A Performance Comparison of DSDV & AODV Routing Protocols for MANETs

Presented By : Chander Mohan, SSIET DERABASSI, 9996016992

Outline

• Purpose of this work• Wired & Wireless Networks• Introduction to MANETs• Routing in MANETs• Compare Two Protocols

– DSDV– AODV

• Simulation– ns extensions– Protocol implementations

• Simulation results

Purpose of this work

• Wireless ad-hoc networks have gained a lot of importance in wireless communications.

• Wireless communication is established by nodes acting as routers and transferring packets from one to another in ad-hoc networks.

• Routing in these networks is highly complex due to moving nodes and hence many protocols have been developed.

• Table driven (DSDV) & Source on demand (AODV) strategies are compared.

Wired & Wireless Networks

Wired Network• Connected with the help of wires• Very High Speed • Expensive to maintain

Wireless Network

• Connected with the help of Radio Frequencies

• Speed is not very high due to interference, multiple connections.

• Large coverage areaNode

1

Node 3

Node 2

Node1

Node 2

Node 3

Introduction to MANETs

• Wireless network without any pre-existing infrastructure

• Dynamic nature of nodes i.e mobility• Every node act as a router• A MANET can be a standalone network or it

can be connected to external networks like (Internet)

Example of MANET

IEEE 802.11b (WLAN) & MANET

Why Ad Hoc Networks?• Setting up of fixed access points and backbone infrastructure

is not always viable– Infrastructure may not be present in a disaster area or war

zone– Infrastructure may not be practical for short-range radios;

Bluetooth (range ~ 10m)• Ad hoc networks– Do not need backbone infrastructure support– Useful when infrastructure is absent, destroyed or

impractical

Applications• Personal area networking– cell phone, laptop

• Military environment– soldiers, tanks, planes

• Civilian environment– taxi cab network– meeting rooms– sports stadiums– boats, small aircraft

• Emergency operations– search-and-rescue– policing and fire fighting

Challenges in Mobile Environments· Limitations of the Wireless Network

· packet loss due to transmission errors· frequent disconnections/partitions· limited communication bandwidth

· Limitations Imposed by Mobility· dynamically changing topologies/routes· lack of mobility awareness by system/applications

· Limitations of the Mobile Computer· short battery lifetime

Working of MANET

Features of MANETs

• Autonomous Terminal• Distributed Operation• Multi hop Routing• Dynamic Topology

Routing in MANETs

• Routing is the act of moving information from a source to a destination

• Routing involves two activities- Determining optimal routing path- Transferring the packets

Classification of Routing Protocols in MANETs

Table Driven (Proactive)

• The nodes maintain a table of routes to every destination in the network

• Keeping routes to all destinations up-to-date, even if they are not used, is a disadvantage with regard to the usage of bandwidth and of network resources

• Low latency, suitable for real-time traffic

On-demand (Reactive)

• These protocols were designed to overcome the wasted effort in maintaining unused routes, Routing information is acquired only when there is a need for it

• Saves energy and bandwidth during inactivity

• Flooding is used for route discovery

• Significant delay might occur as a result of route discovery

DSDV (Destination Sequenced Distance Vector) Protocol

• Based on Bellman-Ford Routing Algorithm (BFRA)

• Each node maintains a routing table which stores– next hop, cost metric towards each destination– a sequence number that is created by the destination itself

• Each route is tagged with a sequence number; routes with greater sequence numbers are preferred

• When a node decides that a route is broken, it increments the sequence number of the route and advertises it with infinite metric

DSDV (Destination Sequenced Distance Vector) Protocol

• When X receives information from Y about a route to Z– Let destination sequence number for Z at X be S(X), S(Y) is sent from Y

– If S(X) > S(Y), then X ignores the routing information received from Y – If S(X) = S(Y), and cost of going through Y is smaller than the route

known to X, then X sets Y as the next hop to Z– If S(X) < S(Y), then X sets Y as the next hop to Z, and S(X) is updated to

equal S(Y)

X Y Z

AODV (Ad Hoc On-Demand Distance Vector Routing) Protocol

• Route Requests (RREQ) are forwarded to discover a route

• When a node re-broadcasts a Route Request, it sets up a reverse path pointing towards the source

• When the intended destination receives a Route Request, it replies by sending a Route Reply (RREP)

• Route Reply travels along the reverse path set-up when Route Request is forwarded

Route Discovery in AODV

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Source

Destination

Propagation of Route Request (RREQ) packet

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

Route Discovery in AODV

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Source

Destination

Path taken by Route Reply (RREP) packet

Simulation

• Network Simulator ns-2.34 based on- Otcl (an object oriented extension of Tcl)- C++

Simulation Scenario

Tcl Script

C++ Implementation

1 2

set ns_ [new Simulator]

set node_(0) [$ns_ node]

set node_(1) [$ns_ node]

class MobileNode : public Node {

friend class PositionHandler;public: MobileNode();

••

}

What we need in one simulation?

• Appearance: the whole topology view of sensor network or mobile network– The position of nodes: (x, y, z) coordinate– The movement parameters

• Starting time• To what direction• Speed

• Internal work: which nodes are the sources? what are the connections? and using what kind of connection?

• Drive the simulation: What about the configuration network components on sensor node? Where to give out the simulation results? How to organize a simulation process?

Simulation Parameters

• Simulation Scenario

Packet Drop in AODV & DSDV at 70 sec

AODV

DSDV

Results & Discussion

• AODV • DSDV

Throughput Analysis

Conclusion

• DSDV routing protocol consume more bandwidth, because of frequent broadcasting of updates

• AODV is much better than DSDV as it results in less overhead and more bandwidth

THANK YOU

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