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Chapter-1

MOBILE AD-HOC NETWORKS

In the past few years, we have seen a rapid expansion in the field of mobile computing due to the

proliferation of inexpensive, widely available wireless devices. However, current devices,

applications and protocols are solely focused on cellular or wireless local area networks

(WLANs), not taking into account the great potential offered by mobile ad hoc networking.

A mobile ad hoc network is an autonomous collection of mobile devices (laptops, smart phones,

sensors, etc.) that communicate with each other over wireless links and cooperate in a distributed

manner in order to provide the necessary network functionality in the absence of a fixed

infrastructure. This type of network, operating as a stand-alone network or with one or multiple

points of attachment to cellular networks or the Internet, paves the way for numerous new and

exciting applications. Application scenarios include, but are not limited to: emergency and rescue

operations, conference or campus settings, car networks, personal networking, etc this paper

provides insight into the potential applications of ad hoc networks and discusses the

technological challenges that protocol designers and network developers are faced with. These

challenges include routing, service and resource discovery, Internet connectivity, billing and

security.

1.1Introduction:

The field of wireless and mobile communications has experienced an unprecedented growth

during the past decade. Current second-generation (2G) cellular systems have reached a high

penetration rate, enabling worldwide mobile connectivity. Mobile users can use their cellular

phone to check their email and browse the Internet. Recently, an increasing number of wireless


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local area network (LAN) hot spots are emerging, allowing travelers with portable computers to

surf the Internet from airports, railways, hotels and other public locations. Broadband Internet

access is driving wireless LAN solutions in the home for sharing access between computers. In

the meantime, 2G cellular networks are evolving to 3G, offering higher data rates, infotainment

and location-based or personalized services

However, all these networks are conventional wireless networks, conventional in the sense that

as prerequisites, a fixed network infrastructure with centralized administration is required for

their operation, potentially consuming a lot of time and money for set-up and maintenance.

Furthermore, an increasing number of devices such as laptops, personal digital assistants

(PDAs), pocket PCs, tablet PCs, smart phones, MP3 players, digital cameras, etc. are provided

with short-range wireless interfaces. In addition, these devices are getting smaller, cheaper, more

user friendly and more powerful. This evolution is driving a new alternative way for mobile

communication, in which mobile devices form a self-creating, self-organizing and self-

administering wireless network, called a mobile ad hoc network.

1.2 History of Ad Hoc Networks:

Opposed to infrastructure wireless networks, where each user directly communicates with anaccess point or base station, a mobile ad hoc network, or MANET, does not rely on a fixed

infrastructure for its operation (Figure 1).The network is an autonomous transitory association of

mobile nodes that communicate with each other over wireless links. Nodes that lie within each

others send range can communicate directly and are responsible for dynamically discovering

each other. In order to enable communication between nodes that are not directly within each

others send range, intermediate nodes act as routers that packets generated by other nodes to

their destination. These nodes are often energy-constrainedthat is, battery-powered devices

with a great diversity in their capabilities. Furthermore, devices are free to join or leave the

network and they may move randomly, possibly resulting in rapid and unpredictable topology

changes. In this energy-constrained, dynamic, distributed multi-hop environment, nodes need to

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organize themselves dynamically in order to provide the necessary network functionality in the

absence of fixed infrastructure or central administration. The specific characteristics and

complexities, which are summarized in Table 1, impose many design challenges to the network

protocols. In addition, these networks are faced with the traditional problems inherent to wireless

communications such as lower reliability than wired media, limited physical security, time-

varying channels, interference, etc.

Fig 1.1.: Cellular networks/mantes

Despite the many design constraints, mobile ad hoc networks offer numerous advantages. First

of all, this type of network is highly suited for use in situations where a fixed infrastructure is not

available, not trusted, too expensive or unreliable. Because of their self-creating, self-organizing

and self-administering capabilities, ad hoc networks can be rapidly deployed with minimum user

intervention. There is no need for detailed planning of base station installation or wiring.

