Multipath Fault Tolerant Routing Protocol in MANET

International Journal on AdHoc Networking Systems (IJANS) Vol. 2, No. 1, January 2012
DOI : 10.5121/ijans.2012.2103 23
MULTIPATH FAULT TOLERANT ROUTING
PROTOCOL IN MANET
V. Jayalakshmi1
and Dr. R. Rameshkumar2
1
Department of Computer Applications, Sudharsan Engineering College, Tamilnadu
jayasekar1996@yahoo.co.in
2
Principal, Lalgudi Cooperative Polytechnic College, Lalgudi, Tamilnadu
rramesh1968@gmail.com
ABSTRACT
Mobile ad hoc networks (MANETs) consist of a collection of wireless mobile nodes which dynamically
exchange data among themselves without the reliance on a fixed base station or a wired backbone network
and it the makes the routing a crucial issue to the design of the MANET. Multiple path routing protocols
are shown to be performance-effective alternatives over single-path routing for ad hoc networks and it
represents a promising routing method for wireless mobile ad hoc networks. Multi-path routing achieves
load balancing and is more resilient to route failures..In this paper we propose an energy efficient
multipath fault tolerant routing protocol to improve the reliability of data routing in Mobile ad hoc
networks. The proposed RFTA is a multi objective routing protocol that meets diverse application
requirements by considering the changing conditions of the network. The efficiency of the proposed
protocol has been evaluated on different scenarios and there has been a noticeable improvement in the
packet delivery ratio and also in the reduction of end-to-end delay comparing to SMR,SMS and MDSR.
KEYWORDS
MANET, Multipath routing,SMR, SMS and MDSR
1. INTRODUCTION
Wireless local area networks based on the 802.11a, b, g and n standards became one of the most
ubiquitous ways of networking with mobile nodes. Most of these networks, however, are
deployed in the configuration which can be called “wired everywhere, except the first hop”. If the
goal of the user of the mobile computer is to connect to a website located halfway around the
world, the best strategy is to escape as quickly as possible from the challenges of wireless domain
and enter the reliability of fiber optic networks and time-tested networking protocols. In such
networks, all the nodes connect to an access point which usually has a wired connection to the
Internet. From the point of view of the network and higher layers, this first hop can be
approximated as an Ethernet-type shared medium. In this scenario the nodes connected to the
same wireless LAN communicate with each other only indirectly.
There are, however, many important applications where this model is not applicable. First, even if
the goal is Internet access, the access point might not be able to cover all the relevant mobile
nodes due to limitations in transmission range, cost or access rights considerations. Another case

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is when Internet access is not desired (or is secondary importance), the main application being to
communicate locally among a group of (potentially mobile) nodes.
These scenarios can be serviced only if we allow some (possibly all) routing hops to be
performed in the wireless domain. Such networks can be set up in any location in an ad hoc
manner, without the need of an existing wired infrastructure. These networks are known as ad hoc
wireless networks [1], other proposed names being infrastructure less wireless networks, instant
infrastructure [2] and mobile-mesh networking.
Mobile Ad Hoc Networks (MANETs) are collections of wireless mobile nodes, constructed
dynamically without the use of any existing network infrastructure or centralized administration.
Due to the limited transmission range of wireless network interfaces, multiple hops may be
needed for one node to exchange data with another one across the network. MANETs are
characterized by limited power resource, high mobility and limited bandwidth.
One of the major technological challenges of such networks is that they require new types of
routing protocols. As opposed to the wired infrastructure, there are no dedicated router nodes: the
task of routing needs to be performed by the user nodes, which can be mobile, unreliable and
have limited energy and other resources.
Routing in MANETs can be accomplished through either single path or multiple paths. When
using single-path routing protocols, the traffic is distributed through one route and is therefore
less flexible than in multi-path routing protocols. It was shown that multi-path routing mechanism
provides better throughput than single-path routing protocols [3], [4]. Although research on multi-
path routing protocols has been covered quite thoroughly in wired networks, similar research for
wireless networks is still in its infancy. Some multi-path routing protocols for MANETs have
been proposed in [5], [6], [7], [8], [9].
The typical problems encountered in designing single path protocols for a mobile wireless
environment also arise in designing multipath protocols. Mobility makes it difficult or impossible
to maintain a global view of the network. Mobility also has implications in terms of caching
policies. If cached information at intermediate nodes is frequently out of date, caching can
degrade routing performance because detecting inaccurate routing. Information is not
instantaneous. In addition to the dynamic topology, unreliable and range limited wireless
transmission makes resiliency a requirement rather than an enhancement in a routing solution.
Since mobile transmitters are likely to be battery powered, routing protocols need to minimize the
communication for coordinating network nodes. At the protocol level, the design of multipath
routing [9] needs to consider failure models, characteristics of redundant routes, coordinating
nodes to construct routes, mechanisms for locating mobile destination and intermediate
forwarding nodes, and failure recovery.
Considering the existing problems in both single-path stable routing and backup routing schemes,
this paper proposes a robust fault tolerant multipath routing mechanism. This algorithm sets up
the primary path and the corresponding local-backup paths based on contention-based
mechanism. It has the following attractive advantages: (1) the route length of
this algorithm is approximately equal to that calculated by the shortest path algorithm; (2) the
local-backup path remains available when the primary path fails (a prediction method is
introduced to achieve this function); and (3) It greatly reduces the network overhead. For a
network with N nodes, the number of route discovery packets for the proposed protocol is of
order O(√N), while this number is of order O(N) for flooding and limited flooding.

