NS应用实例4

set ns [new Simulator]

set tracefd [open trace.tr w]

$ns trace-all $tracefd

set namtracefd [open namtrace.nam w]

$ns namtrace-all $namtracefd

set f0 [open out0.tr w]

set f1 [open out1.tr w]

set f2 [open out2.tr w]

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

set n4 [$ns node]

$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 $n4 $n3 1Mb 100ms DropTail

#参数的意义: node sink size burst idle rate

# node:数据流的发起节点

# sink:数据流对应的接收代理

# size、idle、rate:数据包大小、idle 时间、发包速率

proc attach-expoo-traffic { node sink size burst idle rate } {

#生成 simulator 实例对象,用于整个仿真过程

set ns [Simulator instance]

#创建 UDP 代理,并与 soure 节点相关联

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

}

proc record {} {

#注意:自己写采样过程时,把要用到的变量做声明很重要!

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

#这点很重要,以重新采样时不受前一次的影响,与 NS2 实现机制有关,暂时可忽略!

$sink0 set bytes_ 0

$sink1 set bytes_ 0

$sink2 set bytes_ 0

#Re-schedule the procedure

$ns at [expr $now+$time] "record"

}

#LossMonitor 的特点:?

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

#调用过程 proc attach-expoo-traffic { node sink size burst idle rate }

#可以很方便的设置同一类型的数据流

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]

proc finish {} {

global f0 f1 f2 tracefd namtracefd

close $f0

close $f1

close $f2

close $tracefd

close $namtracefd

exec nam namtrace.nam &

#Call xgraph to display the results

exec xgraph out0.tr out1.tr out2.tr -geometry 800x400 &

exit 0

}

$ns at 0.0 "record"

$ns at 10.0 "$source0 start"

$ns at 10.0 "$source1 start"

$ns at 10.0 "$source2 start"

$ns at 50.0 "$source0 stop"

$ns at 50.0 "$source1 stop"

$ns at 50.0 "$source2 stop"

$ns at 60.0 "finish"

$ns run

程序运行效果图：