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Performance Evaluation of AODV and DYMO

Routing Protocols in MANET

Dong-Won Kum, Jin-Su Park, You-Ze Cho, and Byoung-Yoon Cheon

School of Electrical Engineering and Computer Science, Kyungpook National University, Daegu, Korea

Communication R&D Lab, LIG Nex1, Yongin, Korea

{80kumsy, pjsu01, yzcho}@ee.knu.ac.kr

Abstract- Routing protocols for mobile ad hoc networks(MANETs) have been explored extensively in recent years.Among these routing protocols, Ad Hoc On-demand DistanceVector (AODV) and Dynamic Manet On-demand (DYMO)routing protocols have been standardized by the IETF MANET

WG and are the most popular reactive routing protocols forMANETs. Therefore, in this paper, we present the results of thecomparison of two reactive routing protocols, namely AODV and

DYMO, based on packet-level simulations using an ns-2 simulator.Simulations are run to estimate the total throughput, routingoverhead, and average packet size of the routing control packets.

I. INTRODUCTIONMobile Ad-hoc Networks (MANETs) have attracted a lot of

interest in the research community. The Ad Hoc On-demand

Distance Vector (AODV) and Dynamic Manet On-demand

(DYMO) are the two most popular reactive routing protocols

for MANETs, where the reactive property means that a route is

only requested when needed. AODV has already been

standardized by the IETF MANET WG as experimental

category [1], while DYMO was more recently standardized in

the standard category [2].

In the case of AODV, whenever a source node needs a route

to a destination node for which it does not have a route, itbroadcasts a route request (RREQ) packet to all its neighbors.

A neighbor receiving a RREQ may send a route reply (RREP)

packet if it is either the destination or if it has an unexpired

route to the destination. Along the path back to the source,

intermediate nodes that receive the RREP create forward route

entries for the destination node in their routing tables.

In order to maintain the routes, AODV normally uses link

layer feedback and hello packets. When a link break in an

active route is detected by the above mentioned method, the

node notifies this link break by sending a route error (RERR)

packet to the source node. Upon receiving the RERR packet,

the source node newly initiates the procedure for route

discovery.

However, despite its status as the most popular protocol for

reactive MANET routing, AODV has a heavy routing

overhead and complexity problem as regards implementation.

Thus, to improve on previous reactive routing protocols,

especially AODV, DYMO has a somewhat simpler design

based on, reducing the routing overhead using a path

accumulation function, and simplifying the protocol

implementation. Similar to AODV, the basic operations of the

DYMO protocol are also route discovery and route

maintenance.

During route discovery, the originators DYMO router

initiates the dissemination of a RREQ throughout the network

to find a route to the destinations DYMO router. Upon

receiving the RREQ, each intermediate DYMO router records

a route to the originator and rebroadcasts the RREQ including

its own information which is called the path accumulation

function. When the destinations DYMO router receives the

RREQ, it sends a RREP to the originator. When the originator

receives the RREP, the route is established. The route

maintenance of DYMO is similar to that of AODV. As

mentioned above, the path accumulation function of DYMO

includes source routing characteristics, thereby allowing nodes

listening to routing messages to acquire knowledge about

routes to other nodes without initiating route request

discoveries themselves. As a result, this path accumulation

function can reduce the routing overhead, although the packet

size of the routing packet is increased.

Accordingly, this paper evaluates the performance of AODV

and DYMO with respect to mobility through packet-level

simulations using an ns-2 simulator.II. PERFORMANCE EVALUATION

A. Simulation environmentsAn ns-2 [3] is used to evaluate the performance of AODV

and DYMO. The AODV model of ns-2 is based on [1], and the

DYMO model used is based on [2][4]. In the simulation, to

force the evaluation of control packets for route discovery,

link-layer feedback is employed to detect the link failures.

The Distributed Coordination Function (DCF) of IEEE

802.11 is used as the Medium Access Control (MAC) layer.

