From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f48.google.com (mail-qg0-f48.google.com [209.85.192.48]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 83A6E21F2C7 for ; Sun, 21 Jun 2015 18:51:11 -0700 (PDT) Received: by qgev13 with SMTP id v13so14214330qge.1 for ; Sun, 21 Jun 2015 18:51:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-type:content-transfer-encoding; bh=qOACgFP/odzsO6ysXzAcIURdTqKzFxBJaaNEXjhzjHw=; b=VwIE39tTYJiI5+CBkBjFLBzMoSYoufu5SsCupalrqOphux93D3ZC5S3OKbIZGUJ3L+ YUcp2B3YcJ0ACohwW9c+GKCcW2gbzU3ygxAa659AbL56sVTuxxmp5gRcngL4Vu/ZUmI/ Ej+MN78V0OUpxfsuShEOWd2Cckn4pkcr2FFAedT4xs5lzz1eVbomV0D9ENhgffriHxzq RaqwmOyFsS1fSKR+xgGt+o6V2wkgZZcvRKU1EBRmppbIhjlTa3UiXvfUrNUaMcGIMdB0 5u8gV1sdVsh/mc8h86MROxefhSafhVpWVOgLPSzFx5R/3Dk9iUUuGXfFTFOYDC3y4kf3 QwFQ== X-Gm-Message-State: ALoCoQliCkh8SimXCi7w0cSS/cIjuRyhgSogGEHNqGRK4ybdIHnK/LYM0pVdpdM0Vd152CnYK5rz X-Received: by 10.140.135.6 with SMTP id 6mr36779911qhh.101.1434937869852; Sun, 21 Jun 2015 18:51:09 -0700 (PDT) Received: from uryu.home.lan (64-199-199-12.ip.mcleodusa.net. [64.199.199.12]) by mx.google.com with ESMTPSA id i64sm9530389qkh.3.2015.06.21.18.51.09 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 21 Jun 2015 18:51:09 -0700 (PDT) Date: Sun, 21 Jun 2015 21:50:52 -0400 From: Stephen Hemminger To: Benjamin Cronce Message-ID: <20150621215052.0fbdcace@uryu.home.lan> In-Reply-To: References: X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: bloat Subject: Re: [Bloat] TCP congestion detection - random thoughts X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 22 Jun 2015 01:51:39 -0000 You just reinvented delay based congestion control. This has been tried int many forms dating back to TCP Vegas. https://en.wikipedia.org/wiki/TCP_Vegas Unfortunately, it often failed in practice (which no one ever wanted to publish), Some of the reasons are: * Delay based CC is sensitive to cross traffic congestion where the perceived congestion event was not caused by that flow. I.e other elephant stomps on ant. * Delay based CC is not aggressive enough to compete with loss-based CC. Vegas flows lose to Reno. * Delay based CC requires careful tuning, one variant was FAST TCP which was highly tuned for 1G networks in research. It went proprietary never heard how well it works in modern networks. * Delay based CC was sensitive to middleboxes, polling intervals and other timing effects in the wild. * RTT data has a noise to signal ratio, a flow has to be consistently maintaining a given rate in order to get consistent feedback. Google has some delay based congestion control that is promised to be released some time, I am waiting.