Download - Dynamic Source Routing Sink hole attack
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Outline
Introduction
Reactive Routing ProtocolDSRAODV
Advantages and Disadvantages
Summary
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Wireless Network
Wireless LAN Infrared or radio links very flexible within the reception area low bandwidth compared to wired networks.
Adhoc Networks useful when infrastructure not available, impractical or expensivemilitary applications, rescue, home networking
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Mobile Adhoc NetworksFrequent Host movement Frequent Topology change
No infrastructureData must be routed via intermediate nodes
AB
DC A
D
B
C
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Why Adhoc Network ?Setting up of fixed Access point and backbone infrastructure is not always viable
Infrastructure may not be present in the disaster area or war zone Infrastructure may not be practical for short range radios
Adhoc NetworksDo not need backbone infrastructure supportAre easy to deployUseful when infrastructure is absent, destroyed or impractical
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Many Applications Personal area networking
Cell phone, laptop, ear phone, wrist watch
Military environments Soldiers, tanks, planes
Civilian environments Taxi cab networks Meeting rooms Sports stadiums Boats, small aircraft
Emergency operations Search and rescue Policing and fire fighting
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MANET protocol stack
Application layerTransport layer
UDPNetwork layer
DSR/AODVData Link layer
802.11 b MACPhysical layer
802.11 b PHY
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Routing Protocols Proactive protocols
Traditional distributed shortest-path protocols Maintain routes between every host pair at all times Based on periodic updates; High routing overhead Example: DSDV (destination sequenced distance vector)
Reactive protocols Determine route if and when needed Source initiates route discovery Example: DSR (dynamic source routing)
Hybrid protocols Adaptive; Combination of proactive and reactive Example : ZRP (zone routing protocol)
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Protocol Trade-offsProactive protocols
Always maintain routesLittle or no delay for route determinationConsume bandwidth to keep routes up-to-dateMaintain routes which may never be used
Reactive protocolsLower overhead since routes are determined on demandSignificant delay in route determinationEmploy flooding (global search)Control traffic may be bursty
Which approach achieves a better trade-off depends on the traffic and mobility patterns
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Two basic mechanisms
Route Discovery•Route Request (RREQ) •Route Reply (RREP)
Route Maintenance•Route Error (RERR)•Acknowledgement.
Dynamic source Routing protocol (DSR)
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DSRBasic Processes
Route DiscoveryRoute message creation (RREQ, RREP)
Route message processing at each nodeCheck route table for destination address route entryReverse route entry for originator and precursors
Route Discovery- Node Actions
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DSRWhen node A wants to send a packet to node G, but does not know a route to G, node A initiates a route discovery
Source node A floods Route Request (RREQ)
Each node appends own identifier when forwarding RREQ
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Route Discovery in DSR
A
B
C
E
D
G
H
F
A
A
A-B
A-C
A-C-E
A-C-EA-C-E
A-B-DA has Data
Destination
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Route Discovery in DSR
Destination G on receiving the first RREQ, sends a Route Reply (RREP)
RREP is sent on a route obtained by reversing the route appended to received RREQ
RREP includes the route from A to G on which RREQ was received by node G
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Route Discovery in DSR
A
B
C
E
D
G
H
F
A
A
A-B
A-C
A-C-E
A-C-EA-C-E
A-B-D
A-B-D-GA-B-D-GA-B-D-G
Route reply
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DSRNode A on receiving RREP, caches the route included in the RREP
When node A sends a data packet to G, the entire route is included in the packet header
hence the name source routing
Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwarded
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Route Maintenance in DSR
A
B
C
E
D
G
H
F
G
RERRRERR
Route Cache (A)G: A, B, D, G G: A, C, E, H, GF: B, C,E, F
Route Cache (A) G: A, C, E, H, GF: A, C,E, F
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AdvantagesRoutes are discovered only they are neededReduces overhead of route maintenanceRoute caching reduce the cost of route discovery A single route discovery may yield many routes to the destination due to intermediate nodes may reply route request from local caches.
DisadvantagesPacket header size grows with route length due to source routing inefficiencyRoute request packet may reach all nodes in the network.REQ floodingIncreased contention if too many route replies come backRoute Reply Storm
DSR: Advantages/ Disadvantages
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Summary
In this lecture we discussed the Dynamic SourceRouting Protocol (DSR)
❍ Route Discovery• Source Routing (Accumulation of routes in the packet header)• Role of route cache in speeding up the route discovery andreducing the propagation of RREQs/RREPs
❍ Route Maintenance• Route cache and the role it plays in route maintenance
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