[e2e] end2end-interest Digest, Vol 14, Issue 16

[Arjuna Sathiaseelan]

Dear Faisal,
  Even though this question should be directed to the ns-2 list :) -
yes the cwnd can grow beyond the rwnd - but the amount of data that is
being sent - i.e. the sending window is always the min of the cwnd and
the rwnd. So the best way is to set to a window that is equal to the
bandwidth delay product - if you want to utilize the link to its
fullest.

Regds,
Arjuna

On 4/16/05, end2end-interest-request at postel.org
<end2end-interest-request at postel.org> wrote:
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> Today's Topics:
> 
>   1. Re: Resilient UDP (Christian Huitema)
>   2. Can TCP's congestion window go beyond receiver's maximum
>      advertised window? (Syed Faisal Hasan)
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Fri, 15 Apr 2005 16:52:09 -0700
> From: "Christian Huitema" <huitema at windows.microsoft.com>
> Subject: Re: [e2e] Resilient UDP
> To: "Zhi Li" <tolizhi at gmail.com>, <end2end-interest at postel.org>
> Message-ID:
>        <DAC3FCB50E31C54987CD10797DA511BA0E3D5601 at WIN-MSG-10.wingroup.windeploy.ntdev.microsoft.com>
> 
> Content-Type: text/plain;       charset="us-ascii"
> 
> > I recently came aross a term called "reslient UDP".
> > I couldn't find any related document on the web.
> > Does anyone know the detail operations?  Or, could you please suggest
> > me some references or papers about it?
> 
> It is a version of UDP used with military intelligence.
> 
> -- Christian Huitema
> 
> ------------------------------
> 
> Message: 2
> Date: Sat, 16 Apr 2005 10:12:52 +0000
> From: "Syed Faisal Hasan" <rony3000us at hotmail.com>
> Subject: [e2e] Can TCP's congestion window go beyond receiver's
>        maximum advertised window?
> To: end2end-interest at postel.org
> Message-ID: <BAY15-F211369C54E8EAE65ADD342C0370 at phx.gbl>
> Content-Type: text/plain; format=flowed
> 
> Dear Folks,
> 
> I was trying to do a simple simulation using NS-2.27 and  I found
> something interesting.
> 
> The topology is as follows
> [n0]---------------[n1]
> 
> n0 is running a ftp application on top of tcp.
> TCP receiver's advertised maximum window size is set to 20 (that is
> the default in NS)
> 
> Congestion window (cwnd) should never go beyond receive window (rwnd),
> right?
> Then why in the simulation, cwnd grows beyond rwnd? cwnd reaches to
> 24, while rwnd is fixed at 20.
> 
> If this is a silly question, I 'm sorry for asking. But I 'ld like to
> have an explanation.
> 
> Faisal
> #==========================================
> #The NS script is below
> #===========================================
> set ns [new Simulator]
> 
> set file1 [open testout.tr w]
> $ns trace-all $file1
> 
> set file2 [open ./temp/namtest.nam w]
> $ns namtrace-all $file2
> set windowfile [ open ./temp/WindowFile w]
> 
> proc finish {} {
> 
> global ns file1 file2
> $ns flush-trace
> close $file1
> close $file2
> 
> exec nam ./temp/namtest.nam &
> exec xgraph ./temp/WindowFile -geometry 800x600 &
> exit 0
> 
> }
> 
> set n0 [$ns node]
> set n1 [$ns node]
> $ns duplex-link $n0 $n1 0.2Mb 500ms DropTail
> $ns duplex-link-op $n0 $n1 orient right
> 
> set tcp [new Agent/TCP/Sack1]
> $ns attach-agent $n0 $tcp
> $tcp set window_ 20
> 
> set tcpsink [new Agent/TCPSink]
> $ns attach-agent $n1 $tcpsink
> $ns connect $tcp $tcpsink
> 
> set ftp [new Application/FTP]
> $ftp attach-agent $tcp
> 
> proc getwindow {source file } {
> 
> global ns
> set now [$ns now]
> set time 0.1
> set cwnd [$source set cwnd_]
> puts $file "$now $cwnd"
> $ns at [expr $now+$time] "getwindow $source $file"
> 
> }
> 
> $ns at 0.1 "getwindow $tcp $windowfile"
> 
> $ns at 0.0 "$ftp start"
> $ns at 9.0 "$ftp stop"
> $ns at 10 "finish"
> $ns run
> #===================================
> 
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> End of end2end-interest Digest, Vol 14, Issue 16
> ************************************************
>