From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-x136.google.com (mail-lf1-x136.google.com [IPv6:2a00:1450:4864:20::136]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id A3D763B2A4 for ; Tue, 22 Dec 2020 15:15:22 -0500 (EST) Received: by mail-lf1-x136.google.com with SMTP id y19so34733914lfa.13 for ; Tue, 22 Dec 2020 12:15:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=hxWN+l9zlAYdOar+CdZXEQfsGLElEVYnEMLhMtxiRMU=; b=jv2n9RU43kUIoYyBqfu7zYIh3r55V57tAAx7g1EUdealfDnq6P7S4W+yOKDljYtBUw W+qIIerqzHz5DHLg084bCblaRLam193ABNcjguMuzVpc8Y/DMxFYviI+kOrIif9M80US iEQe/RSWYO2d5qjEIxpIVDXIoWBIV+sDKhoAfTlYunkw1npUVYC+/EaKWM1hzoHK2833 OXYcX+TWFtXzt+/ZkiD4IDcCNpFIqFWMBEejv1vAdWpFsXJptNxvWkWzXkGEl0u3hWs6 sHBBCVg6VLkPVjl/AANtv2/hLm/1Bn0+sgRYgyvHhFTyV+GQNp8t3fmWo+RtvoyGVbFk yQiA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=hxWN+l9zlAYdOar+CdZXEQfsGLElEVYnEMLhMtxiRMU=; b=JhFQJss/1xdMQ88kQzkoCEf7FjVMeNGthHR73bWBabIYNwJTAqow5/Sjzz/4UTttZO CxwEy0ZVxa0loKUv2nxUuM3VO0+e5eKU0P5JZx9hDqf/MvhF9qOc5IruLP27boQgM6Rp ETSHHuVd/bHYfsJ4Qzvx4gpepn9uvo/HmDEoLdeRTifVde3BwjqHn2F4pxeeXrDXlk2B 0nvLhvHrXjPAYKEDkKTeUkn7yyMyZL3pwYYcJUUtXAN9BDfOykpmoi+ABWJs+riBFfOF 5n5HrDA/T4odgQHh1iMNh8kHh0QLlUeAfy0+TUl+gppZA0TYTHz01WQlfmBoEG/6ry+v cfSA== X-Gm-Message-State: AOAM531yRlrNW0UVQIyvp9SDAqjhszLxoo2Oj09tCoJENmd2ijlbk5/5 HaWTGUoKPnwpXJ20Cutbn6Q= X-Google-Smtp-Source: ABdhPJzlORYf6jDNU6XRFYGEOEmFUPgc8Q2rtJbfVTCctPrHQgTj5h9D6YXMUrb9g61eQVtFJDfJaA== X-Received: by 2002:ac2:43d6:: with SMTP id u22mr8850432lfl.596.1608668121580; Tue, 22 Dec 2020 12:15:21 -0800 (PST) Received: from jonathartonsmbp.lan (178-55-231-236.bb.dnainternet.fi. [178.55.231.236]) by smtp.gmail.com with ESMTPSA id t17sm2144598lfr.5.2020.12.22.12.15.20 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 Dec 2020 12:15:20 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.7\)) From: Jonathan Morton In-Reply-To: <421ffd89-0c2c-1187-380c-03a0968f4095@gmail.com> Date: Tue, 22 Dec 2020 22:15:19 +0200 Cc: cake@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: References: <421ffd89-0c2c-1187-380c-03a0968f4095@gmail.com> To: xnor X-Mailer: Apple Mail (2.3445.9.7) Subject: Re: [Cake] ECN not working? X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Dec 2020 20:15:22 -0000 > On 22 Dec, 2020, at 10:06 pm, xnor wrote: >=20 > The client initiates the IPv4 TCP connection with: > IP Differentiated Services Field: 0x02 (DSCP: CS0, ECN: ECT(0)) > TCP Flags: 0x0c2 (SYN, ECN, CWR) > Seq=3D0 Win=3D64240 Len=3D0 MSS=3D1460 WS=3D256 SACK_PERM=3D1 >=20 > The server responds: > Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT) > Flags: 0x012 (SYN, ACK) > Seq=3D0 Ack=3D1 Win=3D64240 Len=3D0 MSS=3D1460 SACK_PERM=3D1 WS=3D128 >=20 > Shouldn't the server respond with ECT set in the SYN ACK packet > and possibly also have ECN-related flags set in the TCP header? Not all servers have ECN support enabled. A SYN-ACK without the ECE bit = set indicates it does not. The connection then proceeds as Not-ECT. I'm reasonably sure Akamai has specifically enabled ECN support. A lot = of smaller webservers are probably running with the default passive-mode = ECN support as well (ie. will negotiate inbound but not initiate = outbound). - Jonathan Morton=