The Optimized Link State Routing Protocol (OLSR) is an IP routing protocol optimized for mobile ad hoc networks, which can also be used on other wireless ad hoc networks. OLSR uses hello and topology control (TC) messages to discover and then disseminate link state information throughout the mobile ad hoc network. Contents which are covered here: Classification of Ad-Hoc Routing Protocol Link State Routing Problems of Link State Routing Optimized Link State Routing Protocol 1 Hop and 2 Hop Neighbors Hello Packet MPR Selection Topology Table MPR Information Declaration *** Animated figure/diagram might not be visible in PDF view. Please consider it. *** OLSR Model, OLSR Protocol, Optimized Link-State Routing Protocol

1. OPTIMIZED LINK STATE ROUTING
PROTOCOL (OLSR)
Presented By
Tamzida Azad
1

2. CONTENTS
1. Classification of Ad-Hoc Routing Protocol
2. Link State Routing
3. Problems of Link State Routing
4. Optimized Link State Routing Protocol
5. 1 Hop and 2 Hop Neighbors
6. Hello Packet
7. MPR Selection
8. Topology Table
9. MPR Information Declaration
10. References
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3. AD-HOC ROUTING PROTOCOL CLASSIFICATION
Table driven
Source-Initiated
On demand
DSDV
CGSR
OLSR TBRPF
AODV DSR LMR
TORA
ABR
SSR
Ad Hoc Routing
Protocols
proactive reactive
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4. LINK STATE ROUTING PROTOCOL
 Proactive & Table-driven
 Link State Routing
 Each node expands a spanning tree
 Each node can obtain the whole network
topology
 Utilizes a technique to reduce
message flooding
 MultiPoint Relaying (MPR)
Figure 1: LSR
Protocol
Figure 2: OLSR Protocol
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5. LINK STATE ROUTING
 Each node periodically floods status of
its links
 Each node re-broadcasts link state
information received from its neighbors
 Each node keeps track of link state
information received from other nodes
 Each node uses above information to
determine next hope to each destination
24 retransmissions to diffuse a
message up to 3 hops
Retransmission node
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6. LINK STATE ROUTING
 Only selected neighbors (MultiPoint
Relays, MPRs) retransmit messages
 Select MPRs such that they cover all
2hop neighbors
 2-hop neighbors taken from neighbors'
HELLO messages
11 retransmission to diffuse
a message up to 3 hops
Retransmission node -
MPR
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7. L I N K S T A T E R O U T I N G
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8. L I N K S T A T E R O U T I N G
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9. L I N K S T A T E R O U T I N G
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10. L I N K S T A T E R O U T I N G
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11. L I N K S T A T E R O U T I N G
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12.  LS advertisements are flooded
 Flooding cause reception of multiple
copies of same LS advertisements
 MANET devices are mobile and battery
powered. Flooding cause high battery
consumption.
LINK STATE ROUTING PROBLEMS
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13. OLSR PROTOCOL
OLSR is an optimization of the classical link state, optimized for mobile ad hoc networks,
which can also be used on other wireless ad hoc networks.
 Optimizes the pure forwarding mechanism called multipoint relaying.
 Optimizes the pure link state routing protocol.
 Avoid unnecessary transmission of LS packets.
 Each node decides which of its neighbors can flood LS packet these nodes. These nodes
are known as MPR.
 Only MPR can retransmit
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14. OLSR PROTOCOL
Optimizations are done in two ways
 By reducing the size of the control packets
 By reducing the number of links that are used for forwarding the link state
packets
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15. N E I G H B O R N O D E
Neighbors of A: H, F, G, C, B
Neighbor Node:
Node A is Neighbor Node of B if B can hear A.
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16. 2 - H O P N E I G H B O R
2 Hop Neighbor of A: I, J, A, B, C, E, D
Strict 2 Hop Neighbor of A: I, J, E, D
2-Hop Neighbor :
Node which can be heard by neighbor.
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17. Strict 2-Hop Neighbor :
Node which can be heard by neighbor excluding node itself and its neighbor.
S T R I C T 2 - H O P N E I G H B O R
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18. M U L T I P O I N T R E A LY
MPR :
Node which is selected by it’s 1-hop neighbor to
retransmit all broadcast message received by it.
MPR Selector:
Node which has selected its 1-hop neighbor as
MPR.
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19. L I N K
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20. S Y M M E T R I C 1 - H O P
N E I G H B O R H O O D
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21. S Y M M E T R I C 2 - H O P
N E I G H B O R H O O D
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22. S T R I C T S Y M M E T R I C 2 - H O P
N E I G H B O R H O O D
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23. OLSR-TYPES
OF PACKET
Hello Packet
Topology Control Packet
MID Packets
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24. H E L L O P A C K E T
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25. H E L L O P A C K E T
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26. M P R S E L E C T I O N A L G O R I T H M
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27. M P R S E L E C T I O N A L G O R I T H M
First step:
Select nodes in N1(u) which cover “isolated
points” of N2(u).
u
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28. M P R S E L E C T I O N A L G O R I T H M
Second step :
Consider in N1(u) only points which are not already
selected at the first step NPR1(u) and points in N2(u)
which are not covered by the NPR1(u) . While there
exists points in N2(u) not covered by the selected
MPR, select in N2(u), the node which covers the
highest number of non-covered nodes in N2(u).
u
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29. F I N A L M P R
u
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30. TOPOLOGY CONTROL MESSAGE
TC – Topology control message:
 In order to build intra-forwarding database.
 Only MPR nodes forward periodically to declare its MPR selector set.
 Message might not be sent if there are no updates and sent earlier if there are updates.
Contains:
 MPR Selector Table
 Sequence number
Each node maintains a Topology Table based on TC messages. Routing Tables are
calculated based on Topology tables
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31. TOPOLOGY TABLE
Destination
address
Destination’s
MPR
MPR Selector
sequence
number
Holding time
MPR Selector in
the received TC
message
Last-hop node to the destination.
Originator of TC message
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32. MPR INFORMATION DECLERATION
Node A B C select M as their MPR.
For node M, MPR selectors are A,
B, C. M send this information to
other node.
TC
Originator
MPR
Selector
MPR
Selector
Sequence
M A 1
M B 1
M C 1
M send this to node Y & Z
Dest
Address
Dest MPR MPR
Selector
Sequence
A M 1
B M 1
C M 1
… … …
Y Topology Table
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33. MPR INFORMATION DECLERATION
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34. T H A N K Y O U
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