CNlab Vsem Manual 1

Computer Applications (Bangalore Institute of Technology)

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Computer Network Laboratory (15CSL57) V SEM

Lab Experiment 1 :
Implement three nodes point – to – point network with duplex links between them. Set the queue
size, vary the bandwidth and find the number of packets dropped.

Topology-

Source/udp0

n0

n2 n3

router Destination/null

n1

Source/udp1

Code –

#Create Simulator object

set ns [new Simulator]

#Open trace file

set nt [open lab1.tr w]
$ns trace-all $nt

#Open namtrace file

set nf [open lab1.nam w]
$ns namtrace-all $nf

#Create nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]

#Assign color to the packet

$ns color 1 Blue
$ns color 2 Red

#label nodes
$n0 label "Source/udp0"
$n1 label "Source/udp1"
$n2 label "Router"
$n3 label "Destination/null"

#create links, specify the type, nodes, bandwidth, delay and ARQ algorithm for it
$ns duplex-link $n0 $n2 10Mb 300ms DropTail
$ns duplex-link $n1 $n2 10Mb 300ms DropTail

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Computer Network Laboratory (15CSL57) V SEM

$ns duplex-link $n2 $n3 100Kb 300ms DropTail

#set queue size between the nodes

$ns queue-limit $n0 $n2 10
$ns queue-limit $n1 $n2 10
$ns queue-limit $n2 $n3 5

#create and attach UDP agent to n0, n1 and Null agent to n3

set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0

set udp1 [new Agent/UDP]

$ns attach-agent $n1 $udp1

set null3 [new Agent/Null]

$ns attach-agent $n3 $null3

#attach Application cbr to udp

set cbr0 [new Application/Traffic/CBR]
$cbr0 attach-agent $udp0

set cbr1 [new Application/Traffic/CBR]

$cbr1 attach-agent $udp1

#set udp0 packet to red color and udp1 packet to blue color
$udp0 set class_ 1
$udp1 set class_ 2

#connect the agents

$ns connect $udp0 $null3
$ns connect $udp1 $null3

#set packet size and interval for cbr1

$cbr1 set packetSize_ 500Mb
$cbr1 set interval_ 0.005

#finish procedure
proc finish { } {
global ns nf nt
$ns flush-trace
exec nam lab1.nam &
close $nt
close $nf
exit 0
}

$ns at 0.1 "$cbr0 start"

$ns at 0.1 "$cbr1 start"
$ns at 10.0 "finish"
$ns run

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Computer Network Laboratory (15CSL57) V SEM

Awk file-
BEGIN{
count=0;
}
{
if($1=="r") count+
+
}
END{
printf("Number of packets dropped is = %d\n",count);
}

Output-
$awk -f numDrop.awk lab1.tr
Number of packets dropped is = 714

Simulation-

Trace File-

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Computer Network Laboratory (15CSL57) V SEM

Lab Experiment 2 :

Implement transmission of ping messages/trace route over a network topology consisting of 6 nodes and
find the number of packets dropped due to congestion.

Topology-
Ping3
n3
Ping0 Ping4

n0 n4

n5
router

n2
n1 Ping1
Ping2

Code-

#create Simulator object

set ns [new Simulator]

#open trace file

set nt [open prac2.tr w]
$ns trace-all $nt

#open namtrace file

set nf [open prac2.nam w]
$ns namtrace-all $nf

#create nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
set n5 [$ns node]

#label nodes
$n0 label "ping0"
$n1 label "ping1"
$n2 label "ping2"
$n3 label "ping3"
$n4 label "ping4"
$n5 label "router"

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Computer Network Laboratory (15CSL57) V SEM

#create links, specify the type, nodes, bandwidth, delay and ARQ algorithm for it
$ns duplex-link $n0 $n5 1Mb 10ms DropTail
$ns duplex-link $n1 $n5 1Mb 10ms DropTail
$ns duplex-link $n2 $n5 1Mb 10ms DropTail
$ns duplex-link $n3 $n5 1Mb 10ms DropTail
$ns duplex-link $n4 $n5 1Mb 10ms DropTail

#set queue length

$ns queue-limit $n0 $n5 5
$ns queue-limit $n1 $n5 5
$ns queue-limit $n2 $n5 2
$ns queue-limit $n3 $n5 5
$ns queue-limit $n4 $n5 2

$ns color 2 Red

$ns color 3 Blue
$ns color 4 Green
$ns color 5 Yellow

#define ‘recv’ function for class Agent/Ping

Agent/Ping instproc recv {from rtt} {
$self instvar node_
puts "node [$node_ id] received ping answer from $from with round-trip time $rtt ms"
}

#create ping agent and attach them to node

set p0 [new Agent/Ping]
$ns attach-agent $n0 $p0
$p0 set class_ 1

set p1 [new Agent/Ping]

$ns attach-agent $n1 $p1
$p1 set class_ 2

set p2 [new Agent/Ping]

$ns attach-agent $n2 $p2
$p2 set class_ 3

set p3 [new Agent/Ping]

$ns attach-agent $n3 $p3
$p3 set class_ 4

set p4 [new Agent/Ping]

