storage complexity compared to DSDV because more information is required in

WRP to guarantee reliable transmission and loop-free paths. Both periodic and triggered

updates are utilized in WRP and DSDV; therefore, their performance is tightly related with

the network size and node mobility pattern. As a Link State routing protocol, FSR has high

storage complexity, but it has potentiality to support multiple-path routing and QoS routing.



3.5 SECURITY ISSUES IN MANETS

Security is the major issue in wireless Ad Hoc Networks and actually ought to receive

a complete analysis of it than being presented as a part of the study on Ad Hoc Networks.

The use of wireless links renders an ad hoc network susceptible to link attacks ranging from

denial of service, passive eavesdropping to active impersonation, message replay, and

message distortion. Eavesdropping might give an adversary access to secret information,

violating confidentiality. Active attacks might allow the adversary to delete messages, to

inject erroneous messages, to modify messages, and to impersonate a node, thus violating

availability, integrity, authentication, and non-repudiation. Nodes, roaming in a hostile

environment (e.g., a battlefield) with relatively poor physical protection, have non-negligible

probability of being compromised. Therefore, we should not only consider malicious attacks

from outside a network, but also take into account the attacks launched from within the

network by compromised nodes. Therefore, to achieve high survivability, ad hoc networks

should have a distributed architecture with no central entities. Introducing any central entity

into our security solution could lead to significant vulnerability; that is, if this centralized

entity is compromised, then the entire network is subverted.An ad hoc network is dynamic

because of frequent changes in both its topology and its membership (i.e., nodes frequently

join and leave the network). Trust relationship among nodes also changes, for example, when

certain nodes are detected as being compromised.

Unlike other wireless mobile networks, such as mobile IP, nodes in an ad hoc network may

dynamically become affiliated with administrative domains. Any security solution with a

static configuration would not suffice. It is desirable for our security mechanisms to adapt on-

the-fly to these changes. Finally, an ad hoc network may consist of hundreds or even

thousands of nodes. Security mechanisms should be scalable to handle such a large network.

The denial of a service can be caused by such legitimate ways as a radio jamming or battery

exhaustion. An attacker can cause a radio jamming by jamming a wider frequency band and

in that way using more power. The latter can be of real threat, because once a battery runs out

the attacker can walk away and leave the victim disabled. This kind of technique is called the

sleep deprivation torture attack. Symmetric key cryptography is used to provide authenticity

and integrity. Integrity means that no node has been maliciously changed. The devices

themselves should be able to detect security breaches and plug them.



CHAPTER 4

RESULT

Graph of average end to end delay versus offered load

FIG 4.1 GRAPH OF AVGERAGE END TO END DELAY VERSUS OFFERED LOAD

FIG 4.2-SIMULATION OF AD HEC NETWORK ENVIRONMENT



CONCLUSION

This thesis focus on various key issues of MANETs such as impact of scalability on

differentcategory of routing protocols to provide QoS-aware routing support, handling of

cachecoherence problem that arises in routing protocols due to mobility and performance

analysisof routing protocols to provide VOIP support over Hybrid MANETs. Our research

work alsocontributes towards providing trust conscious secure route data communication

support andQoS in term of bandwidth, security for soft real time processing services.

The impact of scalability on various QoS parameters have been analysed by varyingnumber

of nodes, packet size, time interval between packets and mobility.As observed from overall

results and discussion on different scenarios, the AODV protocol isQoS-aware routing

protocol under the impact of scalability. With the increase in networksize, the performance of

DSR decreases due to increase in packet-header overhead size asdata and control packets in

DSR typically carry complete route information. At the same time the performance of DSDV

is not affected by under such parameters and its overallperformance is less than AODV and

DSR protocol. Multimedia real-time session services, such as voice and videoconferencing

with qualityof service support is challenging task over Hybrid MANETs.



FUTURE SCOPE

This thesis improves the understanding of ad hoc networks and advances the state-of

the art through its contributions. Its investigation has revealed areas in ad hoc network where

much work remains to be done. Some possible future directions are identified in this thesis

and are presented as: The work presented in this thesis has only explored the impact of

scalability for QoSawarerouting on reactive and proactive protocols. The impact of scalability

on QoSparameters for other category of protocols such as multicasting and hybrid is also of

great concern. A simulation based performance study will be conducted to evaluate the

proposed dynamic coherence check scheme in terms of cache hit ratio and average query

latency by it with other caching strategies.

The work presented in this thesis dynamically increases the trust directly or through proxy

nodes. In further work, in order to make sure that the node does not perform misbehavior, we

will add the mechanism that computes the direct trust of a node. The accuracy and sincerity

of the immediate neighbouring nodes is measured by observing their contribution to the

packet forwarding so that no node perform selfishness during data transfer from sender to

receiver node.

Wireless networks could be highly heterogeneous. The heterogeneity could be in terms ofthe

roles of the nodes, their inherent capability and security. Heterogeneity implies that not all

nodes or their contents can be treated equally when it comes to trust evaluations. Thus, there

is need to incorporate a layer wise trust evaluation function, when investigating the trust of

heterogeneous nodes.Further on, we will evaluate the performance of our proposed model of

secure QoSenabled on-demand link-state multipath protocol in real world scenario. Beside

this, in future, we will incorporate route break prediction in our proposed QoS-aware routing

protocol. A route break prediction scheme could aid in the quick response of the protocol to

route breaks.



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Mobile adhoc network routing protocols

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