From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.17.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 656053B29E for ; Mon, 13 Mar 2023 14:50:16 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.de; s=s31663417; t=1678733413; i=moeller0@gmx.de; bh=tRdG3P0l1Ct6DUK1hUjwRqbf8kIfUfo/IhOK94VnAtc=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References:To; b=ATWt+kDhV/cF5mtHGJu69snWxd0Xj3ffPe8Oq3Dwmm1sLzTRGnz/RRW1q8uMKCjCN o6egKNS90RCc7+WKbvoN3KL+7xLaI9JxxYf7FS0l+9LQsTGpruPyl1qOLfG1Pen9l5 T+HPTFSTroZ/lQZiTj2Dyrlc4FA4Qx+t61+0CSOsfOEgbzfNeDuVnejyVQHxLhHmvt /qNMhhn/NihMHtfYJURe8IhdcThFugfXeD5Yxi5/KNhVJZn9BsO2ME3QMvCNYlkddg +poilWX/gbrHV8D1jkn8F2YOCvuHvW70cnDKKL7aOB2Yh6C/E+mBYIAq63YCbgAtMO RmFUT5+AwEmQA== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from smtpclient.apple ([134.76.241.253]) by mail.gmx.net (mrgmx105 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MG9kC-1plebh0YVo-00GZeG; Mon, 13 Mar 2023 19:50:13 +0100 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.2\)) From: Sebastian Moeller In-Reply-To: Date: Mon, 13 Mar 2023 19:50:12 +0100 Cc: bloat@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: References: <1672786712.106922180@apps.rackspace.com> <77CCAD19-07E0-4F9E-88C1-D207CF7BF376@cable.comcast.com> <83ffc0dad19e3343e49271889369cefc@rjmcmahon.com> <45AA2C67-CC59-4222-991C-F43D08699F90@gmx.de> To: Dave Collier-Brown X-Mailer: Apple Mail (2.3696.120.41.1.2) X-Provags-ID: V03:K1:Dcum9Gv5+llZi0cE1hAaI1t2HF1/Z2zUZIDlATZDaKZx9JILsO4 u0uXT5Vco+/kHLJB2eMryFcnut395dawcnnUXyQpk6ULa507g0AUroOMW3nuAGYGRp+TlOf eCjjyleva1Mvu5DuZV/dR9WvmYss4JTH5xZNS38OK+Xa0nvfpA6vD1XcHnQkxHEAxb5LkUb TKbyMpX12xAP29ZVxdS5Q== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:1NhVKETLFaU=;fPYioLv3cpY0h1BmhFWdWMSAoqQ lZlwr4nKm5gSGdT1olfOxB5naAIlWXxXbLEiCpUxFdyDVyvDRNE3JUD+O8HtVdNZyl4tmmyHl +ZAC7NMjn+ASn0I86H6CSVEgta8BwBuKq/K2h/+/+hUJeiYcTppKur/upROd0Ob82oF/RIXM4 Mql3rCAABASQiu12mltDnauLC5Ct286LvK/ZITt8a3BYgzgTTjUDUDlZ8Xi/bSokwncMS1y8k 41wHoaB++GgM3dhEEiZFZHxmVX9ph0W/nYxkkdXeRYImYCFAd8Q7KKIfRZMpSRlYvKzmS4x0/ 9n3JKc2miFEm4j6TWNioT1Dbg4hsj0ZxaHsZ0LfOJX1XVVMIC7j1uw37P8oGyYUqfTzEsHuUW n0jj/b1OeOi4qDiwkYFPyXiE8+N5UQvdsbjCEtYIQ/CsD1gZoNvCGg0HFL369eHcAuYy5A2K4 MyKLecKrlcstglfVRMiW97E0eVzPvQe6tySa0cUwuZcFzqDo0RUGiBvXnVnXQkYX+UeUMs0Ts Bt2NTv1tNAxy+q8hjpRixBTMS7jN+KlKSa3mbmVM+I4foP//NhmzSJkQv64tN2X6tc4C8Hq/a FX4gVA3Rgdr4xg/bt5ZHEm5KFSrNOyv4mZjTJZugpwKvdd6Cjurc9btPHQ1SF78RjXCUcUc2k mxGvOudKQITlMlEn+By2qJ7kgJIVZjwuKFbYgODpdkV0P4YeX2vwUFdprM14BIRrs2mDSP28k NBrEnDMlk+yNsDrsIMbXoODst0cs1YeSrASHCvTTSDzJWbN9pzO0LKJ0ObPYXTpZtNhM6cCc+ bnIM2u4lD+P3GmqmDzMGvlARqww75MqWcS1xyCRiRj7FrJ4AF/TtXJAS8OKFhh4/RsVThMqOn B+GkVve8HC3n0U4QvGYcE7HK20Vwwj0vXPOdU5sq6aNjjRRkxi5VTTSuf0V76CeisM46pFbff E6zhvbGtZg/1FwvMUE2d4Bdneu4= Subject: Re: [Bloat] Offtopic: passive ping. was: Researchers Seeking Probe Volunteers in USA X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Mar 2023 18:50:16 -0000 Hi Dave, > On Mar 13, 2023, at 19:22, Dave Collier-Brown via Bloat = wrote: >=20 > On Mon, Mar 13, 2023 at 3:02=E2=80=AFAM Sebastian Moeller via Starlink = wrote: >=20 >> [SM] OK, I will bite, how do you measure achievable throughput = without actually generating it? Packet-pair techniques are notoriously = imprecise and have funny failure modes. >=20 >=20 > When you mention packet-pair techniques, are you referring to Kathleen = Nichols' passive ping work, or some other correlation scheme? [SM] I am referring to what I thought was the classical packet = pair method, send two (or more) packets back to back and measure their = temporal distance at the receiver then deduce