$ns attach-agent $n4 $p4
$p4 set class_ 5
#connect 2 agents
$ns connect $p2 $p4
$ns connect $p3 $p4

proc sendPingPacket { } {
global ns p2 p3

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Computer Network Laboratory (15CSL57) V SEM

set intervalTime 0.001

set now [$ns now]
$ns at [expr $now + $intervalTime] "$p2 send"
$ns at [expr $now + $intervalTime] "$p3 send"
$ns at [expr $now + $intervalTime] "sendPingPacket"
}

proc finish { } {
global ns nt nf
$ns flush-trace

close $nt
close $nf
exec nam prac2.nam &
exit 0
}

$ns at 0.1 "sendPingPacket"

$ns at 2.0 "finish"
$ns run

Awk file-
BEGIN{
count=0;
}
{
if($1=="r") count+
+
}
END{
printf("Number of packets dropped is = %d\n",count);
}

Output-
$ns lab2.tcl
node 3 received ping answer from 4 with round-trip time 66.3 ms
node 3 received ping answer from 4 with round-trip time 66.8 ms
node 3 received ping answer from 4 with round-trip time 66.3 ms
node 3 received ping answer from 4 with round-trip time 66.9 ms
node 3 received ping answer from 4 with round-trip time 66.4 ms
node 3 received ping answer from 4 with round-trip time 66.9 ms
node 3 received ping answer from 4 with round-trip time 66.4 ms
node 3 received ping answer from 4 with round-trip time 66.9 ms
node 3 received ping answer from 4 with round-trip time 66.4 ms
node 3 received ping answer from 4 with round-trip time 66.9 ms
node 3 received ping answer from 4 with round-trip time 66.4 ms
node 3 received ping answer from 4 with round-trip time 67.0 ms
node 3 received ping answer from 4 with round-trip time 66.5 ms
node 3 received ping answer from 4 with round-trip time 67.0 ms
node 3 received ping answer from 4 with round-trip time 66.5 ms
node 3 received ping answer from 4 with round-trip time 67.0 ms
node 3 received ping answer from 4 with round-trip time 66.5 ms

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Computer Network Laboratory (15CSL57) V SEM

$awk -f numDrop.awk prac2.tr

Number of packets dropped is = 41

Simulation-

Trace File-

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Computer Network Laboratory (15CSL57) V SEM

Lab Experiment 3:
Implement an Ethernet LAN using n nodes and set multiple traffic nodes and plot congestion window for
different source / destination.

Topology-

TCP/FTP

n0 TCPSink/TELNET

n2 n3 n5

n1
TCP/TELNET
n4
TCPSink/FTP

Code-
#set ns Simulator
set ns [new Simulator]

#define color for data flow

$ns color 1 Blue
$ns color 2 Red

#open trace file

set tracefile1 [open lab3.tr w]
set winfile [open winfile w]
$ns trace-all $tracefile1

#open namtrace file

set namfile [open lab3.nam w]
$ns namtrace-all $namfile

#define finish procedure

proc finish { } {
global ns tracefile1 namfile
$ns flush-trace
close $tracefile1
close $namfile
exec nam lab3.nam &
exit 0
}

#create 6 nodes
set n0 [$ns node]
set n1 [$ns node]

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Computer Network Laboratory (15CSL57) V SEM

set n2 [$ns node]

set n3 [$ns node]
set n4 [$ns node]
set n5 [$ns node]

$n1 shape box

#create link between nodes
$ns duplex-link $n0 $n2 2Mb 10ms DropTail
$ns duplex-link $n1 $n2 2Mb 10ms DropTail
$ns simplex-link $n2 $n3 0.3Mb 100ms DropTail
$ns simplex-link $n3 $n2 0.3Mb 100ms DropTail

set lan [$ns newLan "$n3 $n4 $n5" 0.5Mb 40ms LL Queue/DropTail MAC/802_3]

#give node position

$ns duplex-link-op $n0 $n2 orient right-down
$ns duplex-link-op $n1 $n2 orient right-up
$ns simplex-link-op $n3 $n2 orient left
$ns simplex-link-op $n2 $n3 orient right

#set queue size of link(n2-n3)

$ns queue-limit $n2 $n3 20

#setup tcp connection

set tcp [new Agent/TCP]
$ns attach-agent $n0 $tcp
set sink [new Agent/TCPSink]
$ns attach-agent $n4 $sink
$ns connect $tcp $sink
$tcp set fid_ 1
$tcp set packetSize_ 552

#set ftp over tcp connection

set ftp [new Application/FTP]
$ftp attach-agent $tcp

#setup a TCP1 connection

set tcp1 [new Agent/TCP]
$ns attach-agent $n1 $tcp1
set sink1 [new Agent/TCPSink]
$ns attach-agent $n5 $sink1
$ns connect $tcp1 $sink1
$tcp1 set fid_ 2
$tcp1 set packetSize_ 552

set telnet0 [new Application/Telnet]

$telnet0 attach-agent $tcp1

#title congestion window1

set outfile1 [open congestion1.xg w]
puts $outfile1 "TitleText: Congestion Window-- Source _tcp"
puts $outfile1 "xUnitText: Simulation Time(Secs)"

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Computer Network Laboratory (15CSL57) V SEM

puts $outfile1 "yUnitText: Congestion WindowSize"

#title congestion window2

set outfile2 [open congestion2.xg w]
puts $outfile2 "TitleText: Congestion Window-- Source _tcp1"
puts $outfile2 "xUnitText: Simulation Time(Secs)"
puts $outfile2 "yUnitText: Congestion WindowSize"

proc plotWindow {tcpSource outfile}

{ global ns
set time 0.1
set now [$ns now]
set cwnd [$tcpSource set cwnd_]
puts $outfile "$now $cwnd"
$ns at [expr $now+$time] "plotWindow $tcpSource $outfile"
}