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The paper is organized in 5 sections. Section 2 gives the related work. Section 3 describes the
proposed RFTA algorithm. Section 4 illustrates the performance evaluation with the other
protocols. Section 5 presents conclusions at the end.
2. RELATED WORK
Most of the multipath routing protocols originate from DSR [11] or AODV [12] protocols.
These multipath routing protocols modify the route discovery and route maintenance mechanisms
of DSR and AODV protocols to improve the performances of a network in terms of delay,
reliability, overhead reduction, energy efficiency and network throughput. In order to have an
understanding of the proposed multipath routing protocols it is necessary to know the basic
mechanisms of the DSR and AODV protocols.
2.1. The DSR protocol
The DSR [11] protocol consists of two basic mechanisms: (1) route discovery and (2) route
maintenance. Route discovery is the mechanism by which a source node discovers a route to a
destination. When a source node wants to send a data packet, it first looks into the route cache to
find a route. If a source cannot find a route in its route cache, the source initiates a route
discovery mechanism by broadcasting a request packet to its neighbours. When a neighbour of a
source receives a request packet, it first checks whether the request packet is intended for it or
not. If a neighbour discovers that it is the destination, it sends a reply back to the source after
copying the accumulated routing information contained in the route request packet into a route
reply packet. If it is not the destination, it checks if there is any route available in the route cache
for that destination. If this neighbouring node is neither a destination nor does it have a route in
the route cache to that destination, it appends its address in the route request packet, and then it
re-broadcasts a route request packet to its neighbours. This process continues until a route request
packet reaches the destination node. Then the destination node replies all route requests. When a
source node receives a route reply packet, it starts sending data packets using the route indicated
in the reply packet. If multiple paths are discovered, it chooses a path that is the shortest one.
Route maintenance is the mechanism by which a node is able to detect any change in the network
topology. When a node detects a broken link, for example, by using missing MAC layer
acknowledgments, it removes the link from its route cache and sends a route error message to
each node that has sent packets over that link.
2.2. The AODV protocol
The AODV protocol [10] is called a pure on-demand routing protocol because a mobile node
does not have to maintain any routing information if it is not located in an active path. Like DSR,
the AODV protocol also consists of a route discovery and a route maintenance mechanism. But
the route request packet structure of the AODV protocol is different from that of the DSR
protocol. To detect a fresh route from a stale route, each node maintains two counters called node
sequence ID and broadcast ID. Each route request packet contains information about the
destination sequence number and the source sequence number in addition to source address and
destination address. The sequence numbers are used to indicate the freshness of a route. Each
neighbour node either sends a reply to a source or re-broadcasts a request message to its
neighbours depending on whether it is the destination or not. If a node is not the destination, it
needs to keep track of a request packet to set up a reverse path as well as a forward path. When a
destination replies back to a source, it uses the reverse path. Mobile nodes can determine whether
a route is a current one or a stale one by comparing the destination sequence number in the route

