From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail2.tohojo.dk (mail2.tohojo.dk [77.235.48.147]) (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 EAEE121F1FF for ; Mon, 27 Apr 2015 03:24:04 -0700 (PDT) X-Virus-Scanned: amavisd-new at mail2.tohojo.dk Received: by alrua-kau.kau.toke.dk (Postfix, from userid 1000) id EE4EFC40134; Mon, 27 Apr 2015 12:23:55 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toke.dk; s=201310; t=1430130236; bh=NcyLBE9tkEE47Ux6yKE/FU8YaIy1ETxd7gdJnr3WjvY=; h=From:To:Cc:Subject:References:Date:In-Reply-To; b=gqFLKP4E25PF/f+YzR0Ml0mME2MXoFejeXCYQWatri1PTULOa7T7ObQDf1SjSG1L7 R1IvYVTLhW7dJvVED7hINTYx7CpodUxnFgWww9kH2juSftV8V/pDOccegXoNsrZSsX CjoTiO9sh/8ygKWGTb5a661wJNfi31324LpbxL5E= From: =?utf-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= To: Paolo Valente References: <87r3r53ncb.fsf@toke.dk> <04A0C729-6E87-49C6-84F7-3428F236CA15@unimore.it> <3DC1A2EA-6DDD-4FF9-AD12-BB509EFB96B8@unimore.it> Date: Mon, 27 Apr 2015 12:23:55 +0200 In-Reply-To: <3DC1A2EA-6DDD-4FF9-AD12-BB509EFB96B8@unimore.it> (Paolo Valente's message of "Mon, 27 Apr 2015 12:19:26 +0200") X-Clacks-Overhead: GNU Terry Pratchett Message-ID: <87k2wx3m4k.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain 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 10:24:33 -0000 Paolo Valente writes: > I am sorry, but I realized that what I said was incomplete. The main > cause of my concern is that, from outside the node, we do not know > whether a VoIP packet departs ad a given time because the application > wants it to be sent at that time or because it has waited in the > buffer for a lot of time. Similarly, we do not know how long the VoIP > application will wait before getting its incoming packets delivered. No, not unless the application tells you (by, for instance, timestamping; depending on where in the network stack the timestamp is applied, you can measure different instances of bloat). Or if you know that an application is supposed to answer you immediately (as is the case with a regular 'ping'), you can measure if it does so even when otherwise loaded. Of course, you also might not measure anything, if the bottleneck is elsewhere. But if you can control the conditions well enough, you can probably avoid this; just be aware of it. In Linux, combating bufferbloat has been quite the game of whack-a-mole over the last several years :) -Toke