$ns at 0.1 "plotWindow $tcp $winfile"

$ns at 0.0 "plotWindow $tcp $outfile1"
$ns at 0.1 "plotWindow $tcp1 $outfile2"
$ns at 0.3 "$ftp start"
$ns at 0.5 "$telnet0 start"
$ns at 49.0 "$ftp stop"

$ns at 49.1 "$telnet0 stop"

$ns at 50.0 "finish"

$ns run

Simulation-

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Computer Network Laboratory (15CSL57) V SEM

Trace File-

Congestion graph-

$ xgraph congestion1.xg $ xgraph congestion2.xg

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Computer Network Laboratory (15CSL57) V SEM

Lab Experiment 4 :

Implement simple ESS and with transmitting nodes in wire-less LAN by simulation and determine the
performance with respect to transmission of packets.

Topology-

TCP0/FTP

bs1 bs2

TCPSink0/FTP
n0 n1 n2 n3

Code-

#create Simulator class

set ns [new Simulator]

#open trace file

set nt [open lab42.tr w]
$ns trace-all $nt

#create Topography object

set topo [new Topography]
#define grid size
$topo load_flatgrid 1000 1000

#open namtrace file

set nf [open lab42.nam w]
$ns namtrace-all-wireless $nf 1000 1000

#specify node configuration

$ns node-config -adhocRouting DSDV \
-llType LL \
-macType Mac/802_11 \
-ifqType Queue/DropTail \
-ifqLen 20 \
-phyType Phy/WirelessPhy \
-channelType Channel/WirelessChannel \
-propType Propagation/TwoRayGround \
-antType Antenna/OmniAntenna \
-topoInstance $topo \
-agentTrace ON \
-routerTrace ON

#create General Operation Director(god) object that stores total number of mobile
nodes. create-god 4
#create nodes and label them
set n0 [$ns node]

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Computer Network Laboratory (15CSL57) V SEM

set n1 [$ns node]

set n2 [$ns node]
set n3 [$ns node]

$n0 label "tcp0"

$n1 label "sink0"
$n2 label "bs1"
$n3 label "bs2"

#give initial x, y, z coordinates to nodes

$n0 set X_ 110
$n0 set Y_ 500
$n0 set Z_ 0

$n1 set X_ 600

$n1 set Y_ 500
$n1 set Z_ 0

$n2 set X_ 300

$n2 set Y_ 500
$n2 set Z_ 0

$n3 set X_ 450

$n3 set Y_ 500
$n3 set Z_ 0

#attach agent and application to nodes and connect them

set tcp0 [new Agent/TCP]
$ns attach-agent $n0 $tcp0

set ftp0 [new Application/FTP]

$ftp0 attach-agent $tcp0

set sink1 [new Agent/TCPSink]

$ns attach-agent $n1 $sink1

$ns connect $tcp0 $sink1

#schedule the event

$ns at 0.5 "$ftp0 start"

#set up destination for mobile nodes. They move to <x><y> coordinates at <s>m/s.
$ns at 0.3 "$n0 setdest 110 500 10"
$ns at 0.3 "$n1 setdest 600 500 20"
$ns at 0.3 "$n2 setdest 300 500 30"
$ns at 0.3 "$n3 setdest 450 500 30"

$ns at 10.0 "$n0 setdest 100 550 5"

$ns at 10.0 "$n1 setdest 630 450 5"

$ns at 70.0 "$n0 setdest 170 680 5"

$ns at 70.0 "$n1 setdest 580 380 5"

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Computer Network Laboratory (15CSL57) V SEM

$ns at 120.0 "$n0 setdest 140 720 5"

$ns at 135.0 "$n0 setdest 110 600 5"

$ns at 140.0 "$n1 setdest 600 550 5"

$ns at 155.0 "$n0 setdest 89 500 5"

$ns at 190.0 "$n0 setdest 100 440 5"

$ns at 210.0 "$n1 setdest 700 600 5"

$ns at 240.0 "$n1 setdest 650 500 5"

proc finish { } {
global ns nt nf
$ns flush-trace
exec nam lab42.nam &
close $nt
close $nf
exit 0
}

$ns at 400 "finish"

$ns run

Awk file-
BEGIN{
PktsSent=0;
PktsRcvd=0;
PktsAtRTR=0;
}

{
if(($1=="s")&&($4=="RTR")&&($7=="tcp"))
{
PktsAtRTR++;
}
if(($1=="s")&&($4=="AGT")&&($7=="tcp"))
{
PktsSent++;
}
if(($1=="r")&&($4=="AGT")&&($7=="tcp"))
{
PktsRcvd++;
}
}

END{
print " Number of Packets Sent :" PktsSent

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Computer Network Laboratory (15CSL57) V SEM

print " Number of Packets Received :" PktsRcvd

print " Pacjet Delivery Ratio :" PktsRcvd/PktsSent*100
print " Routing Load :" PktsAtRTR/PktsRcvd
}

Output-
$awk -f count.awk lab42.tr
Number of Packets Sent :6819
Number of Packets Received :6685
Pacjet Delivery Ratio :98.0349
Routing Load :1.02004

Simulator-

Trace File-

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Computer Network Laboratory (15CSL57) V SEM

Lab Experiment 5 :

Implement and study the performance of GSM on NS2/NS3 (Using MAC layer) or equivalent
environment.

