[ns] TFRC problem

[Michael Welzl <michael@tk.uni-linz.ac.at>]

Hello,

We more or less successfully transferred the ns TFRC code to real life (as
part of an adaptive multimedia app). Now that it should work, we stumbled
upon a problem with the original simulator code (and, thus, our converted
one   :(   ) ...

Please take a look at the attached tcl file (I am copying the code into the
body of this message as well); if you look at the generated file "out.tr",
you will notice that TFRC fails to increase its rate after a certain period
of loss.

We used the code included in the 2.1b7 release of ns.

Please help!

Best regards,
Michael Welzl


------------------------------------------------------------------------
copied tcl code:


#Create a simulator object
set ns [new Simulator]

#Open the nam trace file
set nf [open out.nam w]
#$ns namtrace-all $nf

#Open the output files
set f [open out.tr w]

#Define a 'finish' procedure
proc finish {} {
        global ns nf f
        $ns flush-trace
	#Close the trace files
        close $nf
        close $f
	#Execute nam on the trace file
#        exec nam out.nam &
        exit 0
}

set oldtraffic 0
proc record {} {

        global f tfrc0 ns oldtraffic

	set now [$ns now]
        puts $f "$now [expr [$tfrc0 set ndatapack_]-$oldtraffic]"
	set oldtraffic [$tfrc0 set ndatapack_]

        $ns at [expr $now + 0.1] "record"
}


# Insert your own code for topology creation
# and agent definitions, etc. here

# Topologie:

set n0 [$ns node]
set n1 [$ns node]

$ns duplex-link $n0 $n1 1Mb 10ms DropTail

# Agent:

set tfrc0 [new Agent/TFRC]
$ns attach-agent $n0 $tfrc0

set tfrcsink0 [new Agent/TFRCSink]
$ns attach-agent $n1 $tfrcsink0

$ns connect $tfrc0 $tfrcsink0




#schedule events
$ns at 0.0 "record"

$ns at 0.5 "$tfrc0 start"

$ns rtmodel-at 8.0 down $n0 $n1
$ns rtmodel-at 9.0 up $n0 $n1
# no problem for 8.0 - 8.5 ... but 1 sec seems to long for TFRC

$ns at 54.5 "$tfrc0 stop"

$ns at 55.0 "finish"

#Run the simulation
$ns run

tfrc-test.tcl