Hello
I m working with a network scenario ....where link BW is 1.5Mbps and is
shared by both TCP and UDP flows. I used FTP over TCP and UDP based CBR
background load with the same packet size 512 bytes. ..................
Simulation Time: is 30sec. I have to maintain CBR rate to
At 0-5 sec : 1Mbps
At 5-10 sec: 1.5 Mbps
At 10-15 sec: .8Mbps
At 15-20 sec: .1.3Mbps
At 20-25 sec: 1.5Mbps
At 20-25 sec: .4Mbps
But i dont know how to control cbr rate in TCL script. My outputs are always
close to link BW .....they are not close available BW.
Here is my TCL Script :
set ns [new Simulator]
#Open the Trace files
set file1 [open out.txt w]
set f0 [open output1.txt w]
$ns trace-all $file1
#Open the nam trace file
set nf [open out.nam w]
$ns namtrace-all $nf
$ns color 1 Blue
$ns color 2 Red
#Define a 'finish' procedure
proc finish {} {
global f0 ns nf
$ns flush-trace
#Close the trace file
close $nf
#Execute nam on the trace file
exec nam out.nam &
close $f0
exit 0
}
set n0 [$ns node]
set n1 [$ns node]
$ns duplex-link $n0 $n1 1.5Mb 10ms DropTail
proc record {} {
global sink0 f0
set ns [Simulator instance]
#Set the time after which the procedure should be called again
set time 0.1
#How many bytes have been received by the traffic sinks?
set bw0 [$sink0 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]"
#Reset the bytes_ values on the traffic sinks
$sink0 set bytes_ 0
#Re-schedule the procedure
$ns at [expr $now+$time] "record"
}
set u_src [new Agent/UDP]
$ns attach-agent $n0 $u_src
set u_dst [new Agent/Null]
$ns attach-agent $n1 $u_dst
$ns connect $u_src $u_dst
$u_src set fid_ 1
set cbr [new Application/Traffic/CBR]
$cbr set packetSize_ 512
#$cbr set interval_ 0.250
$cbr attach-agent $u_src
set t_src [new Agent/TCP/Newreno]
$t_src set packetSize_ 512
set sink0 [new Agent/TCPSink]
$ns attach-agent $n0 $t_src
$ns attach-agent $n1 $sink0
$ns connect $t_src $sink0
$t_src set fid_ 2
set ftp [new Application/FTP]
$ftp attach-agent $t_src
$ns at 0.0 "record"
$ns at 0.1 "$cbr start"
$cbr set rate_ 1
$ns at 5.0 "$cbr stop"
$ns at 5.1 "$cbr start"
$cbr set rate_ 1.5
$ns at 10.0 "$cbr stop"
$ns at 10.1 "$cbr start"
$cbr set rate_ .8
$ns at 15.0 "$cbr stop"
$ns at 15.1 "$cbr start"
$cbr set rate_ 1.3
$ns at 20.0 "$cbr stop"
$ns at 20.1 "$cbr start"
$cbr set rate_ 1.5
$ns at 25.0 "$cbr stop"
$ns at 25.1 "$cbr start"
$cbr set rate_ .4
$ns at 30.0 "$cbr stop"
$ns at 1.0 "$ftp start"
$ns at 29.0 "$ftp stop"
$ns at 30.1 "finish"
#Run the simulation
$ns run
If anyone understand my problem ..i will very much appreitate his reply.
Thanks.
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