Re: ECN

[Saku Ytti via NANOG <nanog () lists nanog org>]

Thank you. I wasn't aware of that improvement. Absolutely massive
improvement in observed behaviour, penalties appear to be no more than
50% which is pretty tough ask, if you still want to keep good
performance on the common case, which is legitimate packet loss.

Still bit hilarious justification behind the fix, as it appears as if
dropbox and/or samsung strategically reorder under some design they
have. Despite it being 'fixed', you would still not want to give away
50% of your investment to congestion control technicalities and we can
still fairly argue that if your design strategically reorders, it is
broken design.

On Wed, 3 Dec 2025 at 14:26, Toke Høiland-Jørgensen <toke () toke dk> wrote:
> Saku Ytti via NANOG <nanog () lists nanog org> writes:
>
> > Even if it is unicasted, performance is destroyed due to reordering.
> > All modern TCP stacks use cubic for congestion control, which
> > considers reorder a packet loss.
>
> This is not quite true any longer. Linux implements RACK-TLP (RFC8985)
> which prevents short-term reordering (such as that caused by ECMP) from
> being interpreted as a congestion event.
>
> It seems Windows does too, these days:
> https://techcommunity.microsoft.com/blog/networkingblog/algorithmic-improvements-boost-tcp-performance-on-the-internet/2347061
>
> -Toke


-- 
  ++ytti
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