AD HOC Mobilen1

8/14/2019 AD HOC Mobilen1

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MANET RoutingProtocol and WAP


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Introduction

What is Ad Hoc Network

All nodes are mobile and can be connected

dynamically in an arbitrary manner.

No default router available

Potentially every node becomes a router: must

be able to forward traffic on behalf of others


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Two types of wireless networks

Infrastructured network:A network with fixed and wired gateways.When A mobile unit goes out of range of one

base station, it connects with new base station Infrastructureless (ad hoc) networks:

All nodes of these networks behave as routersand take part in discovery and maintenance of

routes to other nodes.


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Why is Ad Hoc hard

Because of a constantly changing set of nodes.Routing!

Securitynew vulnerabilities, nasty neighbors

Power

running with batteries, little computing power.

Low bandwidth, high error rates.


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DSDV WRPAODV DSR TORA

Ad-Hoc Routing Protocols

Source-initiated On-

Demand Driven

Table Driven

CATEGORIZATION


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What is on-demand

The routes are created when required

The source has to discover a route to thedestination

The source and intermediate nodes have tomaintain a route as long as it is used

Routes have to be repaired in case oftopology changes.


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On-Demand Routing Protocols

1. Ad hoc On-demand Distance VectorRouting

2. Dynamic Source Routing Protocol

3. Temporally Ordered Routing Algorithm


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Ad Hoc On-demand Distance Vector Routing

AODV includes route discovery and routemaintenance.

AODV minimizes the number of broadcasts by

creating routes on-demand AODV uses only symmetric links because the

route reply packet follows the reverse path ofroute request packet.

AODV uses hello messages to know itsneighbors and to ensure symmetric links.


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The node discards the packets having been seen

source

destination

The source broadcasts a route packetThe neighbors in turn broadcast the

packet till it reaches the destination

Reply packet follows the reverse path of route

request packet recorded in broadcast packet

RREQ

RREP


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Route Maintenance

If the source node moves, it reinitiate theroute discovery.

If intermediate node moves, its upstreamnode sends a RREP to the source. The

source restarts the route discovery.


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Dynamic Source Routing Protocol

A node maintains route caches containingthe routes it knows.

Include route discovery and routemaintenance.


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Route discovery

The source sends a broadcast packet which containssource address, destination address, request id and

path.

If a host saw the packet before, discards it.

Otherwise, the route looks up its route caches tolook for a route to destination, If not find, appends

its address into the packet, rebroadcast,

If finds a route in its route cache, sends a routereply packet, which is sent to the source by route

cache or the route discovery.


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destination

source1

65

4

3

2

8

7

(1,4)

(1,2)

(1,3)

(1,3,5,6)(1,3,5)

(1,4,7)

source broadcasts a packet containing address of source and destination

The route looks up its route caches to look for a route to destination

If not find, appends its address into the packet

The destination sends a reply packet to source.

The node discards the packets having been seen


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How to send a reply packet

If the destination has a route to the source inits route cache, use it

Else if symmetric links are supported, usethe reverse of route record

Else if symmetric links are not supported,

the destination initiate route discovery tosource


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Route maintenance

Whenever a node transmits a data packet, aroute reply, or a route error, it must verify

that the next hop correctly receives thepacket.

If not, the node must send a route error tothe node responsible for generating thisroute header

The source restart the route discovery


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a

fe

d

c

b

h

g

(-,-,-,-,d)

(-,-,-,-,b)

(-,-,-,-,c)

(-,-,-,-,f)(-,,-,-,-e)

Only the non-NULL node (destination) responds with a UPD packet.

(0,0,0,0,h)

(-,-,-,-,a)

The source broadcasts a QRY packet with height(D)=0, all others NULL

(0,0,0,4,b)

(0,0,0,4,c)

(0,0,0,3,e)(0,0,0,2,f)

(0,0,0,2,d)(0,0,0,3,a)

source

Dest.

A node receiving a UPD sets its height to one more than UPD

Source receives a UPD with less height

UPD

QRY

QRYQRY

(-,-,-,-,g)(0,0,0,1,g)


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TORA: Height metric

Each node contains a quintuple

Logical time of a link failure

Unique ID of the node that defined the newreference level

Reflection indicator bit

A propagation ordering parameter, height

Unique ID of the node


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Route Maintenance and Erasing No reaction necessary if all nodes still have downstream links.

A new reference level is defined if a node loses its lastdownstream link.

Synchronized clock is important, accomplished via GPS oralgorithm such as Network Time Protocol.

CLR packet to be flooded to clear the invalid packet.


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fe

d

c

b

h

g

(0,0,0,0,h)

(0,0,0,4,b)

(0,0,0,4,c)

(0,0,0,3,e)(0,0,0,2,f)

(0,0,0,2,d)(0,0,0,4,s)

Dest.

(0,0,0,1,g)

Re-establishing route after link failure

(1,d,0,0,d)

A new reference level is defined

UDPas

UDP

(0,0,0,3,a)(1,d,0,-1,a)(1,d,0,-2,s)


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DSR has lower routing load than AODV

Because AODV has to depend on route

discovery more often, DSR limits the overhead

by using route cache

TORA is higher because its overhead is the sumof neighbor discovery plus routing creating andmaintenance


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AODV has less delay than DSR

AODV replies to first RREQ, so it choosesthe least congested route.


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The overhead of TORA is worst. It has abetter delivery ratio in less sources.

DSR is good at all mobility rate andmovement speed. Its performance is poor in ahigher load.

