From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.sms.unimo.it (smtp1.sms.unimo.it [155.185.44.147]) (using TLSv1 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id CAF7921F22F for ; Mon, 27 Apr 2015 04:55:03 -0700 (PDT) Received: from [212.84.39.131] (port=55647 helo=[192.168.15.101]) by smtp1.sms.unimo.it with esmtpsa (TLS1.0:RSA_AES_128_CBC_SHA1:128) (Exim 4.80) (envelope-from ) id 1Ymhcl-0002uR-Oc; Mon, 27 Apr 2015 13:55:01 +0200 Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Content-Type: text/plain; charset=us-ascii From: Paolo Valente In-Reply-To: <72DB0260-F0DF-426F-A3F3-ECF5D8AF228F@pnsol.com> Date: Mon, 27 Apr 2015 13:54:42 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: References: <72DB0260-F0DF-426F-A3F3-ECF5D8AF228F@pnsol.com> To: Neil Davies X-Mailer: Apple Mail (2.1878.6) UNIMORE-X-SA-Score: -2.9 Cc: bloat Subject: Re: [Bloat] Detecting bufferbloat from outside a node 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: Mon, 27 Apr 2015 11:55:32 -0000 Thanks for the pointers. As for the epistemological implications of to = my concerns, I must admit that I find them a little bit frightening :) After browsing some of the presentations, the relevant component for my = problem seems to be the variability V. However, it is not clear to me = how I can measure or infer it in my situation, i.e., if I cannot: 1) have any feedback on the user experience; 2) measure the time that elapses between when a time-sensitive = application puts a message in a socket and when that message is actually = sent by the node in a packet; 3) in the opposite direction, measure the time that elapses between when = a packet arrives to the node and when the application receives the = message contained in the packet. On which documents should I concentrate more to better understand this = point? Thanks, Paolo =20 Il giorno 27/apr/2015, alle ore 11:54, Neil Davies = ha scritto: > Paolo >=20 > Yes, it is - there is a whole methodology for detecting this and = associated algebra for manipulation. It has been used at CERN, in = various telcos and in various large scale, real time distributed systems = to relate end user outcomes to the delay/loss characteristics of the = network. >=20 > Take a look at http://www.pnsol.com/publications.html, you may find = http://www.pnsol.com/public/PP-PNS-2009-02.pdf as a good starting point. >=20 > Neil >=20 > On 27 Apr 2015, at 10:48, Paolo Valente = wrote: >=20 >> Hi, >> a network-monitoring company got curious about bufferbloat issues and = asked me to investigate a little bit the following issue (quite = interesting in my opinion). Is it possible to detect, from outside a = node, if the node is bufferbloated? In particular, the only action = allowed would be to observe the packets entering and leaving the node = (plus, of course, their timing). >>=20 >> If such a general problem is to hard or impossible to solve, do you = think it is still possible at least to understand, for some type of = application, if the application is experiencing a high latency because = of bloated buffers inside the node? (As above, by just observing packet = flows from outside the node.) >>=20 >> Thanks, >> Paolo >>=20 >> _______________________________________________ >> Bloat mailing list >> Bloat@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/bloat >=20 -- Paolo Valente =20 Algogroup Dipartimento di Fisica, Informatica e Matematica =09 Via Campi, 213/B 41125 Modena - Italy =20 homepage: http://algogroup.unimore.it/people/paolo/