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 366C8201728 for ; Mon, 16 May 2011 11:27:49 -0700 (PDT) Received: (qmail invoked by alias); 16 May 2011 18:37:30 -0000 Received: from unknown (EHLO srichardlxp2) [213.143.107.142] by mail.gmx.net (mp025) with SMTP; 16 May 2011 20:37:30 +0200 X-Authenticated: #20720068 X-Provags-ID: V01U2FsdGVkX1/NPT5PUWvNoXqmoDU2MhLEHGWDdjAWD7GkITnmfe cg8Ii+eRxJZyPd Message-ID: <60A7498C842645FBB11A58BAA9467ACD@srichardlxp2> From: "Richard Scheffenegger" To: "Kevin Gross" , References: rg> <012d01cc13cb$61617ed0$24247c70$@gross@avanw.com> Date: Mon, 16 May 2011 20:36:57 +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 V6.00.2900.6090 X-Y-GMX-Trusted: 0 Subject: Re: [Bloat] Jumbo frames and LAN buffers 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: Mon, 16 May 2011 18:27:52 -0000 Kevin, > My understanding is that 802.1au, "lossless Ethernet", was designed > primarily to allow Fibre Channel to be carried over 10 GbE so that SAN and > LAN can share a common infrastructure in datacenters. I don't believe > anyone > intends for it to be enabled for traffic classes carrying TCP. Well, QCN requires a L2 MAC sender, network and receiver cooperation (thus you need fancy "CNA" converged network adapters, to start using it - these would be reaction/reflection points; plus the congestion points - switches - would need HW support too; nothing one can buy today; higher-grade (carrier?) switches may have the reaction/reflection points built into them, and could use legacy 802.3x signalling outside the 802.1Qau cloud). The following may be too simplistic Once the hardware has a reaction point support, it classifies traffic, and calculates the per flow congestion of the path (with flow really being the classification rules by the sender), the intermediates / receiver sample the flow and return the congestion back to the sender - and within the sender, a token bucket-like rate limiter will adjust the sending rate of the appropriate flow(s) to adjust to the observed network conditions. http://www.stanford.edu/~balaji/presentations/au-prabhakar-qcn-description.pdf http://www.ieee802.org/1/files/public/docs2007/au-pan-qcn-details-053007.pdf The congestion control loop has a lot of similarities to TCP CC as you will note... Also, I haven't found out how fine-grained the classification is supposed to be (per L2 address pair? Group of flows? Which hashing then to use for mapping L2 flows into those groups between reaction/congestion/reflection points...). Anyway, for the here and now, this is pretty much esoteric stuff not relevant in this context :) Best regards, Richard ----- Original Message ----- From: "Kevin Gross" To: Sent: Monday, May 16, 2011 3:15 PM Subject: Re: [Bloat] Jumbo frames and LAN buffers > All the stand-alone switches I've looked at recently either do not support > 802.3x or support it in the (desireable) manner described in the last > paragraph of the linked blog post. I don't believe Ethernet flow control > is > a factor in current LANs. I'd be interested to know the specifics if > anyone > sees it differently. > > My understanding is that 802.1au, "lossless Ethernet", was designed > primarily to allow Fibre Channel to be carried over 10 GbE so that SAN and > LAN can share a common infrastructure in datacenters. I don't believe > anyone > intends for it to be enabled for traffic classes carrying TCP. > > Kevin Gross > > -----Original Message----- > From: bloat-bounces@lists.bufferbloat.net > [mailto:bloat-bounces@lists.bufferbloat.net] On Behalf Of Jim Gettys > Sent: Monday, May 16, 2011 5:24 AM > To: bloat@lists.bufferbloat.net > Subject: Re: [Bloat] Jumbo frames and LAN buffers > > Not necessarily out of knowledge or desire (since it isn't usually > controllable in the small switches you buy for home). It can cause > trouble even in small environments as your house. > > http://virtualthreads.blogspot.com/2006/02/beware-ethernet-flow-control.html > > I know I'm at least three consumer switches deep, and it's not by choice. > - Jim > > > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat >