From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from uplift.swm.pp.se (swm.pp.se [212.247.200.143]) (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 C63CE21F240 for ; Wed, 30 Apr 2014 01:30:15 -0700 (PDT) Received: by uplift.swm.pp.se (Postfix, from userid 501) id 772ACA6; Wed, 30 Apr 2014 10:30:12 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=swm.pp.se; s=mail; t=1398846612; bh=mPgRTFiaF9hdORLlcrSWsuzBzQMDr2//hP5t7X+4Ybs=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=TyDqwkLbLeQHvZc3eCTdIwqN1TCagxQuZe0k4vAgGNfxZ7fNYe1LHzrYJZbFSd9Hq ARULSzqPqU0XFGQ3iwGIVSQvzAKSDPccUNkz96nxwivXw2gurfQHvzwmSqDXChRXbw moN+T1BPAKxHlGTFoiWWhVtVUy03z3Yu7UhzAr2U= Received: from localhost (localhost [127.0.0.1]) by uplift.swm.pp.se (Postfix) with ESMTP id 73030A5; Wed, 30 Apr 2014 10:30:12 +0200 (CEST) Date: Wed, 30 Apr 2014 10:30:12 +0200 (CEST) From: Mikael Abrahamsson To: Jan Ceuleers In-Reply-To: <53609DFA.9040708@gmail.com> Message-ID: References: <4130D000-FE28-4A5E-B824-3371C1602472@cisco.com> <87bnvkkr2n.fsf@toke.dk> <53609DFA.9040708@gmail.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) Organization: People's Front Against WWW MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="-137064504-467841536-1398846612=:29282" Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] [aqm] the side effects of 330ms lag in the real world 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: Wed, 30 Apr 2014 08:30:16 -0000 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---137064504-467841536-1398846612=:29282 Content-Type: TEXT/PLAIN; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8BIT On Wed, 30 Apr 2014, Jan Ceuleers wrote: > On 04/29/2014 07:01 PM, Toke Høiland-Jørgensen wrote: >> However, as that graph shows, it is quite possible to completely avoid >> bufferbloat by deploying the right shaping. And in that case fibre >> *does* have a significant latency advantage. The best latency I've seen >> to the upstream gateway on DSL has been ~12 ms. > > I am not an expert, but I believe that this is due to the use of > interleaving. This is a method to improve the strength of forward error > correction by spreading out the effects of impulse noise on DSL lines > across multiple reed-solomon-protected codewords at the expense of > latency. You're exactly correct. ADSL2+ interleaving can be set to 0 (off), 4, 8 or 16 milliseconds in the downstream direction and 0(off), 1, 2 or 4 in the upstream direction (if memory serves me right, it was 8 years ago I did this last). So to avoid lost packets due to impulse noise, most set this to 16+4, and plus the regular encoding delay for ADSL2+, you often end up with around 25ms RTT to the DSLAM. -- Mikael Abrahamsson email: swmike@swm.pp.se ---137064504-467841536-1398846612=:29282--