# a very simple tcp simulation to start with
# run the simulation and view in nam.
# Now change the queue size of r1 and r2 to 10. (Uncomment the 2 lines.)
# Do you see pkt drops in nam?
# Now change the window size of the tcp connection to 10. Do you see drops?


#
# Create a simple four node topology:
#
#        s1                 s2
#         \                 /
# 10Mb,2ms \  1.5Mb,20ms   / 10Mb,4ms
#           r1 --------- r2


set ns [new Simulator]

#set f [open simple.tr w]
#$ns trace-all $f  

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

set node_(s1) [$ns node]
set node_(s2) [$ns node]
set node_(r1) [$ns node]
set node_(r2) [$ns node]

$ns duplex-link $node_(s1) $node_(r1) 10Mb 2ms DropTail 
$ns duplex-link $node_(s2) $node_(r2) 10Mb 4ms DropTail 
$ns duplex-link $node_(r1) $node_(r2) 1.5Mb 10ms RED 
#$ns queue-limit $node_(r1) $node_(r2) 10
#$ns queue-limit $node_(r2) $node_(r1) 10


$ns duplex-link-op $node_(s1) $node_(r1) orient right-down
$ns duplex-link-op $node_(s2) $node_(r2) orient right-up
$ns duplex-link-op $node_(r1) $node_(r2) orient right
$ns duplex-link-op $node_(r1) $node_(r2) queuePos 0
$ns duplex-link-op $node_(r2) $node_(r1) queuePos 0


set tcp [new Agent/TCP/Reno]
set sink [new Agent/TCPSink]
#$tcp set window_ 10
$ns attach-agent $node_(s1) $tcp
$ns attach-agent $node_(s2) $sink
$ns connect $tcp $sink

set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ns at 0.1 "$ftp start"

$ns at 5 "finish"

proc finish {} {
    global ns f nf
    $ns flush-trace
 #   close $f
    close $nf

    puts "running nam..."
    exec nam simple.nam &
    exit 0
}

$ns run