Mobile adhoc network routing protocols
Content
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
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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 recompute 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.
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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.
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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 Hiddenterminal 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.
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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
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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.
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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.
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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-todate 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 DestinationSequenced 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
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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 routedetermination 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 OnDemand Distance Vector (AODV), Dynamic Source Routing (DSR), Associativity Based
Routing (ABR), Signal stability based adaptive Routing (SSR).
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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 BellmanFord 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
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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:
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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.
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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
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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
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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.
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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.
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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
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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 nonNULL 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.
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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.
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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-todate 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)
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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.
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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 onthe-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.
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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
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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.
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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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REFERENCES:
[1] MehranAbolhasan, TadeuszWysocki, and ErykDutkiewicz. “A review of routing protocols
formobile ad hoc networks”. Technical report, Telecommunication and Information Research
Institute,University of Wollongong, Wollongong, NSW 2522; Motorola Australia Research
Centre, 12 LordSt., Botany, NSW 2525, Australia, 2003.
[2] David B. Johnson and David A. Maltz. “Dynamic source routing in ad hoc wireless
networks”.Technical report, Carnegie Mellon University, 1996.
[3] J. Broch, David B. Johnson, David A. Maltz, “A performance comparison of multi-hop
wireless adhoc network routing protocols”. Proc. MOBICOM, 1998, 85-97.
[4] Charles E. Perkins. Ad Hoc Networking. Addision Wesley, 2001.
[5] C. E. Perkins and P. Bhagwat. Highly dynamic Destination-Sequenced Distance-Vector
Routing(DSDV) for mobile computers, ACM Computer Communication Review, Vol. 24,
No.4, (ACMSIGCOMM’94) Oct. 1994, pp.234-244.
[6] Charles E. Perkins and Elizabeth M.Royer. “Ad-hoc on-demand distance vector routing”.
Technicalreport, Sun Micro Systems Laboratories, Advanced Development Group, USA.
[7] Elizabeth M. Royer and Chai-KeongToh. “A review of current routing protocols for ad
hoc mobilewireless networks”. Technical report, University of California and Georgia
Institute of Technology,USA, 1999.
[8] A. S. Tanenbaum, Computer Networks, 3rd ed., Ch. 5, Englewood Cliffs, NJ: Prentice
Hall, 1996, pp.357-58.
[9] R. Dube et al., "Signal Stability based Adaptive Routing (SA) for Ad- Hoc Mobile
Networks," PerS.Commun., Feb. 1997, pp. 36-45.
[10] C-K. Toh, "Associativity-Based Routing for Ad-Hoc Mobile Networks," Wireless Pers.
Commun.,vol. 4, no. 2, Mar. 1997, pp. 1-36.
[11] G. Pei, M. Gerla and T.-W. Chen, Fisheye State Routing in Mobile Ad Hoc Networks. In
Proceedingsof the 2000 ICDCS Workshops, Taipei, Taiwan, Apr. 2000, pp. D71-D78
International Journal of Ad hoc, Sensor & Ubiquitous Computing (IJASUC) Vol.3, No.2,
April 201231
[12] G. Pei, M. Gerla, and X. Hong, LANMAR: Landmark routing for large scale wireless ad
hocnetworks with group mobility. In Proceedings of the ACM Symposium on Mobile Ad
HocNetworking and Computing (MOBIHOC), pages 11-18, 2000.
[13] T.-W. Chen, M. Gerla, Global state routing: a new routing scheme for ad-hoc wireless
networks, in:Proceedings of the IEEE ICC, 1998.
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[14] V.D. Park, M.S. Corson, A highly adaptive distributed routing algorithm for mobile
wirelessnetworks, in: Proceedings of INFOCOM, April 1997.
[15] Krishna Ramachandran, Aodv-st, Technical report, University of California, Santa
Barbara, USA.http://www.cs.ucsb.edu/AODV/adofv.html.
[16] Mohammed Bouhorma, H.Bentaouit& A. Boudhir, “Performance Comparison of Ad
Hoc RouitngProtocols AODV & DSR”, IEEE 2009.[17] M.S. Corson and A. Ephremides, “A
distributed routing algorithm for Mobile Wireless Networks”, ACM/Baltzer Wireless
Networks J., vol. 1, no. 1, Feb. 1995, pp. 61-81.
ACM/Baltzer Wireless Networks J., vol. 1, no. 1, Feb. 1995, pp. 61-81.
[17] M.S. Corson and A. Ephremides, “A distributed routing algorithm for Mobile Wireless
Networks”, ACM/Baltzer Wireless Networks J., vol. 1, no. 1, Feb. 1995, pp. 61-81.
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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
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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 recompute 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.
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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.
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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 Hiddenterminal 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.
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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
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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.
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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.
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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-todate 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 DestinationSequenced 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
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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 routedetermination 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 OnDemand Distance Vector (AODV), Dynamic Source Routing (DSR), Associativity Based
Routing (ABR), Signal stability based adaptive Routing (SSR).
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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 BellmanFord 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
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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:
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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.
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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
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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
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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.
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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.
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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
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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 nonNULL 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.
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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.
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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-todate 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)
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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.
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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 onthe-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.
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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
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Mobile Ad Hoc Network Routing Protocols
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.
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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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