wireless ad hoc networks_final

8/4/2019 Wireless Ad Hoc Networks_Final

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RITM-MTech Seminar by Goni Basappa K

Wireless Ad Hoc Networks

PresentedBy:

Goni Basappa K

5WE09SNZ08

MTech(PT)

Sem IV

Guide:

Mrs. Meenakshi .S

Asst.ProfessorDept. of CSE

RITM


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Agenda

Abstract

Introduction to ad hoc networks

General Ad Hoc Network Characteristics

Ad Hoc Network Applications Implementation of ad hoc networks

IP-Layer Mobile Routing

Routing protocols in the MANETs

Routing Security problems

References


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In this seminar I present about the Wireless Ad Hoc Networks

Abstract


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Ad hocis a Latin Phrase which means "for this purpose". It generallysignifies a solution designed for a specific problem or task, non-generalsable and which cannot be adapted to other purposes.

--source wikipediaA wireless ad hoc network is a collection of autonomous nodes or

terminals that communicate with each other by forming a multi hop radionetwork and maintaining connectivity in a decentralized manner.

Since the nodes communicate over wireless links, they have to contendwith the effects of radio communication, such as noise, fading, andinterference. In addition, the links typically have less bandwidth than in a

wired network


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(cont)

Each node in a wireless ad hoc network functions as both a hostand a router, and the control of the network is distributed among thenodes.

The network topology is in general dynamic, because theconnectivity among the nodes may vary with time due to node

departures, new node arrivals, and the possibility of having mobilenodes.

Hence, there is a need for efficient routing protocols to allow thenodes to communicate over multihop paths consisting of possiblyseveral links in a way that does not use any more of the network

"resources" than necessary.

The vision of mobile ad hoc networking is to support robust andefficient operation in mobile wireless networks by incorporatingrouting functionality into mobile nodes.



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(cont)

Such networks are envisioned to have dynamic,sometimes rapidly-changing, random, multihoptopologies which are likely composed of relativelybandwidth-constrained wireless links.

Within the Internet community, routing support for mobilehosts is presently being formulated as "mobile IP"technology.

This is a technology to support nomadic host "roaming",where a roaming host may be connected through various

means to the Internet other than its well known fixed-address domain space.



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(cont)

The host may be directly physically connected to thefixed network on a foreign subnet, or be connected via awireless link, dial-up line, etc.

Supporting this form of host mobility (or nomadicity)requires address management, protocol interoperabilityenhancements and the like, but core network functionssuch as hop-by-hop routing still presently rely upon pre-existing routing protocols operating within the fixednetwork.

In contrast, the goal of mobile ad hoc networking is to

extend mobility into the realm of autonomous, mobile,wireless domains, where a set of nodes--which may becombined routers and hosts--themselves form thenetwork routing infrastructure in an ad hoc fashion



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Instantly deployable, re-configurable (No fixedinfrastructure)

Created to satisfy a temporary need.

Node portability (eg: sensors), mobility

Limited battery power (Energy-constrained operation:Some or all of the nodes in a MANET may rely onbatteries or other exhaustible means for their energy. )

Multi-hopping ( to save power, overcome obstacles,

enhance spatial spectrum reuse, etc.) The nodes may be located in or on airplanes, ships,

trucks, cars, perhaps even on people or very smalldevices, and there may be multiple hosts per router



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Ad hoc characteristics (cont)

A MANET is an autonomous system of mobile nodes.

Ad Hoc Networks are self organizing, self healing,distributed networks which most often employ wirelesstransmission techniques.

Dynamic topologies: Nodes are free to move arbitrarily. Bandwidth-constrained, variable capacity links: Wireless

links will continue to have significantly lower capacitythan their hardwired counterparts.

Limited physical security: Mobile wireless networks aregenerally more prone to physical security threats thanare fixed- cable nets.



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Ad hoc characteristics (cont)

The increased possibility of eavesdropping, spoofing,and denial-of-service attacks should be carefullyconsidered.

The decentralized nature of network control in MANETsprovides additional robustness against the single pointsof failure of more centralized approaches.

These characteristics create a set of underlying

assumptions and performance concerns for protocoldesign which extend beyond those guiding the design ofrouting within the higher-speed, semi-static topology ofthe fixed Internet



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Example wireless Ad hoc networkdiagram



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Applications



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Ad Hoc Network Applications

When properly combined with satellite-basedinformation delivery, MANET technology canprovide an extremely flexible method forestablishing communications forfire/safety/rescue operations or other scenariosrequiring rapidly-deployable communicationswith survivable, efficient dynamic networking.

