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Re: [iccrg] LEDBAT++, rLEDBAT, and slowdowns

"Bless, Roland (TM)" <roland.bless@kit.edu> Tue, 10 September 2019 07:34 UTC

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To: marcelo bagnulo braun <marcelo@it.uc3m.es>, Luca Muscariello <muscariello@ieee.org>
Cc: Praveen Balasubramanian <pravb@microsoft.com>, iccrg IRTF list <iccrg@irtf.org>, Neal Cardwell <ncardwell@google.com>, Yuchung Cheng <ycheng@google.com>
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From: "Bless, Roland (TM)" <roland.bless@kit.edu>
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Organization: Institute of Telematics, Karlsruhe Institute of Technology
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Date: Tue, 10 Sep 2019 09:34:42 +0200
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Subject: Re: [iccrg] LEDBAT++, rLEDBAT, and slowdowns
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Hi Marcelo,

Am 09.09.19 um 17:34 schrieb marcelo bagnulo braun:
> I am not sure i understand your answer though. I mean the whole problem
> of LEDBAT latecomer advantage is that the late comer misestimates the
> base delay (i.e. RTT_min?) and then it adds the target delay on top of
> the wrongly estiamted base delay.

Yes.

> So, i dont understand what do you mean that the mechanism assumes
> knownledge of the base delay. Clearly, i am missing something here,
> could you educate me?

As Luca wrote, their proposed algorithm requires a _perfect knowledge_
of RTT_min, i.e., transmission and propagation delay
without any queueing delay.

Note that, even if one would have perfect knowledge of queueing delay,
the latecomer advantage would turn into a latecomer disadvantage,
because the latecomer would back-off. Fairness remains still
an issue then...

Regards
 Roland

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