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Re: [rmcat] draft-sarker-rmcat-eval-test-00, test case 4.4 RMCAT Flow competing with a long TCP Flow

"Fred Baker (fred)" <fred@cisco.com> Tue, 29 April 2014 08:01 UTC

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From: "Fred Baker (fred)" <fred@cisco.com>
To: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
Thread-Topic: [rmcat] draft-sarker-rmcat-eval-test-00, test case 4.4 RMCAT Flow competing with a long TCP Flow
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Date: Tue, 29 Apr 2014 08:01:31 +0000
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Cc: Zaheduzzaman Sarker <zaheduzzaman.sarker@ericsson.com>, "rmcat WG (rmcat@ietf.org)" <rmcat@ietf.org>, "varun@comnet.tkk.fi" <varun@comnet.tkk.fi>, "Michael Ramalho (mramalho)" <mramalho@cisco.com>, Erlendur Karlsson <erlendur.karlsson@ericsson.com>, "Xiaoqing Zhu (xiaoqzhu)" <xiaoqzhu@cisco.com>
Subject: Re: [rmcat] draft-sarker-rmcat-eval-test-00, test case 4.4 RMCAT Flow competing with a long TCP Flow
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On Apr 29, 2014, at 3:57 AM, Ingemar Johansson S <ingemar.s.johansson@ericsson.com> wrote:

> Hi
>  
> I am experimenting  with the bottleneck test cases and found an issue with the competing TCP flows test case.
>  
> This test case specifes a Maximum end to end jitter = 30ms. This is implemented as a uniform [0-30ms] random delay in my simulator setup.
> The problem with this is that it creates so much reordering that TCP will trigger CWND reduction, and I guess this is not the intention or ?
>  
> My recommendation is that we should remove the random delay completely in this test case (and also in 4.5)  as the FTP will introduce plenty of jitter anyhow.
 
That’s the problem with simulations; you really have to think about how to make them similar to whatever they are simulating. Network gear rarely uses non-FIFO queues; even when we have parallel queues for various classes of traffic, the sub-queues are FIFO.

If your simulated queuing system isn’t FIFO, its results don’t tell us much about what rmcat will do in real networks.

> /Ingemar
>  
> =================================
> Ingemar Johansson  M.Sc.
> Senior Researcher
>  
> Ericsson AB
> Wireless Access Networks
> Labratoriegränd 11
> 971 28, Luleå, Sweden
> Phone +46-1071 43042
> SMS/MMS +46-73 078 3289
> ingemar.s.johansson@ericsson.com
> www.ericsson.com
>  
> “Those are my principles, and if you don't like them... 
> well, I have others.”  Groucho Marx
> =================================

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