1. UM-OLSR OLSR routing protocol in NS2
郭祐暢

2. Outline Brief overview of OLSR MPR selection algorithm UM-OLSR install
Example
UM-OLSR code

3. Classification Ad Hoc Routing Protocols proactive reactive
Source-Initiated
On demand
Table driven
DSDV
TBRPF
OLSR
CGSR
AODV
DSR
LMR
ABR
TORA
SSR

4. Optimized 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)

5. Optimized Link State Routing Protocol
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

6. Optimized Link State Routing Protocol
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

7. Optimized Link State Routing Protocol
Three main modules
Neighbor/link sensing
Provide topology information up to two hops
MPR selector information notification
(“A select B as A’s MPR” in HELLO message to B)
Optimized flooding/forwarding
MPR set to cover all the two hop neighbors
MPR selector set: set of nodes that select me as one of their MPR set
OLSR-Messages from MPR selector set are to be forwarded
Link-State messaging and route calculation
Topology table
Route table

8. MPR selection Each node select a set of MPR Selectors
Who can be a MPR Selectors
of node N ?
one-hop neighbors of N
MPR set of Node N (Rules)
Set of MPR’s is able to
transmit to all two-hop neighbors
Link between node and it’s
MPR is bidirectional. Y N X M D Z A B

9. Multipoint Relays (MPR)
Every node keeps a table of routes to all known destination through its MPR nodes
Every node periodically broadcasts list of its MPR Selectors (instead of the whole list of neighbors).
Upon receipt of MPR information each node recalculates and updates routes to each known destination

10. MPR selection algorithm
Each point u has to select its set of MPR.
Goal :
Select in the 1-neighborhood of u (N1(u)) a set of nodes as small as possible which covers the whole 2-neighborhood of u(N2(u)).
Step 1: Select nodes of N1(u) which cover isolated points
of N2(u).
Step 2: Select among the nodes of N1(u) not selected at
the first step, the node which covers the highest
number of points of N2(u) and go on till every
points of N2(u) are covered.

11. MPR selection algorithmu
First step: Select nodes in N1(u) which cover “isolated points” of N2(u).

12. MPR selection algorithmu
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).

13. MPR selection algorithmu
Final：MPRs

14. Installation Download UM-OLSR 0.8.8 from
Ns2.27、2.28、2.29 / UM-OLSR 0.8.7、0.8.8
Copy um-olsr tgz to ns-allinone-2.29/ns-2.29/
$ cd ns-allinone-2.29/ns-2.29/
$ tar zxvf um-olsr tgz
$ ln -s ./um-olsr /olsr
$ patch -p1 < olsr/um-olsr_ns-2.29_v0.8.8.patch
$ ./configure
$ make

15. Example Download olsr_example.tcl from

16. OLSR Hello message one hop for
Two hop topology information
MPRs
Transmit two hop top topology information
By MPRs
TC message
Complete Topology Information
Shortest Path Tree calculation (Dijkstra)
Routing table build

17. TC message TC – Topology control message:
Sent periodically. 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

18. 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

19. TC message Upon receipt of TC message:
If there exist some entry to the same destination with higher Sequence Number, the TC message is ignored
If there exist some entry to the same destination with lower Sequence Number, the topology entry is removed and the new one is recorded
If the entry is the same as in TC message, the holding time of this entry is refreshed

20. Routing Table
Each node maintains a routing table to all known destinations in the network
Routing table is calculated from Topological Table, taking the connected pairs
Routing table:
Destination address
Next Hop address
Distance
Routing Table is recalculated after every change in neighborhood table or in topological table

21. UM-OLSR File List (Header)
OLSR.h
header file for OLSR agent and related classes
OLSR_pkt.h
contains all declarations of OLSR packets and messages
OLSR_printer.h
includes all printing functions related to OLSR
OLSR_repositories.h
defined all data structures needed by an OLSR node
OLSR_rtable.h
header file for routing table's related stuff
OLSR_state.h
declares and defines internal state of an OLSR node

22. UM-OLSR File List OLSR.cc OLSR_printer.cc OLSR_rtable.cc OLSR_state.cc
Implementation of OLSR agent and related classes
OLSR_printer.cc
Printing functions used for debugging and tracing are implemented in this file
OLSR_rtable.cc
Implementation of our routing table
OLSR_state.cc
Implementation of all functions needed for manipulating the internal state of an OLSR node