From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rcdn-iport-5.cisco.com (rcdn-iport-5.cisco.com [173.37.86.76]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "rcdn-iport.cisco.com", Issuer "Cisco SSCA2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id C78C621F1DA for ; Wed, 13 Nov 2013 09:50:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=3825; q=dns/txt; s=iport; t=1384365047; x=1385574647; h=from:to:cc:subject:date:message-id:references: in-reply-to:mime-version; bh=FWmlX2R9LdctnpSRvZkHVR/C5pfkQX29F2X/YkpN6R0=; b=RsoXGsFR/sPeJBu0fJz2rIMchxMdbdp9bVhgIsWtdB+FJ+wiFFJyChAj CDucUN47GvXxBLiFS5KOEedcSDVVDK0C3GmUenMNY44r8O+5Sb5fImv1y lSCfqOWSSS1gIYSZTEFVOmXQtlCBoNZ/KKw3yd8kSLQlUOKIfCPAWG5hm c=; X-Files: signature.asc : 195 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AgoFAFm7g1KtJXG+/2dsb2JhbABbgweBC78rgSYWdIIlAQEBAwF5BQsCAQgOODIlAgQOBQ6HbQbAIY9fB4MggREDkDCBMIYwkguDKIIq X-IronPort-AV: E=Sophos;i="4.93,693,1378857600"; d="asc'?scan'208";a="284350905" Received: from rcdn-core2-3.cisco.com ([173.37.113.190]) by rcdn-iport-5.cisco.com with ESMTP; 13 Nov 2013 17:50:46 +0000 Received: from xhc-aln-x05.cisco.com (xhc-aln-x05.cisco.com [173.36.12.79]) by rcdn-core2-3.cisco.com (8.14.5/8.14.5) with ESMTP id rADHokm5014165 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL); Wed, 13 Nov 2013 17:50:46 GMT Received: from xmb-rcd-x09.cisco.com ([169.254.9.122]) by xhc-aln-x05.cisco.com ([173.36.12.79]) with mapi id 14.03.0123.003; Wed, 13 Nov 2013 11:50:46 -0600 From: "Fred Baker (fred)" To: Mikael Abrahamsson Thread-Topic: [Bloat] [aqm] [iccrg] AQM deployment status? Thread-Index: AQHO4JjgklOmh8fMlEaXf65FqFuYEA== Date: Wed, 13 Nov 2013 17:50:45 +0000 Message-ID: References: <20130925143510.GA6191@sesse.net> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: x-originating-ip: [10.19.64.121] Content-Type: multipart/signed; boundary="Apple-Mail=_194E5E8C-8EF8-48F9-B814-C7B192134F7F"; protocol="application/pgp-signature"; micalg=pgp-sha1 MIME-Version: 1.0 Cc: "iccrg@irtf.org" , "aqm@ietf.org" , bloat Subject: Re: [Bloat] [aqm] [iccrg] AQM deployment status? 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: Wed, 13 Nov 2013 17:50:48 -0000 --Apple-Mail=_194E5E8C-8EF8-48F9-B814-C7B192134F7F Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 On Sep 25, 2013, at 12:24 PM, Mikael Abrahamsson = wrote: > For higher end platforms, for instance all cisco CPU based routers = (for some value of "all") can be configured with RED, fair-queue or = similar, but they come with FIFO as default. This has been the same way = since at least the mid 90ties as far as I know, long way back to cisco = 1600 device etc. >=20 > Higher end Cisco equipment such as ASR9k, 12000, CRS etc, all support = WRED, and here it makes sense since they all have ~50ms worth of = buffering or more. They also come with FIFO as default setting. Yes. There are two reasons that we don't deploy RED by default.=20 One is that we operate on a principle we call the "principle of least = surprise"; we try to not change our customer's configurations by = changing the defaults, and at the time I wrote the RED/WRED code the = default was FIFO. Yes, that was quite some time ago, and one could = imagine newer equipment coming out with different defaults on = deployment, but that's not what the various business units do.=20 The other is this matter of configuration. In the late 1990's, Cisco = employed Van and Kathy, and asked them to figure out autoconfiguration = values. That didn't work out. I don't say that as a slam on V+K; it's = simply a fact. They started by recommending an alternative algorithm = called RED-Lite (don't bother googling that; you get discoth=E8ques), = and are now recommending CoDel. Now, there is probably a simplistic = value that one could throw in, such as setting max-threshold to the = queue memory allocated to the queue and min-threshold to some function = logarithmically related to the bit rate that serves as an estimator of = the number of bit-times of delay to tune to. That would probably be = better than nothing, but it would be nice to have some science behind = it. That brings us back to the auto-tuning discussion. To my way of thinking, a simplistic algorithm such as that logarithmic = approach or a lookup table that starts from (perhaps) bit rate and = neighbor ping RTT can come up with an initial set of parameters that the = algorithm's own processes can modify to ambient traffic behavior. = Kathy's simulations in the study I mentioned suggested that a 1.5 MBPS = link might do well with min-threshold at 30 ms (e.g., ~4 MTU-sized = messages or a larger number of smaller messages), and rates higher at = some single digit number of ms, decreasing as the speed increased.=20 CoDel suggests a flat 5 ms value (at 1.5 MBPS, less than a single MTU, = and at one gigabit, 83 12K bit messages). I could imagine the = initialization algorithm selecting 5 ms above a certain speed, and the = equivalent of 4 MTU intervals at lower line speeds where 4*MTU exceeds 5 = ms. I could imagine a related algorithm then adjusting that initial = value to interact well with Google's IW=3D10 behavior or whatever else = it finds on the link.=20 PIE would probably start with a similar set of values, and tune its = mark/drop interval to reach a value that works well with ambient = traffic. --Apple-Mail=_194E5E8C-8EF8-48F9-B814-C7B192134F7F Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="signature.asc" Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iD8DBQFSg7vzbjEdbHIsm0MRAn0LAKCYyZyvzzM2JBDXaIqFzi2kqbUNwACdEeC8 vzgqNpjQSxhvsHrVxVlOG8U= =JLqe -----END PGP SIGNATURE----- --Apple-Mail=_194E5E8C-8EF8-48F9-B814-C7B192134F7F--