From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout-de.gmx.net (mailout-de.gmx.net [213.165.64.23]) by huchra.bufferbloat.net (Postfix) with SMTP id CFBBB20065E for ; Mon, 22 Aug 2011 23:45:37 -0700 (PDT) Received: (qmail invoked by alias); 23 Aug 2011 07:41:43 -0000 Received: from unknown (EHLO srichardlxp2) [213.143.107.142] by mail.gmx.net (mp015) with SMTP; 23 Aug 2011 09:41:43 +0200 X-Authenticated: #20720068 X-Provags-ID: V01U2FsdGVkX18vRN8VQvovjEMtdtMSMhZNXOpeB5RLRRqs0xSJwh ctRlwly6alnFAB Message-ID: From: "Richard Scheffenegger" To: , , References: <20110818050847.GA19458@uio.no> Date: Tue, 23 Aug 2011 09:37:32 +0200 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 V6.00.2900.6109 X-Y-GMX-Trusted: 0 Subject: Re: [Bloat] Not all the world's a WAN 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: Tue, 23 Aug 2011 06:45:38 -0000 Some do. i.e. l3 capable switches, broadcom scorpio (and later) can do ecn marking based on l2 buffer occupancy. see the paper from stanford/microsoft about dctcp - ecn marking based on instantaneous buffer occupancy and proportional tcp reaction (rather than halving cwnd) per rtt... rgds ----- Original Message ----- From: To: ; Sent: Friday, August 19, 2011 4:59 PM Subject: Re: [Bloat] Not all the world's a WAN >> [...]so over short intervals the switch's aggregate incoming bandwidth >> (multiple 10GbE links from >> servers) is larger than its outgoing bandwidth (single 10GbE link to >> client). > > Well, this kind of burstiness is the reason why we have buffers at all. > > Restricting the window size limits the TCP speed and keeps it this way > from overflowing the buffer outside of bursty periods. > > ECN marking helps TCP to distinguish between really available bandwidth > and 'fake' bandwidth that just fills up a buffer, at least if the feedback > loop is fast enough. Do ethernet switches support ECN marking? > > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat