Simulation Of AODV & DSR

Protocol Using NS2

Presented By-Prafull Johri

Simulation◦ ns extensions

Reactive Routing Protocol◦ AODV Protocol

◦ DSR Protocol

AODV V/S DSR

Conclusion

Outline

ns-2 extensionsThe ns-2 network simulator was extended to include:

Node mobility

A realistic physical layer◦ propagation delay, capture effects, carrier sense

Radio network interfaces◦ transmission power, antenna gain, receive sensitivity

IEEE 802.11 MAC protocol using Distributed Coordinated Function (DCF)◦ node contention for wireless medium

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

AODV Protocol 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

Route Discovery in AODV 1

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Source

Destination

Propagation of Route Request (RREQ) packet

Route Discovery in AODV 2

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Source

Destination

Path taken by Route Reply (RREP) 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

AODV Advantage and Disadvantage

Advantage:

The main advantage of this protocol is that routes are established on demand and destination sequence numbers are used to find the latest route to destination. The connection setup delay is less.

Disadvantage:

One disadvantage is that intermediate nodes can lead to inconsistent routes if the source sequence number is very old and the intermediate nodes have a higher but not the latest destination sequence number, thereby having stale entries. Also multiple Route Request packets in response to a single Route Request packet can lead to heavy control overhead.

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

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

Route Discovery 1 (DSR)

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<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

Route Discovery 2 (DSR)

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<1,4,6>

<1,4,6>

<1,4,6>

Source Destination

Propagation of Route Reply with the Route Record

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.

Advantages and

disadvantagesAdvantage: This protocol used a reactive approach which

eliminates the need to periodically flood the network with

table update messages which are in table-driven approach. The

intermediate nodes also utilize the route cache information

efficiently to reduce the control overhead.

Disadvantage: The route maintenance mechanism does not

locally repair a broken link. Stale route cache information

could also result in inconsistencies during the route

reconstruction phase.

DSR uses source routing in which a data packet carries the

complete path to be traversed.

In AODV, the source node and the intermediate nodes store the

next-hop information corresponding to each flow for data packet

transmission.

In DSR, when two neighbours enter communication range of

each other, then this results in a network wide broadcast. Where

as in AODV, such broadcast are not necessary.

In DSR, when two nodes drift apart from each other’s range link

breakage also results in a network wide broadcast.

Whereas in AODV, If a link breakage does not affect on going

transmission then no global broadcast occurs. Only affected

nodes are informed.

AODV Vs DSR

Fig:X graph of 10 sec simulation time of AODV

Fig:X graph of 10 sec simulation time of DSR

Conclusion

It is observed that the packet loss is very less in case of AODV, but it increases substantially on simulation time increases .

In case of DSR simulation he packet loss is very high initially but decreases substantially on simulation time increases .

Conclusion

we can conclude that if MANET has to set up for a small amount of time than AODV should be prefer due to low initial packet loss and DSR should not prefer because the packet loss is very high .

If we have to use MANET for longer duration than both the protocol can be used because after some time both the protocol have same ratio of packet delivering. But AODV is have very good packet receiving ratio in comparison to DSR