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International Journal of Soft Computing and Engineering (IJSCE)
ISSN: 2231-2307, Volume X, Issue-4, September 2011
135
Abstract— Mobile Ad hoc Networks are established
for extemporaneous services customized to application. These
networks exist for limited period of time based on demands. This
infrastructure less networks support data networking services
using routing protocols. Reactive routing protocols serve the
issue over proactive routing protocols [7]. As the communication
is through multiple intermediate nodes, circumstances lead for
the attacks lacking security [12]. Existing proactive routing
protocols does not endow with security aspects within [1]. In this
paper, we introduce an enhanced secured routing protocol and
its performance is compared with the existing protocols namely,
Ad hoc On demand Distance Vector Routing (AODV), Dynamic
Source Routing (DSR) & Zone Routing Protocol (ZRP) in terms
of delay, jitter and throughput using Qualnet simulation
software.
Index Terms— Ad hoc networks, jitter, routing
protocols, secured routing
I. INTRODUCTION
Wireless communication and network systems facilitate
communication between computers using standard networks
without network cabling. Wireless Networks are classified
into two types, viz, Access point networks and Ad-hoc
networks. In access point networks, nodes use an access point
or base station, which acts as a hub providing connectivity
between two different nodes, wired and wireless LAN, a node
and wireless LAN, etc., In Ad-hoc networks, direct
communication between nodes is possible without any access
points. Ad hoc networks serve the issue of mobile nodes, due
to its inherent properties such as self-organizing, self-healing,
multi-hopping, dynamic nature, etc., [6]. Because of its
infrastructure less feature, ad hoc wireless networks provide
the facility for the user to use the network services while
continually moving. The application scenario for the mobile
ad hoc networks is emerging in recent years.
Main issues of ad hoc networks are routing, security,
service location, energy consumption, etc. [4]. Routing the
information using the intermediate nodes in ad hoc networks
becomes the major issue due to its dynamic characteristics.
Each move of the mobile nodes change the topology of the
network in the transmission route which sometime leads to the
disconnection of link. Since the communication is through
radio waves, when there is a poor environment and the
Manuscript received July 09, 2011.
G.Lavanya, Assistant Professor, Department of Information
Technology, KTVR Knowledge Park for Engineering & Technology,
Coimbatore, India, (e-mail: lavanya_joyce@yahool.co.in).
Dr.A.Ebenezer jeyakumar, Director (Academics), Sri Ramakrishna
Engineering College, Coimbatore,
India,(e-mail:ebeyjkumar@rediffmail.com).
distance between the nodes is large, disconnection may occur
[10]. It is necessary that the routing protocols should also
provide good route maintenance after the route discovery.
The distinctive feature of these networks is that the network
nodes need to collaborate with their peers in supporting the
network functionality [5]. More probability exists for a
malicious or selfish node to disrupt or even deny the
communication potentially of any node within the ad hoc
networking domain. Every node in the network is required to
assist in the network establishment, network maintenance and
network operation [4].
Generally, routing protocols are categorized as table
driven and on demand. Table driven routing protocol
maintain consistent and up to date routing information among
the nodes in a routing table. On demand routing protocols
discover a new route, when a route is required from the source
to the destination node. It serves the user’s issue in Ad hoc
mobile networks [6]. Later, combinations of the features of
above two types turn out hybrid routing protocol. Although
few routing protocols provide good performance, they lack in
security. Hence, establishing secured data transmission
through secured routes becomes a predominant issue.
The security techniques employed in paper [18]
increases the routing overhead in transmission. All the
secured routing protocols mentioned in survey paper [1] face
the same issue by using key exchanges and key generations.
This paper introduces a secured dynamic source
routing (SDSR) which includes security aspects in DSR
which does not employ any key exchange mechanisms to
reduce the routing overhead. This paper also shows the
comparative analysis of three existing and well known routing
protocol AODV, DSR & ZRP protocols with enhanced
secured DSR protocol. The following sections provide the
overview of all the above mentioned protocols and new
enhanced secured DSR protocol. Final section discusses the
performance of new protocol over the existing protocol.