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request packet with that of the sequence number stored in the route cache. If the route request
sequence number is greater than the recorded one, it does not send a reply to the source. Instead,
it re-broadcasts that request message. An intermediate node only replies from its route cache if
the route request sequence number is less than or equal to the sequence number stored in the route
cache. If a node does have a current route, it sends a reply using a unicast route reply packet. The
reply packet travels along the reverse path, which was set up previously. When a reply packet
travels back through the reverse path, each intermediate node sets up a forward pointer to the
node from which it receives this reply. When a route reply packet reaches the source, the source
starts sending data packets to the destination using the discovered path. If that source learns more
routes later on, it updates its route cache accordingly.
2.3. Multipath Routing Protocols
Reactive routing protocols like DSR and AODV do not scale well with the network size. The
scalability problem arises from excessive routing overhead, high delay, unreliable data transfer
and energy inefficiency. A reactive routing protocol generates a large number of overhead
control messages in the network during the route discovery process. Excessive overhead packets
cause contention and collision in the wireless medium and occupy a significant portion of useful
bandwidth. Hence, the performance of a network is adversely affected. Discovering multiple
paths by using fewer overhead control messages is one of the objectives of a multipath routing
protocol. Another performance problem of a reactive routing protocol is high end-to-end packet
delay. This delay arises from an inefficient path selection, unfair load distribution and high
overhead. Improving the delay of a network is another objective of a multipath routing protocol.
Unreliable data packet transfer is another problem of a reactive routing protocol. This problem
occurs mainly from the node movements and also from the interference of the wireless medium.
Multipath protocols have been proposed to ensure reliable packet transmission in the network.
Energy inefficiency is another problem of a reactive routing protocol. Energy inefficient routing
protocol incurs node failure in the network. Since a packet travels in a network in a multi-hop
fashion, it is imperative to keep a mobile node operative as long as possible. protocols have been
proposed to make a network energy efficient. Although a multipath routing protocol improves the
performance of a network, it may not be a good choice in all cases. For example, a small network
does not generate a large number of overhead packets. The interference level is also not high in
such a small network. For that reason, a multipath routing protocol may not be a suitable choice
for such a small network. There are cases when both a multipath routing protocol and a single
path routing protocol need to be used depending on the network condition [12] and [13].
2.3.1. Split Multipath Routing Protocol
The main objective of SMR [14] is to reduce the frequency of route discovery processes and
thereby reduce the control overhead in the network. The protocol uses a per packet allocation
scheme to distribute a load into multiple paths. When a destination node receives route request
packets from different paths, it chooses multiple disjoint routes and sends replies back to the
source. The basic route discovery mechanism of the DSR protocol is used in the SMR protocol,
but an intermediate node is not allowed to reply from its route cache if it has some routes
available to that destination. To avoid overlapped multiple paths, the author introduces a different
route request forwarding scheme. In this scheme, instead of dropping a duplicate request
message, an intermediate node forwards this request packet in a different incoming link other
than the link from which the first request was received and whose hop count is not larger than that
of the first request message. When a destination node receives a route request message, it selects
two paths that are maximally disjointed. Between these two routes, the first one is the shortest
path. The shortest path is chosen to minimize the route discovery time because it is the earliest
discovered route. After processing the first request, for the second path selection, a destination

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waits for a certain duration of time to receive more requests and learns all possible routes. After
this it selects a route from one of the alternative paths, which is maximally disjointed with the
shortest path. A maximally disjointed path is the path that has the least number of common nodes
compared to the shortest path. If there is more than one maximally disjointed path is available, the
shortest hop path is selected among them. Another major difference from DSR protocol is that an
intermediate node does not need to maintain a route cache. For this reason, a node has a
smaller cache. Although the SMR protocol uses less frequent route discovery
mechanisms compared to the DSR protocol, one of the drawbacks of MSR is the
redundant overhead packets. Since an intermediate node is not dropping a duplicate request
message, the frequency of route discovery process need to be reduced to curb the overhead.
2.3.2 Multipath dynamic source routing (MDSR) protocol
A multipath extension of DSR protocol called multipath dynamic source routing (MDSR) [15]
protocol has been proposed. MDSR protocol reduces the flooding problem of DSR protocol. One
major disadvantage of DSR protocol is the query flooding that is used to discover new source
route. Such query flooding generates a large number of overhead packets. These overhead
packets occupy a substantial portion of the bandwidth of a network. It is an intelligent multipath
protocol can reduce the frequency of query flooding. In DSR protocol, a destination node replies
to every received request packet. But in MDSR protocol, a destination replies only to a selected
set of request messages. After receiving all requests, a destination replies back only to those route
requests that are link-disjointed from the primary source route (i.e., the shortest path route). A
destination node keeps record of the shortest path and based on the shortest path information, it
figures out which route request it should reply to. A source keeps all the routes in the cache. If the
shortest route is broken, it uses an alternative route, which is the shortest among the remaining
routes in the cache. If this route is also broken, it uses another alternative route. This process of
choosing alternative paths continues until all paths are used. If all routes in a cache are broken, a
source initiates another route discovery. Fig 1 illustrates the idea of MDSR protocol. In this
figure, the primary route is depicted by the link sequence L1–L2– – –Lk. Each node in the primary
route ni has an alternative path Pi to the destination. The source S uses the primary route for
transmitting data packets to a destination node D until it breaks. Let us assume that the link Li is
broken, in this scenario, the node ni responds to the situation by replacing the unused portion of
the route Li– Lk in the data packet header by an alternative route Pi. This will continue until a link
in path Pi breaks. If a link on Pi breaks, it will cause an error packet transmitted backward up to
node ni-1, which will quench the error packet and switch data packets to its own alternative route
Pi-1 by modifying the source route in the packet header as before. Thus, when a route breaks, an
intermediate node makes alternative routing decisions to replace broken links. This process
continues until a source gets an error packet and has no alternative route to fall back. Simulation
results show that although the route discovery frequency is reduced, an alternative path is usually
longer and hence the delay per packet increases. In addition to this delay increase, there may be
only a few intermediate nodes that have alternative paths to a destination and this can trigger
frequent route discoveries and eventually increase overhead.

