Performance comparison of ad-hoc routing protocols AODV and DSR

Abstract

Ad hoc networks are known by many specifications like multi-hop wireless connectivity, frequently changing network topology and the need for efficient dynamic routing protocols that plays an important role. This paper presents a performance comparison between two reactive routing protocols for mobile ad hoc networks: dynamic source routing (DSR), ad hoc on demand distance vector (AODV).Both protocols were simulated using the tool ns-2 and were compared in terms of packet loss ratio, end to end delay, with mobile nodes varying number of nodes and speed. Simulation revealed that although DSR perfectly scales to small networks with low node speeds, AODV is preferred due to its more efficient use of bandwidth.

Full text

Abstract—
Ad hoc networks are known by many specifications like
multi-hop wireless connectivity, frequently changing network
topology and the need for efficient dynamic routing protocols that
plays an important role. This paper presents a performance
comparison between two reactive routing protocols for mobile ad
hoc networks: Dynamic Source Routing (DSR), Ad Hoc On
demand distance Vector (AODV).Both protocols were simulated
using the tool ns-2 and were compared in terms of packet loss ratio,
end to end delay, with mobile nodes varying number of nodes and
speed. Simulation revealed that although DSR perfectly scales to
small networks with low node speeds, AODV is preferred due to its
more efficient use of bandwidth.
Keywords —AODV, DSR, MANET, NS-2
I. INTRODUCTION
Mobile ad-hoc wireless networks hold the promise of the
future, with the capability to establish networks at anytime,
anywhere. Mobile ad hoc networks (MANETs) are collections
of mobile nodes, dynamically forming a temporary network
without pre-existing network infrastructure or centralized
administration. Nowadays a lot of research efforts focus on
Mobile Ad-hoc networks.
Routing protocol plays an important role if two hosts wish to
exchange packets which may not be able to communicate
directly. All nodes are mobile and can be connected
dynamically in an arbitrary manner. All nodes of these
networks behave as routers and take part in discovery and
maintenance of routes to other nodes in the network. This
situation becomes more complicated if more nodes are added
within the network. An Ad-Hoc routing protocol must be able
to decide the best path between the nodes, minimize the
bandwidth overhead to enable proper routing, minimize the
time required to converge after the topology changes.
This paper presents a performance comparison between two
on-demand routing protocols for mobile ad hoc networks:
Dynamic Source Routing (DSR), Ad Hoc On demand distance
Vector Routing (AODV).
Both protocols were simulated using the ns-2 package and
were compared in terms of average throughput, packet loss
ratio, and routing overhead, while varying number of nodes
and speed. Simulation revealed that although DSDV perfectly
scales to small networks with low node speeds, AODV is
preferred due to its more efficient use of bandwidth.
II. A
D-HOC ROUTING PROTOCOLS
The ad-hoc routing protocols can be divided into two
categories:
Table-driven routing protocols: In table driven routing
protocols, consistent and up-to-date routing information to all
nodes is maintained at each node. These protocols require each
node to store their routing information and when there is a
change in network topology updating has to be made
throughout the network.
On-Demand routing protocols: In On-Demand routing
protocols, the routes are created as and when required. This
type of protocols finds a route on demand by flooding the
network with Route Request packets. When a source wants to
send to a destination, it invokes the route discovery
mechanisms to find the path to the destination.
In recent years, a variety of new routing protocols targeted
specifically at this environment have been developed.
TABLE 1 : COMPARISON OF TABLE-DRIVEN AND ON-DEMAND PROTOCOLS
Table-driven On-demand
Availablilty of
Routing Information
Immediately from
route table
After a route
discovery
Route Updates
Periodic
Advertisments
When requested
Routing Overhead
Proportional to the
size of the network
regardless of network
traffic
Proportional to the
number of
communicating nodes
and increases with
increased node
mobility
A. Dynamic Source Routing
The Dynamic Source Routing (DSR) protocol is a source-
routed on-demand protocol [1]. There are two major phases
for the protocol: route discovery and route maintenance. The
key difference between DSR and other protocols is the routing
information is contained in the packet header. Since the
routing information is contained in the packet header then the
intermediate nodes do not need to maintain routing
information. An intermediate node may wish to record the
Mohammed BOUHORMA H. BENTAOUIT, A.BOUDHIR
Département Génie Informatique, ERIT Département Génie Informatique, ERIT
Faculté des Sciences et techniques de Tanger Faculté des Sciences et techniques de Tanger
Tanger Maroc Tanger Maroc
bouhorma@gmail.com
hakim.anouar@gmail.com
Performance Comparison of Ad-hoc
Routing Protocols AODV and DSR

