Download Ad-hoc networks

Routing in
Ad Hoc Networks
Audun Søberg Henriksen
Truls Becken
Overview
Short introduction
 Example of a basic routing algorithm
 Routing protocols
 IP configuring
 Security
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Short introduction to wireless multihop
networks
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Two or more nodes equipped
with wireless communications
and networking capability
Base station is not necessary
A node can communicate directly
with another node that is immediately within radio range
To communicate with nodes outside its own radio range an
intermediate node is used to forward the packet
The network is self-organizing and adaptive
(autonomous distributed control is required)
Nodes are able to detect the presence of other nodes and
join them into the network
The nodes don’t need to be of the same type
(phone, PDA, laptop, sensor, etc.)
Application areas
Tactical military
 Emergencies
 Disaster relief
 Sensor
 Meetings/conferences
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Challenges
Dynamic topologies
 Bandwidth-constrained, variable
capacity links
 Energy-constrained
 Limited physical security
 Scalability
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Simple routing protocol example
Propagation of routing table
 Routing and transmitting
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Routing table
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Each terminal has its own routing table
(in proactive routing algorithms)
Destination
terminal
A
B
C
D
…
Next
node
A
A
E
D
…
Position notification packet
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Used to make and update the Routing Table
Broadcasted in a limited area
Contents of the packet:
ID of terminal
Timestamp for the ID of hop
Hop
which the created created packet
source terminal count
the packet
Renewal of Position Notification Packet
A 1 B 2
A 1 A 1
A
B
A
t =1
A
t =2
A 1 C 3
D
C
A
B
B
B
A C
C C
t =3
t =4
Routing Table in D
Routing
G
B
E
C
To F
Dest Next
A
B
A
B
C
E
D
E
E
F
I
G
E
H
I
I
I
D
A
I
F
H
Routing Table in I
Routing
G
B
E
C
To F
Dest Next
A
B
D
D
C
C
D
E
D
E
F
H
G
E
H
H
I
-
D
A
I
F
H
Routing Table in H
Routing
G
B
E
C
To F
Dest Next
A
B
I
I
C
C
D
E
I
I
F
F
G
C
H
-
I
I
D
A
I
F
H
Basic transmitting procedure
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Request to send (RTS)
 Clear to send (CTS)
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Ready to receive (RTR)
Topology problem
Hidden terminal problem
 Exposed terminal problem
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Busy tones
Ad Hoc routing protocols
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Proactive
– Large overhead
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Reactive
– Delay before first packet
– Doesn’t scale
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Hybrid scheme
– Clusters
Destination Sequenced Distance
Vector (DSDV)
Periodic routing
 Distance vector
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– dest, next hop, distance, seq no
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Two ways to update neighbors
– Full dump
– Incremental update
Dynamic Source Routing (DSR)
On demand
 Source routing
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– Each packet contains full route
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Route discovery
– Flood RREQ packets
– RREP returned when route found
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Route maintenance
– RERR when route is broken
Ad-hoc On-demand Distance
Vector (AODV)
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From DSR
– Route discovery
– Route maintenance
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From DSDV
– Hop-by-hop routing
– Sequence numbers
Zone Routing Protocol (ZRP)
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Predefined zones
– Centered around each node
Proactive local routing
 Reactive global routing
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IP address assignment
No centralized logic
 Small address room in IPv4
 Network splitting
 Network merging
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Two approaches
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A leader
– Responsible for all addresses
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Buddy system
– Start with one node responsible for all
addresses
– Joining node gets half of the addresses
from an existing node
Routing security vulnerabilities
Open medium
 Dynamic topology
 Distributed cooperation
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(absence of central authorities)
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Constrained capability
(energy)
Types of attacks
Black hole
 Denial of service
 Routing table overflow
 Impersonation
 Energy consummation
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