II. ADHOC ON-DEMAND DISTANCE VECTOR
ROUTING PROTOCOL
The Ad hoc On-Demand Distance Vector (AODV)
routing algorithm is a routing protocol designed for Ad hoc
mobile networks. It is an on demand algorithm, meaning that
it builds routes between nodes only as desired by source
nodes. It maintains these routes as long as they are needed by
the source. AODV uses sequence numbers to ensure the
freshness of routes. It is loop-free, self-starting, and scales to
large numbers of mobile nodes. AODV builds routes using a
route request / route reply query cycle. When a source node
desires a route to a destination for which it does not already
have a route, it broadcasts a route request
An Enhanced Secured Dynamic Source
Routing Protocol for MANETS
G.Lavanya, A. Ebenezer Jeyakumar
An Enhanced Secured Dynamic Source Routing Protocol for MANETS
136
(RREQ) packet across the network. Nodes receiving this
packet update their information for the source node and sets
up backward pointers to the source node in the route tables. In
addition to the source node's IP address, current sequence
number, and broadcast ID, the RREQ also contains the most
recent sequence number for the destination of which the
source node is aware. A node receiving the RREQ may send a
route reply (RREP) if it is either the destination or if it has a
route to the destination with corresponding sequence number
greater than or equal to that contained in the RREQ. If this is
the case, it unicasts a RREP back to the source. Otherwise, it
rebroadcasts the RREQ. Nodes keep track of the RREQ's
source IP address and broadcast ID. If they receive a RREQ
which they have already processed, they discard the RREQ
and do not forward it [16].
As the RREP propagates back to the source node, it
sets up forward pointers to the destination. Once the source
node receives the RREP, it may begin to forward data
packets to the destination. If the source later receives a RREP
containing a greater sequence number or contains the same
sequence number with a smaller hop count, it may update its
routing information for that destination and begin using the
better route. As long as the route remains active, it will
continue to be maintained [17]. A route is considered active as
long as there are data packets periodically traveling from the
source to the destination along that path. Once the source
stops sending data packets, the links will time out and
eventually be deleted from the intermediate node routing
tables. If a link break occurs while the route is active, the node
upstream of the break propagates a route error (RERR)
message to the source node to inform about the unreachable
destination. After receiving the RERR, if the source node still
desires the route, it can reinitiate route discovery process.
The absence of source routing and promiscuous listening
allows AODV to gather only a very limited amount of
routing information with each route discovery [14]. Single
route discovery causes large retransmission delay in case of
link failure[10].
III. DYNAMIC SOURCE ROUTING PROTOCOL
The Dynamic Source Routing (DSR) is a reactive
unicast routing protocol that utilizes source routing algorithm
[11]. In source routing algorithm, each data packet contains
complete routing information to reach its dissemination.
Additionally, in DSR each node uses caching technology to
maintain route information that it has learnt.
There are two major phases in DSR, the route
discovery phase and the route maintenance phase. When a
source node wants to send a packet, it initially consults its
route cache. If the required route is available, the source node
includes the routing information inside the data packet before
sending it. Otherwise, the source node initiates a route
discovery operation by broadcasting route request packets. A
route request packet contains addresses of both the source and
the destination and a unique number to identify the request.
Receiving a route request packet, a node checks its route
cache. If the node doesn’t have routing information for the
requested destination, it appends its own address to the route
record field of the route request packet. Then, the request
packet is forwarded to its neighbors. To limit the
communication overhead of route request packets, a node
processes route request packets that both it has not seen
before and its address is not presented in the route record
field. If the route request packet reaches the destination or an
intermediate node has routing information to the destination,
a route reply packet is generated. When the route reply packet
is generated by the destination, it comprises addresses of
nodes that have been traversed by the route request packet.
Otherwise, the route reply packet comprises the addresses of
nodes the route request packet has traversed concatenated
with the route in the intermediate node’s route cache.
After being created, either by the destination or an
intermediate node, a route reply packet needs a route back to
the source. There are three possibilities to get a backward
route. The first one is that the node already has a route to the
source. The second possibility is that the network has
symmetric (bi-directional) links. The route reply packet is
sent using the collected routing information in the route
record field, but in a reverse order. In the last case, there exists
asymmetric (unidirectional) links and a new route discovery
procedure is initiated to the source. The discovered route is
piggybacked in the route request packet [12].
In DSR, when the data link layer detects a link
disconnection, a ROUTE_ERROR packet is sent backward
to the source. After receiving the ROUTE_ERROR packet,
the source node initiates another route discovery operation.
Additionally, all routes containing the broken link should
be removed from the route caches of the immediate nodes
when the ROUTE_ERROR packet is transmitted to the
source.
DSR has increased traffic overhead by containing
complete routing information into each data packet, which
degrades its routing performance. The network is assumed
not be too big, for example, the diameter could be 5-10
nodes [13]. DSR is only applicable to a relatively small
amount of nodes, less than 100. Otherwise, managing the
source routes to every node may become problematic.
IV. ZONE ROUTING PROTOCOL
The Zone Routing Protocol (ZRP) is hybrid routing
protocol for mobile ad- hoc networks. The hybrid protocols
are proposed to reduce the control overhead of proactive
routing approaches and decrease the latency caused by route
search operations in reactive routing approaches[6].
In ZRP, the network is divided into routing zones
according to distances between mobile nodes. Given a hop
distance d and a node N, all nodes within hop distance at most
d from N belong to the routing zone of N. Peripheral nodes of
N are N’s neighboring nodes in its routing zone which are
exactly d hops away from N.
In ZRP, different routing approaches are exploited for
inter-zone and intra-zone packets. The proactive routing
approach, i.e., the Intra-zone Routing protocol (IARP), is
used inside routing zones and the reactive Inter-zone
Routing Protocol (IERP) is used between routing zones,
respectively. The IARP maintains link state information for
International Journal of Soft Computing and Engineering (IJSCE)
ISSN: 2231-2307, Volume X, Issue-4, September 2011
137
nodes within specified distance d. Therefore, if the source
and destination nodes are in the same routing zone, a route
can be available immediately. Most of the existing
proactive routing schemes can be used as the IARP for
ZRP. The IERP reactively initiates a route discovery when
the source node and the destination are residing in different
zones [8]. The route discovery in IERP is similar to DSR
with the exception that route requests are propagated via
peripheral nodes.
The main limitation of ZRP design assumes a
uniform traffic distribution and then optimizes the overall
overhead [15]. When the traffic is non-uniform, these
protocols may not actually be efficient [9].
V. SECURED DYNAMIC SOURCE
ROUTING PROTOCOL
Proposed secured dynamic source routing (SDSR)
protocol solves the issue of secured transmission in DSR.
Fig.1 Route Request process
A common trust key is generated by all the group nodes. Any
node that has the identical generated trust key can participate
in routing. Therefore, the key is generated by each node by
installing a common algorithm. Generated trust key is purely
based on the synchronized system time in seconds. The trust
key is added as an additional field in the route request packet
for identifying the secured route. The route request packet
size is increased in the proposed routing protocol. The trust
key in all the nodes vary for every short time period ‘Td’ to
ensure security, it should not be too small, so that the route
request packet trust key should match with the intermediate
node and destination node’s trust key shown in the Fig.1. Td
should not be too large, because the hackers might try to find
the trust key to participate in routing. The trust key has to be
moderate in order to provide secured routing process. This
secured trust key is generated by all the nodes in the personal
group. Hence, only group nodes participate in the routing
process.
Secured DSR consists of two phases, secured route
discovery and route maintenance. When source node S
requires the route to destination D, S enters the secured route
discovery phase and checks whether adequate fresh routes to
D are already available in the Fresh_route cache. If some
fresh routes to D in Fresh_route cache are found, S runs
Route confirm process.
Fig. 2 Secured Route Discovery Phase
Otherwise, S runs new secured route discovery process to find
a secured new route to the destination node as shown in Fig. 2.
A. New Secured Route discovery process
Source node S broadcasts Route Discovery (RD) request
packet to nearby nodes; RD request includes a sequence
number field to distinguish the route discovery process from
others, the trust key of the source and the route content field
Begin Route Discovery
Phase
Fresh
route
Cache
Is there any
“fresh” route
?
Read the route of the
cache
Send “Route Confirm
Request”
(RC-request)
Broadcast “RD Request with
trust key
Is trust key
same ?
Add the route
information in the
request and broadcast
to neighboring nodes
Receive
RD Reply?
Return the route of the
RD_reply
Return No such route
from S to D
End Route Discovery Phase
Yes No
Yes
No
Yes
No
Broadcast RD request to neighboring nodes
If node =
destination?
Insert address into route content of RD
request
Destination sends RD reply to the source
Is trust key
same ?
Yes
No
No
Yes
Begin
End
An Enhanced Secured Dynamic Source Routing Protocol for MANETS
138
for node address along the path from S to D. After the
intermediate node receives RD request from an upstream
node X, it inserts its address into the route content field of the
RD request only if it is in the same trust key of the source and
then sends this modified RD request to its neighboring nodes
(excluding the upstream node X). The RD request cache of
the intermediate node also records the information, including
the sequence number of the RD request and which
neighboring nodes are sent only if the request is not
duplicated. Otherwise, the duplicated request is discarded.
B. Route Maintenance phase
When a link failure occurs during the data transmission,
route error message is forwarded to the source and source
initiates new rout discovery process. This phase is as same as
DSR explained in section III.