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Fig. 1.
2.3.3. Shortest Multipath Source (SMS)
SMS routing protocol is proposed based on DSR. It builds multiple partial-disjoint paths from
source S to destination D in order to avoid the overhead of additional route discoveries and to
quick recovery in case of route breaks. Improved performance in terms of Fraction of packets
delivered, end-to-end delay and routing overheads is obtained. SMS earns multiple partial-
disjoint paths that will bypass at least one intermediate node on the primary path that is shown in
Fig. 2-a.Consider the case of traffic flowing between nodes Sand D using link A-B as a segment
of the path. In case of a link failure between A and B, the source node will search for an alternate
route that does not contain node B that is shown in Fig. 2-b. An alternative route between source
S and destination D is (S, A, F, C, D)
(a) (b)
Fig. 2 (a) Partial Disjoint Multiple Paths (b) Select the alternate path
3. PROPOSED PROTOCOL : RFTA
This part provides a detailed description of the proposed protocol. Each node gets the position
information of its neighbour nodes by periodically broadcasting one-hop HELLO beacons, which
include node ID and position information (unlike in other velocity-aided routing protocols, the

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HELLO beacons in the RFTA protocol do not contain node velocity information and therefore
have a lower overhead). All nodes maintain a neighbour table, which stores the ID and position of
each neighbour. The data structures maintained by the routing node are as follows:
• Primary path table: stores primary path information for a destination node.
• Backup path table: stores local-backup path information for the links in the primary path.
• Data cache: stores the latest several data packets that have recently been forwarded.
• RREQ_Seen table : each node should save the RREQ messages it receives from
other nodes and has an additional field in RREQ_Seen table of each node, called
Neighbour_Count (N_C) which will be used to count the number of active
neighbours identified after sending the RREQ message
3.1. Route discovery
Each node has a unique IP address or ID. Let S and D denote the source and the
destination, respectively. Route discovery is started before transmitting a data packet if S
cannot find a route to D. In this paper, GPSR is adopted to forward RREQ instead of
data packets. GPSR is a kind of classical geographic information routing protocol. In
GPSR, a packet is normally routed in greedy forwarding manner, and the route switches
to perimeter forwarding when reaching a void [16]. Greedy forwarding uses the positions
of neighbour nodes and a packet’s destination to make packet forwarding decisions.
Specifically, if a node knows its neighbours’ positions, the locally optimal choice of the
next hop is the neighbour that is geographically [19] closest to the packet’s destination. In
this, each RREQ packet has the same structure, including the ID and position of the
destination, the ID, position and velocity of the current node Ni, and the link lifetime
calculated by Ni (the RREQ sent by S does not include the link lifetime, so the initial
value of the link lifetime in the RREQ is set as 0).
Primary path Local-backup path
Fig 3
3.1.1. Primary path discovery procedure
Node Ni (including S, S = N1) unicasts the RREQ to D by using GPSR. Here, we use a modified
MAC scheme for the RREQ forwarding. During the RREQ delivery procedure, the RREQ’s