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Table1.1: Ad- hoc n/w characteristics

Also, ad hoc networks do not need to operate in a stand-alone fashion, but can be attached to the

Internet, thereby integrating many different devices and making their services available to other

users. Furthermore, capacity, range and energy arguments promote their use in tandem with

existing cellular infrastructures as they can extend coverage and interconnectivity. As a

consequence, mobile ad hoc networks are expected to become an important part of the future 4G

architecture, which aims to provide pervasive computer environments that support users in

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accomplishing their tasks, accessing information and communicating anytime, anywhere and

from any device. Table 2 provides an overview of present and future MANET applications. The

concept of mobile ad hoc networking is not a new one and its origins can be traced back to the

DARPA Packet Radio Network project in 1972-73. Then, the advantages such as flexibility,

mobility, resilience and independence of fixed infrastructure, elicited immediate interest among

military, police and rescue agencies in the use of such networks under disorganized or hostile

environments.

For a longtime, ad hoc network research stayed in the realm of the military, and only in the

middle of 1990, with the advent of commercial radio technologies, did the wireless research

community become aware of the great potential and advantages of mobile ad hoc networks

outside the military domain, witnessed by the creation of the Mobile Ad Hoc Networking

working group within the IETF4.

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Table 1.2: mobile ad-hoc network applications.

Currently, mobile ad hoc network research is a very vibrant and active field and the efforts of theresearch community, together with current and future MANET enabling radio technologies,

which are summarized in Table 3, will certainly pave the way for commercially viable MANETs

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and their new and exciting applications, with some of these commercially oriented solutions

already starting to appear (for example Mesh Networks and SPAN works).

1.3 Technological Challenges:

As already stated, the specific characteristics of MANETs impose many challenges to network

protocol designs on all layers of the protocol stack5. The physical layer must deal with rapid

changes in link characteristics. The media access control (MAC) layer needs to allow fair

channel access, minimize packet collisions and deal with hidden and exposed terminals. At the

network layer, nodes need to cooperate to calculate paths The transport layer must be capable of

handling packet loss and delay characteristics that are very different from wired networks.

Applications should be able to handle possible disconnections and reconnections. Furthermore,

all network protocol developments need to integrate smoothly with traditional networks and take

into account possible security problems. In the following sections, technological challenges and

possible solutions related to unicast routing, resource and service discovery, addressing and

Internet connectivity, security and node cooperation are covered in more detail.

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Table 1.3: Mobile ad-hoc n/w enabling technologies.

1.4 Routing:

As mobile ad hoc networks are characterized by a multi-hop network topology that can changefrequently due to mobility, efficient routing protocols are needed to establish communication

paths between nodes, without causing excessive control traffic overhead or computational burden

on the power constrained devices6. A large number of solutions have already been proposed,

some of them being subject to standardization within the IETF. A number of proposed solutions

attempt to have an up-to-date route to all other nodes at all times. To this end, these protocols

exchange routing control information periodically and on topological changes. These protocols,

which are called proactive routing protocols, are typically modified versions of traditional link

state or distance vector routing protocols encountered in wired networks, adapted to the specific

requirements of the dynamic mobile ad hoc network environment. Most of the time, it is not

necessary to have an up-to-date route to all othernodes.

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Therefore, reactive routing protocols only set up routes to nodes they communicate with and

these routes are kept alive as long as they are needed. Combinations of proactive and Reactive

protocols where nearby routes (for example, maximum two hops) are kept up-to-date

proactively, while far-away routes are set up reactively, are also possible and fall in the category

of hybrid routing protocols. A completely different approach is taken by the location-based

routing protocols, where packet forwarding is based on the location of a nodes communication

partner.

Fig 1.2: Overview of existing unicast routing techniques.

Location information services provide nodes with the location of the others, so packets can be

forwarded in the direction of the destination. Fig. provides an overview in terms of routing table

content of the proposed solutions. It provides an extensive overview of routing protocol research.