routing information in its tables to improve performance but it
is not mandatory. Another feature of DSR is that it supports
asymmetric links as a route reply can be piggybacked onto a
new route request packet. DSR is suited for small to medium
sized networks as its overhead can scale all the way down to
zero. The overhead will increase significantly for networks
with larger hop diameters as more routing information will be
contained in the packet headers.
- Two main mechanisms: Route Maintenance and Route
Discovery
- Route Discovery mechanism is similar to the one in
AODV but with source routing instead
- Route Maintenance is accomplished through route
caches
- Entries in route caches are updated as nodes learn new
routes, multiple routes can be stored.
B. Ad hoc On-demand Distance Vector Routing
Ad hoc On-demand Distance Vector Routing (AODV) is an
on-demand version of the table-driven Dynamic Destination-
Sequenced Distance-Vector (DSDV) protocol [1]. To find a
route to the destination, the source broadcasts a route request
packet. This broadcast message propagates through the
network until it reaches an intermediate node that has recent
route information about the destination or until it reaches the
destination. When intermediate nodes forwards the route
request packet it records in its own tables which node the route
request came from. This information is used to form the reply
path for the route reply packet as AODV uses only symmetric
links. As the route reply packet traverses back to the source, the
nodes along the reverse path enter the routing information into
their tables. Whenever a link failure occurs, the source is
notified and a route discovery can be requested again if needed.
- Based on standard Distance Vector Algorithm
- Nodes maintain route cache and uses destination
sequence number for each route entry
- Does nothing when connection between end points is
still valid
- Route Discovery Mechanism is initiated when a route
to new destination is needed by broadcasting a Route
Request Packet (RREQ).
- Route Error Packets (RERR) are used to erase broken
links
Figure 1. DSR Protocol
Figure 2. AODV Protocol
III. SIMULATION ENVIRONMENT
A. Simulation Model
The results reported in this paper are based on the study
conducted on the basis of simulation tool NS2 that is an
object-oriented, discrete event driven network simulator
developed at UC Berkely written in C++ and OTcl. The
overall simulator is described by a Tcl class Simulator. It
provides a set of interfaces for configuring a simulation and
for choosing the type of event scheduler used to drive the
simulation.
When a new simulation object is created in tcl, the
initialization procedure performs the following operations:
• initialize the packet format
• create a scheduler (defaults to a calendar scheduler)
• create a “null agent” (a discard sink used in various places)
We use tcl to configure the topology, the nodes, the channel,
to schedule the events, etc.
Mobile Node is the basic ns Node object with added
functionalities like movement, ability to transmit and receive
on a channel that allows it to be used to create mobile,
wireless simulation environments.
The simulation in NS2 can be described as shown in Fig.3 [3].
The scenario file describes the movement pattern of the nodes.
The communication file describes the traffic in the network.
2
[1]
1
6
8
5
7
3
4
Source
Destination
[1]
[1]
[1,2]
[1,3]
[1,4]
[1,2,6]
[1,3,5]
[1, 3, 5,
7
]
[1,2,6]
[1,2,6]
[1,
26
]
2
RREP
RREP
1
6
8
5
7
3
4
Source
Destination

