Ns2 progrm with data trnsmission shown in color

# Create a simulator object
set ns [new Simulator]
 
# Define different colors 
# for data flows (for NAM)
$ns color 1 Blue
$ns color 2 Red
 
# Open the NAM trace file
set nf [open out.nam w]
$ns namtrace-all $nf
 
# Define a 'finish' procedure

proc finish {} {

global ns nf
$ns flush-trace
close $nf
exec nam out.nam &
exit 0
}
 
# Create four nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
 
# Create links between the nodes
$ns duplex-link $n0 $n2 2Mb 10ms DropTail
$ns duplex-link $n1 $n2 2Mb 10ms DropTail
$ns duplex-link $n2 $n3 1.7Mb 20ms DropTail
 
# Set Queue Size of link (n2-n3) to 10
$ns queue-limit $n2 $n3 10
 
# Give node position (for NAM)
$ns duplex-link-op $n0 $n2 orient right-down
$ns duplex-link-op $n1 $n2 orient right-up
$ns duplex-link-op $n2 $n3 orient right
 
# Monitor the queue for link (n2-n3). (for NAM)
$ns duplex-link-op $n2 $n3 queuePos 0.5
 
 
# Setup a TCP connection
set tcp [new Agent/TCP]
$tcp set class_ 2
$ns attach-agent $n0 $tcp
 
set sink [new Agent/TCPSink]
$ns attach-agent $n3 $sink
$ns connect $tcp $sink
$tcp set fid_ 1
 
# Setup a FTP over TCP connection
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp set type_ FTP
 
 
# Setup a UDP connection
set udp [new Agent/UDP]
$ns attach-agent $n1 $udp
set null [new Agent/Null]
 
$ns attach-agent $n3 $null
$ns connect $udp $null
$udp set fid_ 2
 
# Setup a CBR over UDP connection
set cbr [new Application/Traffic/CBR]
$cbr attach-agent $udp
$cbr set type_ CBR
$cbr set packet_size_ 1000
$cbr set rate_ 1mb
$cbr set random_ false
 
 
# Schedule events for the CBR and FTP agents
$ns at 0.1 "$cbr start"
$ns at 1.0 "$ftp start"
$ns at 4.0 "$ftp stop"
$ns at 4.5 "$cbr stop"
 
# Detach tcp and sink agents
# (not really necessary)
$ns at 4.5 "$ns detach-agent $n0 $tcp ; $ns detach-agent $n3 $sink"
 
# Call the finish procedure after
# 5 seconds of simulation time
$ns at 5.0 "finish"
 
# Print CBR packet size and interval
puts "CBR packet size = [$cbr set packet_size_]"
puts "CBR interval = [$cbr set interval_]"
 
# Run the simulation
$ns run