set ns [new Simulator]
set nf [open lab3.nam w]
$ns namtrace-all $nf
set trf [open lab3.tr w]
$ns trace-all $trf
proc finish {} {
global ns nf trf
$ns flush-trace
close $nf
close $trf
exit 0
}
for {set i 0} {$i < 4} {incr i} {
set n($i) [$ns node]
}
$ns at 0.0 "$n(0) label GBN_sender"
$ns at 0.0 "$n(3) label GBN_receiver"
$ns at 0.0 "$n(1) label SW_sender"
$ns at 0.0 "$n(2) label SW_receiver"
for {set i 0} {$i < 4} {incr i} {
$ns duplex-link $n($i) $n([expr ($i+1)%4]) 2Mb 48ms DropTail
$ns queue-limit $n($i) $n([expr ($i+1)%4]) 150
$ns queue-limit $n([expr ($i+1)%4]) $n($i) 150
}
$ns duplex-link-op $n(0) $n(1) orient right
$ns duplex-link-op $n(1) $n(2) orient down
$ns duplex-link-op $n(2) $n(3) orient left
$ns duplex-link-op $n(3) $n(0) orient up
$ns color 0 blue
$ns color 1 yellow
set tcp0 [new Agent/TCP/Reno]
$tcp0 set packetSize_ 2500
$tcp0 set window_ 8
$tcp0 set syn_ false
$tcp0 set windowInit_ 8
$tcp0 set fid_ 0
$ns attach-agent $n(0) $tcp0
set sink0 [new Agent/TCPSink]
$ns attach-agent $n(3) $sink0
$ns connect $tcp0 $sink0
set ftp0 [new Application/FTP]
$ftp0 attach-agent $tcp0
set tcp1 [new Agent/TCP/Reno]
$tcp1 set packetSize_ 2500
$tcp1 set window_ 1
$tcp1 set syn_ false
$tcp1 set windowInit_ 1
$tcp1 set fid_ 1
$ns attach-agent $n(1) $tcp1
set sink1 [new Agent/TCPSink]
$ns attach-agent $n(2) $sink1
$ns connect $tcp1 $sink1
set ftp1 [new Application/FTP]
$ftp1 attach-agent $tcp1
$tcp0 set window_ 8
$tcp1 set window_ 1
$ns at 1.0 "$ftp0 produce 120"
$ns at 1.0 "$ftp1 produce 120"
$ns at 12.0 "finish"
$ns run