Proposed ad hoc Routing Approaches

1
Proposed ad hoc Routing Approaches

• Conventional wired-type schemes (global routing,
  proactive)
• Distance Vector Link State
• Proactive ad hoc routing
• OLSR, TBRPF
• On- Demand, reactive routing
• DSR (Source routing), MSR
• AODV (Backward learning)
• Scalable routing
• Hierarchical routing HSR, Fisheye
• OLSR Fisheye
• LANMAR (for teams/swarms)
• Geo-routing GPSR, GeRaF, etc
• Motion assisted routing
• Direction Forwarding

2
Where do we stand?

• OLSR and TBRPF can dramatically reduce the
  state sent out on update messages
• They are very effective in dense networks.
• However, the state still grows with O(N)
• Neither of the above schemes can handle large
  scale nets from 10s to thousands of nodes
• What to do?

3
Hierarchical Routing

• The previous schemes reduce control traffic O/H
  but do not significantly reduce routing table
  size
• Solution use hierarchical routing to reduce
  table size
• In the process, reduce also control traffic
  O/H
• Proposed hierarchical schemes include
• Hierarchical State Routing (HSR)
• Fisheye State Routing (FSR)
• Landmark Routing
• Zone routing (hybrid scheme)

4
Hierarchical State Routing (HSR)

• Loose hierarchical routing in Internet
• Main challenge in ad hoc nets maintain/update
  the hierarchical partitions in the face of
  mobility
• Solution distinguish between physical
  partitions and logical grouping
• physical partitions are based on geographical
  proximity
• logical grouping is based on functional affinity
  between nodes (e.g., tanks of same battalion,
  students of same class)
• Physical partitions enable reduction of routing
  overhead
• Logical groupings enable efficient location
  management strategies using Home Agent concepts

5
HSR - physical multilevel partitions
HSR table at node 5
DestID 1 6 7 lt1-2-gt lt1-4-gt lt1-3gt
Path 5-1 5-1-6 5-7 5-1-6 5-7 5-7
HID(5) lt1-1-5gt HID(6) lt3-2-6gt
Hierarchical addresses
(MAC addresses)
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HSR - logical partitions and location management

• Logical (IP like) type address ltsubnet,hostgt
• Each subnet corresponds to a particular user
  group (e.g., tank battalion in the battlefield,
  search team in a search and rescue operation,
  etc)
• logical subnet spans several physical clusters
• Nodes in same subnet tend to have common mobility
  characteristic (i.e., locality)
• logical address is totally distinct from MAC
  address

7
HSR - logical partitions and location management
(contd)

• Each subnetwork has at least one Home Agent to
  manage membership
• Each member of the subnet registers its own
  hierarchical address with Home Agent
• periodical/event driven registration stale
  addresses are timed out by Home Agent
• Home Agent hierarchical addresses propagated via
  routing tables or queried at a Name Server
• After the source learns the destinations
  hierarchical address, it uses it in future
  packets
• Example Landmark Routing

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Scope of Fisheye
Fisheye State Routing (FSR)
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Fisheye State Routing (FSR)

• Topology data base at each node
  - similar to link state
  (e.g., OSPF)
• Routing information is periodically exchanged
  with neighbors only ( Global State Routing)
• similar to distance vector, but exchange entire
  topology matrix
• Routing update frequency decreases with distance
  to destination
• Higher frequency updates within a close zone and
  lower frequency updates to a remote zone
• Highly accurate routing information about the
  immediate neighborhood of a node progressively
  less detail for areas further away from the node

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Message Reduction in FSR TC (Topology Control)
message
LST
HOP
0
LST
HOP
01 10,2,3 25,1,4 31,4 45,2,3 52,4

1 0 1 1 2 2
01 10,2,3 25,1,4 31,4 45,2,3 52,4

2 1 2 0 1 2
1
3
LST
HOP
2
01 10,2,3 25,1,4 31,4 45,2,3 52,4

3 2 1 1 0 1
4
5
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Optimized Fisheye Link State Routing (OFLSR)

• Based on Optimized Link State Routing (OLSR)
• Borrows idea from Fisheye State Routing (FSR)
• Different frequencies for propagating the
  Topology Control (TC) message of OLSR to
  different scopes (e.g. different hops away)

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Scalability Property of OFLSR

