International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 7- Dec 2013
A Complete Study on Unipath Routing
Protocols in MANETs
D.Ganesh Kumar 1, N.Kumar2, M.Ramesh Kumar 3
1, 2, 3
Assistant Professor1, 2, 3
Vel Tech Multi Tech Dr.Rangarajan Dr.Sakunthala Engineering College, Avadi, Chennai,
Tamil Nadu, India.
.
Abstract - Mobile Ad hoc network is a cluster of
wireless mobile nodes making a network with
dynamically changing topology without using
any permanent access point as a base station. To
create connectivity among nodes more than
single hop is needed due to low transmission
range. Increasing of mobile nodes enhances this
overhead. Many standards have been developed
for transmission and to find effective routes from
a source to some destination. In this paper, we
have analyzed the main protocols and issues of
routing in MANETs.
2. Uni-path Routing Protocol
To identify the routes and maintain the
path till the end of communication from
source and destination. In MANET, there are
two main kinds of the routing protocol: ondemand
protocols
(also
called
reactive
protocols) and table-based protocols (also
called proactive protocols)[1] ~ [5].In reactive
Keywords: adhoc networks, routing protocol,
unipath.
routing the nodes updates the routing path
1. Introduction
In proactive protocols every node
maintains a table for updating of the entire
node’s location. Messages with routing
information are exchanged using heart sync
method to keep routing tables up-to-date.
The advantages of both reactive and
proactive protocols are taken for hybrid
protocol. This always has an edge over the two
protocols and definitely handles better.
Mobile Ad hoc network is a cluster of
wireless mobile nodes making a network with
periodically changing topology without any
permanent access point as a base station. To
create connectivity among nodes more than
single hop is needed due to low transmission
range. Increasing of mobile nodes enhances
this overhead. Many standards have been
developed for transmission and to find
effective routes from a source to destination.
Wireless network has issues like low power,
unreliable nodes, unstable path dynamic
protocols, low bandwidth, and security [6].
Because of the very vast features of the
MANET, the research for the routing protocol
has been one of the concerns in the MANET.
The traditional routing algorithms for fixed
networks are not efficient for the changes.
Many protocols have been developed a lot for
routing which can be used in MANET, and
here some typical protocols are analyzed.
Section 2, reactive, proactive and hybrid
routing are discussed. Most of them is
developed from one of the uni-path routing
protocols described in the final section
ISSN: 2231-5381
when they are needed. [1][2][4].
2.1. Reactive Routing
This routing technique uses the
dynamic approach to update the routing path
whenever necessary so it is mostly suited for
large network where scalable is always an
issue. When a node wants to identify the
destination to another node, it triggers a route
discovery process to find the destination path.
It consists of two main phases [6]:
Route discovery: It is the process of seeking a
path between two nodes which is established
either directly or through any other nodes
using n number of hopes through other hosts.
Route maintenance: It is the process of
repairing a broken route or finding an alternate
route in case of a route failure. It examines the
operation of the route and informs the sender
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International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 7- Dec 2013
about the regarding errors. The most known
reactive routing protocols are DSR and
ADOV.
2.1.1. Dynamic Source Routing Protocol
(DSR)
It is a routing technique in which the
sender of a packet determines the entire
sequence of nodes and identifies their location
through using to forward the packet; the sender
of a packet finalizes the transmission of the
packet through the complete sequence of
nodes; the sender uniquely identifies this route
in the packet’s header, identifying subsequent
forwarding “hop” using the address of the next
node to transmit the packet on its path to the
destination node.
When another node receives a ROUTE
REQUEST, if that’s the destination of the
Route Discovery, it returns a ROUTE REPLY
message to the initiator. If not, the current
node attaches its address to the route
information in the ROUTE REQUEST
message and broadcast it by transmitting it as
a local broadcast packet, till the packet attains
its destination.
When the packet reaches its destination, the
node will reply a ROUTE REPLY message.
With the reply message either REPLY
message is returned can be starting a new
Route Discovery or use the sequence in
reverse of the nodes based on the networks
scenario i.e., unidirectional or bidirectional.
The DSR is designed for use in the
wireless environment of a temporary or
emergency situation like an ad hoc network.
There is no regular router discovery nor
advertisement. Instead, whenever a node needs
to reach another host, it identifies the
destination based on the available information
Figure 1 Route Discovery example: from
for the routing obtained from the results of
Node A to Node E
route discovery protocol [1][2].
