Overview of the Fisheye State Routing (FSR) for cellular networks, IDC 2012 By Yoav Francis and Nir Solomon (Part of a performance comparison of various routing algorithms in cellular networks)

1. Fisheye State Routing
Protocol Overview
By:
Nir Solomon
Yoav Francis
Interdisciplinary Center, Herzliya

2. Ad-Hoc Network
A wireless network between mobile nodes
No infrastructure
Limited communication distance
Low-powered users
How to route messages?
Flooding/Broadcast
Not scalable
Using the shortest path from source to
destination
Requires nodes to keep topology data

3. Ad-Hoc Network (cont.)
Node moves cause network topology changes
Results in routes change
Nodes need to update their topology information
A node disconnecting to or from a neighbor needs to notify
other nodes
There are many upates – must make update process efficient
Low overhead
Fast propagation

4. Ad-Hoc Routing algorithms
 Proactive:
 Always monitor network topology
 Advantage: Always know how to route to any node
 Disadvantages:
Routing table storage
Periodic control traffic overhead
 Example protocols: LSR, FSR
 Reactive:
 Look for a route only when need to send a packet
 Advantages:
Low routing table storage
No periodic control traffic
 Disadvantage: route search overhead
 Example protocols: TORA, DSR

5. Link State Routing
Each node holds a routing table with the link state of all
nodes in the network
Periodically or on link change: flood “link state” – list of
neighbors (neighbor = 1 hop)
Re-broadcasts link state information received from neighbors
Use timestamp to distinguish new from stale updates
Routing
The destination is stored in the message header
Each forwarding node finds the shortest path to the destination
according to its routing table
 On each update of the topology map – each node must calculate
the shortest path to all other nodes again.

6. Link State Routing drawbacks
As the number of nodes grow or mobility increases:
Routing tables grow linearly
Link state overhead grow linearly – the overhead
packets will consume most of the bandwidth as
network size increases.
Not scalable

7. • Fish do have 360° (or almost) vision.
• Fishes (and humans) do have a higher
concentration of optic nerves close to they focal
point than elsewhere in they eye.
• As a result fisheye captures with high detail the
points near the focal point
Fisheye Vision

8. Fisheye Vision (Cont.)

9. Published in “Fisheye State Routing in Mobile
Ad Hoc Networks” in 2000, by Guangyu Pei ,
Mario Gerla , Tsu-Wei Chen at ICDCS.
Aim – Reduce routing updates overhead in large
ad-hoc networks.
Background

10. Fisheye State Routing (FSR)
• Proactive link-state routing protocol.
• Similar to link state as it maintains a full topology map at each node
– Periodic exchange of Hello packet.
– Periodic exchange of topology tables within the local neighbors
only (instead of flooding the entire network) .
• Topology tables update frequency decreases with distance to
destination
– Updates for a near destination are propagated more frequently then
updates for a remote destination

11. Fisheye State Routing (Cont.)
Every node holds:
 Neighbor list
 Topology Table
 Next Hop Table
 Distance Table
For large network, in order to reduce the size of the routing
update message, the FSR technique uses different
exchange periods for different entries in the routing table.
Relative to each node, the network is divided into
different scopes.

12. Fisheye State Routing (Cont.)
Central Node
1-hop neighbor
2-hops or more
neighbor
The link state updates of the nodes in scope k are sent every 2k-1
T to all the
neighboring nodes
•K is the hop distance
•T is the link state updates transmission period
Scope 1
Scope 2

13. Fisheye State Routing (Cont.)
 Maintain accurate routing information for immediate neighbors.
 Progressively less detail as distance increases.
 Link state of immediate neighbors are exchanged more frequently.
 The exchange frequency decreases proportionally to the distance.
 As the packet gets closer to the destination, the accuracy
increases.

14. Fisheye State Routing
0
5
1
2
4
3
0:{1}
1:{0,2,3}
2:{5,1,4}
3:{1,4}
4:{5,2,3}
5:{2,4}
1
0
1
1
2
2
LST HOP
0:{1}
1:{0,2,3}
2:{5,1,4}
3:{1,4}
4:{5,2,3}
5:{2,4}
2
1
2
0
1
2
LST HOP
0:{1}
1:{0,2,3}
2:{5,1,4}
3:{1,4}
4:{5,2,3}
5:{2,4}
2
2
1
1
0
1
LST HOP
Entries in black are
exchanged more
frequently

15. Simulation Results

16. FSR – Conclusions
 Major scalability benefit: link state overhead decreases
significantly
 Unsolved problems:
Route table size still grows linearly with network size
Out of date routes to remote destinations

17. Our Project

18. Questions?
Thanks!