From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-22-ewr.dyndns.com (mxout-117-ewr.mailhop.org [216.146.33.117]) by lists.bufferbloat.net (Postfix) with ESMTP id 228D32E00F5 for ; Sun, 13 Mar 2011 07:24:30 -0700 (PDT) Received: from scan-21-ewr.mailhop.org (scan-21-ewr.local [10.0.141.243]) by mail-22-ewr.dyndns.com (Postfix) with ESMTP id 51CBF2E664 for ; Sun, 13 Mar 2011 14:24:29 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 209.85.215.171 Received: from mail-ey0-f171.google.com (mail-ey0-f171.google.com [209.85.215.171]) by mail-22-ewr.dyndns.com (Postfix) with ESMTP id 6A08341D55 for ; Sun, 13 Mar 2011 14:24:24 +0000 (UTC) Received: by eydd26 with SMTP id d26so1585698eyd.16 for ; Sun, 13 Mar 2011 07:24:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:subject:mime-version:content-type:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to:x-mailer; bh=8ZOAb/fi8xyzOd+hM7rDvOxlqT/NJ5mBqBIN52KhrLU=; b=VLjb8QE5EmL0LHI9L5/PWw6tdGWin3XB3ZIn8dpDJKbi6dfQElWoik4I6x7GAAW4xm KTWp9F43/5a7MAnBITwGDebGB4URA6z0KJNw13zCf7fXfVcoVVdEtoDrZ/vwWRh/76w2 yCQ4cfaojz+7Z6RtZDcn1H/eXRoFdw+UKhJaU= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer; b=dp6Jj7Mkx3MfZHpQV1qu5Hkyra8z4z4HcU8bNdqj3mk+8dM0fXLkKIH8hx5Cn0USvV SpdCx+xGVt0upL29jtqQSjTzdG46HndT8jZTM5hBqZOmvVVgNNleuI5FIU7kf9GhSDrG 6ctcSSURZnLmuRc0sblpxm5kyDQzm9MYbM4kU= Received: by 10.213.5.12 with SMTP id 12mr811498ebt.100.1300026263596; Sun, 13 Mar 2011 07:24:23 -0700 (PDT) Received: from [192.168.239.42] (xdsl-83-150-84-172.nebulazone.fi [83.150.84.172]) by mx.google.com with ESMTPS id x54sm5116079eeh.11.2011.03.13.07.24.22 (version=TLSv1/SSLv3 cipher=OTHER); Sun, 13 Mar 2011 07:24:23 -0700 (PDT) Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: text/plain; charset=us-ascii From: Jonathan Morton In-Reply-To: Date: Sun, 13 Mar 2011 16:24:21 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <9F62E180-9379-4567-BA19-87C9F96B6F7E@gmail.com> References: <16808EAB-2F52-4D32-8A8C-2AE09CD4D103@gmail.com> <08621605-30D1-4916-82EE-A4219A653ACD@cisco.com> <4A5D7592-685F-45CC-9429-CE7FC1A289B5@gmail.com> To: Fred Baker X-Mailer: Apple Mail (2.1082) Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] Measuring latency-under-load consistently 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: Sun, 13 Mar 2011 14:24:31 -0000 On 13 Mar, 2011, at 8:54 am, Fred Baker wrote: >>> At the risk of sounding like someone mentioning a product, let me = mention a product. This assumes, of course, that you're using Cisco = equipment. But it allows you to measure delay (how long does it take to = get from here to there), jitter (first derivative of delay/dt), and = packet loss. >>=20 >> Ping does most of this, and is available on your actual computer. A = little post-processing of the output gives you jitter, if it doesn't = supply that natively. >>=20 >> The point is, the existing tools don't typically measure latency = *under load*. >=20 > Actually, SAA uses ping, and is intended precisely to do it under = load. Ping is part of the existing traffic, and measures the RTT as = experienced by traffic following the same path that the ping does. >=20 > Not sure exactly where you're going with that... While you, and I, and other professional researchers and administrators = are quite capable of generating a consistent, relevant load and then = measuring around it... we're the exceptional people. Most people don't = know jitter from a hole in the ground, they just know that Skype doesn't = work. The tool I'm working on does it in an integrated fashion, so the = potential for user errors (or plain old marketing BS) creeping into the = measurement is reduced. That is, it generates the load and measures the = effect on latency in one step. The ability to measure some interesting = things about the bulk flows at the same time is icing on the cake. I do have consumer-grade connections in mind for this, though no doubt = it will also be useful on professional-grade networks - especially = wireless ones. The consumer space is where the worst problems are = currently visible. - Jonathan