the actual capacity from = looking at spacing change as a function of the known packet size... so = if I sent 2 packets of 100 units through a path of 100000 units/time = with a small bottleneck of 10 units/time in the middle, the packets = leave back to back, now they queue behind the bottleneck and the first = starts to squeeze through taking 10 time units before it can be = transmitted further, same for the second packet, now they are spaces = with a distance of 10 time units when they hit the receiver and the = receiver can estimate the bottleneck capacity. Now I am sure this is the packet-pair for dummies variant and real = methods are a bit more refined, but that is the gist. And it is known = not to work robustly and reliably over the internet (some link = technologies actually batch up packets or some links send packets in = parallel*). One can probably make up for that by a healthy amount of = averaging, but doing so makes these capacity estimates less and less = immediate. Side-note: paced chirping, as far as I understand is a clever extension = of this idea, that suffers from the same problem, that packet pair = measurements work great in the lab. less so over the internet. Side-side-note: you can extend the same idea also and use packets of = different length to measure capacity. I did that accidentally as part of = my old ATM over head detector approach, where the linear fit of RTT as = function of ICMP packet size correlated really well with the inverse sum = of uplink and downlink capacity IIRC. Which was neat, but useless and it = required linear fitting, if only due to ATM/AAL5's peculiar quantization = issues, but I digress. > I'm interested in the idea of measuring packet timings to our = customers as a way of detecting short-lived issues, which I find = excessively annoying to detect and quantify (;-)) [SM] Ag, that might actually work, because you are not aiming = for "over the whole internet" but over a well known segment mostly under = your control, no? I assume you address this with an ISP hat on, not with = a content provider hat on? Regards Sebastian *) e,g. measly DSL links essentially use ODFM and send quite a bunch of = bits in parallel, so even if a DSL link is the capacity bottleneck, our = back to back pair might traverse that link in one fell swoop fooling us = about the available capacity. >=20 > --dave >=20 > --=20 > David Collier-Brown, | Always do right. This will gratify > System Programmer and Author | some people and astonish the rest >=20 > dave.collier-brown@indexexchange.com | -- Mark Twain >=20 > CONFIDENTIALITY NOTICE AND DISCLAIMER : This telecommunication, = including any and all attachments, contains confidential information = intended only for the person(s) to whom it is addressed. Any = dissemination, distribution, copying or disclosure is strictly = prohibited and is not a waiver of confidentiality. If you have received = this telecommunication in error, please notify the sender immediately by = return electronic mail and delete the message from your inbox and = deleted items folders. This telecommunication does not constitute an = express or implied agreement to conduct transactions by electronic = means, nor does it constitute a contract offer, a contract amendment or = an acceptance of a contract offer. Contract terms contained in this = telecommunication are subject to legal review and the completion of = formal documentation and are not binding until same is confirmed in = writing and has been signed by an authorized signatory. >=20 > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat