Return-path: Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1Il1mO-0004R7-3o; Thu, 25 Oct 2007 08:25:40 -0400 Received: from pcn by megatron.ietf.org with local (Exim 4.43) id 1Il1mM-0004R0-Jm for pcn-confirm+ok@megatron.ietf.org; Thu, 25 Oct 2007 08:25:38 -0400 Received: from [10.91.34.44] (helo=ietf-mx.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1Il1mM-0004Qs-6v for pcn@ietf.org; Thu, 25 Oct 2007 08:25:38 -0400 Received: from smtp.nokia.com ([131.228.20.171] helo=mgw-ext12.nokia.com) by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1Il1mK-0001l1-RW for pcn@ietf.org; Thu, 25 Oct 2007 08:25:38 -0400 Received: from esebh108.NOE.Nokia.com (esebh108.ntc.nokia.com [172.21.143.145]) by mgw-ext12.nokia.com (Switch-3.2.5/Switch-3.2.5) with ESMTP id l9PCPCVW018377; Thu, 25 Oct 2007 15:25:33 +0300 Received: from esebh103.NOE.Nokia.com ([172.21.143.33]) by esebh108.NOE.Nokia.com with Microsoft SMTPSVC(6.0.3790.1830); Thu, 25 Oct 2007 15:25:13 +0300 Received: from mgw-int02.ntc.nokia.com ([172.21.143.97]) by esebh103.NOE.Nokia.com over TLS secured channel with Microsoft SMTPSVC(6.0.3790.1830); Thu, 25 Oct 2007 15:25:13 +0300 Received: from [172.21.35.48] (esdhcp03548.research.nokia.com [172.21.35.48]) by mgw-int02.ntc.nokia.com (Switch-3.2.5/Switch-3.2.5) with ESMTP id l9PCPBSC016940; Thu, 25 Oct 2007 15:25:12 +0300 In-Reply-To: <75A199C5D243C741BF3D3F1EBCEF9BA5019DC5FC@E03MVZ1-UKDY.domain1.systemhost.net> References: <75A199C5D243C741BF3D3F1EBCEF9BA5019DC5FC@E03MVZ1-UKDY.domain1.systemhost.net> Mime-Version: 1.0 (Apple Message framework v752.3) Message-Id: From: Lars Eggert Subject: Re: [PCN] Architecture draft - probing section & general updates. Date: Thu, 25 Oct 2007 15:25:07 +0300 To: "ext philip.eardley@bt.com" X-Mailer: Apple Mail (2.752.3) X-OriginalArrivalTime: 25 Oct 2007 12:25:13.0468 (UTC) FILETIME=[17AD83C0:01C81702] X-Nokia-AV: Clean X-Spam-Score: 0.0 (/) X-Scan-Signature: 10d3e4e3c32e363f129e380e644649be Cc: pcn@ietf.org, Ruediger.Geib@t-systems.com X-BeenThere: pcn@ietf.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: PCN WG list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============0333129041==" Errors-To: pcn-bounces@ietf.org --===============0333129041== Content-Type: multipart/signed; micalg=sha1; boundary=Apple-Mail-3-259543044; protocol="application/pkcs7-signature" --Apple-Mail-3-259543044 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed On 2007-10-25, at 13:56, ext philip.eardley@bt.com wrote: > Lars, I believe the guess is that there'll be many ingress-egress > pairs > with none or very few flows at a particular moment. Not a random > distribution of calls onto all possible pairs. Basically there are > many > calls between London & Manchester and very few between truro and > Shetland. I can agree with that. But note that that alone is not a problem yet. The problem occurs only when several of these "empty" ingress pairs share a bottleneck *and* when single flows start simultaneously sending across them at a combined rate that will push the bottleneck directly into overload. I don't believe this can be very common. Wouldn't you provision your network such that interior routers could handle at least one flow per ingress/egress pair? In which case there is no issue unless there's a failure. And why not let flow termination handle these rare cases? > I & Ben will try and extract some numbers from the [bt] > predicted future traffic matrix. That'd be *very* useful! We're all guessing probabilities here, and data would help. 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