From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-x22e.google.com (mail-qt0-x22e.google.com [IPv6:2607:f8b0:400d:c0d::22e]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 0406F3B2A4 for ; Tue, 12 Dec 2017 17:41:45 -0500 (EST) Received: by mail-qt0-x22e.google.com with SMTP id i40so1215275qti.8 for ; Tue, 12 Dec 2017 14:41:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=sZqwr4fHda2SZSnz7UATtZGkYkcbA9cixLVKUKsJF/k=; b=OKxwU73gilUkVav9R7zfdLx2RkLhZKH5je+Z5Je3j/5VL6QIuatpDIvSCp3ywzTns9 XYdlq6nIydyynQwZId8dQaqCoi0fVeBaD7HXFWN3y+PMuxjayR04G/FPrR8S3fxNFr8+ 9iszDSyUi5L5G/nAl3799+VPP79B+IvpNar0XcDYqztqxzXfgVSzBy6OvduqcVaOXD64 OYuycbkAe3a53yV3NGBtgoOBTL+ps7Y7xxgtqsivV50Bj/TVEWhsbxIgJfGJH0vp67rN exT5ga+q6TWG2t4OK8vh5cZgs9MFXyfk+SIQtLTYHQvxwzcgW9Lg61QQKKhRp1ru/JCD sKWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=sZqwr4fHda2SZSnz7UATtZGkYkcbA9cixLVKUKsJF/k=; b=H/FqPDHhkvRDtHjFVS8bhJJ4Pc0nXcFrKJcpxVwkayYFIKFx3YGdbd49xoW34MjagU IC465lZGyTmDiD4bewuKktqxOuLF8neMHAwnT4BjBsVoiTghXQtptFu3CXfkYNzrDFoE et7/MMaE/7kI2VbgEHlNDuxdI9d7bh57HtiK9hgocz2KiUmrBNdu182R6ob0Emuq+pxa yRNzTJGaAV15N0fu1gMTrDn1XlxtZUMdT5P1muJ2jq1NnWgKBqJuWacFY5xaQopBkVc0 FrqEcaVoaF/mb5WBrNaidI+eLHlQnnM21kBH3fzyFPfK+x48wnALLP7yhghohvJphyi/ 4orQ== X-Gm-Message-State: AKGB3mJy0HLMYwCHiq5iSDGbx7+2HvsxOvdYGyN/t4a4ov8UR6zFt60r XknCyDrl06yQYMz6W7mXyROviVw3yCJU06SYGEw= X-Google-Smtp-Source: ACJfBovsR34gsCh9fzYRMF1bj37W3lREYsHkYXyWKOnItEP7da1ABAy5B7sX6zpiFOaT5m5RCQoMtO9FQPR7iLgfo/w= X-Received: by 10.237.59.183 with SMTP id r52mr8026261qte.121.1513118505580; Tue, 12 Dec 2017 14:41:45 -0800 (PST) MIME-Version: 1.0 Received: by 10.140.102.179 with HTTP; Tue, 12 Dec 2017 14:41:44 -0800 (PST) Received: by 10.140.102.179 with HTTP; Tue, 12 Dec 2017 14:41:44 -0800 (PST) In-Reply-To: References: <4D0E907C-E15D-437C-B6F7-FF348346D615@gmx.de> <019064B3-835C-4D59-BE52-9E86EE08CD02@gmx.de> From: Jonathan Morton Date: Wed, 13 Dec 2017 00:41:44 +0200 Message-ID: To: David Lang Cc: Benjamin Cronce , bloat Content-Type: multipart/alternative; boundary="94eb2c192110073ca805602c5b5a" Subject: Re: [Bloat] benefits of ack filtering 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: Tue, 12 Dec 2017 22:41:46 -0000 --94eb2c192110073ca805602c5b5a Content-Type: text/plain; charset="UTF-8" Actually, the cost argument goes the other way. You need heavy DSP to *receive* high bandwidths; sending it is much easier computationally. Also, in aggregate a hundred cheap CPE boxes probably have more DSP horsepower than the one head-end box serving them. What the centralised head-end has an advantage in is transmit power, and thus SNR. This feeds into Shannon's equation and supports your argument more directly. In ADSL this is partly compensated for by assigning the lower frequency carriers to the upload direction, since they have less loss than high frequencies on a copper pair. However, in the most extreme examples I've seen, the level of asymmetry has little to do with the underlying link technology and more to do with how the provisioning was arbitrarily set up. Things like ADSL with an unrestricted downlink sync rate but uplink limited to 128k. Or DOCSIS with a huge headline bandwidth for downlink, and no obvious mention (until you've paid for it, set it up and measured it) that the uplink shaper is set to about a fiftieth of that. I seriously doubt that DOCSIS is ever inherently that asymmetric. - Jonathan Morton --94eb2c192110073ca805602c5b5a Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

Actually, the cost argument goes the other way.=C2=A0 You ne= ed heavy DSP to *receive* high bandwidths; sending it is much easier comput= ationally.=C2=A0 Also, in aggregate a hundred cheap CPE boxes probably have= more DSP horsepower than the one head-end box serving them.

What the centralised head-end has an advantage in is transmi= t power, and thus SNR.=C2=A0 This feeds into Shannon's equation and sup= ports your argument more directly.=C2=A0 In ADSL this is partly compensated= for by assigning the lower frequency carriers to the upload direction, sin= ce they have less loss than high frequencies on a copper pair.

However, in the most extreme examples I've seen, the lev= el of asymmetry has little to do with the underlying link technology and mo= re to do with how the provisioning was arbitrarily set up.

Things like ADSL with an unrestricted downlink sync rate but= uplink limited to 128k.=C2=A0 Or DOCSIS with a huge headline bandwidth for= downlink, and no obvious mention (until you've paid for it, set it up = and measured it) that the uplink shaper is set to about a fiftieth of that.= =C2=A0 I seriously doubt that DOCSIS is ever inherently that asymmetric.

- Jonathan Morton

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