利用NS2的产生随机数机制来实现对链路的动态设置(连接建立时间,延迟)

set ns [new Simulator]

set nf [open ex3out.nam w]

$ns namtrace-all $nf

set tf [open ex3out.tr w]

$ns trace-all $tf

set windowVsTime [open win w]

set param [open parameters w]

#Define a 'finish' procedure

proc finish {} {

global ns nf tf

$ns flush-trace

close $nf

close $tf

exec nam ex3out.nam &

exit 0

}

#Create bottleneck and dest nodes

set n2 [$ns node]

set n3 [$ns node]

#Create links between these nodes

$ns duplex-link $n2 $n3 0.7Mb 20ms DropTail

#Set the TCP client is 5

set NumbSrc 5

#设置总共的仿真时间

set Duration 10

#Source nodes

for {set j 1} {$j<=$NumbSrc} { incr j } {

set S($j) [$ns node]

}

# Create a random generator for starting the ftp and for bottleneck link delays

# if the seed is 0, each time will get different num.

set rng [new RNG]

$rng seed 0

# paratmers for random variables for delays

set RVdly [new RandomVariable/Uniform]

$RVdly set min_ 1

$RVdly set max_ 5

$RVdly use-rng $rng

# parameters for random variables for begenning of ftp connections

set RVstart [new RandomVariable/Uniform]

$RVstart set min_ 0

$RVstart set max_ 7

$RVstart use-rng $rng

#We define two random parameters for each connections

for {set i 1} {$i<=$NumbSrc} { incr i } {

set startT($i) [expr [$RVstart value]]

set dly($i) [expr [$RVdly value]]

#把信息输入到文件中的基本方法

puts $param "dly($i) $dly($i) ms"

puts $param "startT($i) $startT($i) sec"

}

#Links between source and bottleneck

for {set j 1} {$j<=$NumbSrc} { incr j } {

$ns duplex-link $S($j) $n2 10Mb $dly($j)ms DropTail

$ns queue-limit $S($j) $n2 100

}

#Monitor the queue for link (n2-n3). (for NAM)

$ns duplex-link-op $n2 $n3 queuePos 0.5

#Set Queue Size of link (n2-n3) to 10

$ns queue-limit $n2 $n3 10

#TCP Sources

for {set j 1} {$j<=$NumbSrc} { incr j } {

set tcp_src($j) [new Agent/TCP/Reno]

}

#TCP Destinations

for {set j 1} {$j<=$NumbSrc} { incr j } {

set tcp_snk($j) [new Agent/TCPSink]

}

#Connections

for {set j 1} {$j<=$NumbSrc} { incr j } {

$ns attach-agent $S($j) $tcp_src($j)

$ns attach-agent $n3 $tcp_snk($j)

$ns connect $tcp_src($j) $tcp_snk($j)

}

#FTP sources

for {set j 1} {$j<=$NumbSrc} { incr j } {

set ftp($j) [$tcp_src($j) attach-source FTP]

}

#Parametrisation of TCP sources

for {set j 1} {$j<=$NumbSrc} { incr j } {

$tcp_src($j) set packetSize_ 552

}

#Schedule events for the FTP agents:

for {set i 1} {$i<=$NumbSrc} { incr i } {

$ns at $startT($i) "$ftp($i) start"

$ns at $Duration "$ftp($i) stop"

}

proc plotWindow {tcpSource file k} {

global ns

set time 0.03

set now [$ns now]

set cwnd [$tcpSource set cwnd_]

puts $file "$k $now $cwnd"

$ns at [expr $now+$time] "plotWindow $tcpSource $file $k" }

# The procedure will now be called for all tcp sources

#注意，5个TCP源的窗口记录都是从0.1开始的

for {set j 1} {$j<=$NumbSrc} { incr j } {

$ns at 0.1 "plotWindow $tcp_src($j) $windowVsTime $j"

}

$ns at [expr $Duration] "finish"

$ns run
http://hi.baidu.com/philipchen/blog/item/6135b2138f482bd1f6039e2f.html