30
MAC address is always the broadcast address (e.g., if the IEEE 802.11 MAC [17] is used, then
the MAC address of RREQ is always -1). When node Ni’s neighbours receive this RREQ, all of
them send it to the routing layer. In other words, although the RREQ is unicasted to the
destination at the routing layer, it is a broadcast frame at the MAC layer. Because the RREQ is a
broadcast frame at the MAC layer, when Ni transmits a RREQ, all Ni’s neighbours
can receive this RREQ.
Let us denote an arbitrary node in Nei(Ni) by N i
j
. Having received this RREQ, N i
j
adds the
corresponding information to its RREQ table. If N i
j
≠ N i+1 and N i
j
≠ N i-1, then N i
j
starts local-
backup path discovery and then discards the RREQ. If N i
j
= N i+1, then N i
j
calculates LET(Ni, N
i+1) and then adds the reverse path to the primary path table. Then, N i+1checks whether it itself is
the destination. If not, N i+1adds LET(Ni, N i+1) as well as its velocity and position information to
the RREQ packet and then sends it to the MAC layer.
When the RREQ is received by D, a RREP is sent back through the reverse path (the RREP is
unicasted in the MAC layer as well as in the routing layer). Upon receiving the RREP, S and the
intermediate nodes set up a primary path to D according to the RREP, and then S can transmit
data packets to D with this route.
3.2.2 Local-backup path discovery
Because the two neighbours obtain each other’s motion values, such as position, velocity, and
transmission range, the duration of a link between these nodes can be determined based on their
positions and velocities of movement [18]. The link expiration time is mentioned by Su et al.
[17].
We take Fig. 3 as an example for the route discovery. When S is about to send data to D and no
route for D is available, then route discovery is started. S selects the node nearest to D (here node
a is selected) from its neighbour table as the next hop and sends RREQ (by RREQS, we denote
the RREQ packet sent by S) to it. Here, the link (S, a) of primary path is established. Nodes a, e, i,
and j may receive this RREQ simultaneously. When a receives RREQS, it records
RREQS in its RREQ table and updates the corresponding fields of RREQ (RREQS) with its ID,
position, velocity, and LET(S, a). Then, node a selects b as its next hop and sends RREQa to b
(RREQa denotes the RREQ that has been updated by a). When e, i, and j receive RREQS, they
add it to their respective RREQ tables. When e and j receive the same RREQa, they calculate
PET(S, e, a) and PET(S, j, a), respectively
Primary path Local-backup path
Fig 4. Illustration of Route Maintanence

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3.2 Route maintenance
The different possible situations in route maintenance are as follows:
• There is a local-backup path between Ni and Ni+1: If link (Ni, Ni+1) in the primary path
fails, then data packets continue to be transported through the corresponding local-backup
path
• There is no local-backup path between Ni and Ni+1, but there is between Ni and Ni+2
data goes through the localbackup path to Ni+2 when neither the primary pathnor local-
backup path to Ni+1 is available.
• There is no local-backup path from Ni to Ni+1 or Ni+2: to reduce the packet loss rate, a
new backup route setup procedure is started when the lifetime of link (Ni, Ni+1) is less
than Remainder_Rate _ LET(Ni, Ni+1). This is a prediction scheme. Ni obtains LET(Ni,
Ni+1) and the Remainder_Rate _ LET(Ni, Ni+1) in the route establishment procedure and
uses them to predict how soon the link will break. In simulations, the protocol parameter
Remainder_Rate is set to 0.2.
• Neither the primary path nor the local-backup path is available: RERR is sent back to the
source, which then initiates a new route discovery process. For example, as shown in Fig.
4, when link (b, c) fails, the local-backup path (b, g, c) is used. When the data packets
reach c, the primary path is used again if it is available,
4. Performance Evaluation Results
4.1. Simulation Environments
The simulation environment is ns2[20]. The network includes 50 mobile host nodes which are
placed in 1000X1000 meter flat area in random and the number of source nodes was 30 of 50
hosts. Each node has a radio propagation range of 250 m and channel capacity was 2Mbps . The
IEEE 802.11 Distribution Coordination Function (DCF) is used as Medium Access Control
(MAC).A traffic generator was random constant bit rate (cbr) . The size of data payload was 512
bytes. The random waypoint model was used as a mobility model. Sending rate of packets was
set to 3 packets per second and the simulation was run in 30 seconds as a pause time. The
maximum and minimum speed was varied between 0 and 10 m/s .
Three important metrics are evaluated:
•Throughput: measured as the ratio of the number of data packets delivered to the number
of data packets sent by the source.
•End-to-end delay: measured as the average end-to-end latency of data packets.
•Routing loads: measured in terms of the total number of routing packets transmitted per
data packet delivered at the destination. Each broadcast transmissions was count as one
single transmission.
4.1.1 Simulation Scenarios
We ran experiments with two different base settings. In the first setting, 100 nodes are
randomly placed inside an area of 1000 x 1000 m2
. For the second setting, then number
of nodes and the size of the simulation area are varied, while keeping the average node
density constant

