From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from srv01.voixit.com (srv01.voixit.com [78.47.68.188]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id 29C7A21F228 for ; Mon, 27 Apr 2015 03:10:45 -0700 (PDT) Received: from [192.168.15.101] (unknown [212.84.39.131]) by srv01.voixit.com (Postfix) with ESMTPS id 830A0C005A; Mon, 27 Apr 2015 12:10:41 +0200 (CEST) Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Content-Type: text/plain; charset=iso-8859-1 From: Paolo Valente In-Reply-To: <87r3r53ncb.fsf@toke.dk> Date: Mon, 27 Apr 2015 12:10:40 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <04A0C729-6E87-49C6-84F7-3428F236CA15@unimore.it> References: <87r3r53ncb.fsf@toke.dk> To: =?iso-8859-1?Q?Toke_H=F8iland-J=F8rgensen?= X-Mailer: Apple Mail (2.1878.6) 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 10:11:14 -0000 Il giorno 27/apr/2015, alle ore 11:57, Toke H=F8iland-J=F8rgensen = ha scritto: > Paolo Valente writes: >=20 >> 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 > Sure. Just measure the timing when the network is unloaded and compare > it to when it is loaded to capacity. We do that all the time. >=20 > The details of course depend on what you define by a 'node', what role > it plays in the network (does it forward or originate packets?), and > what control you have over the traffic flowing through it. :) >=20 Let us consider, for example, a host with a VoIP call and a large-file = transfer in progress. My concern is: from inside the host, we can = measure the delays experienced by the VoIP application, but, form = outside, how can we detect that the application is experiencing a high = latency, or, indirectly, that there is bufferbloat and hence that the = application is likely to be experiencing a high latency? (Of course, I = am also about to read the documents suggested by Neil.) Thanks, Paolo > -Toke -- 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/