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[185.193.85.130]) by smtp.gmail.com with ESMTPSA id jg28-20020a05600ca01c00b004063cd8105csm17302844wmb.22.2023.11.28.00.43.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Nov 2023 00:43:44 -0800 (PST) Message-ID: <158a2dcff6c508998dbda044b4505146d0916dbb.camel@heistp.net> From: Pete Heist To: Dave Taht , ECN-Sane Date: Tue, 28 Nov 2023 09:43:43 +0100 In-Reply-To: References: <20180117015726.93632-1-ycheng@google.com> <20180119.143148.953873341015988293.davem@davemloft.net> Autocrypt: addr=pete@heistp.net; prefer-encrypt=mutual; keydata=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 1CZjXqULawE1mC967Cj76ZbIhFm6j8oDDTOCVnSNO6j0cya0Q43nTym 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 AyPdA9/yne0J7YDZRgjmseajK5/uFBw/E+XwnwJQJyfBk9+nX0KB4nvp VKd6AoJj7BZ0JNS3x/gFiEXaLl7rdHyN4YETksRNjPu0z3go8th3uAiYkP+4ge+IhOWRh5N34pUsOIS55MubvxFHFejgoc4mt5etJj9fCvbzRxBMXhiVIqYwGK5JFMIMhpEI+Z3drl/4fiVxUdCKDbCZdgtZcuF/bjQR/eCOtj2nDvTwcqjJsLhwHtQha1T6Ud9D8ywQvm76OMBspT8WacE3R/PbTQxmcBRx0Tqcz52iQ+M7SPlQ7J8tgUL9HIPRaDB0fPy3dtiAN88RBC7zS+IwJgIDAK1ZKTjqvOkPwNwwZRjZyxnpjTJSacjCr9/t2iVnjXBz95naGvtPOf0WUEjfE= Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-pUfX8/rE1E37l0zAtscR" User-Agent: Evolution 3.50.1 MIME-Version: 1.0 Subject: Re: [Ecn-sane] Fwd: [PATCH net-next] tcp: avoid negotitating ECN for BBR X-BeenThere: ecn-sane@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussion of explicit congestion notification's impact on the Internet List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 28 Nov 2023 08:43:46 -0000 --=-pUfX8/rE1E37l0zAtscR Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable It doesn't look like the patch to set TCP_CONG_DONT_USE_ECN in BBRv1 was ever applied, but it also doesn't look like v1 was ever modified to react to CE, whereas BBRv3 appears to: https://github.com/google/bbr/blob/v3/README.md#enabling-ecn-support I'll post something about ecn_low separately. Pete On Mon, 2023-11-27 at 19:12 -0500, Dave Taht via Ecn-sane wrote: > Was this ever resolved? >=20 > ---------- Forwarded message --------- > From: David Miller > Date: Fri, Jan 19, 2018 at 2:33=E2=80=AFPM > Subject: Re: [PATCH net-next] tcp: avoid negotitating ECN for BBR > To: > Cc: , , > , >=20 >=20 > From: Yuchung Cheng > Date: Tue, 16 Jan 2018 17:57:26 -0800 >=20 > > This patch keeps BBR from negotiating ECN if sysctl ECN is > > set. Prior to this patch, BBR negotiates ECN if enabled, sends > > CWR upon receiving ECE ACKs but does not react to them. This can > > cause confusion from the protocol perspective. Therefore this > > patch prevents the connection from negotiating ECN if BBR is the > > congestion control during the handshake. > >=20 > > Note that after the handshake, the user can still switch to a > > different congestion control that supports or even requires ECN > > (e.g. DCTCP).=C2=A0 In that case, the connection can not re-negotiate > > ECN and has to go with the ECN-free mode in that congestion > > control. > >=20 > > There are other cases BBR would still respond to ECE ACKs with CWR > > but does not react to it like the behavior before this patch. > > First, > > when the user switches to BBR congestion control but the connection > > has already negotiated ECN before. Second, the system has > > configured > > the ip route and/or uses eBPF to enable ECN on the connection that > > uses BBR congestion control. > >=20 > > Signed-off-by: Yuchung Cheng > > Signed-off-by: Neal Cardwell > > Acked-by: Yousuk Seung > > Acked-by: Eric Dumazet >=20 > Well, this is a bit disappointing.=C2=A0 I'm having trouble justifying > applying this. >=20 > Why doesn't BBR react to ECN notifications?=C2=A0 Is it because BBR's > idea of congestion differs from the one ECN is likely indicating? >=20 > This is really unfortunate, because if BBR does become quite > prominent > (that's what you want right? :-) then what little success there has > been deploying working ECN will be for almost nothing, and there > will be little incentive for further ECN deployment. >=20 > And the weird behavior you list in your last paragraph, about how if > the user switches to BBR then ECN will be active, is just a red flag > that shows perhaps this is a bad idea overall. >=20 > ECN behavior should not be so tightly bound to the congestion control > algorithm like this, it's a connection property independant of > congestion control algorithm. >=20 > I'm not applying this for now, sorry.=C2=A0 Maybe if you significantly > enhance the commit message and try to do something sane with the > algorithm switching case it is work a respin. >=20 > Thanks. >=20 >=20 --=-pUfX8/rE1E37l0zAtscR Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQGzBAABCAAdFiEEc6lSCRMow4RuRQyW6fxNO9SZO84FAmVlqD8ACgkQ6fxNO9SZ O84nUgwAwNx6vkD3xDXcmi8Yor3/a92a2EQWWcR72+oydomPiPIYoZPMX7ISdaka K/ExoMQdhyfhXiBdYDsfnxhe++cX+KmVbZh4tK3LMXoV3W2mP7lxhv71tVLw3nqR kOJTd2AMsiclYkKLk5MeakiPH1idiJNCC5NVnae22XlRUAv5YfuWfhfOPq6aCgRM 5uwcRit4niRDOxV8n6CfnjQ+I5WLKJCdwiV8mMjNZyktZU/WqVt8byJpFlMDLRYp R0Mzqwi9eSJdEgKgPLRbuu7UP/alfWT3Q/qSRGgiE5L7XhIaB8j5YdAxkaRcWRyV 2cCiqKo1zfeMzVwSc7BHt5cAo/yKgEjB6SVjwxsVxYW4XPkTTtfRaqeafetxIM8u gOQDI22lk1nYimkpBIRLvbOmateyJzPus9jF0x973uy2bBIAgq2S97w+g65jhgNL 3yav06Qg6G6WqXmjxTSdKqWQLQS2tc5992jW/rmKPQkguxklImkBFF/NbMwXYqQj wuqBIMS4 =7bc8 -----END PGP SIGNATURE----- --=-pUfX8/rE1E37l0zAtscR--