Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement RFC3465
Yoshifumi Nishida <nsd.ietf@gmail.com> Mon, 09 August 2021 08:41 UTC
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From: Yoshifumi Nishida <nsd.ietf@gmail.com>
Date: Mon, 09 Aug 2021 01:40:45 -0700
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To: Neal Cardwell <ncardwell=40google.com@dmarc.ietf.org>
Cc: Vidhi Goel <vidhi_goel=40apple.com@dmarc.ietf.org>, "tcpm@ietf.org" <tcpm@ietf.org>, "mallman@icir.org" <mallman@icir.org>
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Subject: Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement RFC3465
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I don't have a strong opinion on this yet, But, if we *could* move in this direction, it might be good to think about the IW explanation in RFC5681 as well? if we do this, we might not need to discuss promoting RFC6928. -- Yoshi On Sat, Aug 7, 2021 at 7:57 AM Neal Cardwell <ncardwell= 40google.com@dmarc.ietf.org> wrote: > I also agree with Yuchung’s suggestion, for all of the reasons he provided. > > best, > neal > > > On Fri, Aug 6, 2021 at 3:59 PM Vidhi Goel <vidhi_goel= > 40apple.com@dmarc.ietf.org> wrote: > >> I agree with Yuchung’s suggestion for all the reasons he provided. And >> its better to have it at one place. >> >> Vidhi >> >> On Aug 6, 2021, at 12:53 PM, Yuchung Cheng < >> ycheng=40google.com@dmarc.ietf.org> wrote: >> >> Hi WG >> >> I have been wondering if we (= IETF) should just update RFC5681 directly, >> instead of another RFC3465-bis with experimental status. >> >> Appropriate byte counting is essential but the RFC5681 of L=1 is >> detrimental. There are far more people who read RFC5681 to implement the >> new stack instead of RFC3465. So we should fold the experimental RFC3465 >> updates into RFC5681 directly, and obsolete RFC3465. >> >> This is orthogonal to the final value of L :-) >> >> >> >> >> On Tue, Aug 3, 2021 at 9:42 AM Yuchung Cheng <ycheng@google.com> wrote: >> >>> >>> >>> On Mon, Aug 2, 2021 at 6:12 PM Yuchung Cheng <ycheng@google.com> wrote: >>> >>>> >>>> >>>> On Mon, Aug 2, 2021 at 5:53 PM Neal Cardwell <ncardwell= >>>> 40google.com@dmarc.ietf.org> wrote: >>>> >>>>> >>>>> >>>>> On Mon, Aug 2, 2021 at 8:46 PM Praveen Balasubramanian <pravb= >>>>> 40microsoft.com@dmarc.ietf.org> wrote: >>>>> >>>>>> In experiments a few years ago on DC networks, values over L=8 >>>>>> resulted in a noticeable increase in packet drops and retransmissions >>>>>> (without pacing). Windows TCP has been using L=8 for many years now. If we >>>>>> do want to specify a fallback L value for implementations that cannot pace, >>>>>> my suggestion would be to use the value 8. >>>>>> >>>>>> >>>>>> >>>>>> Neal, are there cases where Linux is or can be deployed with infinite >>>>>> L and no pacing? >>>>>> >>>>> >>>>> Yes, "infinite L and no pacing" is the default behavior for Linux TCP, >>>>> starting in 2013 for slow-start and then starting in 2015 for congestion >>>>> avoidance. >>>>> >>>> To be more clear: both fq_pacing and TCP pacing have been disabled by >>>> default in Linux upstream. We do not know how much Linux senders enable >>>> them today besides the Google servers. >>>> >>>> Regarding L = 8, to avoid another round of why or why not. We could say >>>> inf-L causes line-rate burst up to the stretched ACK degree so put a >>>> comfortable L if you prefer, then mention implementation practice like >>>> yours. At the end of the day it's ad-hoc (or "art") and subject to change. >>>> It might be sensible to cap at cwnd to disincentivize receivers / >>>> middle-boxes bunching up 10 rounds of ACKs. >>>> >>> Sorry please ignore my previous message about the cwnd cap. It is >>> completely unnecessary -- since with ack-clocking and appropriate counting, >>> a correct sender would never release more than a cwnd-worth of data. I was >>> imagining the multiple application-limited burst could let the receiver >>> keep holding up ACKs, but that can never exceed a cwnd worth of data. >>> >>> >>>> >>>>> >>>> >>>>> Yuchung pasted the URLs for the exact Linux commits above, which are: >>>>> >>>>> >>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9f9843a751d0a2057f9f3d313886e7e5e6ebaac9 >>>>> >>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9cd981dcf174d26805a032aefa791436da709bee >>>>> >>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c22bdca94782f05b9337d8548bde51b2f38ef17f >>>>> >>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=814d488c61260521b1b3cc97063700a5a6667c8f >>>>> >>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e73ebb0881ea5534ce606c1d71b4ac44db5c6930 >>>>> >>>>> But I understand that not everyone is in a position to read >>>>> GPL-licensed code. :-) >>>>> >>>>> best regards, >>>>> neal >>>>> >>>>> >>>>> >>>>>> >>>>>> >>>>>> *From:* tcpm <tcpm-bounces@ietf.org> *On Behalf Of * Neal Cardwell >>>>>> *Sent:* Monday, August 2, 2021 4:18 PM >>>>>> *To:* Vidhi Goel <vidhi_goel@apple.com> >>>>>> *Cc:* Extensions <tcpm@ietf.org>; Mark Allman <mallman@icir.org> >>>>>> *Subject:* [EXTERNAL] Re: [tcpm] Linux doesn’t implement RFC3465 >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> On Mon, Aug 2, 2021 at 7:02 PM Vidhi Goel <vidhi_goel@apple.com> >>>>>> wrote: >>>>>> >>>>>> >>>>>> >>>>>> On Mon, Aug 2, 2021 at 3:37 PM Mark Allman <mallman@icir.org> wrote: >>>>>> >>>>>> >>>>>> > The fact is that Linux CC has long moved to infinite L since 2031, >>>>>> >>>>>> So, if our experience is with L=\infinity and it is demonstrably OK >>>>>> why don't we say *THAT* instead of "make L=5 or L=10"? I would >>>>>> submit that it makes more sense to leverage experience than it does >>>>>> >>>>>> to make things up. >>>>>> >>>>>> +1 >>>>>> >>>>>> >>>>>> >>>>>> Yes, I agree that would be a great approach to take. >>>>>> >>>>>> >>>>>> >>>>>> So, we are saying it is fine to ignore L completely and simply >>>>>> increase cwnd by bytes_acked during slow start? And if this causes large >>>>>> bursts to be sent out (when an implementation doesn’t do pacing), that is >>>>>> fine? >>>>>> >>>>>> >>>>>> >>>>>> Yes, I think that is the proposal on the table, and it sounds good to >>>>>> me. >>>>>> >>>>>> >>>>>> >>>>>> A rationale would be: >>>>>> >>>>>> >>>>>> >>>>>> (1) Implementations SHOULD pace (RFC 7661). >>>>>> >>>>>> >>>>>> >>>>>> (2) Implementations that don't pace will generally be causing large >>>>>> bursts for many different reasons anyway (data and/or ACK aggregation in >>>>>> the network or end hosts), restart from idle,...) so having a constant L >>>>>> does not provide enough protection from bursts to justify the cost in >>>>>> reduced performance (in the form of slower slow-start). In support of this, >>>>>> experience with this as the default behavior in Linux TCP over the >>>>>> 2013-2021 period suggests this works well enough in practice. >>>>>> >>>>>> >>>>>> >>>>>> neal >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>> _______________________________________________ >>>>> tcpm mailing list >>>>> tcpm@ietf.org >>>>> https://www.ietf.org/mailman/listinfo/tcpm >>>>> >>>> _______________________________________________ >> tcpm mailing list >> tcpm@ietf.org >> https://www.ietf.org/mailman/listinfo/tcpm >> >> >> _______________________________________________ > tcpm mailing list > tcpm@ietf.org > https://www.ietf.org/mailman/listinfo/tcpm >
- [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Neal Cardwell
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Lars Eggert
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Mark Allman
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 Neal Cardwell
- Re: [tcpm] Linux doesn’t implement RFC3465 Mark Allman
- Re: [tcpm] Linux doesn’t implement RFC3465 Neal Cardwell
- Re: [tcpm] Linux doesn’t implement RFC3465 Mark Allman
- Re: [tcpm] Linux doesn’t implement RFC3465 Neal Cardwell
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 Neal Cardwell
- Re: [tcpm] Linux doesn’t implement RFC3465 Mark Allman
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 Mark Allman
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 David Lang
- Re: [tcpm] Linux doesn’t implement RFC3465 Neal Cardwell
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Neal Cardwell
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Praveen Balasubramanian
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Neal Cardwell
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Yuchung Cheng
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Yuchung Cheng
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Yuchung Cheng
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Vidhi Goel
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Neal Cardwell
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Yoshifumi Nishida
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Yuchung Cheng
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Neal Cardwell
- Re: [tcpm] Linux doesn’t implement RFC3465 Mark Allman
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Yoshifumi Nishida
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Vidhi Goel
- Re: [tcpm] [EXTERNAL] Re: Linux doesn’t implement… Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 Yuchung Cheng
- Re: [tcpm] Linux doesn’t implement RFC3465 Mirja Kuehlewind
- Re: [tcpm] Linux doesn’t implement RFC3465 Martin Duke
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Martin Duke
- Re: [tcpm] Linux doesn’t implement RFC3465 Vidhi Goel
- Re: [tcpm] Linux doesn’t implement RFC3465 Michael Tuexen
- Re: [tcpm] Linux doesn’t implement RFC3465 Mark Allman