Military

Automated battlefield



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Ad Hoc Network Applications (cont)

Civilian

Disaster Recovery (flood, fire, earthquakes etc)

Law enforcement (crowd control)

Homeland defense

Search and rescue in remote areas Environment monitoring (sensors)

Space/planet exploration

Commercial

Sport events, festivals, conventions Ad hoc collaborative computing (Bluetooth)

Sensors on cars (car navigation safety); sensors on cows

Networked video games at amusement parks, etc



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Ad Hoc Network Applications (cont)

Opportunistic ad hoc extensions (of Wireless Internet) Indoor W-LAN extended coverage Indoor network appliances (Bluetooth, Home RF) Hot spots (Mesh Networks)

Campus, shopping mall, etc Urban grid

Wireless ad hoc networks can be further classified bytheir application:Mobile ad hoc networksWireless mesh networksWireless sensor networks



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Implementation of ad hoc networks



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RFCs for MANET are 2501,5444. A mobile ad hoc network (MANET) is a type of wireless adhoc

network , and is a self-configuring network of mobile devicesconnected by any number of wireless links.

Every device in a MANET is also a router because it is required toforward traffic unrelated to its own use.

Each MANET device is free to move independently, in any arbitrarydirection, and thus each device will potentially change its links toother devices on a regular basis.

The primary challenge for building a MANET is for each device tocontinuously maintain the information required to properly routetraffic.

Such networks may operate in a standalone fashion, or may beconnected to the larger internet.



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(cont)

Ad hoc applications provide truly wireless solutions

Ad hoc mode allows users to spontaneously form a wireless LAN. For example, a group of people with 802.11-equipped laptops may

gather for a business meeting at their corporate headquarters.

In order to share documents such as presentation charts andspreadsheets, they could easily switch their NICs to ad hoc mode toform a small wireless LAN within their meeting room.

Another example is when you and your associates are waiting for a

flight at the airport, and you need to share a relatively large PDF file.

Through ad hoc mode, you can easily transfer the file from onelaptop to another.



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(cont)

Most installed wireless LANs today utilize "infrastructure"mode that requires the use of one or more accesspoints. With this configuration, the access point providesan interface to a distribution system (e.g., Ethernet),which enables wireless users to utilize corporate servers

and Internet applications.

As an optional feature, however, the 802.11 standardspecifies "ad hoc" mode, which allows the radio networkinterface card (NIC) to operate in what the standard

refers to as an independent basic service set (IBSS)network configuration. With an IBSS, there are noaccess points. User devices communicate directly witheach other in a peer-to-peer manner.



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(cont)

Some product vendors are beginning to base their solutions on adhoc mode. As an example, Mesh networks offers a wirelessbroadband network system based on 802.11 ad hoc mode and apatented peer-to-peer routing technology.

This results in a wireless mesh topology where mobile devices

provide the routing mechanisms in order to extend the range of thesystem.

For example, a user on one side of the building can send a packetdestined to another user on the far side of the facility, well beyondthe point-to-point range of 802.11, by having the signal hope fromclient device to client device until it gets to its destination

This can extend the range of the wireless LAN from hundreds of feetto miles, depending on the concentration of wireless users.



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An improved mobile routing capability at the IP layer canprovide a benefit similar to the intention of the originalInternet, viz. "an interoperable internetworking capabilityover a heterogeneous networking infrastructure".

In this case, the infrastructure is wireless, rather thanhardwired, consisting of multiple wireless technologies,channel access protocols, etc.

Improved IP routing and related networking servicesprovide the glue to preserve the integrity of the mobileinternet work segment in this more dynamicenvironment.



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IP-Layer Mobile Routing (cont)

A real benefit to using IP-level routing in a MANET is to providenetwork-level consistency for multihop networks composed of nodesusing a *mixture* of physical-layer media; i.e. a mixture of what arecommonly thought of as subnet technologies.

A MANET node principally consists of a router, which may bephysically attached to multiple IP hosts (or IP-addressable devices),which has potentially *multiple* wireless interfaces--each interfaceusing a *different* wireless technology.

Thus, a MANET node with interfaces using technologies A and Bcan communicate with any other MANET node possessing aninterface with technology A or B.



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The multihop connectivity of technology A forms a physical- layermultihop topology, the multihop connectivity of technology Bforms *another* physical-layer topology (which may differ fromthat of A's topology), and the *union* of these topologies formsanother topology (in graph theoretic terms--a multigraph), termedthe "IP routing fabric", of the MANET.

