proc create_net_6_DT { } {
        #
        #        s1                    s3
        #          \                   /
        # 10Mb, 1ms \   0.3Mb, 1ms    / 0.1Mb, 300ms
        #           r1 ------------ r2
        # 10Mb, 1ms /                 \ 0.1Mb, 300ms
        #          /                   \
        #        s2                   s4 tcl
        #

        global ns s1 s2 s3 s4 r1 r2
        set s1 [$ns node]
        set s2 [$ns node]
        set r1 [$ns node]
        set r2 [$ns node]
        set s3 [$ns node]
        set s4 [$ns node]

        $ns duplex-link $s1 $r1 10Mb 1ms DropTail
        $ns duplex-link $s2 $r1 10Mb 1ms DropTail
        $ns duplex-link $r1 $r2 0.3Mb 1ms DropTail
        $ns duplex-link $r2 $s3 0.1Mb 300ms DropTail
        $ns duplex-link $r2 $s4 0.1Mb 300ms DropTail

}

set ns [new Simulator]

create_net_6_DT

set stopTime 30

set tFile [open queue.tr w]
$ns trace-queue $r2 $s3 $tFile

set tcp0 [$ns create-connection TCP/Reno $s1 TCPSink $s3 40]
$tcp0 set window_ 100
set ftp0 [$tcp0 attach-source FTP]

set tcp1 [$ns create-connection TCP/Reno $s2 TCPSink $s4 41]
$tcp1 set window_ 100
set ftp1 [$tcp1 attach-source FTP]

# Enable the next line for different sim results !!!
# $ns at 25.0 "puts \"Very strange...\"" 

$ns at 0.0 "$ftp0 start"
$ns at 0.0 "$ftp1 start"

$ns at $stopTime "$ftp0 stop"
$ns at $stopTime "$ftp1 stop"

$ns at $stopTime "puts \"Simulation finished.\""
$ns at $stopTime "exit"

$ns run