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References: <20190404121731.13917-1-olivier.tilmans@nokia-bell-labs.com> <CADVnQy=hsPrDwXoym18j7YzCc36669NJ1kVBR76y+FgK6Meytw@mail.gmail.com>
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From:   Neal Cardwell <ncardwell@google.com>
Date:   Thu, 4 Apr 2019 09:55:19 -0400
Message-ID: <CADVnQyks1T8KZibJF+UWR0zWGvqs+fUBkCYPJFxATx5PU-csSQ@mail.gmail.com>
Subject: Re: [PATCH net-next v2] tcp: Ensure DCTCP reacts to losses
To:     "Tilmans, Olivier (Nokia - BE/Antwerp)" 
        <olivier.tilmans@nokia-bell-labs.com>
Cc:     "De Schepper, Koen (Nokia - BE/Antwerp)" 
        <koen.de_schepper@nokia-bell-labs.com>,
        Bob Briscoe <research@bobbriscoe.net>,
        Lawrence Brakmo <brakmo@fb.com>,
        Florian Westphal <fw@strlen.de>,
        Daniel Borkmann <borkmann@iogearbox.net>,
        Yuchung Cheng <ycheng@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Andrew Shewmaker <agshew@gmail.com>,
        Glenn Judd <glenn.judd@morganstanley.com>,
        "David S. Miller" <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Thu, Apr 4, 2019 at 9:48 AM Neal Cardwell <ncardwell@google.com> wrote:
>
> On Thu, Apr 4, 2019 at 8:24 AM Tilmans, Olivier (Nokia - BE/Antwerp)
> <olivier.tilmans@nokia-bell-labs.com> wrote:
> >
> > From: Koen De Schepper <koen.de_schepper@nokia-bell-labs.com>
> >
> > RFC8257 =C2=A73.5 explicitly states that "A DCTCP sender MUST react to
> > loss episodes in the same way as conventional TCP".
> ...
> > This patch replace the clamping of alpha by setting ssthresh to
> > half of cwnd for both fast retransmissions and RTOs, at most once
> > per RTT. Consequently, the dctcp_clamp_alpha_on_loss module parameter
> > has been removed.
>
> Acked-by: Neal Cardwell <ncardwell@google.com>
>
> Thanks!

FWIW, my vote is that this is an important bug fix that is appropriate
for the net branch and -stable releases, rather than net-next.

neal