From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pz0-f52.google.com (mail-pz0-f52.google.com [209.85.210.52]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id AEBD4200B1B for ; Thu, 3 May 2012 16:37:00 -0700 (PDT) Received: by dadz9 with SMTP id z9so2551685dad.25 for ; Thu, 03 May 2012 16:36:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:mime-version:content-type:from:in-reply-to:date:cc :message-id:references:to:x-mailer; bh=bdv9dGupmOoUIY7IDRFHA3z8vQN45k/dJeV7cDtIYv0=; b=yqd/aan/WEOHXQcyd+soMYd7y248moB01OsHOSlwRsJUlbHjDVbtkiRXCUsO+IP9m0 h7yD2GwqQc4rxP1KlyD0iPhDbhiOBeGBjCNIXNHpYokblrBR2n+zvjubjTtf6e0+ImNU 2JzuT5ta4NjlhPMdMohh2nkhhl6jejlYGLr9NC4a8dOuGQtgBmYbG4A7JQvIuGtMtrCR bl3sud4dWZQ5XbAHBQf25OY6AkqjjywjdqII24V1XUhCVrZstzN++Os72gBQR3XKL/oI Tbe+mgRQlAj9B7JyE0NrG+duH34KUcrROXCHVa59UEMy7SVURewTLFecu8I2EegZdirg SvZw== Received: by 10.68.72.138 with SMTP id d10mr10268686pbv.15.1336088219881; Thu, 03 May 2012 16:36:59 -0700 (PDT) Received: from andrewm-lo.ws.atlnz.lc (gate1.alliedtelesyn.co.nz. [202.49.72.36]) by mx.google.com with ESMTPS id if8sm977473pbc.15.2012.05.03.16.36.56 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 03 May 2012 16:36:58 -0700 (PDT) Mime-Version: 1.0 (Apple Message framework v1257) Content-Type: multipart/signed; boundary="Apple-Mail=_90F39179-A9C1-4036-BA75-E2DA276FA32C"; protocol="application/pkcs7-signature"; micalg=sha1 From: Andrew McGregor In-Reply-To: <4FA3136E.3060502@pollere.com> Date: Fri, 4 May 2012 11:36:52 +1200 Message-Id: <6F1038D7-AE4B-4F70-8F9B-5E99E483B5C2@gmail.com> References: <4FA3136E.3060502@pollere.com> To: Kathleen Nichols X-Mailer: Apple Mail (2.1257) Cc: codel@bufferbloat.net Subject: Re: [Codel] question about "data center" models X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 03 May 2012 23:37:00 -0000 --Apple-Mail=_90F39179-A9C1-4036-BA75-E2DA276FA32C Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii A normal configuration is more like a 300 microsecond RTT with early = marking RED and/or switches configured to backpressure sources with = fairly short queues. There may be enormous amounts of buffer in a switch, but it is usually = divided among a rather large number of queues (ingress and egress queues = per port, plus perhaps several in the forwarder). Data center operators are very concerned about latency because in most = cases the metric they are tracking is the completion time of the last = short flow to complete in a transaction (that will be composed of, say, = 20-odd 500kB or thereabouts TCP connections). There is often a hard = time limit on transaction components; one I've heard of is that all data = for a query must be at the aggregation node in 8ms, or it will be = dropped and the query result quality will go down. On 4/05/2012, at 11:23 AM, Kathleen Nichols wrote: >=20 > So, I thought I'd see what happens with a 1G bottleneck and a 5ms RTT. > I'm still checking > it out, but I thought I'd try to understand the concern. So, under a > constant heavy load, > codel will accept a 5ms standing queue. I got the impression this was = a > concern. I'm > not exactly certain why. How much buffer is normally in the = bottleneck? > If it's enough > for a "nominal" RTT of 100 ms, with drop tail it will just fill up and > stay there under > load. So, 100ms of delay. If it's at a RTT of 5ms, then the buffer = will > fill up and give 5ms > of delay without any ability to absorb bursts. What is the normal > configuration? >=20 > Kathie > _______________________________________________ > Codel mailing list > Codel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/codel --Apple-Mail=_90F39179-A9C1-4036-BA75-E2DA276FA32C Content-Disposition: attachment; filename=smime.p7s Content-Type: application/pkcs7-signature; name=smime.p7s Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIFLjCCBSow ggQSoAMCAQICEQDMQ2ZKvgsUYA5oQg5SjWfVMA0GCSqGSIb3DQEBBQUAMIGTMQswCQYDVQQGEwJH QjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRowGAYDVQQK ExFDT01PRE8gQ0EgTGltaXRlZDE5MDcGA1UEAxMwQ09NT0RPIENsaWVudCBBdXRoZW50aWNhdGlv biBhbmQgU2VjdXJlIEVtYWlsIENBMB4XDTExMTAwMTAwMDAwMFoXDTEyMDkzMDIzNTk1OVowJTEj MCEGCSqGSIb3DQEJARYUYW5kcmV3bWNnckBnbWFpbC5jb20wggEiMA0GCSqGSIb3DQEBAQUAA4IB DwAwggEKAoIBAQC+buTRxzSXTQmMyUqaokLJit3xU5WVudxHijhKbGRSTgJ867L/v8+rNhSoFwCV MdKIu/M7apWgGkkA+MT/LjDFj63jLT+4nTTLIojXZdoezbpp/rQ2ViSbi54AjhZBQ5X+yH2xcXmG KpDhZjeZC1bvKNvBtdOHCAcrx1Ys1BNj+AhwridEX/KD0cq5xSsJhjDggF6XSUOsaiqBHR6fiQMi 7gH8EuFBh83oklb/pdreg1fQ7gKJk/Me/atIbE1gtbIR88oaCtXoHfZxgkFwagwMtBHdkxN+wcZy 9xx78el9Lxrjx2nMq50hRlj/bqg/m4rSox7//DKfx7bfKNZAiSMDAgMBAAGjggHkMIIB4DAfBgNV HSMEGDAWgBR6E04AdFvGeGNkJ8Ev4qBbvHnFezAdBgNVHQ4EFgQUXOXqNkq6sNbrD8B41dPko8Gs JucwDgYDVR0PAQH/BAQDAgWgMAwGA1UdEwEB/wQCMAAwIAYDVR0lBBkwFwYIKwYBBQUHAwQGCysG AQQBsjEBAwUCMBEGCWCGSAGG+EIBAQQEAwIFIDBGBgNVHSAEPzA9MDsGDCsGAQQBsjEBAgEBATAr MCkGCCsGAQUFBwIBFh1odHRwczovL3NlY3VyZS5jb21vZG8ubmV0L0NQUzBXBgNVHR8EUDBOMEyg SqBIhkZodHRwOi8vY3JsLmNvbW9kb2NhLmNvbS9DT01PRE9DbGllbnRBdXRoZW50aWNhdGlvbmFu ZFNlY3VyZUVtYWlsQ0EuY3JsMIGIBggrBgEFBQcBAQR8MHowUgYIKwYBBQUHMAKGRmh0dHA6Ly9j cnQuY29tb2RvY2EuY29tL0NPTU9ET0NsaWVudEF1dGhlbnRpY2F0aW9uYW5kU2VjdXJlRW1haWxD QS5jcnQwJAYIKwYBBQUHMAGGGGh0dHA6Ly9vY3NwLmNvbW9kb2NhLmNvbTAfBgNVHREEGDAWgRRh bmRyZXdtY2dyQGdtYWlsLmNvbTANBgkqhkiG9w0BAQUFAAOCAQEAgmf81vnsAnbcmIAyyqvEKxAK jRHerfreN10DK1ISkUJ//U4uffQV8sAGDtyIErzVFsW6NYRmFCMSE20M1ffbFpWUmXCtm/YTlkf1 5STVjTMNshDzMDhpjx99Z2J5RBJPZpXjwmpQnfKwB7zft9TcUSIb9FvZm33EKdF/XlS12U4Q9fsj 2shZf88RituX2+fCWfHoTWiFEhFUkLRtWf1YpgHpEXr82nqROxs/aWNlqtLnwTTu2ULr/WpUaRDs kom8gFZkMgw5kRfLpSXRrCFSORsZzkH2ooRxaJY7wMwZaCUS1am9DuwVy7gehoc3ZsjsDkMObZeu kx7Cg7GxIkgo+zGCA64wggOqAgEBMIGpMIGTMQswCQYDVQQGEwJHQjEbMBkGA1UECBMSR3JlYXRl ciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRowGAYDVQQKExFDT01PRE8gQ0EgTGltaXRl ZDE5MDcGA1UEAxMwQ09NT0RPIENsaWVudCBBdXRoZW50aWNhdGlvbiBhbmQgU2VjdXJlIEVtYWls IENBAhEAzENmSr4LFGAOaEIOUo1n1TAJBgUrDgMCGgUAoIIB2TAYBgkqhkiG9w0BCQMxCwYJKoZI hvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xMjA1MDMyMzM2NTNaMCMGCSqGSIb3DQEJBDEWBBQiLNF6 LQ2DGac76xxmpCpvK5M/ZzCBugYJKwYBBAGCNxAEMYGsMIGpMIGTMQswCQYDVQQGEwJHQjEbMBkG A1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRowGAYDVQQKExFDT01P RE8gQ0EgTGltaXRlZDE5MDcGA1UEAxMwQ09NT0RPIENsaWVudCBBdXRoZW50aWNhdGlvbiBhbmQg U2VjdXJlIEVtYWlsIENBAhEAzENmSr4LFGAOaEIOUo1n1TCBvAYLKoZIhvcNAQkQAgsxgayggakw gZMxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJHcmVhdGVyIE1hbmNoZXN0ZXIxEDAOBgNVBAcTB1Nh bGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBMaW1pdGVkMTkwNwYDVQQDEzBDT01PRE8gQ2xpZW50 IEF1dGhlbnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0ECEQDMQ2ZKvgsUYA5oQg5SjWfVMA0G CSqGSIb3DQEBAQUABIIBAE1ftvJT+O7O7GSwMf6Z++l+gb+NF6y/AAw7YDqX25ZBUGf8O82ceuKm CBr56W+kM57bZRj8CK4mXRIlSopLOoZx8kJZt+EiEqaWqRn+o7IOkWG1QMTTou4sMc6PqsbyDHRH B30HeBwjfx+bz8bnPEhPl/cRgd9J4v2I/YbAQ6jRG8Lg8Jj4Ednh4GOwHC3S3VpwKD3JRCe9rY1B hz9LNe5Q82oi70q0MxfppYtPrR6UF4HG9Tz43sRg/WXCP+tPT96tWFvhei1p2khzXSuxrcKVvP0n EoujtLOr8w852xahqhjivG5fIjIfW8YPydUF2kiYpYs8bNesPEhnnHnIa7YAAAAAAAA= --Apple-Mail=_90F39179-A9C1-4036-BA75-E2DA276FA32C--