Topology-

Base Station1
1Mbps,1ms
Base Station2
1Mbps,1ms

3Mbps, 10ms
Mobile Station
3Mbps, 50ms

Source
Destination
Code –
#General parameters
set stop 100
set type gsm

#AQM parameters
set minth 30
set maxth 0
set adaptive 1

#traffic generation
set flows 0
set window 30

#plotting statistics
set opt(wrap) 100
set opt(srcTrace) is
set opt(dstTrace) bs2

#default downlink bandwidth in bps

set bwDL(gsm) 9600
#default propogation delay in sec
set propDL(gsm) .500

set ns [new Simulator]

set tf [open Mlab5.tr w]

$ns trace-all $tf

set nodes(is) [$ns node]

set nodes(ms) [$ns node]
set nodes(bs1) [$ns node]
set nodes(bs2) [$ns node]
set nodes(lp) [$ns node]
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Computer Network Laboratory (15CSL57) V SEM

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Computer Network Laboratory (15CSL57) V SEM

proc cell_topo {}
{ global ns nodes
$ns duplex-link $nodes(lp) $nodes(bs1) 3Mbps 10ms DropTail
$ns duplex-link $nodes(bs1) $nodes(ms) 1 1 RED
$ns duplex-link $nodes(ms) $nodes(bs2) 1 1 RED
$ns duplex-link $nodes(bs2) $nodes(is) 3Mbps 50ms DropTail
puts "GSM Cell Topology"
}
proc set_link_params {t} {

global ns nodes bwDL propDL

$ns bandwidth $nodes(bs1) $nodes(ms) $bwDL($t) duplex
$ns bandwidth $nodes(bs2) $nodes(ms) $bwDL($t) duplex

$ns delay $nodes(bs1) $nodes(ms) $propDL($t) duplex

$ns delay $nodes(bs2) $nodes(ms) $propDL($t) duplex

$ns queue-limit $nodes(bs1) $nodes(ms) 10

$ns queue-limit $nodes(bs2) $nodes(ms) 10
}

#RED and TCP parameters

Queue/RED set adaptive_ $adaptive
Queue/RED set thresh_ $minth
Queue/RED set maxthresh_ $maxth
Agent/TCP set window_ $window

#create topology
switch $type {
gsm -
umts {cell_topo}
}

set_link_params $type
$ns insert-delayer $nodes(ms) $nodes(bs1) [new Delayer]
$ns insert-delayer $nodes(ms) $nodes(bs2) [new Delayer]

# set up TCP connection

if {$flows == 0} {
set tcp1 [$ns create-connection TCP/Sack1 $nodes(is) TCPSink/Sack1 $nodes(lp) 0]
set ftp1 [[set tcp1] attach-app FTP]
$ns at 0.8 "[set ftp1] start"
}

proc stop {} {
global nodes opt tf
set wrap $opt(wrap)
set sid [$nodes($opt(srcTrace)) id]
set did [$nodes($opt(dstTrace))
id] set a "Mlab5.tr"

set GETRC "../bin/getrc"

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Computer Network Laboratory (15CSL57) V SEM

set RAW2XG "../bin/raw2xg"

exec $GETRC -s $sid -d $did -f 0 Mlab5.tr | \

$RAW2XG -s 0.01 -m $wrap -r > plot.xgr

exec $GETRC -s $did -d $sid -f 0 Mlab5.tr | \

$RAW2XG -a -s 0.01 -m $wrap >> plot.xgr

exec xgraph -x time -y packets plot.xgr &

exit 0
}
$ns at $stop "stop"
$ns run

Graph-

Trace File-

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Computer Network Laboratory (15CSL57) V SEM

Lab Experiment 6 :

Implement and study the performance of CDMA on NS2/NS3 (Using stack called Call net) or
equivalent environment.

Topology-

Base Station1
1Mbps,1ms
Base Station2
1Mbps,1ms

3Mbps, 10ms
Mobile Station
3Mbps, 50ms

Source
Destination
Code –
#General parameters
set stop 100
set type umts

#AQM parameters
set minth 30
set maxth 0
set adaptive 1

#traffic generation
set flows 0
set window 30

#plotting statistics
set opt(wrap) 100
set opt(srcTrace) is
set opt(dstTrace) bs2

#default downlink bandwidth in bps

set bwDL(umts) 38400
#default propogation delay in sec
set propDL(umts) .150

set ns [new Simulator]

set tf [open Mlab6.tr w]

$ns trace-all $tf

set nodes(is) [$ns node]

set nodes(ms) [$ns node]
set nodes(bs1) [$ns node]
set nodes(bs2) [$ns node]
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Computer Network Laboratory (15CSL57) V SEM

set nodes(lp) [$ns node]

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Computer Network Laboratory (15CSL57) V SEM

proc cell_topo {}
{ global ns nodes
$ns duplex-link $nodes(lp) $nodes(bs1) 3Mbps 10ms DropTail
$ns duplex-link $nodes(bs1) $nodes(ms) 1 1 RED
$ns duplex-link $nodes(ms) $nodes(bs2) 1 1 RED
$ns duplex-link $nodes(bs2) $nodes(is) 3Mbps 50ms DropTail
puts "umts Cell Topology"
}
proc set_link_param {t} {

global ns nodes bwDL propDL

$ns bandwidth $nodes(bs1) $nodes(ms) $bwDL($t) duplex
$ns bandwidth $nodes(bs2) $nodes(ms) $bwDL($t) duplex