AODV performs almost as well as DSR at all

mobility rates and movement. It dependsmore on route discovery which may increaseoverhead in network

Advantage and Disadvantage


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Overview

On-Demand AODV DSR TORAOverallcomplexity

Medium Medium High

Overhead Low Medium MediumLoop-free Yes Yes YesBeaconingrequirements

No No No

Multipleroute support

No Yes Yes

Routesmaintained in

Route table Route cache Route table

Routereconfigurati

onmethodology

Erase route;notify source

Erase route;notify source

Link reversal;route repair

Routingmetric

Freshest andshortest path

Shortest path Shortest path


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Table driven Ad-hoc Routing Protocols

DSDV 1994

Destination Sequenced Distance-Vector

WRP 1996 Wireless Routing Protocol


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Pro-active Ad-hoc Routing Protocols

DSDV 1994




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DSDV

DSDV is based on idea of classical Bellman-Ford

Routing Algorithm

Each node maintains a routing table listing all available destinations.

The attributes of each destination are the next hop, the number of hops

to reach to the destination, and a sequence number, which is originated

by the destination node.

Both periodic and triggered routing updates to maintain table


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Pro-active Ad-hoc Routing Protocols

DSDV 1994




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Wireless Routing Protocol

Each node maintains a distance table, arouting table, a link-cost table and a

message retransmission list. Distance table of node i: (matrix)

For each destination j and each neighbor of

i(k) Distance to j


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Information Exchanged among nodes:

(routing table update messages )

Identifier of the sending node A sequence number assigned by the sending node

An update list of updates or ACKs to update message

A response list of nodes that should send an ACK to

the update message


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Each node will communicate with its neighborsreporting any changes in the system

Each node will keep track of which node shouldsend an acknowledgement

Nodes will keep track of the changes in the systemby periodic transmission of hello messages

This protocol will force nodes to do consistentcheck of their predecessor hence avoiding count-to-infinity problem.


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MANET Application

Tactical networks: military communication, automatedbattlefield.

Emergency Services: Search-and rescue operations,

disaster recovery. Commercial Environments: E-commerce

Vehicular Services: transmission of news, road condition,weather, road/accident/guidance.

Educational application: virtual classroom, online exam. Home and Enterprise networking: home/office WLAN

etc..


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Wireless Application Protocol

Universal open standard providing the users withthe wireless access and the value added services.

WAP becomes the standard for communicationbetween server applications and its clients.

WAP has a browser software that connect to WAPgateway and sends requests to receive data from

web servers.


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WAP: The Protocol Stack

Mobile enhancements to OSI Protocol Stack


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WAP WAE: Application Layer

Provides an environment to execute anddevelop applications

Building blocks: WML: Wireless Markup Language

WLMScript: Lightweight scripting language

2 User Agents: WAE: Microbrowser and text editor

WTA: Wireless Telephony Agent (in development)


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Wireless Session protocol

The WSP provides dialog between client and server.

WSP provides the following services:

1. Opens a session of communication between client andserver.

2. Establishes a protocol and negotiation between clientand server.

3. Exchanges encoded data between client and server.4. Exchanges request and replies between client and server.

5. Supports several asynchronous transmissions of data.


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Wireless Datagram Protocol

WDP acts as the communication layer between theupper level protocols (WTLS, WTP, and WSP),

and the bearer services WDP allows the upper layers to function

independently from the wireless network at hand,

as long as the WTP layer is specifically set to the

settings of the bearer settings.


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Technical Challenges of WAP

Since WAP is designed for portable devices

limited device memory so that not a lot of data can

be stored. Devices have limited range of data transfer.

There are no "cookies" available to hold thesession together


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CONCLUSION

Several routing schemes proposed for ad-hocmobile networks.

WAP, its architecture and its technical challenges. The field of ad-hoc mobile networks and WAP is

rapidly growing and changing, and while there are

still many challenges that need to be met, it is

likely that such networks will see wide-spread usewithin the next few years.


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Reference (cont.)

8. An Introduction to Mobile Ad Hoc Network, by Ming Yu Jiang,http://kiki.ee.ntu.edu.tw/mmnet1/adhoc/

9. A Performance Comparison of Multi-Hop Wireless Ad Hoc Network RoutingProtocols, by Josh Broch, David A. Maltz, David B. Johnson, Yih-Chun Hu, JorjetaJetcheva, http://www1.ics.uci.edu/~atm/adhoc/paper-collection/johnson-performance-comparison-mobicom98.pdf

10. A review of current Routing protocols for ad-hoc Mobile Wireless Networks, byElizabeth M. Royer and C-K Tohhttp://www.cs.ucsb.edu/~vigna/courses/CS595_Fall01/royer99review.pdf

11. Mobile computing today & in the future, by M.J. Fahham and M.K. Hauge.http://www.doc.ic.ac.uk/~nd/surprise_95/journal/vol4/mjf/report.html

12. Performance Comparison of On-demand Routing Protocols in Ad Hoc Network bySohela Kaniz http://fiddle.visc.vt.edu/courses/ecpe6504-wireless/projects_spring2000/pres_kaniz.pdf
http://kiki.ee.ntu.edu.tw/mmnet1/adhoc/http://www.cs.ucsb.edu/~vigna/courses/CS595_Fall01/royer99review.pdfhttp://www.doc.ic.ac.uk/~nd/surprise_95/journal/vol4/mjf/report.htmlhttp://www.doc.ic.ac.uk/~nd/surprise_95/journal/vol4/mjf/report.htmlhttp://www.cs.ucsb.edu/~vigna/courses/CS595_Fall01/royer99review.pdfhttp://kiki.ee.ntu.edu.tw/mmnet1/adhoc/

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AD HOC Mobilen1