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

> On 12. Jan 2023, at 00:47, Praveen Balasubramanian <pravb.ietf@gmail.com> 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 <ncardwell@google.com> 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 <ncardwell@google.com> 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 <internet-drafts@ietf.org> 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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