MANET nodes making routing decisions using the IP fabric canintercommunicate using either or both physical-layer topologiessimultaneously.

As new physical-layer technologies are developed, new devicedrivers can be written and another physical-layer multihoptopology can be seamlessly added to the IP fabric. Likewise,

older technologies can easily be dropped. Such is the functionality and architectural flexibility that IP-layer

routing can support, which brings with it hardware economies ofscale.



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The concept of a "node identifier" (separate and apart from the conceptof an "interface identifier") is crucial to supporting the multigraphtopology of the routing fabric.

It is what *unifies* a set of wireless interfaces and identifies them asbelonging to the same mobile platform.

This approach permits maximum flexibility in address assignment. Node

identifiers are used at the IP layer for routing computations. In the nearterm, it is currently envisioned that MANETs will function as *stub*networks, meaning that all traffic carried by MANET nodes will either besourced or sinked within the MANET.

Because of bandwidth and possibly power constraints, MANETs are notpresently envisioned to function as *transit* networks carrying trafficwhich enters and then leaves the MANET (although this restriction may

be removed by subsequent technology advances). This substantially reduces the amount of route advertisement requiredfor interoperation with the existing fixed Internet.



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For stub operation, routing interoperability in the near term maybe achieved using some combination of mechanisms such asMANET-based any cast and mobile IP.

Future interoperability may be achieved using mechanisms otherthan mobile IP. Interaction with Standard IP Routing will be

greatly facilitated by usage of a common MANET addressingapproach by all MANET routing protocols.

Development of such an approach is underway which permitsrouting through a multi-technology fabric, permits multiple hostsper router and ensures long-term interoperability throughadherence to the IP addressing architecture.

Supporting these features appears only to require identifyinghost and router interfaces with IP addresses, identifying a routerwith a separate Router ID, and permitting routers to havemultiple wired and wireless interfaces.



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Routing protocols in the MANETs



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Routing protocols in MANETs

Routing protocols of MANETs can be classifiedinto two categories

Table-driven

On demand

The routing protocols for a MANET are

Destination-sequenced distance-vector

routing protocol (DSDV)Ad hoc on-demand distance vector (AODV)

Dynamic source routing protocol (DSR)



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On-Demand Routing Protocols

Routes are established on demand as

requested by the source

Only the active routes are maintained byeach node

Channel/Memory overhead is minimized

Two leading methods for route discovery:source routing and backward learning(similar to LAN interconnection routing)



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Dynamic Source Routing (DSR)

Forwarding: source routedriven instead ofhop-by-hop route table driven

No periodic routing update message is

sentThe first path discovered is selected as the

route

Two main phasesRoute Discovery

Route MaintenanceRITM-MTech Seminar by Goni Basappa K


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DSR - Route Discovery

To establish a route, the source floods a Route Requestmessage with a unique request ID

The Route Requestpacket picks up the node IDnumbers

Route Replymessage containing path information issent back to the source either by

the destination, or

intermediate nodes that have a route to the

destination Each node maintains a Route Cachewhich records

routes it has learned and overheard over time



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DSR - Route Maintenance

Route maintenance performed only whileroute is in use

Monitors the validity of existing routes by

passivelylistening to acknowledgments ofdata packets transmitted to neighboringnodes

When problem detected, send Route Errorpacket to original sender to perform newroute discovery



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Attacks can be classified into passive and active attacks.

Active attack can be further divided into external attacksand internal attacks.

Some types of active attacks

Black holeDenial of service

Routing table overflow

Impersonation

Energy consummationInformation disclosure



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Routing Security in MANETs

The External Attack Prevention Model (EAPM)secures the network from external attacks byimplementing message authentication code to

ensure integrity of route request packets.

The Internal Attack Detection Model (IADM) isused to analyze local data traces gathered bythe local data collection module and identify themisbehaving nodes in the network.



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References



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http://www.ietf.org/rfc/rfc2501.txt

http://en.wikipedia.org.wiki/Mobile ad hoc network

http://www.wi-fiplanet.com/tutorials/article.php/1451421

http://people.inf.ethz.ch/stuedip/doc/mobicom.pdf

D. B. Johnson and D. A. Maltz, "Dynamic SourceRouting in Ad-Hoc WirelessNetworks," Mobile Computing, 1994.



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Thank you


wireless ad hoc networks_final

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