• Scalability to Node Mobility
• 100 nodes, 1600mX1600m field, 367m Tx range
• IEEE 802.11 radio, 2Mbps channel rate, 10 CBR
  flows
• OLSR confign hello interval 1s, TC interval
  2s
• OFLSR confign 4 scopes, each scope is 2 hops
  except last one

Data Packet Delivery Ratio
Node mobility speed (m/s)
Data Packet Delivery Ratio
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Scalability Property of OFLSR

• Scalability to Node Mobility

Total of TC relayed
Total of TC received
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Scalability Property of OFLSR

• Scalability to Network Size
• Keep node density, increase of nodes, no
  mobility
• OLSR confign hello interval 2S, TC interval
  4S
• OFLSR confign 4 scopes, each scope is 2 hops
  except last one

Data Packet Delivery Ratio
Network Size ( of nodes)
Delivery rate vs Network Size
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Scalability Property of OFLSR

• Scalability to Network Size

Total of TC relayed
Total of TC received
16
Scalable Ad Hoc Routing using Landmarks and
Backbones

• The challenge
• Tens of thousands of nodes
• Nodes move in various patterns
• QoS communications requirements
• Hostile environment jamming

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Routing

• Current MANET solutions have limitations
• (a) proactive routing solutions (eg, Optimal
  Links State -OLSR) do not scale because of table
  size and control traffic overhead
• (b) on demand routing cannot handle high mobility
  and dense traffic patterns
• (c) explicit hierarchical routing introduces
  excessive address maintenance O/H in high
  mobility
• MANET protocols do not scale in high mobility
• Our approach
• Exploit implicit hierarchy induced by group
  mobility

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Solution Landmark Routing Overlay

• Main assumption nodes move in groups
  (battlefield)
• Groups are predefined or dynamically recognized
• Node address lt group ID , Host addressgt
• Landmark elected in each group
• Landmarks advertisements maintain the landmark
  overlay

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LANMAR Overlay Routing (cont)

• Builds upon existing MANET protocols
• (1) local routing algorithm that keeps
  accurate routes within local scope lt k hops
  (e.g., OLSR)
• (2) Landmark routes advertised to all mobiles
  using DSDV
• Like Internet LS DV

20
LANMAR Overlay Routing (cont)

• Packet Forwarding
• A packet to local destination is routed
  directly using local tables
• A packet to remote destination is routed to
  Landmark corresponding to logical addr.
• Once the landmark is in sight, the direct route
  to destination is found in local tables
• Benefits low storage, low update traffic O/H

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Landmark Routing In action
Landmark
LM2
LM1
LM3
Logical Subnet
dest
source
local routing
Long haul routing

1. Node address subnet ID, Host ID
2. Look up local routing table to locate dest ? fail
3. Look up landmark table to find destination subnet
   ? LM1
4. Send a packet toward LM1

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Link Overhead of LANMAR

• Dramatic O/H reduction from linear to O(N) to O
  (sqrtN)

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LANMAR Local Scope Optimization

• Goal find local routing scope size that
  minimizes routing overhead
• size of landmark distance vector O ( N / G)
• size of local Link State topology map O ( m d
  )
• N total of nodes d avg of one-hop
  neighbors (degree)

H (Routing overhead)
Total O/H
Local route O/H
Landmark O/H
h (scope size)
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LANMAR enhances MANET routing schemes

• We compare
• MANET routing schemes DSDV, OLSR and FSR and
• (b) same MANET schemes, BUT with LANMAR overlay
  on top

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Delivery Ratio

• DSDV and FSR decrease quickly when number of
  nodes increases
• OLSR generates excessive control packets, cannot
  exceed 400 nodes

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Mobile Backbone Overlay

• Landmark Overlay provides routing scalability
• However the network is still flat - paths have
  many hops ? poor TCP and QoS performance!!
• Solution Mobile Backbone Overlay (MBO)
• MBO is a physical overlay ie long links
• MBO provides performance scalability
• LANMAR extends transparently to the MBO

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UAV
Backbone Node
Logical Subnet
source
dest.
Landmark routing concept extends transparently to
the multilevel backbone Fast BB links are
advertised and immediately used When BB link
fails, the many hop alternate path is chosen
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Backbone Node Automatic Deployment

