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 TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id BD0AE3BA8E for ; Fri, 4 Jan 2019 12:43:55 -0500 (EST) Received: by uplift.swm.pp.se (Postfix, from userid 501) id 58B09BD; Fri, 4 Jan 2019 18:43:54 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=swm.pp.se; s=mail; t=1546623834; bh=kMpmX616T27ZLpvp47D9uGWPoqc/yajZvM1ZYfbp0AA=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=h5Oqa5JevO+XqEOxLFzA+4WG8J9ElFMRMmZBOYaIDSYX73CM0GcMJdv8VTLdhlZt3 Wf5rXPUyxT6/Q1BT9O3wZamSq+XSmTcScDUPDnkvph/GFBi5RT2/X90Y44LHETNSaK yUP/xwwTrp0wDWRM6Z41s8EvbenjnaidFfFkCOrE= Received: from localhost (localhost [127.0.0.1]) by uplift.swm.pp.se (Postfix) with ESMTP id 55E36B3; Fri, 4 Jan 2019 18:43:54 +0100 (CET) Date: Fri, 4 Jan 2019 18:43:54 +0100 (CET) From: Mikael Abrahamsson To: Dave Taht cc: cloneman , bloat In-Reply-To: Message-ID: References: User-Agent: Alpine 2.20 (DEB 67 2015-01-07) Organization: People's Front Against WWW MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Subject: Re: [Bloat] Does VDSL interleaving+FEC help bufferbloat? X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 04 Jan 2019 17:43:55 -0000 On Fri, 4 Jan 2019, Dave Taht wrote: > dsl interleave was added primarily to make multicast udp tv streams work > better (as they are very intolerant of packet loss). Often (as in free's > implementation) these streams are "invisible" to the overlying IP > applications. It typically adds at least 6ms of delay to an already slow > technology. ADSL2+ is very prone to short bursts of interference, so setting no interleaving means quite high packet loss. Setting interleaving to 16ms means FEC has a much better chance of correcting errors and thus reduce packet loss. At several jobs ago we actually had several different profiles for customers, they could choose 1, 4 or 16ms interlaving depending on their needs for gaming etc. The 1 and 4 ms interleaving targets had different SNR margin targets so they were sacrificing speed for lower latency, because that's the tradeoff you basically have to do with normal L4 protocols that end customers typically use. -- Mikael Abrahamsson email: swmike@swm.pp.se