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

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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>>
>