Routing in Ad Hoc Networks

Audun Søberg HenriksenTruls Becken

Overview

Short introduction Example of a basic routing algorithm Routing protocols IP configuring Security

Short introduction to wireless multihop networks

Two or more nodes equippedwith wireless communicationsand 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

Challenges

Dynamic topologies Bandwidth-constrained, variable

capacity links Energy-constrained Limited physical security Scalability

Simple routing protocol example

Propagation of routing table Routing and transmitting

Routing table

Destination terminal

Nextnode

A AB AC ED D… …

Each terminal has its own routing table(in proactive routing algorithms)

Position notification packet

ID of terminal which the created the packet

Timestamp for the created packet

ID of hop source terminal

Hop count

Contents of the packet:

Used to make and update the Routing Table Broadcasted in a limited area

Renewal of Position Notification Packet

A B D

t =1 t =2 t =3 t =4

A A A B A C

A 1 A 1 A 1 B 2 A 1 C 3

C

B B CC

Routing

A

B

Routing Table in D

D

G

E

I

C

HF

To F

Dest Next

A AB BC ED -E EF IG E

H II I

Routing

A

B

D

G

E

I

C

HF

To F

Routing Table in I Dest Next

A DB DC CD DE EF HG E

H HI -

Routing

A

B

D

G

E

I

C

HF

To F

Routing Table in H Dest Next

A IB IC CD IE IF FG C

H -I I

Basic transmitting procedure

Request to send (RTS) Clear to send (CTS)

Ready to receive (RTR)

Topology problem Hidden terminal problem Exposed terminal problem

Busy tones

Ad Hoc routing protocols

Proactive– Large overhead

Reactive– Delay before first packet– Doesn’t scale

Hybrid scheme– Clusters

Destination Sequenced Distance Vector (DSDV) Periodic routing Distance vector

– dest, next hop, distance, seq no Two ways to update neighbors

– Full dump– Incremental update

Dynamic Source Routing (DSR)

On demand Source routing

– Each packet contains full route Route discovery

– Flood RREQ packets– RREP returned when route found

Route maintenance– RERR when route is broken

Ad-hoc On-demand Distance Vector (AODV) From DSR

– Route discovery– Route maintenance

From DSDV– Hop-by-hop routing– Sequence numbers

Zone Routing Protocol (ZRP)

Predefined zones– Centered around each node

Proactive local routing Reactive global routing

IP address assignment

No centralized logic Small address room in IPv4 Network splitting Network merging

Two approaches

A leader– Responsible for all addresses

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

(absence of central authorities) Constrained capability

(energy)

Types of attacks

Black hole Denial of service Routing table overflow Impersonation Energy consummation