[e2e] TCP Performance with Traffic Policing

[Alexander Zimmermann]

Hi Barry,

since you does't send the sysctl's, it is hard to correctly interpret the time sequence graph. However, some facts
about the Linux 128kb run:

- The bursty behavior is not a missing delay on the reverse path (sorry my fault), it's a missing queuing delay.

- I never see Limited Transmit. Also, the sender sends almost never new data on incoming new dupacks
during recovery (Linux uses Rate Halving). Maybe we are limited by the send window here...
You can use iperf without the parameter to confirm this.

- NewReno can only send one retransmission per RTT. With your strange policer we have massive bursty
packet loss. We can see loss recovery phases for 4 sec. Use SACK.

- We see 6 RTOs

-  Your receiver is not a linux box ;-) Why? Linux the Quick ACKs (= disabling Delayed ACKs) after an
out-of-oder phase, so that the sender can quickly enlarged his CWND  

- All in all we have nearly more retransmissions than transmissions.Your problem is not TCP, it's your traffic
policer...

Alex


Am 17.08.2011 um 15:30 schrieb Alexander Zimmermann:

> Hi Barry,
> 
> from a quick look of your Linux 64/128 dumps I would say your setup is broken.
> The trace is highly bursty. Do you have a delay on the reverse path? I guess no...
> 
> Alex
> 
> Am 17.08.2011 um 14:56 schrieb Barry Constantine:
> 
>> Alexander,
>>  
>> I could not read your encrypted email.
>>  
>> I saw the email from the postel-moderator and assume the attachment did not go through.
>>  
>> This is the dropbox link to the zip file:
>>  
>> http://dl.dropbox.com/u/10123514/Linux%20versus%20XP%20versus%20Windows7%20Iperf.zip
>>  
>> Thanks,
>> Barry
>>  
>> From: Alexander Zimmermann [mailto:alexander.zimmermann at comsys.rwth-aachen.de] 
>> Sent: Wednesday, August 17, 2011 8:38 AM
>> To: Agarwal, Anil
>> Cc: Barry Constantine; anil at cmmacs.ernet.in; end2end-interest at postel.org
>> Subject: Re: [e2e] TCP Performance with Traffic Policing
>>  
> 
> //
> // Dipl.-Inform. Alexander Zimmermann
> // Department of Computer Science, Informatik 4
> // RWTH Aachen University
> // Ahornstr. 55, 52056 Aachen, Germany
> // phone: (49-241) 80-21422, fax: (49-241) 80-22222
> // email: zimmermann at cs.rwth-aachen.de
> // web: http://www.umic-mesh.net
> //
> 

//
// Dipl.-Inform. Alexander Zimmermann
// Department of Computer Science, Informatik 4
// RWTH Aachen University
// Ahornstr. 55, 52056 Aachen, Germany
// phone: (49-241) 80-21422, fax: (49-241) 80-22222
// email: zimmermann at cs.rwth-aachen.de
// web: http://www.umic-mesh.net
//

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