Routing protocols in Routing protocols in Mobile Ad Hoc NetworkMobile Ad Hoc Network

UNIVERSITY COLLEGE OF ENGINEERING

BURLA, SAMBALPUR

Types of Wireless Networks

Infrastructure based(Cellular Network).

Infrastructureless Network(Mobile Ad hoc NETwork) (MANET).

Characteristics of an Ad-hoc networkCharacteristics of an Ad-hoc network

Collection of mobile nodes forming a temporary network

Network topology changes frequently and unpredictably

No centralized administration or standard support services

Host is also function as router

Why is Routing Different in Ad Hoc ???Why is Routing Different in Ad Hoc ???

Host mobility• Dynamic topology• link failure/repair due to mobility

Distributed Environment Bandwidth constrained Energy constrained

Categorization of Ad-Hoc Routing Protocols

Table Driven Routing ProtocolTable Driven Routing Protocol

Proactive. Each node maintains one or more tables

containing routing information to every other node in the network.

Tables need to be consistent and up-to-date view of the network.

Updates propagate through the network

Source Initiated On demand routing protocolSource Initiated On demand routing protocol

Reactive. on-demand style: create routes only when it is

desired by the source node When a node requires a route to a destination,

it initiates a route discovery process Route is maintained until destination becomes

unreachable, or source no longer is interested in destination.

Table Driven Routing ProtocolTable Driven Routing Protocol

Destination-Sequenced Distance Vector ProtocolDestination-Sequenced Distance Vector Protocol (DSDV) (DSDV)

Basic Routing Protocol Based on Bellman ford routing algorithm with some

improvement Each node maintains a list of all destinations and

number of hops to each destination. Each entry is marked with a sequence number. Periodically send table to all neighbors to maintain

topology

• Two ways to update neighbors:– Full dump– Incremental update

Example of DSDVExample of DSDV

Destination Next Hop Distance Sequence Number

A A 0 S205_A

B B 1 S334_B

C C 1 S198_C

D D 1 S567_D

E D 2 S767_E

F D 2 S45_F

Destination Next Hop Distance Sequence Number

A A 0 S304_A

B D 3 S424_B

C C 1 S297_C

D D 1 S687_D

E D 2 S868_E

F D 2 S164_F

A’s Routing Table Before Change

A’s Routing Table After Change

Clusterhead Gateway Switch RoutingClusterhead Gateway Switch Routing (CGSR) (CGSR)

Similar to DSDV Based on concept of clusters and cluster heads Routing is done via the cluster heads and

gateways A routing table among cluster heads are

maintained

Example of CGSRExample of CGSR

Data forwarding steps:•from cluster head to cluster head–in a hierarchical manner•then from cluster head to cluster members•between two cluster heads, gateways are used to forward the packets

Source Initiated On demand Source Initiated On demand routing protocolrouting protocol

Ad hoc On-demand Distance Vector RoutingAd hoc On-demand Distance Vector Routing(AODV)(AODV)

Pure on-demand protocol Node does not need to maintain knowledge of another

node unless it communicates with it AODV includes route discovery and route maintenance. AODV minimizes the number of broadcasts by creating

routes on-demand AODV uses only symmetric links because the route reply

packet follows the reverse path of route request packet AODV uses hello messages to know its neighbors and

to ensure symmetric links

Path discoveryPath discovery

In the path discovery (RREQ) phase, source broadcasts RREQ message.

Intermediate nodes record in their route tables the address of neighbor from which RREQ is received to establish a reverse path.

When RREQ reaches destination or an intermediate node responds by unicasting a route reply (RREP) back to neighbor.

Path maintenancePath maintenance

If source node moves, reestablish the path. If destination or intermediate node moves,

send link failure notification message to each of its active upstream.

Then reinitiate path discovery .

Dynamic Source Routing Protocol Dynamic Source Routing Protocol (DSR)(DSR)

on-demand A node maintains route cache containing the

routes it knows Two main phases

• Route discovery• Route maintenance

Basic Operation is similar to AODV. Main difference

• To use routing cache for link failure.• When route discovery phase, node send route

request message with its own address.

Example of DSRExample of DSR

Hybrid Routing Protocols

Zone Routing ProtocolZone Routing Protocol

Hybrid of table-driven and on-demand!! From each node, there is a concept of “zone”.

• Within each zone, the routing is performed in a table-driven manner (proactive).

• However, a node does not try to keep global routing information.

For inter-zone routing, on-demand routing is used.

Example of ZPRExample of ZPR

Three types of nodes:• Border Nodes• Peripherals Nodes• Interior Nodes

ComparisonComparison

Parameters On Demand Table Driven

Availability of routing

information

Available when

needed

Always available regardless of need

Routing philosophy Flat Mostly flat, except for

CGSR

Periodic route updates Not required Required

Coping with mobility Use localized route discovery

Inform other nodes to achieve a consistent routing

table

Signaling traffic generated Grows with

increasing mobility

Greater than that of on

demand routing

ReferencesReferences

Elizabeth M. Royer, Chai-Keong Toh, A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks,Proc. IEEE,1999.

David B. Johnson, " Routing in Ad hoc Networks of Mobile Hosts", Proc

IEEE Workshop on Mobile Computing Systems and Applications. Nicklas Beijar “Zone Routing Protocol “. www.cse.wustl.edu/~jain/cis788-99/adhoc_routing/ http://www.comp.brad.ac.uk/~sburuha1/index.htm www.computingunplugged.com/

issues/issue200407/00001326001.html http://www.ietf.org/rfc/rfc3561.txt

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