Re: [ns] Reg bandwidth utilization!!

["T. Chitti Babu" <chitti@it.iitb.ac.in>]

hi,

here's a program to calculate RTT for every 0.01 secs.
u may take the average and ofcourse half the value of that average would
give u END-TO-END DELAY.

proc roundtrip {} {
global ns tcp1 trace_rtt
 
set time 0.01  

# if u want to know the rtt for each packet u may set
#time as 1/(rate) or interval-time....

set curr_rtt [$tcp1 set rtt_]
set now [ns now]
puts $trace_rtt "$now $curr_rtt"
ns at [expr $now+$time] "roundtrip"
}

do correct me if i am wrong....

hope this helps.
regards
chitti


On Mon, 9 Jul 2001, Ganesh wrote:

> Hi ,
> 
> I got two questions...
> 
> 1) For this to work, dont we have to declare bytes_ in tcp-sink.cc and
> tcp.sink.h ?? And increment it accordingly ?? Or is it a different bytes_
> that you are referring to ? and this gives me the effective throughput /
> goodput seen  by the sink , right ?
> 
> 2) How do we measure end-end delay using this method ? Which variable gives
> me this info ?
> 
> Thanks.
> 
> - Ganesh
> 
> "T. Chitti Babu" wrote:
> 
> > ANOTHER OPTION WOULD BE TO...
> >
> > set f0 [open src0.tr w]
> >
> > proc finish {} {
> >         global ns nf f0
> >         $ns flush-trace
> >         close $f0
> >         exec xgraph -m src0.tr  -geometry 800x400 &
> >         exit 0
> > }
> >
> > #Define a procedure which periodically records the bandwidth received by
> > the #traffic sink sink0 and writes it to the file f0.
> >
> > proc record {} {
> >         global sink0  f0
> >
> >         set ns [Simulator instance]
> >
> >         #Set the time after which the procedure should be called again
> >         set time 0.5
> >
> >         #How many bytes have been received by the traffic sink?
> >         set bw0 [$sink0 set bytes_]
> >
> >         #Get the current time
> >         set now [$ns now]
> >
> >         #Calculate the bandwidth (in MBit/s) and write it to the file
> >         puts $f0 "$now [expr $bw0/$time*8/1000000]"
> >
> >         #Reset the bytes_ values on the traffic sink
> >         $sink0 set bytes_ 0
> >
> >         #Re-schedule the procedure
> >         $ns at [expr $now+$time] "record"
> > }
> >
> > U NEED TO CALL THIS PROCEDURE INITIALLY IN THE MAIN PROGRAM.
> > $ns at 0.0 "record"
> > $ns at 100.0 "finish"  // to stop  the simulation.
> >
> > THEN THE FILE TO WHICH "f0" is the file descipter shows the o/p as
> > 0.0 0.00
> > 0.5 6.7
> > 1.0 6.9
> > 1.5 8.4
> >
> > --
> >
> > T.Chitti Babu (H-7, # 133)
> > KReSIT , IITBombay
> > MUMBAI-400076
> >
> > ---------------------------------------------
> >
> > INTERNAL PH NOS:
> >         KReSIT Lab -- 5785
> >         Hostel 7 No - 5607
> >
> > EXTERNAL PH NOS:
> >         HOSTEL 7 Nos : 5721049, 5720105
> 
> --
> 
> 

-- 

T.Chitti Babu (H-7, # 133)
KReSIT , IITBombay
MUMBAI-400076


---------------------------------------------

INTERNAL PH NOS:
	KReSIT Lab -- 5785
	Hostel 7 No - 5607

EXTERNAL PH NOS:
	HOSTEL 7 Nos : 5721049, 5720105