Simulation studies have revealed that the performance of routing protocols in terms of

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throughput, packet loss, delay and control overhead strongly depends on the network conditions

such as traffic load, mobility, density and the number of nodes8. Ongoing research at Ghent

University therefore investigates the possibility of developing protocols capable of dynamically

adapting to the network.

Chapter -2

SERVICE AND RESOURCE DISCOVERY

MANET nodes may have little or no knowledge at all about the capabilities of, or services

offered by, each other. Therefore, service and resource discovery mechanisms, which allow

devices to automatically locate network services and to advertise their own capabilities to the rest

of the network, are an important aspect of self-configurable networks10. Possible services or

resources include storage, access to databases or files, printer, computing power, Internet access,

etc. Directory-less service and resource discovery mechanisms, in which nodes reactively request

services when needed and/or nodes proactively announce their services to others, seem an

attractive approach for infra structure less networks. The alternative scheme is directory-based

and involves directory agents where services are registered and service requests are handled.

This implies that this functionality should be statically or dynamically assigned to a subset of the

nodes and kept up-to-date. Existing directory-based service and resource discovery mechanisms

such as UPnP or Salutation are unable to deal with the dynamics in ad hoc networks.

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Fig 2.1: Logical overview of service and resource

Currently, no mature solution exists, but it is clear that the design of these protocols should be

done in close cooperation with the routing protocols and should include context-awareness

(location, neighborhood, user profile, etc.) to improve performance. Also, when ad hoc networks

are connected to fix infrastructure (for example, Internet, cellular network, etc.), protocols and

methods are needed to inject the available external services offered by service and content

providers into the ad hoc network.

2.1 Addressing and Internet connectivity:

In order to enable communication between nodes within the ad hoc network, each node needs an

address. In stand-alone ad hoc networks, the use of IP addresses is not parsing obligatory, as

unique MAC addresses could be used to address nodes. However, all current applications are

based on TCP/IP or UDP/IP. In addition, as future mobile ad hoc networks will interact with IP-

based networks and will run applications that use existing Internet protocols such as transmission

control protocol (TCP) and user datagram protocol (UDP), the use of IP addresses is inevitable.

Unfortunately, an internal address organization with prefixes and ranges like in the fixed Internet

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is hard to maintain in mobile ad hoc networks due to node mobility and overhead reasons and

other solutions for address assignment are thus needed.

One solution is based on the assumption (and restriction) that all MANET nodes already have a

static, globally unique and pre-assigned IPv4 or IPv6 address. This solves the whole issue of

assigning addresses, but introduces new problems when interworking with fixed networks.

Connections coming from and going to the fixed network can be handled using mobile IP ,

where the pre-assigned IP address serves as the mobile nodes home address (HoA). All traffic

sent to this IP address will arrive at the nodes home agent (HA) (step 1). When the node in the

ad hoc network advertises to its home agent the IP address of the Internet gateway as its care- of-

address (CoA), the home agent can tunnel all traffic to the ad hoc network (step 2), on which it is

delivered to the mobile node using an ad hoc routing protocol (step 3). For outgoing connections,

the mobile node has to route traffic to an Internet gateway, and for internal traffic an ad hoc

routing protocol can be used. The main problem with this approach is that a MANET node needs

an efficient way to figure out if a certain address is present in the MANET or if it is necessary to

use an Internet gateway, without flooding the entire network. Another solution is the assignment

of random, internally unique addresses. This can be realized by having each node picking a more

or less random address from a very large address space, followed by duplicate address detection

(DAD) techniques in order to impose address uniqueness within the MANET.

Strong DAD techniques will always detect duplicates, but are difficult to scale in large networks.

Weak DAD approaches can tolerate duplicates as long as they do not interfere with each other;

that is, if packets always arrive at the intended destination. If interconnection to the Internet is

desirable, outgoing connections could be realized using network address translation (NAT), but

incoming connections still remain a problem if random, not globally routable, addresses are used.

