From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-01-ewr.dyndns.com (mxout-065-ewr.mailhop.org [216.146.33.65]) by lists.bufferbloat.net (Postfix) with ESMTP id 831232E018E for ; Thu, 17 Mar 2011 18:36:09 -0700 (PDT) Received: from scan-02-ewr.mailhop.org (scan-02-ewr.local [10.0.141.224]) by mail-01-ewr.dyndns.com (Postfix) with ESMTP id 676C91F5AD1 for ; Fri, 18 Mar 2011 01:36:08 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 74.125.82.171 Received: from mail-wy0-f171.google.com (mail-wy0-f171.google.com [74.125.82.171]) by mail-01-ewr.dyndns.com (Postfix) with ESMTP id E0A3F1F5AC4 for ; Fri, 18 Mar 2011 01:36:06 +0000 (UTC) Received: by wyb32 with SMTP id 32so4071107wyb.16 for ; Thu, 17 Mar 2011 18:36:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=NFQFpGqEV0eyhuVAIdq6B96KHh+/FhKD5tiA3NtRHR0=; b=HLZ5M2RT3FPWrQiZHUUIWgUD2F0IYB0RF2TXaWAYCkfaJOvniD+g/MFkiSIt5JKrEV VB/y3FTEKdZ+FesrThgmOtBbtIbVu6BBGU619iZW4+hzlQMUgq3FG8dBxmLPaQ7EEG9d JqR13+wtc9xLoDQ0VBthGlsQse8C32cUjOWfQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=gT7r+ZCx+Y0S7KsYxsfmnJgZf8jx7tARR0xNM+nXbVrCs9beFYalPO0tPVJdAhx/0w JUevt5BTuhvOS+EbyjdsQgDEMJNVJkckQlmZKnXO7Kqw1aZZa6uRUWH2j7Pgh56nIbTY 8N0q8tr7mrHEjzMgC7Rx3S2dNQ38f8i/TulkM= MIME-Version: 1.0 Received: by 10.227.182.135 with SMTP id cc7mr533612wbb.91.1300412166179; Thu, 17 Mar 2011 18:36:06 -0700 (PDT) Received: by 10.227.141.129 with HTTP; Thu, 17 Mar 2011 18:36:05 -0700 (PDT) In-Reply-To: <845EB260-932A-42F4-800C-005196B32D48@gmail.com> References: <4D7F4121.40307@freedesktop.org> <20110315175942.GA10064@goldfish> <1300212877.2087.2155.camel@tardy> <20110315183111.GB2542@tuxdriver.com> <29B06777-CC5F-4802-8727-B04F58CDA9E3@gmail.com> <20110315205146.GF2542@tuxdriver.com> <219C7840-ED79-49EA-929D-96C5A6200401@gmail.com> <20110316004722.GD28663@tuxdriver.com> <66469263-763A-4D5A-B689-026D0603C170@gmail.com> <1300386132.2087.2345.camel@tardy> <44F5E713-4AB2-4D34-9DD5-97FBE92E401F@gmail.com> <1300400436.2087.2401.camel@tardy> <845EB260-932A-42F4-800C-005196B32D48@gmail.com> Date: Thu, 17 Mar 2011 21:36:05 -0400 Message-ID: From: Justin McCann To: Jonathan Morton Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] Random idea in reaction to all the discussion of TCP flavours - timestamps? 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: Fri, 18 Mar 2011 01:36:09 -0000 On Thu, Mar 17, 2011 at 6:56 PM, Jonathan Morton wr= ote: > > On 18 Mar, 2011, at 12:20 am, Rick Jones wrote: > >>>> So initialRTO is specced currently to be 3 seconds, with a small but >>>> non-trivial effort under way to reduce that, but once established >>>> connections have a minimum RTO of less than or equal to a second don't >>>> they? >>> >>> If the RTT they measure is low enough, then yes. =A0If the queues >>> lengthen, the measured RTT goes up and so does the RTO, once the >>> connection is established. >> >> Right. =A0I should have been more explicit about "You know it won't >> retransmit any sooner than N." (for some, changing value of N :) > > I think there is a minimum value, on the order of 100ms - I don't know pr= ecisely. The current TCP_MIN_RTO is 200ms on Linux (http://lxr.linux.no/linux+v2.6.38/include/net/tcp.h#L124). Apparently it's 30ms on FreeBSD, if this old thread still holds true (http://www.postel.org/pipermail/end2end-interest/2004-November/004402.html= ). >From the DCTCP paper, it looks like Windows has a 300 ms RTO. There were several papers the last couple of years about the minimum RTO causing low throughput in data center with very small nominal RTTs. The DCTCP paper has been mentioned here several times already; it has a lot of relevant discussion about buffer sizing, latency, AQM, and the difficulties of tuning RED. Justin