The radio model uses characteristics similar to a commercial

radio interface, Lucents WaveLAN, which is modeled as a

shared-media radio with a 2 Mbps nominal bit rate and 250 mnominal radio range. The protocol evaluation is based on a

simulation of 50 wireless nodes forming an ad hoc network,

moving about over a rectangular (1500 m x 500 m) flat space

for 400 seconds of simulated time. The nodes in the simulation

move according to a random waypoint model. The movement

scenario files used for each simulation are characterized by the

maximum speeds of the nodes (from 1 to 15m/s) and a 150

second pause time. In the simulation, Constant Bit-Rate (CBR)

978-1-4244-5176-0/10/$26.00 2010 IEEE

This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE CCNC 2010 proceedings

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traffic flows are used with 20 packets/second and a packet size

of 512 bytes. 20 CBR source flows are randomly located in the

network.

B. Performance metricsThe following metrics are used to evaluate the performance

of AODV and DYMO:

Total throughput: the amount of data transmitted throughthe network per unit time. Relative routing overhead: the ratio of the number of

routing control packets over the sum of the number of

delivered data packets and the routing control packets.

Average packet size of routing packets: the averagepacket size of the RREQ and RREP routing packet.

C. Simulation resultsFig. 1 shows the effect of the node mobility on the relative

routing overhead when increasing the mobility of the nodes.

This figure shows that the relative routing overhead of DYMO

is certainly lower than that of AODV, due to the path

accumulation function that reduced the number of RREQ

messages.

1 3 5 7 9 11 13 150

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Moving speed (m/s)

Relative

routing

overhead

AODV

DYMO

Figure 1. Comparison of relative routing overhead.

30 40 50 60 700

20

40

60

80

100

120

Number of nodes

Av

erage

packetsize

ofrouting

packets(bytes)

AODV

DYMO

Figure 2. Comparison of average packet size of routing packets.

Fig. 2 compares the average packet size of the routing

packets with AODV and DYMO when increasing the number

of nodes in the network. To investigate how the path

accumulation function of DYMO affects the control packet

size for route discovery, a random network topology is used

while varying the number of nodes from 30 nodes to 70 nodes

and keeping all the nodes stationary. All the other simulation

parameters are the same as mentioned above. Fig. 2 shows that,

as the number of nodes increases, the size of routing packets

with AODV are constant and lower than that of DYMO. Plus,

as the number of nodes increases, the average packet size of

the routing packets with DYMO increases due to the path

accumulation function.

0 1 2 3 4 5 6 7 8 90

1

2

3

4

5

6

7

8

9x 10

5

Moving speed (m/s)

Totalthroughput(bps)

AODV

DYMO

Figure 3. Comparison of total throughput.

Fig. 3 shows the total throughput of AODV and DYMO

when increasing the mobility of the nodes. This figure shows

that, as the moving speed of the nodes increases, the total

throughput of the two routing protocols is reduced. Plus, even

though DYMO achieves a relative reduction in the routing

overhead, at a higher mobility (moving speed > 9m/s), the total

throughput of DYMO is lower than that of AODV. The reason

for this is that wrong route information from the intermediate

routers with DYMO due to frequent topology changes causes

more route failure than with AODV.

III. CONCLUSIONThis paper briefly described the key features of the AODV

and DYMO routing protocols and evaluated them based on

packet-level simulations using an ns-2 simulator. The

simulation results showed that while the path accumulation of

DYMO reduced the routing overhead, the size of the routing

packet was increased. Plus, at moving speeds between 1m/s

and 9m/s, the total throughput of DYMO could outperform that

of AODV. However, at moving speeds between 11m/s and

15m/s, AODV could achieve a higher throughput than DYMO.

ACKNOWLEDGMENT

This research was supported by the National Research Foundation

of Korea (NRF) funded by the Korean Government (2009-0076947),and the Dual-Use Technology Center of Korea (08-DU-IC-02).

REFERENCES

[1] C. Perkins, E. Belding-Royer, and S. Das, Ad hoc On-Demand DistanceVector (AODV) Routing,IETF RFC 3561, July 2003.

[2] I. Chakeres and C. Perkins, Dynamic MANET On-Demand (DYMO)Routing, IETF Internet-Draft, draft-ietf-manet-dymo-17.txt, Mar. 2009.

[3] NS-2. Available from: http://www.isi.edu/nsnam/ns/>.[4] DYMO-Implementations. Available from: < http://www.ianchak.com/d

ymo/index.php>.

This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE CCNC 2010 proceedings