Also, the use of NAT remains problematic when multiple Internet gateways are present. If a

MANET node switches to another gateway, a new IP address is used and ongoing TCP

connections will break. Another possible approach is the assignment of unique addresses that all

lie within one subnet (comparable to the addresses assigned by a dynamic host configuration

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protocol (DHCP) server). When attached to the Internet, the ad hoc network can be seen as a

separate routable subnet.

Fig 2.2 : Possible approaches to internet connectivity and addressing

This simplifies the decision if a node is inside or outside the ad hoc network. However, no

efficient solutions exist for choosing dynamically an appropriate, externally routable and unique

network prefix (for example, special MANET prefixes assigned to Internet gateways), handling

the merging or splitting of ad hoc networks, handling multiple points of attachment to the

Internet, etc. The above discussion makes clear that, although many solutions are being

investigated12, no common adopted solution for addressing and Internet connectivity is available

yet. New approaches using host identities, where the role of IP is limited to routing and not

addressing, combined with dynamic name spaces, could offer a potential solution.

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2.2 Security and node cooperation:

The wireless mobile ad hoc nature of MANETs brings new security challenges to the network

design13. As the wireless medium is vulnerable to eavesdropping and ad hoc network

functionality is established through node cooperation, mobile ad hoc networks are intrinsically

exposed to numerous security attacks. During passive attacks, an attacker just listens to the

channel in order to discover valuable information. This type of attack is usually impossible to

detect, as it does not produce any new traffic in the network. On the other hand, during active

attacks an attacker actively participates in disrupting normal operation of the network. This type

of attack involves deletion, modification, replication, redirection and fabrication of protocol

control packets or data packets. Securing ad hoc networks against malicious attacks is difficult to

achieve. Preventive mechanisms include among others authentication of message sources, data

integrity and protection of message sequencing, and are typically based on key-based

cryptography. Incorporating cryptographic mechanisms is challenging, as there is no centralized

key distribution centre or trusted certification authority. These preventative mechanisms need to

be sustained by detection techniques that can discover attempts to penetrate or attack the

network. The previous problems were all related to malicious nodes that intentionally damage or

compromise network functionality. However, selfish nodes, which use the network but do not

cooperate to routing or packet forwarding for others in order not to spill battery life or networkbandwidth, constitute an important problem as network functioning entirely relies on the

cooperation between nodes and their contribution to basic network functions.

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Chapter -3

MOBILE COMPUTING

The term Mobile Computing emphasizes the basic feature of mobility which refers to a person or

a device that moves between different geographical locations or different networks or different

communication devices or in different applications. So mobile computing is a process that deals

with the way of communication by using a Mobile Computer. The communication in a Mobile

Computer can be done by using different Networks which includes various protocols for

different issues. A protocol is necessary for transferring the information from one node to other

through wireless medium. So different protocols are used for different purposes and according to

the type of Network connection. This paper mainly concerned with the popular Mobile Network

called the MANET (Mobile Ad Hoc Network) and its design issues and operations. It also

includes the routing concept and the different routing protocols that are used in MANETs. Since

it is the most powerful Network used in military applications researches were going on to

improve manageability, security, and availability of communication through this type of

technology.

3.1 Introduction to mobile computing:

3.1.1 Mobility: Mobility means a person / device that moves between different geographical

locations or different networks or different communication devices or in different applications.

3.1.2 Mobile Computer Definition: A Portable Computer, which retains its Network

Connection (wireless interface) even on move is called mobile computer.

