From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x730.google.com (mail-qk1-x730.google.com [IPv6:2607:f8b0:4864:20::730]) (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 DF3253CB38; Wed, 4 Aug 2021 14:28:28 -0400 (EDT) Received: by mail-qk1-x730.google.com with SMTP id 14so3687555qkc.4; Wed, 04 Aug 2021 11:28:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=q/orTbOxMFXsdT03Rd63uTtLbEyCrL6ctC7mNzMqvlY=; b=cg2llZ5RacyqMO/R6tBxl1o4J0Hzo4jdHrzhR+jT39YWFigO2WCjSugqDTGdgTS5Wd UbAtQMIp4M5M1+1PhF49se8lh1CQ/zOmIRQWvRAE/dUVQZvyeToZyAUEa6jHb60oVyor gS8q9kaWqh+7uVlTmadmVc3nQnsHDvXH8gJHh1mXr9b0TIYn+1J+d2JPeo/C2xD54JPl yPWD725bUu+XOXBq2nwsNrkXLDtJL1NoSG64ZTe/vy+1775bsB7zq9HmukyBIDn516G7 fYdICTPnSIiInnyoWhZT1qNDE1Dn3wZdN7nOsrts6VToRpcur3w7hoIk7wL1ipYlRyuH UdGQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=q/orTbOxMFXsdT03Rd63uTtLbEyCrL6ctC7mNzMqvlY=; b=ii0QRbWLIBlJCMF3HF/HkSzeLK4clxUV68W6xWokI0KX2bpzTd09ZMYupp4v9oVFds 9ud+YdEscH9NliAqaXym7IJZpdU6pgvUW/8ccElEaqbBDslXE8OWTtR4HtGhBX4X0doV OjqAuhthQL+uHnX5w4cWSl0FVFLUQorJiBjpX0IAuzGpSDwhGTvq+jecwVT9ehXXm31q ld6B5Zkw+Oa2IYPSp3ha5yjGRhctpnhnrC7cn4Oc10eXy7XJ5v+ggGo3mPd4KHhcH9pM caPuxltbgiT1Qxsb4ZvJOUQyeGbc1pFqMxZu11bufzasaTPiggSgKyhvY/QXYolmFYDi uOGw== X-Gm-Message-State: AOAM533Zxkpu0xCc8Q6cNjm7e2GEyIqpg5+NO1tsQc8r627lDrBN2C1z oycPBPeTnkN4G4p0TWn3feZwGBn+g9hF0lJm/GM= X-Google-Smtp-Source: ABdhPJxfEGSRy3yJbXGmm6YE+gUnY6SBkouhuv5dIr5QOuYKeFgYxDZzWZXXu7z5x9i+eTzG1uQwWZ0pVjLJ4KItroY= X-Received: by 2002:a37:2d04:: with SMTP id t4mr828984qkh.160.1628101708354; Wed, 04 Aug 2021 11:28:28 -0700 (PDT) MIME-Version: 1.0 References: <058681B8-89EB-42ED-8E82-4048BA3C9504@cable.comcast.com> <649DC4B024D74B8BA6926ABFCD52DC79@SRA6> <5C65BC6E-1ABD-4432-B2CE-AC8BACDA363D@gmx.de> <8393833B-BE11-4B97-92CC-95C2B48305B9@gmx.de> In-Reply-To: <8393833B-BE11-4B97-92CC-95C2B48305B9@gmx.de> From: Jonathan Morton Date: Wed, 4 Aug 2021 21:28:17 +0300 Message-ID: To: Sebastian Moeller Cc: Mikael Abrahamsson , Mikael Abrahamsson via Bloat , starlink@lists.bufferbloat.net, dickroy@alum.mit.edu Content-Type: text/plain; charset="UTF-8" Subject: Re: [Bloat] [Starlink] Of interest: Comcast AQM Paper 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: Wed, 04 Aug 2021 18:28:29 -0000 I firmly believe this is due to an I/O bottleneck in the SoC between the network complex and the CPU complex, not due to any limitation of the CPU itself. It stems from the reliance on accelerated forwarding hardware to achieve full line-rate throughput. Even so, I'd much rather have 40Mbps with Cake than 400Mbps with a dumb FIFO. (Heck, 40Mbps would be a big upgrade from what I currently have.) I think some of the newer Atheros chipsets are less constrained in this respect. There are two reasonably good solutions to this problem in the hands of the SoC vendors: 1: Relieve that I/O bottleneck, so that the CPU can handle packets at full line rate. I assume this is not hugely complicated to implement, and just requires a sufficient degree of will to select the right option from the upstream fabless IP vendor's design library. 2: Implement good shaping, FQ, and AQM within the network complex. At consumer broadband/LAN speeds, this shouldn't be too difficult (unlike doing the same at 100+ Gbps), but it does require a significant amount of hardware design and validation, and that tends to have long lead times. There is a third solution in the hands of us mere mortals: 3: Leverage the Raspberry Pi ecosystem to build a CPE device that meets our needs. This could be a Compute Module 4 (which has the necessary I/O throughput) mounted on a custom PCB that provides additional Ethernet ports and some reasonable Wifi AP. It could alternatively be a standard Pi 4B with some USB Ethernet and Wifi hardware plugged into it. Either will do the job withhout any Ethernet bottlenecks, although the capabilities of USB Wifi dongles are usually quite limited. - Jonathan Morton