From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-11-ewr.dyndns.com (mxout-190-ewr.mailhop.org [216.146.33.190]) by lists.bufferbloat.net (Postfix) with ESMTP id 0AE0D2E0226 for ; Wed, 16 Feb 2011 10:49:01 -0800 (PST) Received: from scan-12-ewr.mailhop.org (scan-12-ewr.local [10.0.141.230]) by mail-11-ewr.dyndns.com (Postfix) with ESMTP id 0F29592C894 for ; Wed, 16 Feb 2011 18:49:00 +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-11-ewr.dyndns.com (Postfix) with ESMTP id A83E692BFC3 for ; Wed, 16 Feb 2011 18:48:58 +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 213225EF5A for ; Wed, 16 Feb 2011 11:48:58 -0700 (MST) Received: by cruithne.co.teklibre.org (Postfix, from userid 1000) id 0BFE5121B07; Wed, 16 Feb 2011 11:48:56 -0700 (MST) From: d@taht.net (Dave =?utf-8?Q?T=C3=A4ht?=) To: Sean Conner Organization: Teklibre - http://www.teklibre.com References: <20110216174627.GA20215@brevard.conman.org> Date: Wed, 16 Feb 2011 11:48:56 -0700 In-Reply-To: <20110216174627.GA20215@brevard.conman.org> (Sean Conner's message of "Wed, 16 Feb 2011 12:46:27 -0500") Message-ID: <87k4gzke7b.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=us-ascii Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] Background Bufferbloat Detector 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, 16 Feb 2011 18:49:01 -0000 Sean Conner writes: > I've been thinking about this background bufferbloat detector, and I > am wondering why you are bothering with NTP? I understand about the > timestamps, but wouldn't it be easier if you had a program that sent > packets at a known fixed rate? I wrote a simple program that sends a > UDP packet every 20ms; the receiver (same program, different options) > records when it received the packet (which should be 20ms since the > last packet received). It then records the actual delta to a file > (which can later be graphed). We can do the same with voip or tcp connections that are also timestamped. The problem is that it requires active measurement, and both ends to be co-operating. The NTP idea: NTP is a "background" process, one that uses statistically sparse data spread across millions of machines, that can be cut up in a dozen different interesting ways. There are only 10s of thousands of NTP servers in the world. Nearly every vendor configures their own NTP server choice for their OS or platform. Nearly ever ISP provides NTP servers. And they are all mostly slaved to atomic clocks. NTP also is sourced on port 123 and dest 123 - so we can tell the difference between NATTed and non-natted hosts I obviously am loving this idea... But it involves building a tool that the ISP or pool operator can run, in order to detect it server side. > Running it I do see variations in the timings; I'm wondering if what I did > is actually relevent to detecting bufferbloat? Might be. > > -spc (Also, just to mention: it can be used on an IPv6 network, and can > handle multicast addresses for sending and receiving) > > > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat -- Dave Taht http://nex-6.taht.net