From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-01-iad.dyndns.com (mxout-235-iad.mailhop.org [216.146.32.235]) by lists.bufferbloat.net (Postfix) with ESMTP id EDFF62E04FF for ; Tue, 8 Feb 2011 21:18:05 -0800 (PST) Received: from scan-01-iad.mailhop.org (scan-01-iad.local [10.150.0.206]) by mail-01-iad.dyndns.com (Postfix) with ESMTP id 6D4CF6DA6D for ; Wed, 9 Feb 2011 05:18:04 +0000 (UTC) X-Spam-Score: 0.1 () X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 75.145.127.229 Received: from gw.co.teklibre.org (75-145-127-229-Colorado.hfc.comcastbusiness.net [75.145.127.229]) by mail-01-iad.dyndns.com (Postfix) with ESMTP id 43DC46D9CA for ; Wed, 9 Feb 2011 05:18:02 +0000 (UTC) Received: from cruithne.co.teklibre.org (unknown [IPv6:2002:4b91:7fe5:2:21c:25ff:fe80:46f9]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "cruithne.co.teklibre.org", Issuer "CA Cert Signing Authority" (verified OK)) by gw.co.teklibre.org (Postfix) with ESMTPS id ACD065E82F for ; Tue, 8 Feb 2011 22:18:01 -0700 (MST) Received: by cruithne.co.teklibre.org (Postfix, from userid 1000) id C52A9121FA3; Tue, 8 Feb 2011 22:18:00 -0700 (MST) From: d@taht.net (Dave =?utf-8?Q?T=C3=A4ht?=) To: bloat Organization: Teklibre - http://www.teklibre.com References: <87fwry821f.fsf@cruithne.co.teklibre.org> Date: Tue, 08 Feb 2011 22:18:00 -0700 In-Reply-To: <87fwry821f.fsf@cruithne.co.teklibre.org> ("Dave =?utf-8?Q?T?= =?utf-8?Q?=C3=A4ht=22's?= message of "Tue, 08 Feb 2011 17:49:48 -0700") Message-ID: <87vd0t7pmf.fsf@cruithne.co.teklibre.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Bloat] monitoring bufferbloat at the DC using ntp? 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, 09 Feb 2011 05:18:06 -0000 d@taht.net (Dave T=C3=A4ht) writes: > I may have had a wacking good idea this morning. > > See ongoing thread on comp.protocols.time.ntp at: > > http://lists.ntp.org/pipermail/questions/2011-February/028577.html The discussion over there continues. Encouraging news is that it is not only possible to track the originating timestamp on ntp servers, but that there are snmp mibs available for queue lengths. (More details over on that thread)=20 It's not clear to me what percentage of hosts are local timestamping their origination, I'm under the impression this is a relatively new feature.=20 Also in my experiments thus far today: the version of ntp I have always uses 123 as it's originating port number on the client, rather than an ephemeral port. I am curious as to whether other versions of ntp (mac, windows, other platforms, other versions) also originate on 123. If so, this leads to an easy way to distinguish between natted and non-natted origination of requests. If members of this list could take a look at their own platforms with something like wireshark, and trace a few ntp packets going by, that would be helpful. Repeating the same capture while performing a latency under load test would also be good. You will have to run the test a fairly long time (1024+ seconds) in order to get enough ntp packets going by. There is a great deal more data we could derive from ntp server side data sets, but I'm unwilling to speculate further without talking to an ntp expert.=20 There may be many flaws in this methodology, including the jitter already in the network before bufferbloat was diagnosed client side. But I'm really looking forward to flamage, criticism, or confirmation in the morning. --=20 Dave Taht http://nex-6.taht.net