• Objectives
• Robust and autonomous backbone network
  maintenance
• Uniform distribution to cover the field
• Approach
• Dynamic backbone node election Deploy redundant
  backbone capable nodes and select a few
• Backbone node automatic placement Relocate
  backbone nodes from dense to sparse regions

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Backbone Network and LANMAR

• Why a Backbone physical hierarchy?
• To improve coverage, scalability and reduce hop
  delays
• Backbone deployment
• automatic placement Relocate backbone nodes from
  dense to sparse regions (using repulsive forces)
• Key result LANMAR automatically adjusts to
  Backbone
• Combines low routing O/H (LANMARK logical
  hierarchy) low hop distance and high bandwidth
  (Backbone physical hierarchy)

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Backbone Node Deployment

• Deployment algorithm
• Assumption Backbone nodes know their position
  (from GPS)
• Each BN broadcasts its position periodically via
  scoped flooding.
• Let the distance between x and y Dxy. We define
  the repulsive force between them
  
  where A is a constant.
• Vector sum of repulsive forces from neighbors
  determines direction and speed of motion

31

32
Extending Landmark to Hierarchical Network

• Backbone nodes are independently elected
• All nodes (including backbone nodes) are running
  the original LANMAR
• In addition, backbone nodes re-broadcast landmark
  information via higher level links
• Backbone Routes preferred by landmark (they are
  typically shorter)

33
Extending Landmark (cont)

• If backbone node is lost, Landmark routing fills
  the gap while a replacement backbone node is
  elected
• Advantages
• Seamless integration of flat ad hoc landmark
  routing with the backbone environment provides
  instant backup in case of failures
• Easy deployment, simple changes to ordinary
  ground nodes
• Remove limitations of strictly hierarchical
  routing

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Variable number of Backbone Nodes

• Decrease of average end-to-end delay while
  increasing of backbone nodes

35
Variable number of Backbone Nodes

• Increase of delivery fraction while increasing
  of backbone nodes

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Variable Speed with 1000 nodes

• Delivery fraction while increasing mobility speed

37
LANMAR implementation in IPv6 LINUX environment

• Use IPv6s Group ID to distinguish groups
• Support many more members in each group (than
  IPv4)
• A packet to remote destination is routed to
  corresponding Landmark based on IPv6 address
  lookup

IPv6
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Case study apply Direct Forwarding (DFR) to
LANMAR Routing

• LANMAR builds upon existing routing protocols
• (1) local routing algorithm that keeps
  accurate routes within local scope lt k hops
  (e.g., OLSR, FSR)
• (2) Landmark routes advertised to all mobiles
  using a Distance Vector approach

39
LANMAR (cont)

• A packet to local destination is routed
  directly using local tables
• A packet to remote destination is routed to
  Landmark corresponding to logical address
• Once the landmark is in sight, the direct
  route to destination is found in local tables.

40
LANMAR DFR

• LANMAR has proved to be very scalable to size
• However, as speed increases, performance
  degrades, even with group mobility!
• Problem was traced to failure of DV route
  advertising in high mobility
• We first tried to refresh more frequently it did
  not work!
• Next step try DFR

41
Simulation Experiments

• Simulator QualNet 3.8
• Standard IEEE 802.11 radio with a channel rate
  of 2Mbps and transmission range of 367 meters.
• Network field size 2250m by 2250m
• LANMAR is the protocol hosting DFR
• 225 nodes (or 360 nodes) equally distributed in
  9 groups
• Mobility model Group Mobility model
• Traffic CBR, 1 packets/sec, 512 bytes/packet
• The of source-destination pairs is varied in
  the simulations to vary the offered traffic load

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Performance as a function of speed
DFR
LANMAR
Delivery ratio vs. speed (Including packet loss
due to disconnected destination)
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Performance as a function of speed (cont.)
DFR
LANMAR
Delivery ratio vs. speed (Excluding packet loss
due to disconnected destination)
44
Performance as a function of speed (cont.)
DFR
LANMAR
Aggregated throughput vs. speed
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Conclusions and Future Work

• DFR new forwarding strategy for table driven
  routing
• Direction Forwarding can improve LANMAR
  performance dramatically at high speeds
• Future Work
• Test DFR under local reference system
• Apply DFR concept to AODV - Hybrid
• TCP over LANMAR, AODV DFR
• Compare DFR with other backup route schemes
• Test DFR under more general mobility models