example4.tcl

NS的教程

#Create a simulator object
set ns [new Simulator]

#Open the output files
set f0 [open out0.tr w]
set f1 [open out1.tr w]
set f2 [open out2.tr w]

#Create 5 nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]

#Connect the nodes
$ns duplex-link $n0 $n3 1Mb 100ms DropTail
$ns duplex-link $n1 $n3 1Mb 100ms DropTail
$ns duplex-link $n2 $n3 1Mb 100ms DropTail
$ns duplex-link $n3 $n4 1Mb 100ms DropTail

#Define a 'finish' procedure
proc finish {} {
	global f0 f1 f2
	#Close the output files
	close $f0
	close $f1
	close $f2
	#Call xgraph to display the results
	exec xgraph out0.tr out1.tr out2.tr -geometry 800x400 &
        exit 0
}


#Define a procedure that attaches a UDP agent to a previously created node
#'node' and attaches an Expoo traffic generator to the agent with the
#characteristic values 'size' for packet size 'burst' for burst time,
#'idle' for idle time and 'rate' for burst peak rate. The procedure connects
#the source with the previously defined traffic sink 'sink' and returns the
#source object.
proc attach-expoo-traffic { node sink size burst idle rate } {
	#Get an instance of the simulator
	set ns [Simulator instance]

	#Create a UDP agent and attach it to the node
	set source [new Agent/UDP]
	$ns attach-agent $node $source

	#Create an Expoo traffic agent and set its configuration parameters
	set traffic [new Application/Traffic/Exponential]
	$traffic set packetSize_ $size
	$traffic set burst_time_ $burst
	$traffic set idle_time_ $idle
	$traffic set rate_ $rate
        
        # Attach traffic source to the traffic generator
        $traffic attach-agent $source
	#Connect the source and the sink
	$ns connect $source $sink
	return $traffic
}


#Define a procedure which periodically records the bandwidth received by the
#three traffic sinks sink0/1/2 and writes it to the three files f0/1/2.
proc record {} {
        global sink0 sink1 sink2 f0 f1 f2
	#Get an instance of the simulator
	set ns [Simulator instance]
	#Set the time after which the procedure should be called again
        set time 0.5
	#How many bytes have been received by the traffic sinks?
        set bw0 [$sink0 set bytes_]
        set bw1 [$sink1 set bytes_]
        set bw2 [$sink2 set bytes_]
	#Get the current time
        set now [$ns now]
	#Calculate the bandwidth (in MBit/s) and write it to the files
        puts $f0 "$now [expr $bw0/$time*8/1000000]"
        puts $f1 "$now [expr $bw1/$time*8/1000000]"
        puts $f2 "$now [expr $bw2/$time*8/1000000]"
	#Reset the bytes_ values on the traffic sinks
        $sink0 set bytes_ 0
        $sink1 set bytes_ 0
        $sink2 set bytes_ 0
	#Re-schedule the procedure
        $ns at [expr $now+$time] "record"
}


#Create three traffic sinks and attach them to the node n4
set sink0 [new Agent/LossMonitor]
set sink1 [new Agent/LossMonitor]
set sink2 [new Agent/LossMonitor]
$ns attach-agent $n4 $sink0
$ns attach-agent $n4 $sink1
$ns attach-agent $n4 $sink2

#Create three traffic sources
set source0 [attach-expoo-traffic $n0 $sink0 200 2s 1s 100k]
set source1 [attach-expoo-traffic $n1 $sink1 200 2s 1s 200k]
set source2 [attach-expoo-traffic $n2 $sink2 200 2s 1s 300k]

#Start logging the received bandwidth
$ns at 0.0 "record"
#Start the traffic sources
$ns at 10.0 "$source0 start"
$ns at 10.0 "$source1 start"
$ns at 10.0 "$source2 start"
#Stop the traffic sources
$ns at 50.0 "$source0 stop"
$ns at 50.0 "$source1 stop"
$ns at 50.0 "$source2 stop"
#Call the finish procedure after 60 seconds simulation time
$ns at 60.0 "finish"

#Run the simulation
$ns run