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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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RITM-MTech Seminar by Goni Basappa K
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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RITM-MTech Seminar by Goni Basappa K
In this seminar I present about the Wireless Ad Hoc Networks
Abstract
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Introduction to ad hoc networks
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Introduction to ad hoc networks
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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Introduction to ad hoc networks
(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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Introduction to ad hoc networks
(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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Introduction to ad hoc networks
(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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General Ad Hoc Network Characteristics
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General Ad Hoc Network Characteristics
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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Implementation of ad hoc networks
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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Implementation of ad hoc networks
(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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Implementation of ad hoc networks
(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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Implementation of ad hoc networks
(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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IP-Layer Mobile Routing
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IP-Layer Mobile Routing
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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IP-Layer Mobile Routing (cont)
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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IP-Layer Mobile Routing (cont)
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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IP-Layer Mobile Routing (cont)
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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Routing Security problems
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Routing Security problems
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
RITM-MTech Seminar by Goni Basappa K