Fig.3. Simulation Procedure
B. Traffic and Mobility models
In this paper we use traffic and mobility model based on
Continuous bit rate (CBR) traffic sources.
Only 512-byte data packets are used. To change the offered
load in the network the number of source-destination pairs and
the packet sending rate in each pair is varied
The mobility model uses the random waypoint model [13] in a
rectangular field. The field configurations used is: 500 m x
500 m field with 10, 20 50 and 100 nodes. Here, each packet
starts its journey from a random location to a random
destination with a randomly chosen speed (uniformly
distributed between 0-20 m/s). Simulations are run for 100
simulated seconds. Identical mobility and traffic scenarios are
used across.
The simulation parameters which have been considered or
doing the performance comparison of two on-demand routing
protocols is given below in Table-2.
TABLE 2: PARAMETERS USED IN EXPERIMENT SCENARIO
Parameter Value
Protocols
AODV, DSR
Traffic source
Constant bit rate CBR
Simulation time
100 seconds
Packet Size
512 bytes
Max speed
20m/s
Area
500 m x 500 m
Number of nodes
10 20 50 100
Mobility model
Random way point
IV. R
ESULTS AND DISCUSSIONS
The simulation was implemented with light speeds using
the random way-point mobility pattern. In this model, nodes
select random way-points within the roaming area, and travel
there with a constant speed randomly. After reaching its
destination, the node waits for some pause time then moves to
the next waypoint. This scenario is applicable to networks
such as conferences, wireless sensors, and emergency
situations with people walking as nodes. We assume low
mobility for ad-hoc energy studies since in a high mobility
system the data transmission energy may be negligible
compared to the energy used for the mobility.
The following four important performance metrics are
considered for evaluation of these two on demand routing
protocols.
Packet delivery fraction: The ratio of the data packets
delivered to the destinations to those generated by the CBR
sources.
The following table shows the rate of packet loss for each
of the protocols AODV and DSR, simulated under the same
conditions with 10 sources and at the same time comparing
their rates of control packets used for the routing function.
From this table (Table 3), we find that among all the
generated packets in the AODV protocol, 0.44% represents
the control packets, whereas in the DSR protocol, 12.34% of
control packets. In addition, the rate of successfully received
packets by use of the AODV protocol is 92.44% (5431/5875)
and the packet lost 7.56% (444/5875). However using the
DSR protocol was 87.82% (7500/8540) packets received and
12.18% (1040/8540) of lost packets
T
ABLE 3: STATISTICS OF PACKETS SENT, RECEIVED AND OF CONTROL FOR
BOTH DSR AND
AODV PROTOCOLS
packets
Type
Received
Sent
Generated
Rate
DSR
Total
7500 6435 8540 --------
packets
Control
1042 1004 1054
12,34%
Rate
87,82% Lost : 12,18%
AODV
Total
5431 4988 5875
--------
packets
Control
24 16 26
0,44%
Rate
92,44% Lost : 7,56%

Mobility: Mobility is the major parameter of an ad hoc
network. Since an ad-hoc network is primarily characterized
by its ever-changing topology, so mobility of nodes is an
important consideration. Mobility of a node is a function of
both speed and movement patterns.
This simulation analysis is made from the Fig. 3 for 10
sources. First we analyze the first parameter Packet delivery
ratio with respect varied Maximum speed of nodes.
Figure 3 shows the relative performance test result of the
AODV and DSR routing protocols. All of the protocols
deliver a greater percentage of the originated data packets
when there is little node mobility, converging to 90% delivery
ratio when there is no node motion.
The On-demand protocol AODV performed particularly well,
while DSR could not achieve good packet delivery ratio when
moving more frequently.
End-To-End Delay: Fig. 4 shows the delay comparison of
the two protocols. For on-demand-driven protocols, it is hard
to say their performance relationship between the pause times.
The curve jumped a lot with the pause time change.
The second parameter Normalized End-To-End delay with
varied pause times is analyzed and it is found that for DSR it
is less when compared to AODV and we see that it is fairly
stable even with increase number of sources.
Further experiments should be done in order to make
definitely conclusion.
Figure 3. Packet Delivery Ratio as function of Maximum Speed Mobility
Figure 4. End-To-End Delay (sec)
V. CONCLUSION
In this paper the basic actions related to the two routing
protocols namely AODV and DSR were studied in detail. On-
demand driven protocols, as AODV, DSR, performed very
well for packet delivery with fast movement and mobility rate.
AODV seems to perform better than DSR on some
situations. However, when mobility increases AODV has
generally better performance. The On-demand protocol
AODV performed particularly well, while DSR could not
achieve good packet delivery ratio when moving more
frequently.
DSR is source routing protocol, which means that byte
overhead in each packet can affect the total byte overhead
when the load offered and size of the network increases. On
advantage with source routing is that during route discovery
operation it learns more routes. A combination of the
protocols can be used for good result
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End-To-End Delay (sec)
Pause Time
Packet Delivery Ratio
Maximum Speed (m/sec)