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 AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 6E9273B260 for ; Mon, 6 Jun 2016 14:37:17 -0400 (EDT) Received: by uplift.swm.pp.se (Postfix, from userid 501) id AED88A2; Mon, 6 Jun 2016 20:37:15 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=swm.pp.se; s=mail; t=1465238235; bh=fxceVeOWRtyHyGAF8A+kFsdxSVPXcWh0EtWR9kyiIM8=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=o8ZtP1dT0hiFyAey7oHFMxMz2LWSwTwgnnnN8hG5Cz2V9AwdpkKj0U2lv4MSC4i1e 61cOJ0j9sJSB6DtlyulT4TptBYen/BevJPx/JEct/lhte3iNW0PgDy3vIUGsA6BOnu Md6gX2SOtIou7dCGlo27reyxHZT3EzRMtsO6maLw= Received: from localhost (localhost [127.0.0.1]) by uplift.swm.pp.se (Postfix) with ESMTP id A60E0A1; Mon, 6 Jun 2016 20:37:15 +0200 (CEST) Date: Mon, 6 Jun 2016 20:37:15 +0200 (CEST) From: Mikael Abrahamsson To: Jonathan Morton cc: "cerowrt-devel@lists.bufferbloat.net" In-Reply-To: <3D32F19B-5DEA-48AD-97E7-D043C4EAEC51@gmail.com> Message-ID: References: <55fdf513-9c54-bea9-1f53-fe2c5229d7ba@eggo.org> <871t4as1h9.fsf@toke.dk> <3D32F19B-5DEA-48AD-97E7-D043C4EAEC51@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="-137064504-1449229387-1465238235=:28955" Subject: Re: [Cerowrt-devel] trying to make sense of what switch vendors say wrt buffer bloat X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 06 Jun 2016 18:37:17 -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. ---137064504-1449229387-1465238235=:28955 Content-Type: TEXT/PLAIN; charset=utf-8; format=flowed Content-Transfer-Encoding: 8BIT On Mon, 6 Jun 2016, Jonathan Morton wrote: > At 100ms buffering, their 10Gbps switch is effectively turning any DC > it’s installed in into a transcontinental Internet path, as far as peak > latency is concerned. Just because RAM is cheap these days… Nono, nononononono. I can tell you they're spending serious money on inserting this kind of buffering memory into these kinds of devices. Buying these devices without deep buffers is a lot lower cost. These types of switch chips either have on-die memory (usually 16MB or less), or they have very expensive (a direct cost of lowered port density) off-chip buffering memory. Typically you do this: ports ---|------- ports ---| | ports ---| chip | ports ---|------- Or you do this ports ---|------|---buffer ports ---| chip |---TCAM -------- or if you do a multi-linecard-device ports ---|------|---buffer | chip |---TCAM -------- | switch fabric (or any variant of them) So basically if you want to buffer and if you want large L2-L4 lookup tables, you have to sacrifice ports. Sacrifice lots of ports. So never say these kinds of devices add buffering because RAM is cheap. This is most definitely not why they're doing it. Buffer memory for them is EXTREMELY EXPENSIVE. -- Mikael Abrahamsson email: swmike@swm.pp.se ---137064504-1449229387-1465238235=:28955--