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[185.193.85.130]) by smtp.gmail.com with ESMTPSA id o19-20020a05600c4fd300b0040b45356b72sm8595209wmq.33.2023.11.28.08.28.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Nov 2023 08:28:01 -0800 (PST) Message-ID: <643b47a4cc08666f4a34328144146e796ef01f36.camel@heistp.net> From: Pete Heist To: Sebastian Moeller Cc: ECN-Sane Date: Tue, 28 Nov 2023 17:28:00 +0100 In-Reply-To: <35C94031-C0B0-428B-822B-68AC0AB4A540@gmx.de> References: <35C94031-C0B0-428B-822B-68AC0AB4A540@gmx.de> 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="=-gujrQpQa2i1s+l2l4MgI" User-Agent: Evolution 3.50.1 MIME-Version: 1.0 Subject: Re: [Ecn-sane] BBRv3 ecn_low per-route feature and the CE confusion 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 16:28:04 -0000 --=-gujrQpQa2i1s+l2l4MgI Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2023-11-28 at 16:21 +0100, Sebastian Moeller wrote: > Hi Pete, >=20 >=20 > > On Nov 28, 2023, at 13:57, Pete Heist via Ecn-sane > > wrote: > >=20 > > Regarding the per-route ecn_low feature in BBRv3: > > https://github.com/google/bbr/blob/v3/README.md#introducing-the-ecn_low= -per-route-feature > >=20 > > When set, any incoming CE marks from an ecn_low flagged route will > > be > > treated as an L4S/RFC9331 CE, while CE marks from routes without > > that > > flag will be treated as a regular RFC3168 CE. >=20 > I am probably blind, but looking at > https://github.com/google/bbr/blob/v3/net/ipv4/tcp_bbr.c > I do not see this fall back to a rfc3168 compliant response, as far > as I read this this is DCTCP or nothing...=20 > Or did you just mean that BBRv3 will treat CE just like BBRv1 and > silently ignore it? TBH, I hadn't read the code but I think you're right. The doc makes it sound like enabling ECN support could be done with or without the ecn_low feature, implying that it would react properly to either type of CE. It appears to still ignore CE though unless ecn_low is flagged, and other conditions are met. So yes, L4S/DCTCP response or bust. Same result though, this confusion is harmful to the ECN field. Pete > > Obviously this is > > problematic, as the two CE marks mean very different things, and > > outside of closed environments, there's no reliable way to know > > which > > type of CE you're receiving. The consequences of confusing them > > range > > from massive self-induced bloat, to driving competing traffic in > > the > > same queue down to minimum cwnd. The solution here is to just punt, > > so > > at least tests and demos can be made to work. >=20 > The per-route feature looks like a desirable safety... as > does the default 5ms rtt "low-pass", where IIUC ECN will only be > evaluated if the RTT is below 5ms... >=20 >=20 > > This isn't a problem with BBR. The problem is, we've started an > > experiment [RFC9331] that redefines the meaning of CE in a way > > that's > > incompatible with existing RFC3168 middleboxes. This feature in BBR > > is > > just a reflection of that. CCA developers are now tasked with > > somehow > > deciding which type of CE they're seeing. > >=20 > > Speaking of ecn "sane", does anyone else see this as not? :) and as > > a > > problem that needs solving? >=20 > Yes, however I assume this will solve it self, as is this > usage of CE is over-promising and under-delivering, so I do not see > this "winning the internet" in spite of the amount of thrust is put > behind it... >=20 > Regards > Sebastian >=20 >=20 > >=20 > > Pete > >=20 > > _______________________________________________ > > Ecn-sane mailing list > > Ecn-sane@lists.bufferbloat.net > > https://lists.bufferbloat.net/listinfo/ecn-sane >=20 --=-gujrQpQa2i1s+l2l4MgI Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQGzBAABCAAdFiEEc6lSCRMow4RuRQyW6fxNO9SZO84FAmVmFRAACgkQ6fxNO9SZ O87J7wv6AhIefFYl2V2Knmkyzn2Af6JXWfiBmL0Xb2D5kwksjZ0M1XPAMTlY9YNF 7vZlSrZ1trabscOoC7ZuI9Gq446z/JC0LMntOieIwOcVRD4zh8quumB6rRgt8A7V UwzqUJbaRmObg3Nu85MnyX5xDYHU4M1aBRN9sZgxZXrioBf/kDZsnvohQaAZ7OTp wfCKE5lOh4WLNN3zvy+S9+ZAi+D32358izSzKtHZ2DQkIlcpeOD+ksiu9UBrtX6M gzlWGxp9DC2UdSf6VEF2ayA9uHEUiVmSsyTqnV2Y/BDDkQVIPZym9smnI/vnBcwk NOZtKj7yIgeKNP1oTFJWUztDc1v5ggfUbxOQp5dJDKR6p5rvaaRj6jQoQxyigrR5 r/MkiyjkNltexLJZolPOzNYOztuZttMVcFsDDhHU3qfTcd7U1mWT5VSEoTzDLIDO HBXkbrin7lSmkv3Pl6K5Fp5oYG+0w0xZPBfjJmnjS+vOmavLaCkYlcF4UbjtWdf6 RmErAhNj =atxX -----END PGP SIGNATURE----- --=-gujrQpQa2i1s+l2l4MgI--