set ns [new Simulator]
set nf [open lab3.nam w]
$ns namtrace-all $nf
set tf [open lab3.tr w] 
$ns trace-all $tf
set n0 [$ns node] 
$n0 color "magenta" 
$n0 label "src1"
set n1 [$ns node]
set n2 [$ns node] 
$n2 color "magenta" 
$n2 label "src2"
set n3 [$ns node] 
$n3 color "blue" 
$n3 label "dest2"
set n4 [$ns node]
set n5 [$ns node] 
$n5 color "blue" 
$n5 label“dest1”
$ns make-lan "$n0 $n1 $n2 $n3 $n4" 100Mb 100ms LL Queue/DropTail Mac/802_3 
$ns duplex-link $n4 $n5 1Mb 1ms DropTail
set tcp0 [new Agent/TCP] 
$ns attach-agent $n0 $tcp0
set ftp0 [new Application/FTP] 
$ftp0 attach-agent $tcp0 
$ftp0 set packetSize_ 500
$ftp0 set interval_ 0.0001 
set sink5 [new Agent/TCPSink]
$ns attach-agent $n5 $sink5 
$ns connect $tcp0 $sink5
set tcp2 [new Agent/TCP] 
$ns attach-agent $n2 $tcp2
set ftp2 [new Application/FTP]
$ftp2 attach-agent $tcp2 
$ftp2 set packetSize_ 600
$ftp2 set interval_ 0.001 
set sink3 [new Agent/TCPSink]
$ns attach-agent $n3 $sink3 
$ns connect $tcp2 $sink3 
set file1 [open file1.tr w] 
$tcp0 attach $file1 
set file2 [open file2.tr w]
$tcp2 attach $file2 
$tcp0 trace cwnd_ 
$tcp2 trace cwnd_ 
proc finish { } {
global ns nf tf 
$ns flush-trace
close $tf 
close $nf 
exec nam lab3.nam &
# exec cat file1.tr > a1
# exec cat file2.tr > a2
# exec xgraph a1 a2
exit 0 
} 
$ns at 0.1 "$ftp0 start" 
$ns at 5 "$ftp0 stop" 
$ns at 7 "$ftp0 start" 
$ns at 0.2 "$ftp2 start"
$ns at 8 "$ftp2 stop" 
$ns at 14 "$ftp0 stop" 
$ns at 10 "$ftp2 start" 
$ns at 15 "$ftp2 stop" 
$ns at 16 "finish" 
$ns run