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3.2 Limitations of mobile computer:

Short battery lifetime (max ~ 5 hours)

Subject to theft and destruction => unreliable

Highly unavailable (normally powered-off to conserve battery)

Limited capability (display, memory, input devices, and disk space)

Lack of de-facto general architecture: hand-held, communicators, laptops, and other

devices

Fig 3.1: Mobile

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3.3 Mobile computing applications:

Objects and events can be thought of as the building blocks of mobile computing

applications

Set of interoperable objects at different mobile hosts

Object collaborate via message passing among themselves

On the occurrence of events, objects take corresponding actions (event-action paradigm)

3.4 Characteristics:

Migration

Inheritance

Hoarding

Cloning Sharing

Synchronization

3.4.1 Migration: Hand-off during migration of a host from one cell to other may create

disconnection and duration of such disconnection could be unpredictable. Hence, an application

must have some contingency plan to deal with such unwanted incidents.

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3.4.2 Inheritance: A new task created by an application may have to inherit some properties of

the host device. Since properties of all mobile hosts are not same, the inherited properties of a

task may differ at different devices. So, applications must be able to adapt themselves according

to the environment and must have the capabilities to inherit the properties of computing ambient.

3.4.3 Hoarding: In order to continue computation in disconnected mode, applications may need

to hoard some file/information from databases of fixed network/MSS) in local memory prior to

disconnection. Changes made to files during disconnection period have to be consolidated with

the databases after reconnection

3.4.4 Cloning: Task/Process/Object cloning and migration across different hosts and/or MSSs

may take place in the environment. This requires that applications must be able to save the state

of task prior to migration and to create a new task with a predetermined state.

3.4.5 Sharing and Synchronization: When more than one mobile host want to share

information/data present at fixed network, applications must be aware of the need for read/ write

synchronization with other mobile users. Also, when there is an update to shared data, there has

to be some mechanism to inform all potential users about the update. There are mainly two types

of mobile networks.

Conventional(With infrastructure)

Ad hoc networks(MANETs)

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Chapter -4

MANET

Mobile Ad Hoc Network is an autonomous collection of mobile users that communicate over

relatively bandwidth constrained wireless links. It is a network architecture that can be rapidly

deployed without relying on pre-existing fixed network infrastructure. The nodes in a MANET

can dynamically join and leave the network, frequently, often without warning, and possibly

without disruption to other nodes communication Groups of nodes that have a common goal can

create formations (clusters) and migrate together, similarly to military units on missions or to

guided tours on excursions. Examples of network nodes are pedestrians, soldiers, or unmanned

robots. Examples of mobile platforms on which the network nodes might reside are cars, trucks,

buses, tanks, trains, planes, helicopters or ships.

MANETs are distinguished from other ad-hoc networks by rapidly changing network topologies,

influenced by the network size and node mobility. Such networks typically have a large span and

contain hundreds to thousands of nodes. The MANET nodes exist on top of diverse platforms

that exhibit quite different mobility patterns. Within a MANET, there can be significant

variations in nodal speed (from stationary nodes to high-speed aircraft), direction of movement,

acceleration/deceleration or restrictions on paths (e.g., a car must drive on a road, but a tank does

not.

4.1 I.P addresses allocation issues in Manets:

A new node joining a MANET has to acquire an IP address it can use for communication

with other nodes. When it leaves the MANET gracefully, it relinquishes the address.

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If a node crashes or leaves the MANET without relinquishing the address, the address has

to be reclaimed.

4.2 Designing issues and operations:

The main challenges in the design and operation of the MANETs, compared to more traditional

wireless networks, stem from the lack of a centralized entity, the potential for rapid node

movement, and the fact that all communication is carried over the wireless medium. In standard

cellular wireless networks, there are a number of centralized entities (e.g., the base stations, the

Mobile Switching Centers (MSCs), the Home Location Register (HLR), and the Visitor Location

Register (VLR)). The centralized entities in the cellular networks perform the function of

coordination. The lack of these entities in the MANETs requires distributed algorithms to

perform these functions.

4.2.1 Drawbacks in Manets:

All communications between all network entities in ad-hoc networks are carried over

the wireless medium. Additionally, as the wireless bandwidth is limited, its use

should be minimized.

