Optimized Link State Routing Protocol for Ad Hoc Networks

1
Optimized Link State Routing Protocol for Ad Hoc
Networks

• Presented by Yuyan Xue

2
Overview

• The Optimized Link State Routing Protocol (OLSR)
  is a table driven, proactive protocol, i.e.,
  exchanges topology information with other nodes
  of the network regularly.
• Each node selects a set of its neighbor nodes as
  "multipoint relays" (MPR).
• Only nodes, selected as such MPRs, are
  responsible for forwarding control traffic,
  intended for diffusion into the entire network.

3
Feature

• Inherit Stability of Link-state protocol
• Multipoint Relays (MPR) employed for selective
  flooding
• Control traffic by reducing the number of
  transmissions required.

4
Protocol Operation

• Neighbor Sensing
• MPR Selection
• MPR Information Declaration
• Routing Table Construction

5
Neighbor Sensing Hello Message

• Each node periodically broadcasts Hello
  message
• List of neighbors with bi-directional link
• List of other known neighbors.
• Hello messages permit each node
• to learn topology up to 2 hops
• Based on Hello messages each
• node selects its set of MPRs

6
MPR Selection

• Each node select a set
• of MPR Selectors
• Who can be a MPR Selectors
• of node N ?
• - one-hop neighbors of N

Y
S
X
M

• MPR set of Node N (Rules)
• (1) Set of MPRs is able to
• transmit to all two-hop neighbors
• (2) Link between node and its MPR is
• bidirectional.

D
Z
A
7
MPR Selection Con.
Node 1 Hop Neighbors 2 Hop Neighbors
MPR(s) B A,C,F,G
D,E C
10

• Node B will select C as its
• MPR So all the other nodes know
• that they can reach B via C

5
10
3
60
40
25

• D-gtB route is D-C-B, whose
• bottleneck BW is 3 ( Not BW
• optimal)

110
50
100
30
8
MPR Information Declaration

• Topology Control Message (TC)
• Send if there are updates
• Contains
• MPR Selector Table
• Sequence number
• Topology Table
• Each node maintains a Topology Table based on TC
  messages
• Routing Tables are calculated based on Topology
  tables

9
Routing Table Construction

• Each node maintains a routing table to all
  known
• destinations in the network
• Routing table
• Destination address
• Next Hop address
• Distance
• Routing Table is calculated from Topology
  Table and
• recalculated after every change in
  neighborhood table
• or in topological table

10
References

• G. Pei, M. Gerla, and X. Hong, " LANMAR Landmark
  Routing for Large Scale Wireless Ad Hoc Networks
  with Group Mobility," In Proceedings of IEEE/ACM
  MobiHOC 2000, Boston, MA, Aug. 2000.
• Thomas Clausen, Philippe Jacquet, " Optimized
  Link State Routing Protocol (OLSR) ," IETF
  Internet Draft , July 3 2003.
• X. Hong, K. Xu, and M. Gerla, " Scalable Routing
  Protocols for Mobile Ad Hoc Networks " IEEE
  Network Magazine, July-Aug, 2002, pp. 11-21