MPR Extension for

1
65th IETF OSPF WG in Dallas, March 23rd 2006

• MPR Extension for
• OSPF on MANETs
• draft-baccelli-ospf-mpr-ext-01.txt
• Emmanuel Baccelli

2
Agenda

• MANET-OSPF background
• Topology reduction with MPR links
• Flooding optimization with MPR extension

3
Keys to efficient OSPF on MANETs

• MANET-OSPF DT results
• Need overhead reduction
• Need to focus on LSUpdate
• Reduction can be achieved
• with flooding optimization
• with topology reduction
• with adjacency limitation

benchmark results Henderson, Spagnolo et al.
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OSPF extensions for MANET

• No change to traditional OSPF
• Existing code/protocol unaltered
• MANET instabilities wont affect OSPF stability
• Leverage existing code/mechanisms
• Changes concern only OSPF MANET interfaces
• Specific MANET interface type addressing
• highly dynamic topology, scalability, radio link
  fading
• draft-baccelli-ospf-mpr-ext-01 proposes
• topology and adjacency reduction
• flooding optimization

5
MPR Multi-Point Relays

• MPR selects a subset of
• links and nodes to achieve
• optimized network coverage.

MPR
MPR
MPR
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Topology Reduction withMPR Links Adjacency
Limitation

• MPR yields naturally adjacency limitation
• Adjacencies are between
• MPR and MPR-selectors (MPR links)
• Some routers form adjacencies with every neighbor
• Hybrid routers (with both traditional and MANET
  interfaces)
• Results in lossless topology reduction

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MPR links guarantee shortest paths
2-WAY link
Adjacency
MANET-OSPF
MANET-OSPF
Case 1

• MANET source hop
• may be 2-WAY

Case 2
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OSPF Heterogeneous Topologies
MANET-OSPF

• paths to/through a MANET
• made of adjacencies
• the best paths (shortest)

OSPF
S
D
MANET-OSPF
Case 1
OSPF
OSPF
S
Case 2
2-WAY link
Adjacency
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Path costs are minimal
2-WAY link
Adjacency
MANET-OSPF
1
1
1
1
1
1
1
S
OSPF
no out-of-track forwarding
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MPR Links Topology Reduction Evaluation
Unit Disk Graph simulations speed 60 mph, radio
range 1 mile, 40 - 100 routers
Full topology
Full topology
MPR-OSPF
MPR-OSPF
number of links in advertized topology
MANET LSUpdate overhead (number of
advertized links per minute)
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Flooding Optimization with MPR

• MPR selection can also be used to optimize
  flooding
• Only MPRs retransmit
• The whole network is covered
• The number of retransmitters is drastically
  reduced

MPR
S
S
MPR
12
Flooding Optimization with MPR
Unit Disk Graph simulations 2x2 miles, radio
range 1 mile, 40 - 100 routers
Traditional flooding
MPR flooding
Number of retransmitters to complete flooding
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OSPF MPR Extension in a Nutshell

• MPR information is signalled only on MANET
  interface, with HELLO packets appended LLS
  information.

• MPR is validated to be simple and efficient by
  manet-wg
• Drastic overhead reduction (topology flooding)
• No loss in connectivity
• Guaranteed no route-stretch
• Simple leverage of existing code base, extensible
• Performs well in all cases (including high
  mobility)

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Next Step

• MPR extension must be evaluated for OSPF on MANETs