The transmission radius of each mobile is limited, and channels assigned to mobiles

are typically spatially reused. Consequently, since the transmission radius is much

smaller than the network span, communication between two nodes often needs to be

relayed through intermediate nodes; i.e., multi-hop routing is used.

Frequent network reconfiguration may trigger frequent exchanges of controlinformation to reflect the current state of the network. Thus, the bandwidth used for

distribution of the routing update information is wasted.

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In spite of these attributes, the design of the MANETs still needs to allow for a high

degree of reliability, survivability, availability, and manageability of the network.

4.3 Routing concepts:

A MANET is a peer-to-peer network that allows direct communication between any two nodes,

when adequate radio propagation conditions exist between these two nodes and subject to

transmission power limitations of the nodes. If there is no direct link between the source and the

destination nodes, multi-hop routing is used. In multi-hop routing, a packet is forwarded from

one node to another, until it reaches the destination. Of course, appropriate routing protocols are

necessary to discover routes between the source and the destination, or even to determine the

presence or absence of a path to the destination node. Because of the lack of central elements,

distributed protocols have to be used.Most research effort has been put in the routing protocols

since the advent of the MANET. They can be divided into the following categories:

Uncast routing protocols

Topology-based routing protocols

Proactive routing protocols Reactive routing protocols

Hybrid routing protocols

Geographical-based routing protocols

Multicast routing protocols

Broadcast algorithms although there are many kinds of routing protocols competing for

uncast, multicast and broadcast. Communication for the MANET, it seems that one

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protocol cannot fit all the different scenarios and traffic patterns of MANET applications.

For example, proactive routing protocols are well suited for a small-scale, broad-band

MANET with high mobility, while reactive routing protocols are well suited for a large-

scale, narrow-band MANET with moderate or low mobility. If the mobile nodes in the

MANET move too quickly, they have to resort to broadcast to achieve peer-to-peer

communication. In a summary, every routing protocol has its strengths and drawbacks,

and aims at a specific application. As a result, the prospective standard for routing

protocols in the MANET is very likely to combine some of the most competitive

schemes.

4.3.1 Routing protocols for ad-hoc networks:

The network routing protocols could be divided into Proactive protocols and Reactive protocols.

4.3.2 Proactive protocols: These are continuously learning the topology of the network by

exchanging topological information among the network nodes. Thus, when there is a need for a

route to a destination, such route information is available immediately. The early protocols that

were proposed for routing in ad hoc networks were proactive Distance Vector protocols based on

the Distributed Bellman-Ford (DBF) algorithm.

4.3.3 Problems in the bf algorithms:

Convergence and

Excessive control traffic, these are especially issues in resource-poor ad hoc networks.

4.4: Addressing the problems:

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An approach taken to address the convergence problem is the application of the Link State

protocols to the ad hoc environment. An example of the latter is the Optimized Link State

Routing protocol (OLSR).Another approach taken by some researchers is the proactive Path

finding algorithms. In this approach, which combines the features of the Distance Vector and

Link State approaches, every node in the network constructs a Minimum Spanning Tree (MST),

using the information of the MSTs of its neighbors, together with the cost of the link to its

neighbors. The Path Finding algorithms allow reducing the amount of control traffic, to reduce

the possibility of temporary routing loops, and to avoid the "counting to-infinity" problem. An

example of this type of routing protocols is the Wireless Routing Protocol (WRP).

4.5 Applications in proactive protocols:

The main issue with the application of proactive protocols to the ad hoc networking environment

stems from the fact, that as the topology continuously changes, the cost of updating the

topological information may be prohibitively high. Moreover, if the network activity is low, the

information about the actual topology is may even not be used and the investment of limited

transmission and computing resources in maintaining the topology is lost.

