routing in ad hoc network

1. Introduction to Wireless
Ad-Hoc Networks Routing
Dr. Noman Islam
https://sites.google.com/a/nu.edu.pk/noman-islam/
http://facebook.com/sir.noman.islam

2. Outline
Challenges
Design Goals Specified by MANET
Types of Routing
Protocols in Detail
Conclusion

3. Challenges
Dynamic Topologies
Bandwidth-constrained, variable capacity links
Energy-constrained
Limited Physical security
Scalability

4. Types of routing
Flat Proactive Routing
• Link state Fish-Eye Routing, GSR, OLSR.
• Table driven: Destination-Sequenced Distance Vector (DSDV), WRP)
On-Demand or Reactive Routing
• Ad hoc On-demand Distant Vector (AODV)
• Dynamic Source Routing (DSR)
Hybrid Schemes
• Zone Routing ZRP, SHARP (proactive near, reactive long distance)
• Safari (reactive near, proactive long distance)
Geographical Routing
Hierarchical: One or many levels of hierarchy
Routing with dynamic address
• Dynamic Address RouTing (DART)

5. Proactive Protocols
Proactive: maintain routing information
independently of need for communication
Update messages send throughout the network
periodically or when network topology changes.
Low latency, suitable for real-time traffic
Bandwidth might get wasted due to periodic
updates
They maintain O(N) state per node, N = #nodes

6. On-Demand or Reactive Routing
Reactive: discover route only when you need it
Saves energy and bandwidth during inactivity
Can be bursty -> congestion during high activity
Significant delay might occur as a result of route
discovery
Good for light loads, collapse in large loads

7. Hybrid Routing
Proactive for neighborhood, Reactive for far
away (Zone Routing Protocol, Haas group)
Proactive for long distance, Reactive for
neighborhood (Safari)
Attempts to strike balance between the two

8. Hierarchical Routing
Nodes are organized in clusters
Cluster head “controls” cluster
Trade off
• Overhead and confusion for leader election
• Scalability: intra-cluster vs intercluster
One or Multiple levels of hierarchy

9. Geographical Routing
Nodes know their geo coordinates (GPS)
Route to move packet closer to end point
Protocols DREAM, GPSR, LAR
Propagate geo info by flooding (decrease
frequency for long distances)

10. Types of routing
Flat Proactive Routing
• Link state Fish-Eye Routing, GSR, OLSR.
• Table driven: Destination-Sequenced Distance Vector (DSDV), WRP)
On-Demand or Reactive Routing
• Ad hoc On-demand Distant Vector (AODV)
• Dynamic Source Routing (DSR)
Hybrid Schemes
• Zone Routing ZRP, SHARP (proactive near, reactive long distance)
• Safari (reactive near, proactive long distance)
Geographical Routing
Hierarchical: One or many levels of hierarchy
Routing with dynamic address
• Dynamic Address RouTing (DART)

11. Proactive: DSDV - Destination-Sequenced
Distance Vector Algorithm
By Perkins and Bhagvat
Based on Bellman Ford algorithm
• Exchange of routing tables
• Routing table: the way to the destination, cost
Every node knows “where” everybody else is
• Thus routing table O(N)
Each node advertises its position
• Sequence number to avoid loops
• Maintain fresh routes

12. DSDV details
Routes are broadcasted from the “receiver”
• Nodes announce their presence: advertisements
Each broadcast has
• Destination address: originator
• No of hops
• Sequence number of broadcast
The route with the most recent sequence is used

13. Reactive: Ad-Hoc On-demand Distance
Vector Routing (AODV)
By Perkins and Royer
Sender tries to find destination:
• broadcasts a Route Request Packet (RREQ).
Nodes maintain route cache and use destination
sequence number for each route entry
State is installed at nodes per destination
Does nothing when connection between end points is
still valid
When route fails
• Local recovery
• Sender repeats a Route Discovery

14. Route Discovery in AODV 1
1
2
3
4
5
6
7
8
Source
Destination
Propagation of Route Request (RREQ) packet

15. Route Discovery in AODV 2
1
2
3
4
5
6
7
8
Source
Destination
Path taken by Route Reply (RREP) packet

16. In case of broken links…
Node monitors the link status of next hop in
active routes
Route Error packets (RERR) is used to notify
other nodes if link is broken
Nodes remove corresponding route entry after
hearing RERR

17. Dynamic Source Routing (DSR)
Two mechanisms: Route Maintenance and Route
Discovery
Route Discovery mechanism is similar to the one
in AODV but with source routing instead
Nodes maintain route caches
Entries in route caches are updated as nodes
learn new routes.
Packet send carries complete, ordered list of
nodes through which packet will pass

18. When Sending Packets
Sender checks its route cache, if route exists,
sender constructs a source route in the packet’s
header
If route expires or does not exist, sender initiates
the Route Discovery Mechanism

19. Route Discovery 1 (DSR)
1
2
3
4
5
6
7
8
<1>
<1,2>
<1,3,5>
<1,3,5,7>
<1,4,6>
<1,4>
<1>
<1>
<1,3>
Source
Destination
Building Record Route during Route Discovery

20. Route Discovery 2 (DSR)
1
2
3
4
5
6
7
8
<1,4,6>
<1,4,6>
<1,4,6>
Source Destination
Propagation of Route Reply with the Route Record

21. Route Maintenance
Two types of packets used: Route Error Packet and
Acknowledgement
If transmission error is detected at data link layer, Route
Error Packet is generated and send to the original sender
of the packet.
The node removes the hop is error from its route cache
when a Route Error packet is received
ACKs are used to verify the correction of the route links.

22. The Zone Routing Protocol (ZRP)
Hybrid Scheme
Proactively maintains routes within a local
region (routing zone)
Also a globally reactive route query/reply
mechanism available
Consists of 3 separate protocols
Protocols patented by Cornell University!

23. Intrazone Routing Protocol
Intrazone Routing Protocol (IARP) used to
proactively maintain routes in the zone.
Each node maintains its own routing zone
Neighbors are discovered by either MAC
protocols or Neighbor Discovery Protocol (NDP)
When global search is needed, route queries are
guided by IARP via bordercasting

24. Interzone Routing Protocol
Adapts existing reactive routing protocols
Route Query packet uniquely identified by
source’s address and request number.
Query relayed to a subset of neighbors by the
bordercast algorithm

25. Comparisons
FSR AODV DSR ZPR
Source
Routing
No No Yes No
Periodic
message
Yes No No Yes
(Locally)
Functioning
Proactively
Yes No No Yes
(Locally)
Functioning
Reactively
No Yes Yes Yes
(Globally)
DSDV

26. Conclusion
On-demand routing protocols (AODV and DSR)
are gaining momentum.
More analysis and features are needed
(Performance comparison between protocols,
QoS extension and analysis, multicast, security
issues etc…)
Good paper (though old):
A review of current routing protocols for ad-hoc
mobile wireless networks, E. Royer, C.K. Toh

27. Performance?
End-to-end data throughput and delay
Route acquisition time
Percentage of out-of-order delivery
Efficiency:
• Average number of data bits transmitted/data bits delivered
• Average number of control bits transmitted/data bits delivered
• Average number of control and data packets transmitted/data
packet delivered

28. Parameters
Network Size
Connectivity (average degree of a node)
Topology rate of change
Link capacity (bps)
Fraction of unidirectional links
Traffic patterns
Mobility
Fraction/frequency of sleeping nodes