VI. SIMULATION RESULTS
This section describes briefly the results that are
examined in simulating the routing protocols AODV, DSR,
ZRP & SDSR. Simulation is carried out using Qualnet
software. The routes identified by the new secured route
discovery process is among the group nodes was ensured.
The identified routes are found to be long, secured and
lingered route. The following table below (Table. 1) shows
the simulation parameters that are considered. Performance
metrics such as average jitter, throughput and end to end
delay [13] are analyzed by simulating for node variation
between 10 and 50.
PARAMETERS VALUE
Simulation Time 700s
Mobility 15m/s
Dimension 1500 x1500
Pause time 10s
No. of buffer size 64
Traffic Type CBR
Packet Size 512 bytes
Zone radius 2
Time Delay ’Td’ 5 s
Table 1. Simulation environment
A. Impact on Average Jitter
• AODV has higher jitter than the other routing
protocols
• ZRP has an inconsistent jitter
• DSR and SDSR has the same level of jitter, which
ensures that by adding trust key does not affects the
variation in average jitter as shown in Fig.3.
B. Impact on Throughput
Fig.4 shows the throughput variation for different scale
networks.
• AODV has high throughput for more nodes with less
reliability.
• ZRP leads to more variation in throughput.
• SDSR provides slightly higher throughput than the
DSR, hence including the security aspect in route
discovery process does not affect the throughput.
C. Impact on end to end delay
Fig .5 shows the end to end delay variation for different
scale networks.
• Delay is higher for less number of nodes in AODV
protocol.
• DSR too has a tolerable delay for less number of
nodes.
• ZRP protocol has tolerable delay for more number of
nodes
• SDSR has consistently less delay irrespective of the
number of nodes.
D. Impact on Route Request Packet Time
Deviation in time taken by the source initiated route request
packet to reach the destination is shown in Fig.6
• SDSR shows the longer time to forward the route
request packet than DSR.
• ZRP takes intolerable time to do the same .
• Though SDSR seizes a sufficient delay in discovering
a route, offer a secured route.
Simulation results expose that the enhanced secured
dynamic source routing provides security without
comprimising the data communication performance. It
delivers information as equivalent to the DSR
performane.There is no key exchange mechanism employed
in the protocol in order to resist the increase of routing
overhead.
Fig.3 Average Jitter Vs Nodes
International Journal of Soft Computing and Engineering (IJSCE)
ISSN: 2231-2307, Volume X, Issue-4, September 2011
139
Fig. 4 Throughput Vs Nodes
Fig. 5 Delay Vs Nodes
Fig. 6 Route Request time Vs Nodes
VII. CONCLUSION
In this paper, we have investigated SDSR protocol
whose novelty is the trust key based on time as the additional
security aspect of transferring data through trusted group
nodes. Comparative analysis was done to evaluate the routing
performance of new proposed routing protocol SDSR with
existing routing protocols namely, AODV, DSR, ZRP based
on CBR traffic in terms of measuring average jitter,
throughput & delay by varying the density of the network, i.e
the number of nodes. The results show that the proposed
SDSR protocol affords almost equivalent performance as
DSR with the secured way of transferring data through the
trusted nodes. The overall performance of SDSR is better than
all the other three on demand routing protocols. Future work
is devised to study the performance based on TCP traffic and
compare SDSR with the prevailing secured routing protocols.
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G.Lavanya is working as an Assistant Professor in
Department of Information Technology in KTVR
Knowledge Park For Engineering and Technology,
Coimbatore, India. She received her B.E Degree in
Electrical and Electronics Engineering from
Bharathiar University, Coimbatore, India in the year
1998 and M.Tech Degree in Information Technology
from Anna University of Technology, Coimbatore,
India in the year 2009. She has 11 publications in the
field of Adhoc Networks.
Dr. A.Ebenezer Jeyakumar is the Director
(Academics) in SNR Sons Charitable Trust, Sri
Ramakrishna Engineering College, Coimbatore, India.
He received his B.E Degree in Electrical and
Electronics Engineering from Annamalai
University,Chidambaram, India in the year 1972 and
M.E Degree in High Voltage Engineering from
University of Madras,Chennai,India in the year
1974.He has completed his Ph.D in Anna University,
Chennai, India in the year 1992. He is a member of
IEEE, ISTE, and IE. Being an eminent Professor in Anna University, many
scholars have registered their Ph.D and MS (by research) under him. His
main research interest includes Network Security, Mobile Computing, High
Voltage Engineering and other related areas. He has nearly 45 publications
in National & International Journals.
