From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-x241.google.com (mail-pf0-x241.google.com [IPv6:2607:f8b0:400e:c00::241]) (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 CDAC33B25E for ; Thu, 27 Oct 2016 13:52:09 -0400 (EDT) Received: by mail-pf0-x241.google.com with SMTP id i85so3220027pfa.0 for ; Thu, 27 Oct 2016 10:52:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=dG2jWkbdnURAT1XfIj1urkUOCxecTT6sB0ChbV4u/yU=; b=O1r7vu4CSPwaRhZ2QLjHpZt/3H2ccZOfKGjDmLtbdBuEhytW5wf/PfuiPuIRhkCV7e lShn1f8Ti+84gBQ6sIZfd8sWwyVFuvJBaNXLqfNrqdIATgLH6z4UBQLAwsmOZQs367a4 l9uHI0jeVqUK+WfMBsNxMDdC8hDHQ1bn84QhrJ+LaEew0jqDke0Av5VUCZPImrMmLxCK Sj/LSjNJpwa0G9yCjA9Xch9A10ZqmFmfK09WwyYSv8rIPzTnMncEGiuDYVWDa3H1j1/i Jnr+/giFzzG+X8wRpxJa9rzZgE+g2AkF7jTxA7vpqWxeX40vAXWFStU9hVv1T8J8Gpwz o0Kw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=dG2jWkbdnURAT1XfIj1urkUOCxecTT6sB0ChbV4u/yU=; b=P/EjD13RVncekGFhtywQbe24coopHPEGxuK2dmQxSbxheixApW9QAJAwV0oINoYxkV vBZXtimCu7RapGd/hSBnc55uJbfa74X5YgwssHDJ38P6oI1d+8RWY0o5mNKyGIzcYc5/ 7EqlVjAqTx35PpNJ+omnAfHFvWRnEC5CJPHhM+Y6ikv59dkYjd0FmwcswygQKMeYk5bc I0jckLsy5FeYLwHATRnAyzsq+KQ8U+Zd6+t20VCcCAFoplbAmHIyebdXYWpivfi6o9iX gkoG3HZTM+EK4XaneGMe1OFxWubDC2pYWaIzM3nSuRpF8sYRsSnhy+x1z2k9r/ogYM/l 2T0g== X-Gm-Message-State: ABUngvdiRQOZsp7iCRNPuVp4V1ChFoELeL3PQ7+TnTM5ajOw/rYd5lk7TiAX6OFP/8iYvw== X-Received: by 10.98.14.6 with SMTP id w6mr16353480pfi.153.1477590729104; Thu, 27 Oct 2016 10:52:09 -0700 (PDT) Received: from ?IPv6:2620:0:1000:1704:3cc0:3d9e:81fe:171a? ([2620:0:1000:1704:3cc0:3d9e:81fe:171a]) by smtp.googlemail.com with ESMTPSA id u28sm8131942pfk.25.2016.10.27.10.52.08 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Oct 2016 10:52:08 -0700 (PDT) Message-ID: <1477590728.7065.231.camel@edumazet-glaptop3.roam.corp.google.com> From: Eric Dumazet To: Dave Taht Cc: "Steinar H. Gunderson" , bloat Date: Thu, 27 Oct 2016 10:52:08 -0700 In-Reply-To: References: <20161021084726.GA1913@sesse.net> <20161027170447.GA28383@sesse.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [Bloat] "BBR" TCP patches submitted to linux kernel X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Oct 2016 17:52:10 -0000 On Thu, 2016-10-27 at 10:33 -0700, Dave Taht wrote: > At the moment my biggest beef with BBR is that it ignores ECN entirely > (and yet negotiates it). Note that switching cubic to any other CC like BBR is allowed at any time, way after ECN was negotiated. So BBR can not solve the issue you mention in a reliable way. There must be a reason sysctl_tcp_ecn default value is 2 on linux [1], don't you think ??? _You_ chose to change this sysctl, do not blame BBR for being silly ! ECN was a nice attempt, but suffers from implementation bugs. For a start, linux does not implement RFC 3540. If someone cares enough of ECN, then it should cook linux patches to implement RFC 3540. Hint hint hint. Then you need to make sure all the nodes between your peers are not messing with ECN. BBR simply works, because it is a sender side thing. You do not have to fix everything in the Internet. [1] Documentation/networking/ip-sysctl.txt tcp_ecn - INTEGER Control use of Explicit Congestion Notification (ECN) by TCP. ECN is used only when both ends of the TCP connection indicate support for it. This feature is useful in avoiding losses due to congestion by allowing supporting routers to signal congestion before having to drop packets. Possible values are: 0 Disable ECN. Neither initiate nor accept ECN. 1 Enable ECN when requested by incoming connections and also request ECN on outgoing connection attempts. 2 Enable ECN when requested by incoming connections but do not request ECN on outgoing connections. Default: 2