From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-x22c.google.com (mail-qk0-x22c.google.com [IPv6:2607:f8b0:400d:c09::22c]) (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 D3B9021FBA6 for ; Wed, 8 Jul 2015 10:53:07 -0700 (PDT) Received: by qkeo142 with SMTP id o142so168711463qke.1 for ; Wed, 08 Jul 2015 10:53:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=content-type:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=ch8mEr5lWMohv2n5QvZMIaWZHt6zo4a57LN61RDP2yk=; b=uOSSbwA990HTJsRdFr3OSg6A8lcOpJ4e2SKyAi16/hrWeVMsyn+hxHNvU4C3wKkqaI XzDvTmdhq9C9NTthHR0oSuOeYMff0UNRt5PTsFtKv8OYKnU7vk3xfIPj45B/BgCYE767 ue5OshOaR5PmFiQJj2Wz4idIeAtnrp5vuIJ9jqTYIfB0hrhFE/JO3ph6xYjWV0jgSj+b wHxThQn5xTVHW7GVf2lOcdqOHMMU+ZIFtDhaCpkY0jFvTjMiUyi+eWX3wNbycMfzKBFE tp5M1Ux5PgMgznRKRwa716jMNppBBrxLtlrCvJyCj+ZTSJe6y7njCItq49gaBl0M34Ky 1ZXA== X-Received: by 10.140.94.100 with SMTP id f91mr17729241qge.101.1436377986396; Wed, 08 Jul 2015 10:53:06 -0700 (PDT) Received: from richs-mbp-13524.lan (pool-70-105-232-212.port.east.myfairpoint.net. [70.105.232.212]) by smtp.gmail.com with ESMTPSA id 67sm1729863qhw.43.2015.07.08.10.53.05 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 08 Jul 2015 10:53:05 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) From: Rich Brown In-Reply-To: Date: Wed, 8 Jul 2015 13:53:03 -0400 Content-Transfer-Encoding: quoted-printable Message-Id: <48CA84D9-1D39-4F50-831B-8FD2570C76BA@gmail.com> References: <20150708102317.A8994406057@ip-64-139-1-69.sjc.megapath.net> To: Dave Taht X-Mailer: Apple Mail (2.1878.6) Cc: Hal Murray , bloat Subject: Re: [Bloat] Graph of bloat 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: Wed, 08 Jul 2015 17:53:36 -0000 On Jul 8, 2015, at 11:55 AM, Dave Taht wrote: > On Wed, Jul 8, 2015 at 3:23 AM, Hal Murray = wrote: >> I was monitoring Google's time servers over the recent leap second. = That >> graph happened to include some good examples of bloat. >>=20 >> http://www.megapathdsl.net/~hmurray/bloat/google-off-smear-bloat.png >>=20 >> I have a slow DSL line with almost 4 seconds of buffering. >>=20 >> The blobs at -20 and -15 seconds are typical of a single large = download. The >> column at -6 seconds is typical of several active connections. >=20 > That is a very interesting graph! Does ntp adjust system time backward > based on getting nearly all it's samples with well over a 1/2 second > of induced delay? There was a good discussion of this on the NANOG list about a week or so = ago, lamenting the leap-second. Lots of learned (and other) people = chimed in on the pro's and con's. = http://mailman.nanog.org/pipermail/nanog/2015-June/076540.html if you're = terminally interested. I think that chart is the clock offset of the Google time servers = compared to the Menlo Park NTP server (which is "true time"). At 10 = hours before midnight (and the arrival of the leap second), the Google = servers report the seconds to be a tiny bit longer than a true second, = so that by midnight, they're a full 500 msec (half-second) "ahead". When = the leap-second drops in, they're a half-second behind "true" time, and = it continues the ramp for the next 10 hours to be back "in sync". (I may have the sense/direction of this wrong, but you get the idea...) Rich=