Re: [tcpm] [EXTERNAL] Questions on HyStart++ draft 02

Junho Choi <junho.choi@gmail.com> Wed, 08 April 2020 00:33 UTC

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From: Junho Choi <junho.choi@gmail.com>
Date: Tue, 07 Apr 2020 17:32:19 -0700
Message-ID: <CAJ5e+HC0CZX2KL7dKgnOOFb78aZH8r_Kmjnp2ESn0dHOzujHXg@mail.gmail.com>
To: Yi Huang <huanyi@microsoft.com>
Cc: Praveen Balasubramanian <pravb@microsoft.com>, "tcpm@ietf.org" <tcpm@ietf.org>
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tcpm/n1txp_VMGHEcTRzgVL0t9-s633I>
Subject: Re: [tcpm] [EXTERNAL] Questions on HyStart++ draft 02
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Ok, thanks for clarifying!

On Tue, Apr 7, 2020 at 5:24 PM Yi Huang <huanyi@microsoft.com> wrote:

> Yeah, it does nothing for the first round.
>
>
>
> *From:* Junho Choi <junho.choi@gmail.com>
> *Sent:* Thursday, April 2, 2020 12:55 AM
> *To:* Yi Huang <huanyi@microsoft.com>
> *Cc:* Praveen Balasubramanian <pravb@microsoft.com>; tcpm@ietf.org
> *Subject:* Re: [EXTERNAL] Questions on HyStart++ draft 02
>
>
>
> Hi Yi,
>
>
>
> Thanks. See inline for my following question.
>
>
>
> On Wed, Apr 1, 2020 at 5:04 PM Yi Huang <huanyi@microsoft.com> wrote:
>
> 1. Section 4.2 -- each round is initialized as
>
>
>
>    lastRoundMinRTT = currentRoundMinRTT
>
>    currentRoundMinRTT = infinity
>
>    rttSampleCount = 0
>
>
>
> In the very beginning of the connection, what is "currentRoundMinRTT" when
>
> there is no previous value?
>
>
>
> I am using current rtt (or initial rtt value) and is it ok?
>
>
>
> [Yi]: In our implementation, lastRoundMinRTT and currentRoundMinRTT are
> initialized to 0xffffffff as sentinel values. We only compare
> lastRoundMinRTT with currentRoundMinRTT when both of them are valid values.
> Using currRTT seems to essentially behave the same as assigning a sentinel
> value.
>
>
>
> So in the beginning of the connection lastRoundMinRTT is <inf>. When ack
> is received currentRoundMinRTT = min_rtt but
>
> lastRoundMinRTT is still <inf>. When the 1st round ends, it looks always
> doing nothing because the following if() is always false?
>
>
>
>   if (currentRoundMinRTT >= (lastRoundMinRTT + RttThresh))
>
>
>
>
>
>
>
> 2. Section 4.2 -- When used with cubic, CA_cwnd() is based on cubic
> algorithm I think.
>
>  This means I need to do cubic variables calculation during slow start
>
>  such as K and W_cubic. When is considered as a start of
>
>  congestion avoidance and what W_max will be?
>
>
>
>  Currently I use a start of limited slow start as a beginning of
> congestion recovery
>
>  and use cwnd at the time for W_max. Is my understanding correct?
>
>
>
> [Yi]: Yes, that’s exactly what we do in Windows.
>
>
>
> Sound great. Thanks.
>
>
>
> Best,
>
>
> --
>
> Junho Choi <junho dot choi at gmail.com
> <https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgmail.com%2F&data=02%7C01%7Chuanyi%40microsoft.com%7C5ed42de0b38e497d502a08d7d6db4055%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637214109469856737&sdata=%2FA2fvoRO0452I5P2CnWRyoDOhO38wHDyOAF6n58UDLY%3D&reserved=0>
> >
>


-- 
Junho Choi <junho dot choi at gmail.com>

[tcpm] Questions on HyStart++ draft 02 Junho Choi
Re: [tcpm] [EXTERNAL] Questions on HyStart++ draf… Yi Huang
Re: [tcpm] [EXTERNAL] Questions on HyStart++ draf… Junho Choi
Re: [tcpm] [EXTERNAL] Questions on HyStart++ draf… Yi Huang
Re: [tcpm] [EXTERNAL] Questions on HyStart++ draf… Junho Choi
Re: [tcpm] [EXTERNAL] Questions on HyStart++ draf… Junho Choi
Re: [tcpm] [EXTERNAL] Questions on HyStart++ draf… Yi Huang