2.1.1.1. Route Discovery
When some node S needs to send a new
packet to other node D, it fits packet header
source route details giving the sequence of
hops that the packet should follow on its way
to D. Eventually, S will obtain a suitable
source route by seeking its temporary memory
of route information obtained. If routes are not
found in its cache, it will trigger the Route
Discovery protocol to find a new route to D
dynamically. In the above scenario, we say S
the provoker and D the solution of Route
Discovery.
For example, if node A is trying to seek a
path to node E. A transmits a ROUTE
REQUEST message as a single local broadcast
packet, which contains a distinctive request id.
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When triggering a Route Discovery, the
source node saves a copy of the original packet
in a local temporary memory called the Send
Buffer. The Send Buffer contains a copy of
every packet that is unsuccessful in
transmitting by this node since source route is
missing for destination. When a packet resides
in the Send Buffer, the node should try for
route discovery every now and then.
2.1.1.2. Route Maintenance
When sending a packet using a source
route, every node sending the packet holds
responsible for verifying that the packet has
been received by the next node in the sequence
of hop along the source route; the packet is
transmitted again and again till confirmation is
received till the maximum attempts possible.
It returns an error message ROUTER
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International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 7- Dec 2013
ERROR to the sender if no confirmation for
node’s details to identify the destination
receipt is received, finding the connection
over which the packet could not be furthered.
instead of source routing. Wherein the DSR,
which uses source routing. It maintains routing
The source node then eradicate this broken
information at its intermediate host’s routing
link from its temporary memory, and habit
table to identify the path.
another route in the Route Cache, or triggers a
new Route Discovery.
2.1.2.1. Route Discovery
There are also some additional features
introduced in [1] to improve the performance
of Route Maintenance: Packet Salvaging;
Automatic Route Shortening; Increased
Spreading of ROUTE ERROR Messages;
Caching Negative Information
DSR, there are quite a few advantages:
First, unlike orthodox routing protocols, it
uses no constant routing advertisement
messages, in so doing reducing network
bandwidth overhead, especially there is an
negative movement of the host. Second, it
doesn’t need the transmission in bidirectional
between hosts. It can change quickly to
changes such as mobility in host, yet requires
no routing protocol overhead for the above
mentioned changes do not occur.
Yet, The Route Maintenance protocol do
not locally repair a broken link. The sender is
informed about the error. The DSR protocol is
Similar to DSR, the route discovery
process is initiated when a source needs to
send packet but lacks the destination. The
source node floods the network with a RREQ
packet specifying the destination for which the
route is requested. When the destination
receives the RREQ packet, the node generates
a RREP packet, which is sent back to the
source along the reverse path. Each node along
the reverse path sets up a forward pointer to
the node it received the RREP from. This
create a path for the destination.
2.1.2.2. Route Maintenance
When a node detects a disconnected
link while transmitting, it generates a RERR
packet to send to all sources using the
disconnected link. The RERR packet erases all
better served if the number of nodes is
restricted to about 200 nodes. Overhead occurs
when there is an increase in node’s movement
and count, hence the nodes can only traverse
around in this case with a controllable speed.
routes using the link along the way. If a source
Overflowing the network can cause collisions
among the packets. There is a lag at the initial
stage of the connectivity because the sender
must identify the target before starting of
free routing, optional multicast and reduced
transmission [9].
detect a unidirectional link [10].
2.1.2. Ad-hoc On-Demand Distance Vector
Routing (AODV)
2.2. Proactive Routing
receives a RERR packet and route to
destination is needed, it initiates a new route
discovery process.
The advantages of AODV are: loop
control overhead. But overhead is produced by
the delay caused by route discovery process
and bidirectional connection needed in order to
In Proactive Routing, also called
AODV is a reactive routing protocol
[5] which doesn’t relies on any related routing
information. AODV utilizes a broadcasting
mechanism used in DSR. But it uses dynamic
route table which update of intermediate
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table-driven Routing, routes are calculated
even before transmission. The protocol tries to
keep routing information to all nodes every
time up-to-date. The update of the tables can
be heart synched by events.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 7- Dec 2013
2.2.1. Optimized
Protocol (OLSR)
Link
State
Routing
In [3], a proactive routing protocol,
called Optimized Link State Routing for
MANET is proposed. The protocol obtains the
stability of the link state algorithm. Due to its
proactive nature, it has an advantage of having
the routes available when needed. OLSR is an
optimization of a pure link state protocol for
MANET. First, it reduces the size of control
packets by creating only a subset of links with
its neighbors who are its multipoint relay
selectors instead of entire links, it minimizes
flooding of this control traffic by using only
the selected nodes, called multipoint relays
(MPR), to diffuse its message in the network.
