Re: [tcpm] [EXTERNAL] Questions on HyStart++ draft 02
Junho Choi <junho.choi@gmail.com> Tue, 28 April 2020 00:30 UTC
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From: Junho Choi <junho.choi@gmail.com>
Date: Mon, 27 Apr 2020 17:29:42 -0700
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To: Yi Huang <huanyi@microsoft.com>
Cc: Praveen Balasubramanian <pravb@microsoft.com>, "tcpm@ietf.org" <tcpm@ietf.org>
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Subject: Re: [tcpm] [EXTERNAL] Questions on HyStart++ draft 02
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FYI, I made a PR https://github.com/cloudflare/quiche/pull/476 for implementing HyStart++ in quiche, based on draft 02. The algorithm is modified for QUIC a little (e.g. tcp sequence number vs quic packet number) but in general it's same. Best, On Tue, Apr 7, 2020 at 5:32 PM Junho Choi <junho.choi@gmail.com> wrote: > 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> > -- 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