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CHAPTER 4 FLOODING REDUCED - DESTINATION SEQUENCED...
Transcript of CHAPTER 4 FLOODING REDUCED - DESTINATION SEQUENCED...
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CHAPTER 4
FLOODING REDUCED - DESTINATION SEQUENCED
DISTANCE VECTOR ROUTING PROTOCOL
4.1 INTRODUCTION
The chapter two describes the analysis and implementation on the
impact of broadcast mechanism in routing protocols such as DSR, AODV and
DSDV with respect to the network performance. The simulation results show
the overhead due to the broadcast mechanisms used in all three routing
scenarios using the performance metrics namely sent and received broadcast
packets, network load, MAC load, throughput and dropped packets due to
error and collision. From the obtained results, it is proved that the DSDV and
AODV are the protocols having high overhead due to the heavy use of
“broadcasting” in their protocol design.
The overhead realized in DSDV protocol is due to the periodic and
triggered timer route updates which flood in the network very often with a
route update packet of different sizes. In addition to that the performance of
the DSDV in terms of throughput is also poor in high mobility. Hence, it is
considered to improve the performance of the DSDV protocol with respect to
MAC load, routing load, throughput, and power consumption by
implementing the proposed method namely Flooding Reduced-Destination
Sequenced Distance Vector Routing Protocol (FR-DSDV).
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4.2 DESTINATION SEQUENCED DISTANCE VECTOR
ROUTING PROTOCOL
The DSDV is a proactive or table-driven routing protocol, requiring
each Mobile Node (MN) to broadcast routing updates periodically for
determining the route in a Mobile Ad hoc Network (MANET). In a MANET,
a MN acts as a router and so each MN maintains a routing table for all
possible destinations, and the number of hops to each destination node. Using
this routing table information of each MN, the packets are forwarded between
the MN of a MANET. With this feature, routing information can be always
readily available, regardless of which the node requires the information or
not.
Each route entry in the routing table marked with a sequence
number assigned by the destination MN. It enables the MN to distinguish the
stale route from new routes for avoiding the route loop problem in MANET.
The sequence number is linked to a destination node and is originated by the
sender node. The sequence number is maintained by the destination node of a
route entry and is increased whenever the MN broadcast or publishes its
routing information. The value of the sequence number is used by all the other
nodes in the network to determine the freshness of the route information
contained in a route update for the destination. Since the value is incremented,
a higher sequence number implies that the routing information is newer.
The link failure may be detected by the MAC layer (layer 2) which
may be denoted as infinity. When a route or link is broken due to mobility and
node power in a network then immediately that metric is assigned as infinity
and issues a route update to the other nodes regarding the link status. The
routing table updates are periodically broadcast throughout the network in
order to maintain consistency in the table. To alleviate potentially large
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network traffic due to routing updates, the updates are done in periodic and
triggered fashion. The periodic update occurs at predetermined regular
intervals, a node broadcasts its entire routing table in a packet termed as full
dump.
The incremental routing update packets are used when triggered
significant topological change cases such as node mobility, link breakages,
and node power. The incremental dump packets are used to transmit only the
information that has changed since the last full dump. The triggered updates
with incremental dump packets result in the reduced overhead incurred by the
protocol. When a network is stable, incremental updates are sent and full
dump is usually infrequent. On the other side, full dumps will be more
frequent in a fast moving network.
When a node receives the new routing broadcasts contain the
following parameters in a routing table:
i) Address of the destination node,
ii) The hop count of the current node to the destination node, and
iii) The highest known sequence number for the destination.
After receiving the route update packet, the neighbors update their
routing tables with incrementing the metric and rebroadcast the update packet
to the corresponding neighbors of the node in a network. This process will be
repeated until all the nodes in the network received a copy of the update
packet. When a node receives a route entry for a particular destination node
with a higher sequence number its old route entry is replaced with the newer
route. Since the new entry is greater or newer than the old entry. If a node
receives duplicate update packets or two update packets with the same
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sequence number, the node will consider the update packet with the shortest
hop count and ignore the rest. For example, a node S receives a route
advertisement from node I for destination node D with sequence number n
and metric m (shortest path). The node S will determine the following
procedures based on the situations.
If the value of the sequence number n is greater or newer than
the sequence number in node S’s current route entry, node S
replaces its current entry with the new route through the node I.
The Node S accepts the new route if the sequence number is
the same, but the metric m (shortest path) is better than the
metric of the current route.
If node S has no route to destination node D, then it accepts
the new route. Otherwise, node S simply ignores the new
route advertisement.
4.3 DSDV ROUTING PROTOCOL OVERVIEW WITH
EXAMPLES
The node N4 wishes to send a packet to the node N5 as shown
in the Figure 4.1.
1 The node N4 looks up its routing table and locates that the next
hop for routing the packet. Here, the next hop is node N6 for
the destination N5.
2 The node N4 sends the packet to N6 as shown in Table.4.1.
The Table. 4.1 shows the routing protocol of node N4 at one
instance.
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3 The node N6 looks up the next hop for the destination node N5
in its routing table when it receives the packet.
4 The node N6 then transmits the packet to the next hop N7 as
specified in the routing table. It is shown in the Table 4.2. The
Table 4.2 shows the routing table of node N6.
5 The node N7 checks its routing table to locate the destinations
node N5.
This above routing procedure repeated along the path until the
packet finally arrives its destination node N5.
Figure 4.1 An Example of MANET
N5
N7
N2
N3 N4
N8
N6
N1
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Table 4.1 Node N4 transmits a packet to node N6 for forwarding
NodeDestination
nodeNext Hop Metric
Seq.
No.
Seq. No.
Assigned by
N1 N2 2 S380 N1
N2 N2 1 S125 N2
N3 N2 2 S440 N3
N4 N4 0 S226 N4
N5 N6 4 S380 N5
N6 N6 1 S065 N6
N4
N7 N6 21 S180 N7
.
Table 4.2 Node N6 transmits a packet to node N7 for forwarding
NodeDestination
node
Next
HopMetric
Seq.
No.
Seq. No.
Assigned by
N1 N4 3 S380 N1
N2 N4 2 S125 N2
N3 N4 3 S440 N3
N4 N4 1 S226 N4
N5 N7 3 S380 N5
N6 N6 0 S065 N6
N6
N7 N7 1 S180 N7
Route update procedure
The following procedures illustrate how a node processes an update
packet under different situations. The nodes accept the update packets with
higher sequence numbers and it is entered into the routing table, regardless of
whether they have a higher metric or not. The route update changes are made
in the routing table which is denoted by using the symbol
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Situation I
1. The route update packet is accepted for updating the route
entry in the current routing table of node N3. Here, the value of
sequence number in route update packet (Table 4.3b) is newer
than the old route entry (Table 4.3a) in the routing table. The
Table 4.3c shows the updated routing table of the node N3.
Table 4.3 Node N3 accept the update packets
a Node N3 routing table
Destination Metric Next Hop Seq. #
N1 2 N2 S48
N2 1 N2 S34
N4 2 N2 S45
b Route update packet of the Node N3
Destination N1
Metric 2
Next Hop N2
Seq. # S56
c Updated routing table of Node N3
Destination Metric Next Hop Seq. #
N1 2 N2 S56.
N2 1 N2 S34
N4 2 N2 S45
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Situation II
2. The route update packet is ignored for updating the route entry
in the current routing table of node N3. Here, the value of
sequence number in update packet (Table 4.4b) is lesser than
the old route entry (Table 4.4a) in the routing table, even
though the shortest hop count in the route entry. The
Table 4.4c shows the updated routing table of the node N3.
Table 4.4 Node N3 ignore the update packets
a Node N3 routing table
Destination Metric Next Hop Seq. #
N1 2 N2 S48
N2 1 N2 S34
N4 2 N2 S45
b Route update packet of the Node N3
Destination N4
Metric 1
Next Hop N2
Seq. # S35
c Updated routing table of Node N3
Destination Metric Next Hop Seq. #
N1 2 N2 S48
N2 1 N2 S34
N4 2 N2 S45
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Each node in the network must periodically transmit its entire
routing table to its neighbors using update packets. The neighbors will update
their tables based on this information, if required. Likewise each node will
listen to its neighbors update packets and update its own routing table. The
Table 4.5 illustrates an example of the link broken. Assume that the link
between the node N6 and N7 is broken as shown in the Figure 4.1. The node
N6 detects the link broken due to timer expired and this link status is
broadcasted to node N4 through the broadcast packet (Table 4.5a).
Table 4.5: An example of Links broken between the nodes N4 and N6
a Node N6 advertised table
Destination Next hop Metric Sequence number
N7 N7 (Infinite) S237-N7
N4 N4 1 S123-N4
b Node N4 routing table
Destination Next hop Metric Sequence number
N6 N6 1 S345-N6
N2 N2 1 S213-N2
N7 N6 2 S236-N7
c Updated routing table of Node N4
Destination Next hop Metric Sequence number
N6 N6 1 S126-N6
N2 N2 1 S365-N2
N7 N6 (Infinite) S237-N7
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The Table 4.5b shows the routing table of the node N4 before
updating. The Node N4 updates its routing table with the newly received
routing information (odd sequence number – S237-N7 and metric) of entry
N7 (Table 4.5c). It means that the link to node N7 is broken. If any other
nodes send route update information of node N7 with even sequence numbers
generated by node N7 previously, it is smaller than the current sequence
number – S237-N7 in Table 4.5c, to node N4, which knows that the route
information is stale, thus routing loop is prevented. If other nodes generate a
new odd sequence number with infinity metric for node N7 and it is sent to
node N4 which knows that the link to node N7 is broken via the odd sequence
number and infinity metric.
An odd sequence number indicates a distance equal to infinity and
is used for those destinations that become unreachable. The Even sequence
number generated and used by the destination to stamp route updates. In
DSDV, routes with a metric of infinity are advertised without a delay, while
the others can be delayed according to an average settling time. The routes to
a lost node will be re-established when the lost node comes back to the
network and broadcasts its next update message with an equal or later
sequence number and a finite metric. The update message will be propagated
over the whole network to indicate that the broken links have come back into
service again.
Settling time
Each route entry has an associated with Settling Time (ST) and
Weighted Settling Time (WST). The ST of a route entry with a given
sequence number is defined as the amount of time between when a route with
the sequence number is first received, and the time when the best route with
the same sequence number is received. The WST is the weighted average of
the settling time for recent sequence numbers, and is updated whenever a
route with a new sequence number is received.
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The WST is used together with triggered updates to quickly
propagate best routes through the network, while avoiding an explosion of
broadcasts. Whenever a node replaces a route entry with a newly received
entry, it propagates the new route to its neighbors by sending a triggered
update which contains only the changed information. However, the triggered
updates have not been sent until at least WST * 2 have passed since first
hearing the current sequence number. Then it is likely that no better route will
be heard for that sequence number, and the best route heard so far should be
propagated.
This prevents nodes from advertising a new route which will likely
be replaced later by a better route. In addition, regardless of each route entry’s
WST, triggered updates are sent at no more than a maximum specified rate.
Each mobile node keeps two routing tables, one for forwarding the packets,
the other for advertising the incremental routing information packets. The
settling time is stored in the latter with fields, destination address, last settling
time, and average settling time shown in Table 4.6. It is calculated by
maintaining a running, weighted average over the most recent updates of the
routes for each destination. The average settling time is used to determine the
delay of an update advertisement. The nodes can reduce the network traffic by
delaying the broadcast of a routing update by the settling time.
Table 4.6 Route settling time table of N6 at one instant
Destination
Address
Last settling time
(Sec.)
Average settling
time (Sec.)
N1 15 13
N2 13 11
N3 15 13
N4 8 8
N5 8 8
N6 8 8
N7 8 8
N8 12 11
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Suppose that a new routing information update arrives at N6, and
sequence number in the new entry is newer than the sequence number in the
currently used entry but has a worse metric. Then N6 must use the new entry
in making subsequent forwarding decisions. However, N6 does not have to
advertise the new route immediately and can consult its route settling time
table to decide how long to wait before broadcasting the update. The average
settling time is used to decide the delay (e.g., delay = Average settling time ×
2) before advertising a route.
4.4 THE PROPOSED METHOD - FLOODING REDUCED-
DSDV ROUTING PROTOCOL
In DSDV, during the broadcasting, the MN will broadcast their
routing tables at predetermined intervals, but due to the frequent movements
of the hosts on the networks, this will lead to a continuous burst of new route
transmissions upon every new sequence number from the destination MN. As
a result, the network will be highly congested due to the greater number of
sent, received control messages and ultimately the network throughput gets
slowed down. However, the DSDV protocol cannot control the broadcast
overhead status and, hence, the efficiency of the network. This motivates the
research work. So, the need for Flooding Reduced-Destination Sequenced
Distance Vector routing protocol, thus, rises. The proposed method FR-
DSDV use the optimum density based flooding method (implemented in
CHAPTER 3) for reducing the broadcast overhead in DSDV. The following
sections recite the importance of broadcasting in routing protocol (DSDV) of
MANET.
Broadcasting in MANET Routing Protocols
In both wired and wireless networks, blind or simple flooding is one
of the broadcasting mechanisms, where each node in the network rebroadcasts
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a message to its neighbors upon receiving for the first time. Each node
forwards a received route request packet once until a destination is reached.
This method is known as simple flooding. Once a route to a destination has
been established, all the intermediate nodes along the route adhere to the
forwarding responsibilities of data packets. Here, all the intermediate nodes
are involved in forwarding and it leads to a serious problem, often known as a
broadcast storm problem. The probability flooding is one of the alternative
approaches to simple flooding that aims to reduce redundancy through pre-
determined probability in an attempt to alleviate the broadcast storm problem.
Optimum Density Based model for probability Flooding
In the fixed probabilistic flooding, if the rebroadcast probability p
for a node is set to a far smaller value, then the reachability will be poor. On
the other hand, if the rebroadcast probability p for a node is set to a far larger
value, then many redundant rebroadcasts, channel contention, and packet
collision will be generated. So, the need for optimum density based model for
probabilistic flooding, thus, rises. This optimum density based model
increases the rebroadcast probability if the value of the number of neighbors
is too low, which indirectly causes the probability at neighboring hosts to be
incremented. Similarly, optimum density based model decrease the
rebroadcast probabilities if the value of a number of neighbors is too high.
Periodic Update and Triggered Update in DSDV
In DSDV, there are two types of update message functions namely
periodic update messages and triggered update messages. This will be
controlled by scheduled timers. It means those functions will be called
systematically and periodically throughout the functioning of the routing
algorithm.
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The routing table updates are periodically broadcasted throughout
the network in order to maintain consistency in the table. If a neighbor node
N of node S detects that its link to S is failed due to mobility, it will broadcast
a triggered route update containing an infinite metric for S. In this triggered
update, the sequence number will be greater than the last sequence number
broadcast by node S. Each node receives this update will store an infinite
metric for destination S and will propagate the information further. This
scenario concludes that node S is unreachable from all the nodes in the
network until node S broadcasts a new sequence number in a periodic update,
in the meantime a large number of packets can be dropped.
DSDV can use either of two strategies for determining when to send
triggered updates.
A node sends a triggered update each time it receives a new
sequence number for the destination node.
The triggered update will be sent only when a new metric is
received for a destination.
In the normal implementation of DSDV, the periodic update
messages are scheduled at pre-determined interval and the triggered update
messages are scheduled with respect to the situation. Each node in the
network re-broadcast the duplicate update messages for updating the routing
table. In the proposed DSDV model FR-DSDV, the periodic update messages
and triggered update messages are scheduled with respect to the density of the
node in which the scheduling is happening currently.
In this method, the rebroadcast probability value of broadcasting
should be dynamically set high on the host contains a lesser number of
neighbors and low at the host contains a greater number of neighbors area for
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avoiding duplicate update messages. In FR-DSDV, if the density of the node
is high, then the probability value for broadcasting the route update messages
will be lesser for reducing the broadcast overhead, on the other side, if the
density of the node is less, then the probability value will be higher for better
reachability to the neighboring nodes. It is explained as follows:
On Update ()
{
if < 2 then
DoTheUpdate ()
ReScheduleTheUpdate ()
} else {
SkipTheUpdateNow ()
}
is a probability (randomly chosen between 0 and 1)
2 is the probability in which it should re-broadcast the packet.
Where,
2 = 1 / i *
i - neighbor count of node i
- minimum neighbors threshold
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The above On Update () segment is executed according to the type
of update messages received by the node; it may be a periodic or triggered
update with respect to the situation. This code segment is reducing the
flooding overhead in DSDV without affecting it's functionality and
performance. The FR-DSDV reduces the flooding overhead by reducing the
duplicate update messages which will reduce the congestion of the network at
high density regions.
In addition to that, the other layer broadcast messages are also
controlled in the same way.
OnMessageBroadcast ()
{
If < 2 then
BroadcastThePacket ()
} else {
SkipTheBroadcast ()
FreeThePacket ()
}
probability (randomly chosen between 0 and 1)
2 is the probability in which it should re-broadcast the packet.
Where, 2 = 1 / i *
i - neighbor count of node i
- minimum neighbors threshold
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4.5 PERFORMANCE ANALYSIS AND COMPARISON OF
FR-DSDV WITH DSDV
4.5.1 Simulation Parameters
The Table 4.7 shows the simulation parameters used for DSDV and
FR-DSDV routing protocol in ns2 simulation.
Table 4.7 Simulation parameters used for DSDV and FR-DSDV
Simulation Parameters Value
Channel type WirelessChannel
Radio-propagation model TwoRayGround
Antenna type OmniAntenna
Interface queue type DropTail/PriQueue
MAC type 802_11
Max packets in Queue 50
Topographical Area 800m x 800m
Routing protocols DSDV / FR_DSDV
Nodes in the Network 10,20,30,40 and 50
Mobility Model Random Waypoint Mobility
Traffic CBR over UDP
CBR Packet Size 512 Bytes
CBR Interval 0.1 s
CBR sources 25 % Nodes
CBR sinks 25 % Nodes
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4.5.2 Performance Metrics and Results
The performance of the new method FR-DSDV is implemented and
compared to normal DSDV routing protocol. It is demonstrated that a new
method has superior performance characteristics with respect to the metrics
such as MAC load, routing load, throughput, dropped packets, and power
consumption. The following important performance metrics are considered
for evaluation of FR-DSDV routing protocol.
MAC load
In this study, MAC load represents the number of control packets
generated and disseminated throughout the network during the flooding
process in the network. The average number of control packets produced per
mobile node.
Routing load
The routing load means the average number of routing messages
generated at the network layer in the overall network to each data packet
successfully delivered to the destination.
Throughput
Throughput is defined as the total number of data packets received
(bytes) at destinations in one second.
Dropped packets
In this study, dropped packets are considered as a metric and it
indirectly measured the overhead/impact due to excess flooding.
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Power consumption
It is measured as the total consumed energy (in joules) for delivery
of ‘n’ packets.
The following simulation results show the comparison of DSDV
and FR-DSDV with respect to transmitted and received control messages,
routing load, MAC load, throughput, dropped packets, and power
consumption.
Figure 4.2 Comparisons of transmitted control messages – DSDV and
FR-DSDV
Figures 4.2 and 4.3 show the performance of DSDV and FR-DSDV
routing protocols with respect to transmitted and received control messages in
the network. Broadcasting in DSDV is done periodically to maintain routing
updates and local connectivity, informing each neighbor node of other nodes
in its neighborhood. In FR-DSDV, the periodic update messages and triggered
update messages are scheduled with respect to the density of the node. Hence,
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the FR-DSDV protocol generates a less number of transmitted and received
control messages when compared to DSDV protocol. The Tables 4.8 and 4.9
show the value of the transmitted and received control packets with respect to
the number of nodes in DSDV and FR-DSDV.
Table 4.8 Comparison of Transmitted control messages – DSDV and
FR-DSDV
Nodes DSDV FR-DSDV
10 256.00 268.00
20 508.00 480.00
30 876.00 715.00
40 1222.00 942.00
50 1714.00 1244.00
Figure 4.3 Comparisons of received control messages – DSDV and
FR-DSDV
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Table 4.9 Comparison of received control Messages – DSDV and FR-
DSDV
Nodes DSDV FR-DSDV
10 549.00 580.00
20 2507.00 2144.00
30 6269.00 4600.00
40 10122.00 6749.00
50 16270.00 10578.00
Figure 4.4 Comparisons of routing load - DSDV and FR-DSDV
Table 4.10 Comparison of routing load – DSDV and FR-DSDV
Nodes DSDV FR-DSDV
10 5.69 7.66
20 5.35 5.45
30 6.49 4.93
40 12.73 6.41
50 24.49 13.98
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Figures 4.4 and 4.5 show the performance of DSDV and
FR-DSDV with respect to routing load and MAC load. The DSDV uses
routing tables, one route per destination, and destination sequence numbers, a
mechanism to prevent loops and to determine the freshness of routes. Due to
the number of duplicate update messages generated by the all the nodes,
overhead in DSDV is more when the network is large and it becomes harder
to maintain the routing table at every node. The MAC load is consistently low
in FR-DSDV and DSDV especially for a small number of nodes. The FR-
DSDV reduces the number of duplicate update messages by applying density
based flooding methods and thereby the congestion will be decreased. Hence,
the FR-DSDV has very low MAC load and routing load than the DSDV.
Figure 4.5 Comparisons of MAC Load - DSDV and FR-DSDV
The Tables 4.10 and 4.11 shows the comparison of routing load and
MAC load in DSDV and FR-DSDV.
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Table 4.11 Comparison of MAC Load – DSDV and FR-DSDV
Nodes DSDV FR-DSDV
10 19.44 23.66
20 13.19 13.50
30 16.13 13.29
40 33.94 21.76
50 60.66 44.67
Figure 4.6 Comparisons of throughput - DSDV and FR-DSDV
In Figure 4.6, throughput decreases comparatively in DSDV as it
needs to advertise periodic updates at pre-determined interval and event-
driven updates are scheduled with respect to the situation. On the other side,
throughput increases in FR-DSDV since the periodic update and triggered
update messages are scheduled with respect to the density of the node and its
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probabilities, instead of on a periodic triggered update as in basic DSDV.
The Table.4.12 shows the comparison of throughput – DSDV and FR-DSDV.
Table 4.12 Comparison of throughput – DSDV and FR-DSDV
Nodes DSDV FR-DSDV
10 2.54 2.95
20 5.36 4.96
30 7.64 8.18
40 5.42 8.27
50 3.96 5.02
Figure 4.7 Comparisons of dropped packets - DSDV and FR-DSDV
In Figure 4.7, the number of dropped packets during the flooding
will be decreased since the minimum number of nodes involved in
broadcasting the update packets. The density based flooding concept is used in
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periodic and triggered update messages of FR-DSDV which will reduce the
flooding the number of messages based on the density of the nodes. The
Table 4.13 shows the comparison of dropped packets – DSDV and FR-DSDV.
Table 4.13 Comparison of dropped packets - DSDV and FR-DSDV
Nodes DSDV FR-DSDV
10 150.00 158.00
20 159.00 158.00
30 558.00 263.00
40 1069.00 690.00
50 1588.00 1208.00
Figure 4.8 Comparisons of average remaining power-DSDV and FR-
DSDV
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The Figure 4.8 shows the average remaining power used by the
DSDV and FR-DSDV. This graph shows that the average remaining power of
FR-DSDV is high when compared to the DSDV protocol. In FR-DSDV,
periodic and triggered update messages are transmitted based on the
probability value of the node. In case of DSDV, all the nodes involved in
broadcasting the periodic and triggered update messages in the network. The
Table.4.14 shows the comparison of average remaining power – DSDV and
FR-DSDV with respect to different number of nodes.
Table 4.14 Comparison of average remaining power-DSDV and
FR-DSDV
Nodes DSDV FR-DSDV
10 996.59 996.51
20 996.50 996.52
30 996.47 996.49
40 996.46 996.48
50 996.44 996.45
The Figure 4.9 shows the average consumed power used by the
DSDV and FR-DSDV. This graph shows that the average consumed power of
FR-DSDV is very less when compared to the DSDV protocol. The
dissemination of transmitted and received control messages of a node is
controlled in FR-DSDV by implementing density based flooding in periodic
and trigger update messages in the network. DSDV consumes valuable
network resources such as bandwidth and node power due to the number of
duplicate update messages are broadcasted on the network. The Table 4.15
shows the comparison of average consumed power – DSDV and FR-DSDV.
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Figure 4.9 Comparisons of average consumed power-DSDV and
FR-DSDV
Table 4.15 Comparison of average consumed power-DSDV and
FR-DSDV
Nodes DSDV FR-DSDV
10 3.41 3.49
20 3.50 3.48
30 3.53 3.51
40 3.54 3.52
50 3.56 3.55
4.6 SUMMARY
This chapter has presented a new approach namely Flooding
Reduced Destination Sequence Distanced Vector Routing protocol for
reducing the broadcast overhead in the DSDV routing protocol. This chapter
has compared the performance of FR-DSDV against the normal DSDV with
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respect to MAC load, routing load, power consumption, throughput, and
dropped packets. The simulation results reveal that this approach FR-DSDV
can generate less broadcast overhead due to periodic and triggered update
messages than the DSDV by implementing the density based probability
flooding approach in FR-DSDV.
This study has also revealed that DSDV use the periodic update
messages which are scheduled periodically and the triggered update messages
which are scheduled with respect to the situation. In the proposed DSDV
model, FR-DSDV, the periodic update messages and triggered update
messages are scheduled with respect to the density of the node. In FR-DSDV,
if the density of the node is high, then the probability value for broadcasting
the route update messages will be lesser for reducing the broadcast overhead,
on the other side, if the density of the node is less, then the probability value
will be higher for better reachability to the neighboring nodes. As can be seen
the overhead increases when increase the number of nodes for FR-DSDV and
DSDV routing protocols, in both scenarios. The FR-DSDV routing protocol is
best suited for general small ad-hoc networks as it consumes less bandwidth
and lower overhead when compared with the DSDV routing protocol.
As growing of the mobility and number of nodes in the network,
network bandwidth, power consumption of the node and routing updates will
also be grows simultaneously. Due to these reasons, the overhead for
maintaining and updating these tables will also be increased correspondingly
in DSDV and FR-DSDV. The throughput is relatively high for both DSDV
and FR-DSDV protocols, and it decreases as the number of nodes is
increased. This is mainly due to the fact that when increase the number of
nodes, the computation also increases. Due to the high mobility of the nodes,
the simulation results prove that the throughput keeps decreasing as increase
the number of nodes, as opposed to the scenario where nodes are static.