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 3B52021F210 for ; Fri, 24 Apr 2015 06:58:17 -0700 (PDT) X-Virus-Scanned: amavisd-new at mail2.tohojo.dk Received: by alrua-kau.kau.toke.dk (Postfix, from userid 1000) id D01A0C40258; Fri, 24 Apr 2015 15:58:03 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toke.dk; s=201310; t=1429883884; bh=w1EmJQBZQjaYj5mFnjr/Mkuwqu+vK8ENdSvJR3MHJDo=; h=From:To:Cc:Subject:References:Date:In-Reply-To; b=liEBb5oSwZeQNDCurXeTWZ9A3hbmlwwsKZd2zwtGEAB0TqDD3PGLdQjJQ2WkS2DKY 21ueoZerK4p0UGMx9CdvYCTkHbK943yqp/YJTVjyQg/D5J/O+sbFTkbws18iOydIav tW9iVnlwKQUYCOX/EqFPsnojdIJyB49POhX4JrCA= From: =?utf-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= To: jb References: <20150422040453.GB36239@sesse.net> <1429676935.18561.42.camel@edumazet-glaptop2.roam.corp.google.com> <12383_1429692679_55376107_12383_9099_1_p7gmr0psut68sen0sao8o4lp.1429692550899@email.android.com> <1429710657.18561.68.camel@edumazet-glaptop2.roam.corp.google.com> <25065_1429716388_5537BDA4_25065_2328_1_63pyislbvtjf653k3qt8gw2c.1429715929544@email.android.com> <1429717468.18561.90.camel@edumazet-glaptop2.roam.corp.google.com> <5537CDB7.60301@orange.com> <1429722979.18561.112.camel@edumazet-glaptop2.roam.corp.google.com> <5537DA20.1090008@orange.com> <5537DE4D.8090100@orange.com> <1429771718.22254.32.camel@edumazet-glaptop2.roam.corp.google.com> <6C0D04CF-53AA-4D18-A4E4-B746AF6487C7@gmx.de> <87wq123p5r.fsf@toke.dk> <2288B614-B415-4017-A842-76E8F5DFDE4C@gmx.de> <87sibp526w.fsf@toke.dk> Date: Fri, 24 Apr 2015 15:58:03 +0200 In-Reply-To: (jb's message of "Fri, 24 Apr 2015 23:32:22 +1000") X-Clacks-Overhead: GNU Terry Pratchett Message-ID: <87k2x14oic.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain Cc: bloat Subject: Re: [Bloat] DSLReports Speed Test has latency measurement built-in 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: Fri, 24 Apr 2015 13:59:03 -0000 jb writes: > Ok I think I talked myself around in a complete circle: a buffer is > only bad IF it increases latency under load. Not because of its size. Exactly! :) Some buffering is actually needed to absorb transient bursts. This is also the reason why smart queue management is needed instead of just adjusting the size of the buffer (setting aside that you don't always know which speed to size it for). > It might explain why these fiber connection tests don't show much > latency change, because their buffers are really inconsequential at > those higher speeds? Well, bufferbloat certainly tends to be *worse* at lower speeds. But it can occur at gigabit speeds as well. For instance, running two ports into one on a gigabit switch can add quite a bit of latency. For some devices, *driving* a fast link can be challenging, though. So for fibre connections you may not actually bottleneck on the bloated link, but on the CPU, some other link that's not as bloated as the access link, etc... -Toke