From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout-de.gmx.net (mailout-de.gmx.net [213.165.64.22]) by huchra.bufferbloat.net (Postfix) with SMTP id DB50E20175B for ; Mon, 16 May 2011 11:37:52 -0700 (PDT) Received: (qmail invoked by alias); 16 May 2011 18:47:33 -0000 Received: from unknown (EHLO srichardlxp2) [213.143.107.142] by mail.gmx.net (mp064) with SMTP; 16 May 2011 20:47:33 +0200 X-Authenticated: #20720068 X-Provags-ID: V01U2FsdGVkX1/4ReIwqOn4SXLMPLr/CJaigCoen5mkSLvQLTZWTF 4xgTsybzRy28nd Message-ID: <5BEAA2E0AC0742ECA603E3EFEAFBD1DB@srichardlxp2> From: "Richard Scheffenegger" To: "Kevin Gross" , Date: Mon, 16 May 2011 20:40:50 +0200 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response 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 18:37:53 -0000 Also found this: http://www.stanford.edu/~balaji/papers/QCN.pdf Jim, you may notice that the congestion feedback probability function looks just like the basic RED marking function :) Regards, Richard ----- Original Message ----- From: "Richard Scheffenegger" To: "Kevin Gross" ; Sent: Monday, May 16, 2011 8:36 PM Subject: Re: [Bloat] Jumbo frames and LAN buffers > 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 >> >