4.5.1 Reactive routing protocols: These are based on some type of "query-reply" dialog.Reactive protocols do not attempt to continuously maintain the up-to-date topology of the

network. Rather, when the need arises, a reactive protocol invokes a procedure to find a route to

the destination; such a procedure involves some sort of flooding the network with the route

query. As such, such protocols are often also referred to as on demand.

Examples: The Temporally Ordered Routing Algorithm (TORA), the Dynamic Source Routing

(DSR), and Ad hoc On Demand Distance Vector (AODV).

In TORA, the route replies use controlled flooding to distribute the routing information

through a form of a Directed Acyclic Graph (DAG), which is rooted at the destination.

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The DSR and the AODV protocols, on the other hand, use uncast to route the reply back

to the source of the routing query, along the reverse path of the query packet.

Chapter -5

SINGLE SCOPE ROUTING PROTOCOL

5.1: Ad Hoc on-Demand Distance Vector Routing (AODV):

This incorporates the destination sequence number technique of Destination-Sequenced

Distance-Vector Routing (DSDV) routing into an on-demand protocol. In DSDV technique each

node keeps a next-hop routing table containing the destinations to which it currently has a route.

A route expires if it is not used or reactivated for a threshold amount of time. If a source has no

route to a destination, it broadcasts a route request (RREQ) packet using an expanding ring

search procedure, starting from a small Time-To-Live value (maximum hop count) for the

RREQ, and increasing it if the destination is not found. The RREQ contains the last seen

sequence number of the destination, as well as the source node's current sequence number. Any

node that receives the RREQ updates its next-hop table entries with respect to the source node. A

node that has a route to the destination with a higher sequence number than the one specified in

the RREQ uncast a route reply (RREP) packet back to the source. Upon receiving the RREP

packet, each intermediate node along the RREP routes updates its next-hop table entries with

respect to the destination node, dropping the redundant RREP packets and those RREP packets

with a lower destination sequence number than one previously seen. When an intermediate node

discovers a broken link in an active route, it broadcasts a route error (RERR) packet to itsneighbors, which in turn propagate the RERR packet up-stream towards all nodes that have an

active route using the broken link. The affected source can then re-initiate route discovery if the

route is still needed.

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5.2 Multicast Operation of AODV Routing Protocol:

This is an extension of AODV to support multicasting and it builds multicast trees on demand to

connect group members. Route discovery in MAODV [Roy99b] follows a route request/route

reply discovery cycle. As nodes join the group, a multicast tree composed of group members is

created. Multicast group membership is dynamic and group members are routers in the multicast

tree. Link breakage is repaired by downstream node broadcasting a route request message. The

control of a multicast tree is distributed so there is no single point of failure. One big advantage

claimed is that since AODV offers both unicast and multicast communication, route information

when searching for a multicast route can also increase unicast routing knowledge and vice-versa.

In [Roy99b], an ad-hoc network consists of laptops in a room (50-100m width, 10m

range)talking to each other, moving at 1 m/s. The results presented only verify working of

AODV and do not compare performance with other multicasting protocols. They show that

AODV attains a high good put ratio and is able to offer this communication with a minimum of

control packet overhead. They also demonstrate its operation under frequent network partitions.

5.2.1 Dynamic Source Routing (DSR): DSR is a source routing on-demand protocol withvarious efficiency improvements. In DSR, each node keeps a route cache that contains full paths

to known destinations. If a source has no route to a destination, it broadcasts a route request

packet to its neighbors. Any node receiving the route request packet and without a route to the

destination appends its own ID to the packet and re-broadcasts the packet. If a node receiving the

route request packet has a route to the destination, the node replies to the source with a

concatenation of the path from the source to itself and the path from itself to the destination. If

the node already has a route to the source, the route reply packet will be sent over that route.

Otherwise, depending on the underlining assumption of the directionality of links, the route reply

packet can be sent over the reversed source-to-node path, or piggy-backed in the node's route

request packet for the source.

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5.2.2 Advantages of Single-Scope Routing Protocols:

Less complexity.

