Re: [tcpm] I-D Action: draft-ietf-tcpm-hystartplusplus-12.txt

[Martin Duke <[e-mail]>]

While, if it were me, I might attempt to capture the nuance Neal describes
about the Linux default and Google, I do not object to deleting it entirely.

On Sun, Jan 15, 2023 at 1:10 PM Michael Tuexen <
[e-mail]> wrote:

> > On 12. Jan 2023, at 00:47, Praveen Balasubramanian <[e-mail]>
> wrote:
> >
> > I see, thanks Neal for the clarification. I then suggest that we
> eliminate this deployment experience line completely because its not with
> the proposed algorithm in this document and that it will confuse new
> developers as to why the document suggests using pacing with L=infinity
> when the default in Linux contradicts it.
> >
> > Any concerns with just removing this line entirely?
> In general I think providing data points precisely is a good thing,
> even if they are inconclusive.
>
> I think the document can still suggest to use L = infinity, if pacing is
> used.
> Also using L < 2 is not optimal.
>
> The only unclear point is what value of L to use if you do not use pacing.
> Maybe the threshold of 8 is not a hard value for all traffic patterns,
> link characteristics and implementations.
>
> Best regards
> Michael (as an individual)
> >
> > On Wed, Jan 11, 2023 at 2:07 PM Neal Cardwell <[e-mail]>
> wrote:
> > Martin pointed out out-of-band that my various attempts at explaining
> this point have not been clear, so let me try to express this a different
> way:
> >
> > For about the last decade the Linux TCP default has been: [ CUBIC +
> Hystart + L=infinity + unpaced ]. This is because the commonly deployed
> qdiscs for the major Linux distributions do not implement pacing.
> >
> > For 2013-2016 Google/YouTube Linux TCP ran with: [ CUBIC + Hystart +
> L=infinity + paced ]. This was using the fq qdisc to implement pacing.
> >
> > best regards,
> > neal
> >
> >
> > On Tue, Jan 10, 2023 at 10:24 AM Neal Cardwell <[e-mail]>
> wrote:
> > Looks like there is still one significant word in the "Deployments and
> Performance Evaluations" section that needs to be updated to be accurate.
> >
> > Existing draft-ietf-tcpm-hystartplusplus-12 text:
> >
> >   There has been over a decade of experience using the
> >   original Hystart algorithm for all TCP connections in the
> >   Linux operating system with pacing enabled and an
> >   actual L = infinity.
> >
> > Suggested text:
> >
> >   There has been over a decade of experience using the
> >   original Hystart algorithm for all TCP connections in the
> >   Linux operating system with pacing disabled and an
> >   actual L = infinity.
> >
> > I mentioned the rationale in the "Re: [tcpm] Changes to
> draft-ietf-tcpm-hystartplusplus after WGLC" thread on Nov 29:
> >
> >
> https://mailarchive.ietf.org/arch/msg/tcpm/CSzCgxxSLrO9u63dymyyxqB6bD4/
> >
> > cheers,
> > neal
> >
> >
> > On Mon, Jan 9, 2023 at 8:53 PM <[e-mail]> wrote:
> >
> > A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> > This draft is a work item of the TCP Maintenance and Minor Extensions WG
> of the IETF.
> >
> >         Title           : HyStart++: Modified Slow Start for TCP
> >         Authors         : Praveen Balasubramanian
> >                           Yi Huang
> >                           Matt Olson
> >   Filename        : draft-ietf-tcpm-hystartplusplus-12.txt
> >   Pages           : 9
> >   Date            : 2023-01-09
> >
> > Abstract:
> >    This document describes HyStart++, a simple modification to the slow
> >    start phase of congestion control algorithms.  Traditional slow start
> >    can overshoot the ideal send rate in many cases, causing high packet
> >    loss and poor performance.  HyStart++ uses a delay increase heuristic
> >    to find an exit point before possible overshoot.  It also adds a
> >    mitigation to prevent jitter from causing premature slow start exit.
> >
> >
> > The IETF datatracker status page for this draft is:
> > https://datatracker.ietf.org/doc/draft-ietf-tcpm-hystartplusplus/
> >
> > There is also an htmlized version available at:
> > https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-hystartplusplus-12
> >
> > A diff from the previous version is available at:
> >
> https://author-tools.ietf.org/iddiff?url2=draft-ietf-tcpm-hystartplusplus-12
> >
> >
> > Internet-Drafts are also available by rsync at rsync.ietf.org:
> :internet-drafts
> >
> >
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