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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
Destination Sequenced Distance-Vector
WRP 1996 Wireless Routing Protocol
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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
Destination Sequenced Distance-Vector
WRP 1996 Wireless Routing Protocol
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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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Wireless Routing Protocol
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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Wireless Routing Protocol
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/