$ns delay $nodes(bs1) $nodes(ms) $propDL($t) duplex

$ns delay $nodes(bs2) $nodes(ms) $propDL($t) duplex

$ns queue-limit $nodes(bs1) $nodes(ms) 20

$ns queue-limit $nodes(bs2) $nodes(ms) 20
}

#set RED and TCP parameters

Queue/RED set adaptive_ $adaptive
Queue/RED set thresh_ $minth
Queue/RED set maxthresh_ $maxth
Agent/TCP set window_ $window

#create topology
switch $type {
umts {cell_topo}
}

set_link_param $type
$ns insert-delayer $nodes(ms) $nodes(bs1) [new Delayer]
$ns insert-delayer $nodes(ms) $nodes(bs2) [new Delayer]

#set up TCP connection

if {$flows == 0 } {
set tcp1 [$ns create-connection TCP/Sack1 $nodes(is) TCPSink/Sack1 $nodes(lp) 0]
set ftp1 [[set tcp1] attach-app FTP]
$ns at 0.8 "[set ftp1] start"
}

proc stop {} {
global nodes opt tf
set wrap $opt(wrap)
set sid [$nodes($opt(srcTrace)) id]
set did [$nodes($opt(dstTrace)) id]

set a "Mlab6.tr"

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Computer Network Laboratory (15CSL57) V SEM

set GETRC "../bin/getrc"

set RAW2XG "../bin/raw2xg"

exec $GETRC -s $sid -d $did -f 0 Mlab6.tr | \

$RAW2XG -s 0.01 -m $wrap -r > plot6.xgr

exec $GETRC -s $did -d $sid -f 0 Mlab6.tr | \

$RAW2XG -a -s 0.01 -m $wrap >> plot6.xgr

exec xgraph -x time -y packets plot6.xgr &

exit 0
}
$ns at $stop "stop"
$ns run
Graph-

Trace File-

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Computer Network Laboratory (15CSL57) V SEM

Lab Program 7 :

Code –
Write a program for error detecting code using CRC-CCITT (16- bits).

import java.util.Scanner;

public class CRC {

public static int n;

public static void main(String[] args)

{
Scanner sc=new Scanner(System.in);

CRC crc=new CRC();

String copy,rec,code,zero="0000000000000000";

System.out.println("enter the dataword to be sent");

code=sc.nextLine();

n=code.length();

copy=code;
code+=zero;
code=crc.divide(code);

System.out.println("dataword="+copy); copy=copy.substring(0,n)

+code.substring(n);

System.out.print("CRC=");
System.out.println(code.substring(n));

System.out.println("transmitted frame is="+copy);

System.out.println("enter received data:");

rec=sc.nextLine();

if(zero.equals(crc.divide(rec).substring(n)))
System.out.println("correct bits received");
else
System.out.println("received frame contains one or more error");

sc.close();
}

public String divide(String s)

{
String div="10001000000100001";

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int i,j;
char x;

for(i=0;i<n;i++)
{
x=s.charAt(i);

for(j=0;j<17;j++)
{
if(x=='1')
{
if(s.charAt(i+j)!=div.charAt(j)) s=s.substring(0,i+j)
+"1"+s.substring(i+j+1);
else
s=s.substring(0,i+j)+"0"+s.substring(i+j+1);
}
}
}
return s;
}
}

Output 1 –
enter the dataword to be sent
1100
dataword=1100
CRC=1100000110001100
transmitted frame is=11001100000110001100
enter received data:
1100110000010001100
received frame contains one or more error

Output 2 –
enter the dataword to be sent
1100
dataword=1100
CRC=1100000110001100
transmitted frame is=11001100000110001100
enter received data:
11001100000110001100
correct bits received

Output 3 –
enter the dataword to be sent
1101
dataword=1101
CRC=1101000110101101
transmitted frame is=11011101000110101101
enter received data:
11011001000110110010
received frame contains one or more error

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Computer Network Laboratory (15CSL57) V SEM

Lab Program 8 :

Write a program to find the shortest path between vertices using bellman-ford algorithm.

Code –

import java.util.Scanner;

public class bellmanford

{

public int distance[];

public int numb_vert;
public static final int MAX_VALUE=999;

public bellmanford(int numb_vert)

{
this.numb_vert = numb_vert;
distance = new int[numb_vert+1];
}

public void BellmanfordpEvaluation(int source,int adj_matrix[][])

{

for(int node=1;node<=numb_vert;node++)
distance[node]=MAX_VALUE;
distance[source]=0;

for(int node=1;node<=numb_vert-1;node++)
{
for(int src_node=1;src_node<=numb_vert;src_node++)
{
for(int dest_node=1;dest_node<=numb_vert;dest_node++)
{
if(adj_matrix[src_node][dest_node]!=MAX_VALUE)
{
if(distance[dest_node] > distance[src_node] +
adj_matrix[src_node][dest_node])

distance[dest_node] = distance[src_node] +
adj_matrix[src_node][dest_node];
}
}
}
}

for(int src_node=1;src_node<=numb_vert;src_node++)
{
for(int dest_node=1;dest_node<=numb_vert;dest_node++)
{
if(adj_matrix[src_node][dest_node]!=MAX_VALUE)
{
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Computer Network Laboratory (15CSL57) V SEM

if(distance[dest_node] > distance[src_node] +

adj_matrix[src_node][dest_node])
{
System.out.println("The graph contains negative edge cycle");

