ns2 problems with simulation of lan

[pingpingping]

Hello,
recently I use the ns2 simulator to simulate local area network. I
write the tcl code following the manual downloaded from
http://www.isi.edu/nsnam/ns/, but I find that every time I run the
code below, the output is 1.7293548387096773Mb/s,but it shouldn't
be,because I have set the bw of the local area network as 1Mb,how can
 it achieve 1.7Mb, I am quite puzzled with it
I don't kown whether there should be some more settings or some
 other

the code below just simulate a lan which transmits data from node n1
to node n2,the bw between n1 and n2 is set as 1Mb
is there  bugs in the code, please point them out and give me some advice, thanks a lot!
##########################################code########################
set ns [new Simulator]

#Define different colors for data flows (for NAM)
$ns color 1 Blue
$ns color 2 Red

#Open the Trace files
set file1 [open out.tr w]
set winfile [open WinFile w]
$ns trace-all $file1
#Define a 'finish' procedure
proc finish {} {
        global ns file1
        $ns flush-trace
        close $file1
        exec nam out.nam &
        exit 0
}
set n1 [$ns node]
set n2 [$ns node]
set lan [$ns newLan "$n1 $n2" 1Mb 40ms LL Queue/DropTail MAC/Csma/Cd Channel]
set tcp [new Agent/TCP/Newreno]
$ns attach-agent $n1 $tcp
set sink [new Agent/TCPSink/DelAck]
$ns attach-agent $n2 $sink
$ns connect $tcp $sink
$tcp set fid_ 1
$tcp set window_ 65536
$tcp set packetSize_ 1024

#Setup a FTP over TCP connection
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp set type_ FTP

proc get_throughput { tcp } {
#now calculate the average throughtput (in Mb/s)
        puts "[expr [$tcp set ndatapack_]*8.0/1000/124]Mb/s"
}
$ns at 1.0 "$ftp start"
$ns at 124.0 "$ftp stop"
$ns at 124 "get_throughput $tcp"
$ns at 125.0 "finish"
$ns run
########################################################

[HaiderSa]

this is bcoz of the the nam is reading the previous history of the file.
so u must delete the out.tr and out.nam both before re-running the simulation.

pingpingping wrote:

Hello,
recently I use the ns2 simulator to simulate local area network. I
write the tcl code following the manual downloaded from
http://www.isi.edu/nsnam/ns/, but I find that every time I run the
code below, the output is 1.7293548387096773Mb/s,but it shouldn't
be,because I have set the bw of the local area network as 1Mb,how can
 it achieve 1.7Mb, I am quite puzzled with it
I don't kown whether there should be some more settings or some
 other

the code below just simulate a lan which transmits data from node n1
to node n2,the bw between n1 and n2 is set as 1Mb
is there  bugs in the code, please point them out and give me some advice, thanks a lot!
##########################################code########################
set ns [new Simulator]

#Define different colors for data flows (for NAM)
$ns color 1 Blue
$ns color 2 Red

#Open the Trace files
set file1 [open out.tr w]
set winfile [open WinFile w]
$ns trace-all $file1
#Define a 'finish' procedure
proc finish {} {
        global ns file1
        $ns flush-trace
        close $file1
        exec nam out.nam &
        exit 0
}
set n1 [$ns node]
set n2 [$ns node]
set lan [$ns newLan "$n1 $n2" 1Mb 40ms LL Queue/DropTail MAC/Csma/Cd Channel]
set tcp [new Agent/TCP/Newreno]
$ns attach-agent $n1 $tcp
set sink [new Agent/TCPSink/DelAck]
$ns attach-agent $n2 $sink
$ns connect $tcp $sink
$tcp set fid_ 1
$tcp set window_ 65536
$tcp set packetSize_ 1024

#Setup a FTP over TCP connection
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp set type_ FTP

proc get_throughput { tcp } {
#now calculate the average throughtput (in Mb/s)
        puts "[expr [$tcp set ndatapack_]*8.0/1000/124]Mb/s"
}
$ns at 1.0 "$ftp start"
$ns at 124.0 "$ftp stop"
$ns at 124 "get_throughput $tcp"
$ns at 125.0 "finish"
$ns run
########################################################