This document summarizes several routing protocols for ad hoc wireless networks. It describes the challenges in this domain including dynamic topologies and limited resources. It then categorizes and explains several types of routing protocols, including proactive protocols like DSDV, reactive protocols like AODV and DSR, hybrid protocols like ZRP, and geographic routing. It provides details on the route discovery and maintenance mechanisms of some of these prominent protocols. It also discusses theoretical limits on network capacity and the impact of mobility and hierarchy.

1. Introduction to Wireless
Ad-Hoc Networks Routing
Michalis Faloutsos
Some slides borrowed
From Guor-Huar Lu

2. Outline
Challenges
Design Goals Specified by MANET (for now…)
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. Theoretical perspective
The capacity of a wireless
network is
Where N nodes, and C channel
capacity
Explanation: N nodes in the field
Destinations are random
On average N^0.5 hops per path
Each node has N^0.5 paths go through
Gupta Kumar paper

11. Mobility increases capacity
Grossglausser and Tse (infocom 2001)
Statement: if nodes move they will enentually carry the
info where you want
Protocol:
• sender send one copy to receiver or one neighbor
• Sender and relay will at some run into destination and send the
packet
All paths are at most two hops
They show that the capacity of the network does not go
to zero
Tradeoff?

12. Hierarchical routing: bounds
Cluster nodes, and route between and within clusters
Location management: finding where
Routing finding how to get there
Multiple levels: log(N) levels
Location Mgm: Each nodes stores O(N) locations
Routing overhead: O(log^3N)
Dominating factor: location management and not the
routing
Location mgmt handoff: O(log^2N)
See Susec Marsic, infocom 02

14. 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)

15. 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

16. 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

17. 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

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

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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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.

26. 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!

27. 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

28. 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

29. Comparisons 1
Things in common:
• IP based operation
• Distributed operation
• Loop-free routing
• Very little or no support for sleep period operation
and security

30. Comparisons 2
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

31. 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

33. 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

34. 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

35. References
Mobile Ad hoc Networking (MANET): Routing Protocol Performance
Issues and Evalution Considerations (RFC 2501)
P. Misra., “Routing Protocols for Ad Hoc Mobile Wireless Networks”,
http://www.cis.ohio-state.edu/~jain/cis788-99/adhoc_routing/
The Zone Routing Protocol (ZRP) for Ad Hoc Networks <draft-ietf-manet-
zone-zrp-04.txt>
Fisheye State Routing Protocol (FSR) for Ad Hoc Networks <draft-ietf-
manet-fsr-03.txt>
Ad hoc On-demand Distance Vector (AODV) Routing <draft-ietf-manet-
aodv-11.txt>
The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks (DSR)
<draft-ietf-manet-dsr-07.txt>

36. Fisheye State Routing (FSR)
Node stores the Link State for every destination in the
network
Node periodically broadcast update messages to its
neighbors
Updates correspond to closer nodes propagate more
frequently

37. Multi-Level Scope (FSR)
• Central node (red dot)
has the most accurate
information about
nodes in white area and
so on.
•Parameters: Scope
level/radius size

38. ZPR architecture
NDP IARP IERP ICMP
BRP
ZRP
IP
A B Information passed from protocol A to B
A B Exchange of packets between protocol A and B

39. Design Goals
Peer-to-peer mobile routing capability in mobile,
wireless domain.
Intra-domain unicast routing protocol:
• Effective operation over a wide range of mobile networking
scenarios and environments
• Supports traditional, connectionless IP services
• Efficiently manages topologies changes and traffic demands

40. Desired properties
Distributed operation
Loop freedom
Demand-based operation
Proactive operation
Security
“Sleep” period operation
Unidirectional link support