}
}
}
}

System.out.println("Routing Table for Router " + source+"

is"); System.out.println("Destination Distance\t");

for(int vertex=1;vertex<=numb_vert;vertex++) System.out.println(+vertex+"\t\t\
t"+distance[vertex]);

public static void main(String args[])

{

int numb_vert=0;
int source;
Scanner scan = new Scanner(System.in);

System.out.println("Enter the number of vertices");

numb_vert = scan.nextInt();

int adj_matrix[][] = new int[numb_vert+1][numb_vert+1];

System.out.println("Enter the adjacency matrix");
for(int src_node=1;src_node<=numb_vert;src_node++)
for(int dest_node=1;dest_node<=numb_vert;dest_node++)
{
adj_matrix[src_node][dest_node] = scan.nextInt();
if(src_node==dest_node)
{
adj_matrix[src_node][dest_node]=0;
continue;
}

if(adj_matrix[src_node][dest_node]==0) adj_matrix[src_node]
[dest_node]=MAX_VALUE;
}

for(int i=1;i<=numb_vert;i++)
{
bellmanford bellmanford = new bellmanford(numb_vert);
bellmanford.BellmanfordpEvaluation(i,adj_matrix);
}
scan.close();
}
}

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Computer Network Laboratory (15CSL57) V SEM

Output 1 –
5
Enter the number of vertices
6
Enter the adjacency matrix
0 2 5 1 999 999
2 0 3 2 999 999 3
5 3 13 1 5 2 3
1 2 3 0 1 999
999 999 1 1 0 2 5
999 999 5 999 2 0 2
Routing Table for Router 1 is
Destination Distance 1 2 3 6
1
1 0
2 2
3 3 1 2
4 1
5 2
4 5
6 4 1
Routing Table for Router 2 is
Destination Distance
1 2
2 0
3 3
4 2
5 3
6 5
Routing Table for Router 3 is
Destination Distance
1 3
2 3
3 0
4 2
5 1
6 3
Routing Table for Router 4 is
Destination Distance
1 1
2 2
3 2
4 0
5 1
6 3
Routing Table for Router 5 is
Destination Distance
1 2
2 3
3 1
4 1
5 0
6 2
Routing Table for Router 6 is

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 Computer Network Laboratory (15CSL57) V SEM

Destination Distance
1 4
2 5
3 3
4 3
5 2
6 0

Output 2 –
Enter the number of vertices
5
Enter the adjacency matrix
0 1 3 999 999 5
1 0 7 5 2 4
3 7 0 3 4
2
999 5 3 0 4 1
999 2 4 4 0 2 3
Routing Table for Router 1 is 7 4
Destination Distance 1
1 0
2 1 3
3 3 3 5
4 6 4
5 3
Routing Table for Router 2 is
Destination Distance
1 1
2 0
3 4
4 5
5 2
Routing Table for Router 3 is
Destination Distance
1 3
2 4
3 0
4 3
5 4
Routing Table for Router 4 is
Destination Distance
1 6
2 5
3 3
4 0
5 4
Routing Table for Router 5 is
Destination Distance
1 3
2 2
3 4
4 4
5 0

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 Computer Network Laboratory (15CSL57) V SEM

Output 3 –
4
Enter the number of vertices 2 4
5
Enter the adjacency matrix 3
0 999 3 1 4 7
999 0 4 999 7 1
5
3 4 0 5 999
1 999 5 0 999 4 1
4 7 999 999 0
Routing Table for Router 1 is 3 5
Destination Distance
1 0
2 7
3 3
4 1
5 4
Routing Table for Router 2 is
Destination Distance
1 7
2 0
3 4
4 8
5 7
Routing Table for Router 3 is
Destination Distance
1 3
2 4
3 0
4 4
5 7
Routing Table for Router 4 is
Destination Distance
1 1
2 8
3 4
4 0
5 5
Routing Table for Router 5 is
Destination Distance
1 4
2 7
3 7
4 5
5 0

Dept. of CS&E, BIT, 2017 – 18 28

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Computer Network Laboratory (15CSL57) V SEM

Lab Program 9 :

Using TCP/IP sockets, write a client – server program to make the client send the file name and to make
the server send back the contents of the requested file if present.

Code –

import java.util.*;
import java.net.*;
import java.io.*;

public class tcpclient

{

public static void main(String args[])

{

try
{
Scanner ser=new Scanner(System.in);
Socket s=new Socket("localhost",998);

DataInputStream dis=new DataInputStream(s.getInputStream());

DataOutputStream dos=new DataOutputStream (s.getOutputStream());

dos.writeUTF("connected to 127.0.0.1 \n");

System.out.println(dis.readUTF());

System.out.println("\n enter the full path of the the file to be displayed");

String path=ser.nextLine();

dos.writeUTF(path);
System.out.println(new String (dis.readUTF()));

dis.close();
dos.close();

s.close();
ser.close();
}
catch(IOException e)
{
System.out.println("IO: "+e.getMessage());
}

