From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-24-ewr.dyndns.com (mxout-059-ewr.mailhop.org [216.146.33.59]) by lists.bufferbloat.net (Postfix) with ESMTP id F10B52E03C0 for ; Wed, 16 Mar 2011 15:22:21 -0700 (PDT) Received: from scan-21-ewr.mailhop.org (scan-21-ewr.local [10.0.141.243]) by mail-24-ewr.dyndns.com (Postfix) with ESMTP id E6BC35CE35A for ; Wed, 16 Mar 2011 22:22:15 +0000 (UTC) X-Spam-Score: 0.0 () X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 213.165.64.23 Received: from mailout-de.gmx.net (mailout-de.gmx.net [213.165.64.23]) by mail-24-ewr.dyndns.com (Postfix) with SMTP id 967F55CE190 for ; Wed, 16 Mar 2011 22:22:11 +0000 (UTC) Received: (qmail invoked by alias); 16 Mar 2011 22:22:10 -0000 Received: from unknown (EHLO srichardlxp2) [213.143.107.142] by mail.gmx.net (mp023) with SMTP; 16 Mar 2011 23:22:10 +0100 X-Authenticated: #20720068 X-Provags-ID: V01U2FsdGVkX19Y6WNwmQRYuRf6ht1uUB5kMUkv/DXuNWfyv2Kw4m VHgYDPFDeWKRUf Message-ID: From: "Richard Scheffenegger" To: "Jonathan Morton" , =?iso-8859-1?Q?=22Dave_T=E4ht=22?= References: <4D7F4121.40307@freedesktop.org><20110315175942.GA10064@goldfish><1300212877.2087.2155.camel@tardy><20110315183111.GB2542@tuxdriver.com><29B06777-CC5F-4802-8727-B04F58CDA9E3@gmail.com><20110315205146.GF2542@tuxdriver.com><219C7840-ED79-49EA-929D-96C5A6200401@gmail.com><20110315151946.31e86b46@nehalam><1300228592.2087.2191.camel@tardy><1300229578.2565.29.camel@edumazet-laptop><87fwqo54n7.fsf@cruithne.co.teklibre.org><823E2A7B-4F46-4159-8029-BD3B075CC4CE@gmail.com><87bp1b6fo0.fsf@cruithne.co.teklibre.org><87bp1b4yh4.fsf@cruithne.co.teklibre.org> <35010A85-C5A4-4133-8707-4E114C65A8C6@gmail.com> Date: Wed, 16 Mar 2011 23:22:24 +0100 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994 X-Y-GMX-Trusted: 0 Cc: Stephen Hemminger , bloat Subject: Re: [Bloat] Random idea in reaction to all the discussion of TCPflavours - timestamps? 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, 16 Mar 2011 22:22:22 -0000 Heretical question: Why must the congestion notification implemented as a (distributed) function of the network itself, and take the reaction of the end hosts into consideration. If the signaling would only indicate the local congestion state, but then move the reaction to that into the end hosts, i think the design would be much more simple. If the network would let the (reactive) senders know the extent of the current congestion, the end hosts can use more smarts and react to it properly. However, AQMs are designed with the standard TCP reaction in mind - half the sending rate at any indication of congestion within one RTT. (See DCTCP, Conex for additional information). Furthermore, I learned that a couple of 10G switch vendors are planning to have up to 4 GB of buffer RAM in their next generation of switches. So we are not talking about thousands of packets in the buffer, but of millions of packets (think of up to 400ms buffering if only a single 10G egress port is being loaded in such a switch). Compared to the base RTT of a 10G network (a few tens of microseconds, some vendors go even below a microsecond), this is even more extreme than the home router / DSLAM scenario... Regards, Richard ----- Original Message ----- From: "Jonathan Morton" With that said, at 10GE speeds you are approaching a megapacket per second if jumbo frames are not a significant fraction of the traffic. I think something like SFQ can be made to work at those speeds, but simply getting the data through the computer that fast is a fairly tough job. So I agree that if the NIC can do it by itself, so much the better. On the flip side, at a megapacket per second, a thousand-packet buffer empties in a millisecond. That's less than a disk seek. - Jonathan _______________________________________________ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat