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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

136

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.

137

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

138

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.