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Computer Network Laboratory (15CSL57) V SEM

import java.util.*;
import java.net.*;
import java.io.*;
public class tcpserver
{
public static void main (String args[])
{
try
{
ServerSocket s=new ServerSocket(998);

System.out.println("server ready \n waiting for connection \n");

Socket s1=s.accept();

DataOutputStream dos=new DataOutputStream(s1.getOutputStream());

DataInputStream dis=new DataInputStream(s1.getInputStream());

System.out.println(dis.readUTF());

dos.writeUTF("connected to server \n");

String path=dis.readUTF();
System.out.println("\n request received \n processing.......");
try
{
File myfile=new File(path);
Scanner scr=new Scanner(myfile);
String st=scr.nextLine();
st="\n the context of file is \n "+st;
while(scr.hasNextLine())
{
st=st + "\n" + scr.nextLine();
}
dos.writeUTF(st);
dos.close();
s1.close();
scr.close();
}
catch(FileNotFoundException e)
{
System.out.println("\n,,,error...\n file not found");
dos.writeUTF("...error \n file not found");
}
}
catch(IOException e)
{
System.out.println("IO: "+e.getMessage());
}
finally
{

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Computer Network Laboratory (15CSL57) V SEM

System.out.println("\n connection terminated");

}
}
}

Output –

Client Side

$ javac tcpclient.java
$java tcpclient
connected to server

enter the full path of the the file to be displayed

/root/cn/udp_tcp/text

the context of file is

Hi
how are you
tcp/ip program
112233

Server Side

$javac tcpserver.java
$ java tcpserver
server ready
waiting for connection

connected to 127.0.0.1

request received
processing.......

connection terminated

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Computer Network Laboratory (15CSL57) V SEM

Lab Program 10(a):

Write a program on datagram socket for client/server to display the messages on client side, typed at the
server side.

Code –

import java.net.*;
import java.io.*;

public class UDPClient

{
public static void main(String args[])
{
DatagramSocket aSocket=null;
int clientPort=998;

try
{
aSocket=new DatagramSocket(clientPort);
byte[] buf=new byte[1000];

DatagramPacket data=new DatagramPacket(buf,buf.length);

System.out.println("Waiting for server\n");

aSocket.receive(data);
byte[] msg=new byte[1000];
msg=data.getData();
System.out.println("\n msg:"+(new String(msg,0,data.getLength())));

}
catch(SocketException e)
{
System.out.println("Socket:" +e.getMessage());
}
catch(IOException e)
{
System.out.println("IO:" +e.getMessage());
}
finally
{
if(aSocket!=null)
aSocket.close();
}

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import java.net.*;
import java.util.*;
import java.io.*;

public class UDPServer {

public static void main(String args[])

{

DatagramSocket aSocket = null;

Scanner scn=new Scanner(System.in);
int serverPort =999;

System.out.println("Server Ready\n Waiting for connection....\n");

try
{

aSocket=new DatagramSocket(serverPort);

byte[] buffer=new byte[1000];

System.out.println("\nEnter message to be sent:");

String str=scn.nextLine();

buffer=str.getBytes();

DatagramPacket data = new DatagramPacket(buffer,buffer.length,

InetAddress.getLocalHost(),998);
aSocket.send(data);

}
catch(SocketException e)
{
System.out.println("Socket:"+e.getMessage());
}
catch(IOException e)
{
System.out.println("Io:"+e.getMessage());
}
finally
{
System.out.println("\nMessage sent\nConnection terminated"); if(aSocket!

=null)
aSocket.close();

scn.close();
}

}
}

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Output –

Client Side

$ javac UDPClient.java
$# java UDPClient
Waiting for server

msg:hello, this is server

Server Side

$javac UDPServer.java
$ java UDPServer
Server Ready
Waiting for connection....

Enter message to be sent:

hello, this is server

Message sent
Connection terminated

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Computer Network Laboratory (15CSL57) V SEM

Lab Program 11:

Write a program for simple RSA algorithm to encrypt and decrypt the data.

Code –

import java.math.BigInteger;
import java.util.Random;

public class rsalab

{
private BigInteger p;
private BigInteger q;
private BigInteger n;
private BigInteger phi;
private BigInteger e,d;
private int bitlength=256;

private Random r;
long p1;
public rsalab()
{
r=new Random();

p=BigInteger.probablePrime(bitlength, r);
q=BigInteger.probablePrime(bitlength, r);
n=p.multiply(q);
phi=p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));
e=BigInteger.probablePrime(bitlength/2, r);

while(phi.gcd(e).compareTo(BigInteger.ONE)>0 && e.compareTo(phi)<0)

{
e.add(BigInteger.ONE);
}

d=e.modInverse(phi);

public rsalab(BigInteger e,BigInteger d,BigInteger n)

{
this.e=e;
this.d=d;
this.n=n;
}

public byte[] encrypt(byte[] message)

{
return (new BigInteger(message)).modPow(e,n).toByteArray();
}

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Computer Network Laboratory (15CSL57) V SEM

public byte[] decrypt(byte[] message)

{
return (new BigInteger(message)).modPow(d,n).toByteArray();
}
}

import java.lang.*;
import java.math.BigInteger;
import java.util.Random;
import java.io.*;

public class rsal {

public static void main(String[] args) throws IOException

{

rsalab rsa=new rsalab();

DataInputStream in=new DataInputStream(System.in);

