Re: [ns] TCP seq nos

[Lloyd Wood <l.wood@eim.surrey.ac.uk>]

On Tue, 3 Apr 2001, Priya Mahadevan wrote:

> Thanks a lot - but even after setting the show_tcphdr_ all the trace file
> gives me is ack number and header length. Is there any way to get the seq
> nos and congestion window size ?

Write out a tracefile that gets it from the bound variable. That's the
entire point of bound variables; grasping this bit (schedule a writing
procedure that schedules itself from then on to record each data
point) seems to be conceptually hard/unfamiliar, but once you have you
can do a lot with ns. The below code snippet should help.


[blah normal tracefiles topology setup nodes link blah]

proc record {} {
         global ns tcp0 trace_wnd trace_ack trace_seq
         
         set time_delta 0.01

         #Get the variables of interest
         set curr_dupack [$tcp0 set dupacks_]
         set curr_cwnd [$tcp0 set cwnd_]
         set curr_maxseq [expr fmod([$tcp0 set maxseq_], 100)]

         #Get the current time
         set now [$ns now]
         #Write the variables of interest vs. time
         puts $trace_ack "$now $curr_dupack"
         puts $trace_wnd "$now $curr_cwnd"
	 puts $trace_seq "$now $curr_maxseq"

         #Re-schedule the procedure
         $ns at [expr $now+$time_delta] "record"
}

set trace_wnd [open outnewrenoshort.wnd w]
set trace_ack [open outnewrenoshort.dup w]
set trace_seq [open outnewrenoshort.seq w]

# Attach agents
set tcp0 [new Agent/TCP/Newreno]
$ns attach-agent $g(0) $tcp0
set ftp0 [new Application/FTP]
$ftp0 attach-agent $tcp0

$tcp0 set fid_ 1
$ns color 1 Red

$tcp0 set window_ 20

set null0 [new Agent/TCPSink]
$ns attach-agent $g(38) $null0
$ns connect $tcp0 $null0

$ns at 29.0 "record"
$ns at 30.0 "$ftp0 start"

$ns at 200.0 "$ftp0 stop"

$ns at 200.5 "end"
$ns at 201.0 "finish" 

proc end {} {
    global ns trace_ack trace_wnd trace_seq
    close $trace_wnd
    close $trace_ack
    close $trace_seq
}

and the finish routine closes the 'normal' trace-all and
namtrace-all tracefiles, throws up nam, graphing programs, etc.

L.

<L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>