Unit II Topic 8-15 Routing Protocols for Ad Hoc Wireless Networks

Department of Computer Science and EngineeringKalasalingam University

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CSE 6007 Mobile Ad Hoc Wireless Networks

Outline

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IntroductionTopic 8 : Issues in Designing A Routing Protocol for Ad

Hoc Wireless NetworksTopic 9 : Classification of Routing ProtocolsTopic 10 : Table Driven Routing Protocols Topic 11 : On-Demand Routing ProtocolsTopic 12 : Hybrid Routing Protocols Topic 13 : Routing Protocols with Efficient Flooding

MechnismsTopic 14 : Hierarchical Routing ProtocolTopic 15 : Power Aware Routing Protocol

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The main routing problems for MANETs

Node mobility

Routing path broken frequently

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Traditional ad-hoc routing protocols

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1211

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Dest NextNode Dist seqNo2 2 1 223 2 2 264 5 2 325 5 1 1346 6 1 1447 2 3 1628 5 3 1709 2 4 186

10 6 2 14211 6 3 17612 5 3 19013 5 4 19814 6 3 21415 5 4 256

Routing table for Node 1

Table-driven routing protocol – DSDV (cont.)

Example:

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Routing table for Node 1

Dest NextNode Dist seqNo2 2 1 223 2 2 264 5 2 325 5 1 1346 6 1 1447 2 3 1628 5 3 1709 2 4 186

10 6 2 14211 5 4 18012 5 3 19013 5 4 19814 6 3 21415 5 4 256

Table-driven routing protocol – DSDV (cont.)

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Route Discovery in DSR

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S E

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J

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IK

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Represents a node that has received RREQ for D from S

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Route Discovery in DSR

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S E

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J

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IK

Represents transmission of RREQ

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YBroadcast

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[S]

[X,Y] Represents route record stored in RREQ

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Route Discovery in DSR

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S E

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IK

• Node H receives packet RREQ from two neighbors: potential for collision

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[S,E]

[S,C]

[S,B]

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Route Discovery in DSR

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S E

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J

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G

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• C receives RREQ from G and H, but does not forward

it again, because C has already forwarded RREQ once

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[S,C,G]

[S,E,F][S,B,A]

[S,B,H]

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Route Discovery in DSR

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S E

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J

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IK

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J and K both broadcast RREQ to D Their transmissions may collide at D

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[S,C,G,K]

[S,E,F,J]

[S,B,H,I]

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Route Discovery in DSR

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S E

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D does not forward RREQ, because D is the intended target

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[S,E,F,J,M]

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Route Reply in DSR

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RREP [S,E,F,J,D]

Represents RREP control message

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An Example of Route Maintenance

J sends a route error to S along route J-F-E-S when it finds link [J-D] broken

Nodes hearing RERR update their route cache to remove all invalid routes related with link J-D

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RERR [J-D]

Route Error Packet : RERR

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Use of Route Caching Can Speed up Route Discovery

When node Z sends a route request for node C, node K sends back a routereply [Z,K,G,C] to node Z using a locally cached route

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[S,E,F,J,D][E,F,J,D]

[C,S]

[G,C,S]

[F,J,D],[F,E,S]

[J,F,E,S]

RREQ

[K,G,C,S]RREP

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Use of Route Caching Can Reduce Propagation of Route Requests

Route Replies (RREP) from node K and D limit flooding of RREQ.

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[S,E,F,J,D][E,F,J,D]

[C,S]

[G,C,S]

[F,J,D],[F,E,S]

[J,F,E,S]

RREQ

[K,G,C,S]RREP

[D,K,G,,C]

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Route Requests in AODV

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JC

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IK

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Represents a node that has received RREQ for D from S

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D

S

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Route Requests in AODV

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JC

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IK

Represents transmission of RREQ

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YBroadcast transmission

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S

D

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Route Requests in AODV

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JC

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IK

Represents links on Reverse Path

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S

D

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Reverse Path Setup in AODV

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JC

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• Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once

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Reverse Path Setup in AODV

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JC

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IK

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Reverse Path Setup in AODV

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JC

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• Node D does not forward RREQ, because node D is the intended target of the RREQ

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Forward Path Setup in AODV

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JC

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Forward links are setup when RREP travels alongthe reverse path

Represents a link on the forward path

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Route Maintenance

The link from node 3 to D is broken as 3 has moved away to a position 3´.

Node 2 sends a RERR message to 1 and 1 sends the message in turn to S.

S initiates a route discovery if it still needs the route to D.

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S D

RERR RERR3´

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