String teststring;
System.out.println("Enter the plain text:");
teststring = in.readLine();

bts s1=new bts();

System.out.println("Encrypting string: " +teststring);
System.out.println("String in
bytes:"+s1.bytesToString(teststring.getBytes()));

bts s2=new bts();

byte[] encrypted=rsa.encrypt(teststring.getBytes());

System.out.println("Encrypted string

:"+s2.bytesToString(encrypted)); bts s3=new bts();

byte[] decrypted=rsa.decrypt(encrypted);
System.out.println("Decrypted string in bytes :"+s3.bytesToString(decrypted));
System.out.println("Decrypted string :" + new String(decrypted));

class bts
{
public String bytesToString(byte[] encrypted)
{
String test="";
for(byte b:encrypted)
{
test+=Byte.toString(b);
}

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Computer Network Laboratory (15CSL57) V SEM

return test;

}
}

Output 1–
Enter the plain text:
Hello World
Encrypting string: Hello World
String in bytes:721011081081113287111114108100
Encrypted string :45-2467-21-4376-10110519-45-12653101-11-9795-122111108-43-8077-1169-40-1172-85714-
5930-21-25-117-112-20-36-9110768-11395-20-5336-77-125147457-85-4748107-33-5578-87-1819-111-72-63-
705785179011914
Decrypted string in bytes :721011081081113287111114108100
Decrypted string :Hello World

Output 2–
Enter the plain text:
This is a sample
Encrypting string: This is a sample
String in bytes:841041051153210511532973211597109112108101
Encrypted string :7-38-64-487597-725231-45-87-6981-29-17-73-34127-101108-1289-126-769143-126-56-22-
21-27-7819120852868-91-81-47-105-7937-75-48-10681-6651-43-74-126-28-10468-853610941-38-58-127-126-
10910936-63347-69127
Decrypted string in bytes :841041051153210511532973211597109112108101
Decrypted string :This is a sample

Output 3–
Enter the plain text:
rsa algorithm
Encrypting string: rsa algorithm
String in bytes:114115973297108103111114105116104109
Encrypted string :3-56-1172220151939-1055135-16-4771-43127-58-2160117-3011961-46-323011771-125-
5612-175326-89480-23-102-111-94-239089983410156-12-113-128-50-9787-32-49-12033110-113-75-1611-23-
12671-86-852-62-70
Decrypted string in bytes :114115973297108103111114105116104109
Decrypted string :rsa algorithm

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Computer Network Laboratory (15CSL57) V SEM

Lab Program 12:

Write a program for congestion control using leaky bucket algorithm.

Code –

import java.util.Scanner;

public class bucket {

public static void main(String[] args)

{

Scanner sc=new Scanner(System.in);

int bucket=0;
int op_rate,i,n,bsize;

System.out.println("Enter the number of packets");

n=sc.nextInt();

System.out.println("Enter the output rate of the bucket");

op_rate=sc.nextInt();

System.out.println("Enter the bucket size");

bsize=sc.nextInt();

System.out.println("Enter the arriving packets(size)");

int pkt[]=new int[n]; for(i=0;i<n;i+
+)
{
pkt[i]=sc.nextInt();
}

System.out.println("\nSec\tpsize\tBucket\tAccept/Reject\tpkt_send");
System.out.println(" ");
for(i=0;i<n;i++)
{
System.out.print(i+1+"\t"+pkt[i]+"\t");
if(bucket+pkt[i]<=bsize)
{
bucket+=pkt[i]; System.out.print(bucket+"\tAccept\t\
t"+min(bucket,op_rate)+"\n" +""); bucket=sub(bucket,op_rate);

}
else
{ int reject=(bucket+pkt[i]-bsize);
bucket=bsize;
System.out.print(bucket+"\tReject "+reject+"\t"+min(bucket,op_rate)+"\n");

bucket=sub(bucket,op_rate);
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Computer Network Laboratory (15CSL57) V SEM

}
}
while(bucket!=0)
{
System.out.print((++i)+"\t0\t"+bucket+"\tAccept\t\t"+min(bucket,op_rate)+"\t");
bucket=sub(bucket,op_rate);
}
}

static int min(int a,int b)

{
return ((a<b)?a:b);
}

static int sub(int a,int b)

{
return (a-b)>0?(a-b):0;
}
}

Output 1–

Enter the number of packets

4
Enter the output rate of the bucket
7
Enter the bucket size
8
Enter the arriving packets(size)
6895

Sec psize Bucket Accept/Reject pkt_send

1 6 6 Accept 6
2 8 8 Accept 7
3 9 8 Reject 2 7
4 5 6 Accept 6

Output 2–

Enter the number of packets

4
Enter the output rate of the bucket
6
Enter the bucket size
8
Enter the arriving packets(size)
4 5 6 10

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Computer Network Laboratory (15CSL57) V SEM

Sec psize Bucket Accept/Reject pkt_send

1 4 4 Accept 4
2 5 5 Accept 5
3 6 6 Accept 6
4 10 8 Reject 2 6
5 0 2 Accept 2

Output 3–

Enter the number of packets

5
Enter the output rate of the bucket
5
Enter the bucket size
5
Enter the arriving packets(size)
46375

Sec psize Bucket Accept/Reject pkt_send

1 4 4 Accept 4
2 6 5 Reject 1 5
3 3 3 Accept 3
4 7 5 Reject 2 5
5 5 5 Accept 5

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