This reduces the number of retransmissions in
MPR information declaration: routing
packet Database is required to build the intraforwarding, each broadcasts specific control
messages called Topology Control (TC)
messages. This message is sent periodically by
every node in the network to declare its MPR
Selector set. Each node of the network
maintains a topology table with information
about the topology of the network obtained
from the TC messages.
Routing table calculation: Each node
maintains a routing table. Because the routing
table is based on the information contained in
the neighbor table and the topology table, any
change in these tables leads to updating of
route information.
a flooding or broadcast procedure.
Figure 2: Multi point relays (b)
Only the MPRs of a node retransmit
the packet from the node .For this purpose,
each node maintains a set of its neighbors
which are called MPR Selectors of the node. It
is explained in the followed figure 2.
The protocol working includes:
Neighbor sensing: Each node regularly
broadcast its HELLO messages and their link
status to their neighbor. These control
messages are limited to single hop and allow
each node to understand the information of its
neighbor’s within a maximum of two hops.
Multipoint Relay selection: The MPR set
is calculated such that it contain a subset of
single hop neighbors along with their two hop
neighbors.
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Figure 3: OLSR information repositories
relation overview
Figure 3 displays an overview of the
information repositories in OLSR and relations
to message processing, message generation
and route calculation [4].
OLSR has minimal latency, and is ideal
in density and large networks. OLSR can
easily be extended to QoS monitoring by
including bandwidth and channel quality
information in link state entries. Thus, the
quality of the path is known prior to
transmission.OLSR has high control overhead,
high computation, and complex to implement.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 7- Dec 2013
2.3. Hybrid Routing
As seen previously, both pro-active
and reactive approaches for MANET have
their
disadvantages.
The
hybrid
routing
scheme, try to utilize advantage of both.
Normally, it use pro-active discovery within a
node’s local neighborhood, and using a
reactive protocol for communication between
these neighborhoods.
Figure 4: The different components of the ZRP
The proactive protocol offers better
performances for CBR (Constant Bit Rate)
2.3.1. Zone Routing Protocol (ZRP)
In [7], a hybrid routing, called Zone
Routing Protocol is proposed. ZRP divides
the topology into zones and seek to utilize
different routing protocols within and
between the zones based on the weaknesses
and strengths of these protocols. ZRP is
totally modular, meaning that any routing
protocol can be used within and between
zones.
ZRP refers to the locally proactive
routing component as the Intra-zone Routing
Protocol (IARP). The globally reactive
routing component is named Inter-zone
Routing Protocol (IERP). IERP and IARP
are not specific routing protocols.
Information about local zone of every
node can be used to reduce traffic when
global route discovery is needed. ZRP uses a
concept called bordercasting instead of
broadcasting packets.
Bordercasting
utilizes
the
topology
information provided by IARP to direct query
request to the border of the zone. The
bordercast packet delivery service is provided
by the Bordercast Resolution Protocol (BRP).
The performance evaluation in [11] shows that
the traffic load, the mobile node mobility and
the network density all have impact on the
performance of the routing protocol.
sources and it guaranties lowest delay and
jitter but consumes large bandwidth. And
when the mobility is low, the reactive protocol
performance is low. The hybrid ZRP is a
framework than a routing protocol, and it
depends on well-defined and robust routing
protocols to be utilized in and between the
zones. The need for ZRP might arise when the
basic protocols are well tested and their
limitations have been proven.
3. Conclusions
Mobile ad hoc networks is cluster of
mobile nodes which periodically transfers data
among them without depending on any
permanent base station or a fixed network for
an interactive backbone support, which makes
the wireless network a sensitive network to
handle. In this analysis, we examined the main
protocols and issues of routing in MANETs
and especially discussed the Unipath protocol.
However, there is a scope for many
other research opportunities have to be made
in routing protocol’s architecture. Among
those the primary goal is the inventing of the
dynamic routing protocol that can optimally
find routes between two nodes for
communication. In order to analyze and
improve existing or even better a new
MANET routing protocols, it is keen to
examine metrics like power factor, fault
tolerance, hop count and jitter in various
mobility and traffic models.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 6 Number 7- Dec 2013
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