22.2 Example

More examples are available in the tcl/ex/delaybox/ directory of the ns source code. The validation script test-suite-delaybox.tcl is in tcl/test/ and can be run with the command test-all-delaybox from that directory.

# test-delaybox.tcl - NS file transfer with DelayBox

# setup ns
remove-all-packet-headers;            # removes all packet headers
add-packet-header IP TCP;             # adds TCP/IP headers
set ns [new Simulator];               # instantiate the simulator

global defaultRNG
$defaultRNG seed 999

# create nodes
set n_src [$ns node]
set db(0) [$ns DelayBox]
set db(1) [$ns DelayBox]
set n_sink [$ns node]

# setup links
$ns duplex-link $db(0) $db(1) 100Mb 1ms DropTail
$ns duplex-link $n_src $db(0) 100Mb 1ms DropTail
$ns duplex-link $n_sink $db(1) 100Mb 1ms DropTail

set src [new Agent/TCP/FullTcp]
set sink [new Agent/TCP/FullTcp]
$src set fid_ 1
$sink set fid_ 1

# attach agents to nodes
$ns attach-agent $n_src $src
$ns attach-agent $n_sink $sink

# make the connection
$ns connect $src $sink
$sink listen

# create random variables
set recvr_delay [new RandomVariable/Uniform];     # delay 1-20 ms
$recvr_delay set min_ 1 
$recvr_delay set max_ 20
set sender_delay [new RandomVariable/Uniform];    # delay 20-100 ms
$sender_delay set min_ 20
$sender_delay set max_ 100
set recvr_bw [new RandomVariable/Constant];       # bw 100 Mbps
$recvr_bw set val_ 100
set sender_bw [new RandomVariable/Uniform];       # bw 1-20 Mbps
$sender_bw set min_ 1
$sender_bw set max_ 20
set loss_rate [new RandomVariable/Uniform];       # loss 0-1% loss
$loss_rate set min_ 0
$loss_rate set max_ 0.01

# setup rules for DelayBoxes 
$db(0) add-rule [$n_src id] [$n_sink id] $recvr_delay $loss_rate $recvr_bw
$db(1) add-rule [$n_src id] [$n_sink id] $sender_delay $loss_rate $sender_bw

# output delays to files
$db(0) set-delay-file "db0.out"
$db(1) set-delay-file "db1.out"

# schedule traffic
$ns at 0.5 "$src advance 10000"
$ns at 1000.0 "$db(0) close-delay-file; $db(1) close-delay-file; exit 0"

# start the simulation
$ns run