Easy to implement, both in simulations and in practical systems (ex: - IETF MANET).

Battery power and wireless bandwidth can be conservatively utilized.

No routing delay or query traffic.

5.2.3 Disadvantages of Single-Scope Routing Protocols:

Therefore, the single scope routing protocols may not scale well as the network size

increases.

Routing delay is there.

unnecessary control traffic

5.3: Optimized Link State Routing (OLSR):

It is a link-state protocol where the link information is disseminated through an efficient

flooding technique. The key concept in OLSR is multipoint relay (MPR). A node's MPR set is a

subset of its neighbors whose combined radio range covers all nodes two hops away. Heuristics

are proposed for each node to determine its minimum MPR set based on its two-hop topology.

Each node obtains the two-hop topology through its neighbors' periodic broadcasting of HELLO

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packets containing the neighbors' lists of neighbors. As with a conventional link-state protocol, a

node's link information update is propagated throughout the network. However, in OLSR, when

a node forwards a link updating packet, only those neighbors in the node's MPR set participate in

forwarding the packet (similar to ZRP's border-casting with 1-hop zone radius).Furthermore, a

node only originates link updates concerning those links between itself and the nodes in its MPR

set. Therefore, routes are computed using a node's partial view of the network topology.

5.3.1: Advantages of Multi-Scope Routing Protocols:

Scalability.

Control traffic is reduced.

5.3.2: Disadvantages of Multi-Scope Routing Protocols:

Difficult to implement.

More complexity compared to single scope.

5.4: Security schemes for ad-hoc networks:

Efforts to incorporate security measures in the ad hoc networking environment have mostly

concentrated on the aspect of data forwarding, disregarding the aspect of topology discovery. On

the other hand, solutions that target route discovery have been based on approaches for fixed-

infrastructure networks, defying the particular MANET challenges. For the problem of secure

data forwarding, two mechanisms that detect misbehaving nodes and report such events and each

node may choose the best route, comprised of relatively well-behaved nodes

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5.4.1: Uses of the Manets are:

Tactical operation - for fast establishment of military communication during the

deployment of forces in unknown and hostile terrain.

Rescue missions - for communication in areas without adequate wireless coverage.

National security - for communication in times of national crisis, where the existing

communication infrastructure is non-operational due to a natural disaster or a global war.

Law enforcement - for fast establishment of communication infrastructure during law

enforcement operations;

Commercial use - for setting up communication in exhibitions, conferences, or sales

resentations;

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CONCLUSIONS

The interesting fact is that although the military has been experimenting and even using this

technology for the last three decades, the research community has been coping with the rather

frustrating task of finding a "killer" non-military application for ad hoc networks.

A major challenge that has been perceived as a possible "show stopper" for technology transfer

is the fact that commercial applications do not necessarily conform to the collaborative"

environment that the military communication environment does. Other challenges in deployment

of ad hoc networks relate to the issues of manageability, security, and availability of

communication through this type of technology. Future extensions of the cellular infrastructure

could be carried out using this type of technology and May, very well, be the basis for fourth

generation (4G) of wireless systems. Other possible applications include sensing system the

rapid evolution in the field of mobile computing is driving a new alternative way for mobile

communication, in which mobile devices form a self-creating, self-organizing and self-

administering wireless network, called a mobile ad hoc network. Its intrinsic flexibility, lack of

infrastructure, ease of deployment, auto-configuration, low cost and potential applications make

it an essential part of future pervasive computing environments. As a consequence, the seamless

integration of mobile ad hoc networks with other wireless networks and fixed infrastructures will

be an essential part of the evolution towards future fourth-generation communication networks.

From a technological point of view, the realization of this vision still requires a large number of

challenges to be solved related to devices, protocols, applications and services. The concise

discussion in this paper shows that, despite the large efforts of the MANET research community

and the rapid progress made during the last years, a lot of challenging technical issues remains

unanswered.

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