From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-xd2c.google.com (mail-io1-xd2c.google.com [IPv6:2607:f8b0:4864:20::d2c]) (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 356263B29E for ; Wed, 28 Aug 2019 22:08:55 -0400 (EDT) Received: by mail-io1-xd2c.google.com with SMTP id t3so3589141ioj.12 for ; Wed, 28 Aug 2019 19:08:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=92cioV7RGP9IGcASUTbKoQL46hI81j2vtjPJL8VFr78=; b=lOmKdIiv2puTSaSx3cuRpWE3K60f9zts07/Y3t6T7dmeoSCkaa1eAgMiW3rxyZIYmV UXWvhe93eS2qDLKJW7Rc7rnxg7ZfHzgbtwOl7EchjNijzyyAaGxk7M1f3Bd2aPCwDbro PPn9qZsnIxdMU3/YeTIfl++rD4RaKCemXyPYfPPXR7mxay1npsEha3tHCUWLo1CHb3dq FdqSFrmmL5uk1sRyZIVO0S5PIVqAi7LlYDhbFhDe1rF/BWpfOZme4r6LM9Yul1TAA4g4 XRV3MbeexeyusLt6UZSKs1dK6oAsFb8c+a49nz4thItZVswmNXo50TV8j+052IaqulMc 3+Pw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=92cioV7RGP9IGcASUTbKoQL46hI81j2vtjPJL8VFr78=; b=i0zNPyxYuMzxbEwBojcf9FQ4SEtDmyHYsO+mzkvGIho5KCr/lr7qp6VZ3AdISm405b DUnVX6dn/N8Bj9HdaItKFzsz8KaJQzZQOvh8ODGNBfax7zVeDrgNxsrP8o5zzUt87gs0 7ODrVydBVzDhdSH1lUA/p2JJPa3eHuBLFkVmy+Fi6aZqhogJ0RWeYm9nj58/1O1YB8GA nEUr3/QNLaagVcgcdlUHcpZvzJZIxm0iX+CIybsCcDWHRq1SZXrgui4SeWbIgJFi2GXP 5HtObnt/Ck33pPn/n5NkRxC3aZ7fLLjFh39F0NKC2afjBCI9IKkcZnQaWk923l8VZrWA IjWA== X-Gm-Message-State: APjAAAURNSOAir/59KnmgN22WerbDYAVSdA4nodhNHUDFcl/d3isI11C 42fBDgk9fJI4vrQjp0+w1j15zAS6BbpByTqJzw3QCQdc0WI= X-Google-Smtp-Source: APXvYqxJ4WM+5I/KY9oCz/HFFywCTH5cNNMGtufUtJOoaevc/j8DtDOIPI9pGZdH0sTftMPFyesoD3u0B4RgUwo6ypw= X-Received: by 2002:a5e:9818:: with SMTP id s24mr8861298ioj.0.1567044534423; Wed, 28 Aug 2019 19:08:54 -0700 (PDT) MIME-Version: 1.0 From: Dave Taht Date: Wed, 28 Aug 2019 19:08:47 -0700 Message-ID: To: ECN-Sane Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: [Ecn-sane] rfc3168 sec 6.1.2 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: Thu, 29 Aug 2019 02:08:55 -0000 It would explain a lot if this was not actually implemented in Linux. I'm afraid to look. cwnd reduction is capped to 2. 1 should put you in quickack mode AND to go lower seemingly it's supposed to then rely on the retransmit timer. ... If the congestion window consists of only one MSS (maximum segment size), and the sending TCP receives an ECN-Echo ACK packet, then the sending TCP should in principle still reduce its congestion window in half. However, the value of the congestion window is bounded below by a value of one MSS. If the sending TCP were to continue to send, using a congestion window of 1 MSS, this results in the transmission of one packet per round-trip time. It is necessary to still reduce the sending rate of the TCP sender even further, on receipt of an ECN-Echo packet when the congestion window is one. ^^^^^^^^^^^^^^^^^^^^^^^^ We use the retransmit timer as a means of reducing the rate further in this circumstance. Therefore, the sending TCP MUST reset the ^^^^^^^^^^^^^^^^^^^^^^^^ retransmit timer on receiving the ECN-Echo packet when the congestion window is one. The sending TCP will then be able to send a new packet only when the retransmit timer expires. --=20 Dave T=C3=A4ht CTO, TekLibre, LLC http://www.teklibre.com Tel: 1-831-205-9740