Comparison of AODV and DSR Protocol

1. Simulation Of AODV & DSR
Protocol Using NS2
Presented By-
Prafull Johri

2.  Simulation
◦ ns extensions
 Reactive Routing Protocol
◦ AODV Protocol
◦ DSR Protocol
 AODV V/S DSR
 Conclusion
Outline

3. ns-2 extensions
The 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

4. 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

5. 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

6. Route Discovery in
AODV 1
1
2
3
4
5
6
7
8
Source
Destination
Propagation of Route Request (RREQ) packet

7. Route Discovery in
AODV 2
1
2
3
4
5
6
7
8
Source
Destination
Path taken by Route Reply (RREP) packet

8. 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

9. 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.

10. 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

11. 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

12. Route Discovery 1
(DSR)
1
2
3
4
5
6
7
8
<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

13. Route Discovery 2 (DSR)
1
2
3
4
5
6
7
8
<1,4,6>
<1,4,6>
<1,4,6>
Source Destination
Propagation of Route Reply with the Route Record

14. 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.

15. Advantages and
disadvantages
Advantage: 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.

16.  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

17. Fig:X graph of 10 sec simulation time of AODV

18. Fig:X graph of 10 sec simulation time of DSR

19. 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 .

20. 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