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4.2. Simulation Results
In the first scenario, to evaluate capability of the protocols for different node mobility, we change
node mobility by varying the maximum speed. The number of nodes and pause time was fixed at
100 nodes and 1 second, respectively.
Figures 3 and 4 show the evolution of the packet delivery ratio and average delay for increasing
node speed (from 10 to 50 m/s) in a random waypoint model
Throughput of the four protocols is shown in Fig. 5. In moderately loaded networks, the loss of
RREP packets results in the failure of the route discovery process. In on demand protocols the
source uses an exponential back-off algorithm to limit the rate at which new route discoveries are
initiated. Since the back-off time is large compared to send buffer capacity, application packets
within the back-off time may be dropped due to buffer overflow. But with this proposed RFTA
algorithm uses local-backup paths which prolongs the route lifetimes shows higher
Throughput than the other protocols.
Fig. 5
The end-to-end delay of the four protocols is shown in Fig 6. SMR has the longest delay in
mobile scenarios because it delivers data packets on routes longer than those of SMR. In addition,
MP-DSR yields longer delays in reconstructing routes and the period of time the data packets are
buffered at the source node during route recovery results in larger end-to-end delays.
Fig .6

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SMR uses the remaining valid route when one of the multiple routes is disconnected, and hence
no route acquisition latency is required. The availability of shorter alternate routing paths in the
former eliminates route discovery latency that contributes to the delay when an active route fails.
When a congestion state occurs in a path, the source node can re-distribute incoming data packets
to alternative routing paths, thereby reducing the queue waiting time of data packets.
The proposed algorithm routing outperforms the other protocols at lower mobility and node
densities. SMS finds the shortest alternative routes in a single route discovery process, reducing
delay and routing overheads incurred when recovering from route breaks. SMR overloads the
network with control messages and data packets are dropped at full buffer of intermediate nodes.
Routing load savings for M-DSR at higher nobilities and node densities came from a large saving
on route requests.
Fig 7
Fig 7 shows the PDRs of the 4 protocols with varying mobility speed. We observe that the PDR
of the MP-DSR decreases quickly as the node velocity increases. On the contrary, RFTA has the
highest PDR because it uses the local-backup paths when the primary path fails and repairs a
broken route locally. Thus, an available route in RFTA usually lasts longer and more data packets
can be delivered. As the node velocity increases, the PDR of the proposed protocol RFTA is still
above 90%, which indicates that RFTA is stable and has a good tolerance of varying node
velocity. When both the primary path and the local-backup path corresponding to the broken link
fail, an RERR is sent back to the source to initiate a new route discovery process immediately to
prevent further packet loss.
5 . CONCLUSIONS
Node mobility does not guarantee multimedia transmission in a network with a dynamic
topology. This paper presents a fault tolerant routing protocol to improve route stability in mobile
ad hoc networks. Route discovery for the primary path established in this proposed protocol
approximately achieves the smallest hop count. Simultaneously, local-backup paths are
constructed during the primary path discovery procedure according to the lifetime of each link.
When a link in the primary path fails, the upstream node of the failed link in the primary path can
continue the data delivery through the local-backup path. Compared with some representative
existing stable and source -based routing protocols such as SMR, SMS, MDSR. The simulation
results show that there has been a noticeable improvement in the packet delivery ratio and
also in the reduction of end-to-end delay comparing to other protocols. The main direction

34
of our future research is to consider other issues in RFTA such as routing overheads, QoS,
security, and load balance.
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35
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Authors
V. Jayalakshmi is Assistant Professor in the Computer Applications Department of the
Sudharsan Engineering College Pudukottai, India and has 12 years of experience in
teaching and 5 years in research. She has received her MCA and MPhil degrees in
Madras University and Bharathidasan University respectively. She is currently pursuing
her Doctoral degree in Computer Science. Her area of interest is Network Security, Data
mining and Mobile Adhoc Networks. She has published 6 papers in International and 4
papers in National.

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