From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from EUR01-HE1-obe.outbound.protection.outlook.com (mail-eopbgr130078.outbound.protection.outlook.com [40.107.13.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 2CF513B29D for ; Thu, 7 May 2020 05:11:09 -0400 (EDT) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Ex+5tA5AuBB3KpjIAMC7R6on4/mvL7UsD7AIbeLS1EpRGV90dB9sGEmlSnU8gwIuLDOsz8Esfu9hpVvHiHN+6NT/yW5zDGqJKUv00TyMxc3Q1tOKgJBSRaRQAIOk8dOVlEEaiRFHcsPzXrdv82x0WsWydDcrnj/F4dDkwXjFkEGxkG0JCGPtnFjWDnUQmxMvO122o74ioJ+Mx6SOIrL5NCt79yWg2EJSDgAJEXQ+H6/A0ExR+2kAjqnLxehFCywp+NGoJvBPbpyKufWzAXQ6TVNIGT9/IcjeU2cII86Cds4kj67dfhxL0XXip6edMtaUh0ERTTWi3MI7jBbO7Z08gw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=LCui7ceppJkfiv8+0I42T3BgVec+yz0WXrbT2mf55jc=; b=dk8LUuCbTtGDIDYhyzLJS3M/79yeWOSCCusEcRz73wTAfN+ZtbJ9+2yrDQYt0mChDd0vWb8FaLz6RyuorkZBqBLiuO15W+ZlT4F7Auutz739LMKpL1WOuTkhmjZS+xFY0wtUVqqYIzhUWmAOmnmP8wEd70J1e41HsskjtYcjLER+Cil+H9g/k7tpOqNXiPm5yFIzzyaMfCRdQIfvSVAQlnI+/efnQZvUO0RKYUMHNbhrBSpss57ETJMkRL3Z3Vq3GD+jpdlYQ7flp92T4Vyn9brLQzI9OZ4qGTwWHkOxmu6ssnDW3DM0BN4dvAedv+ORQNuWbdvLHIh/7WuHHsuktw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=darbyshire-bryant.me.uk; dmarc=pass action=none header.from=darbyshire-bryant.me.uk; dkim=pass header.d=darbyshire-bryant.me.uk; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=darbyshire-bryant.me.uk; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=LCui7ceppJkfiv8+0I42T3BgVec+yz0WXrbT2mf55jc=; b=rJLAujOP+TcteN0d2DjLJ7p+hQHKBb2rFH2Zg7TS+5/xE9gD9zzZV5zvxAMM9JYhOKHupiE4m6vzHeBw5rPFatz4NSVZ9ldrKwFWhV3zJwicFCcQQH9YGPbDpv486tnLrz3lK3QFYDpKKSdYPGSHsvRakbiRaf3rE+RA34RTK6o= Received: from VI1PR03MB4575.eurprd03.prod.outlook.com (2603:10a6:803:59::12) by VI1PR03MB6542.eurprd03.prod.outlook.com (2603:10a6:800:199::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2958.20; Thu, 7 May 2020 09:11:07 +0000 Received: from VI1PR03MB4575.eurprd03.prod.outlook.com ([fe80::982d:7d6a:5f6f:74a2]) by VI1PR03MB4575.eurprd03.prod.outlook.com ([fe80::982d:7d6a:5f6f:74a2%4]) with mapi id 15.20.2958.033; Thu, 7 May 2020 09:11:07 +0000 From: Kevin Darbyshire-Bryant To: Jonathan Morton CC: Cake List Thread-Topic: [Cake] Latency target curiosity Thread-Index: AQHWJEU7YDANxZ+4XEGJtOgdU5bzl6icRROAgAARQwA= Date: Thu, 7 May 2020 09:11:07 +0000 Message-ID: References: In-Reply-To: Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.80.23.2.2) authentication-results: gmail.com; dkim=none (message not signed) header.d=none;gmail.com; dmarc=none action=none header.from=darbyshire-bryant.me.uk; x-originating-ip: [2a02:c7f:1243:8e00::dc83] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 9e5db89a-9dfb-4c99-6fbc-08d7f26693cf x-ms-traffictypediagnostic: VI1PR03MB6542: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:9508; x-forefront-prvs: 03965EFC76 x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 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 x-forefront-antispam-report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:VI1PR03MB4575.eurprd03.prod.outlook.com; PTR:; CAT:NONE; SFTY:; SFS:(366004)(376002)(346002)(39830400003)(136003)(396003)(33430700001)(86362001)(2616005)(4326008)(316002)(6506007)(53546011)(71200400001)(2906002)(45080400002)(99936003)(33656002)(33440700001)(6512007)(64756008)(66476007)(66616009)(66556008)(508600001)(76116006)(91956017)(66446008)(66946007)(83320400001)(83280400001)(6916009)(186003)(8936002)(5660300002)(6486002)(8676002)(36756003)(83300400001)(83310400001)(83290400001); DIR:OUT; SFP:1101; x-ms-exchange-antispam-messagedata: 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 x-ms-exchange-transport-forked: True Content-Type: multipart/signed; boundary="Apple-Mail=_2638F57F-47AD-41F5-BD24-427D0BEFA8D4"; protocol="application/pgp-signature"; micalg=pgp-sha256 MIME-Version: 1.0 X-OriginatorOrg: darbyshire-bryant.me.uk X-MS-Exchange-CrossTenant-Network-Message-Id: 9e5db89a-9dfb-4c99-6fbc-08d7f26693cf X-MS-Exchange-CrossTenant-originalarrivaltime: 07 May 2020 09:11:07.5306 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 9151708b-c553-406f-8e56-694f435154a4 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Krj6AbrsA0U44g6WzpnvZSe7580ilZzBdK5b1sEBi8g/tZnvKGEbnkhQ6MWRuJqu7VAFMC8ePq6DB6ZJZBUpHbEtCQIwSZUimyZqogdA2B4= X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR03MB6542 Subject: Re: [Cake] Latency target curiosity X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 May 2020 09:11:09 -0000 --Apple-Mail=_2638F57F-47AD-41F5-BD24-427D0BEFA8D4 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 > On 7 May 2020, at 09:09, Jonathan Morton = wrote: >=20 >> On 7 May, 2020, at 10:58 am, Kevin Darbyshire-Bryant = wrote: >>=20 >> A curiosity has arisen: I use diffserv4 mode on a 20Mbit egress = link. Bulk tin has =E2=80=98capacity=E2=80=99 threshold of 1.2Mbit and = because it=E2=80=99s a slow =E2=80=99tin', the default target & interval = values get overridden to 14.6ms and 109.6ms respectively. The 3 other = tins are 5ms & 100ms defaults. >>=20 >> I have a backup job that bulk uploads 5 simultaneous flows to = Onedrive. The sparse_delay, average_delay & peak_delay figures settle = on 32, 38 & 43 ms respectively with around 9 drops per second on that = tin. >>=20 >> I=E2=80=99m curious as to why the reported delays are over double the = target latency? >=20 > It's likely that there's a minimum cwnd in your sender's TCP stack, = which may be as large as 4 segments. In Linux it is 2 segments. No = matter how much congestion signalling is asserted, the volume of data in = flight (including retransmissions of dropped packets) will always = correspond to at least that minimum per flow. If the path is short, = most of that volume will exists in queues instead of on the wire. This is a Qnap NAS box running (a form of) Linux but to say I don=E2=80=99= t trust the IP stack as being vanilla is an understatement. I=E2=80=99ve = seen it do some really odd things when enabling ECN on egress=E2=80=A6I = don=E2=80=99t know if that=E2=80=99s a qnap or onedrive issue. >=20 > Fortunately, backups are unlikely to suffer from a small amount of = extra latency, and Cake will isolate their influence from other flows = that may be more sensitive. Absolutely! That=E2=80=99s why the traffic is in the Bulk tin, I = don=E2=80=99t care about its =E2=80=98interactivity=E2=80=99, I just = want the data transferred eventually :-) Cake does really well, I=E2=80=99= ve had these backups running for days, maxing out the line but I simply = couldn=E2=80=99t tell. I can also reasonably reliably classify facetime = calls, so I put those in =E2=80=98Video=E2=80=99, so just for fun, = whilst the other half was engaged on a 2 hour(!) facetime call with = family I started backups, ran speed tests etc to try to disturb that = call. Cake just kept that video call running smoothly all the time, = brilliant! I know that=E2=80=99s more of a tin isolation test rather = than a flow isolation test but it=E2=80=99s still great! Cheers, Kevin D-B gpg: 012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A --Apple-Mail=_2638F57F-47AD-41F5-BD24-427D0BEFA8D4 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEASyssijGxT6XdZEjs6I4m53iM0oFAl6z0KoACgkQs6I4m53i M0ogIQ//bML9rG5MTvB0b8EwvuDNjhCmuDQoJA7MB9AVcRwvBkch/rwGnQ1a5upd kJjfFwDqY3dcdZtl4O3kYgNiA3l6nhOKX20BHdK826vEwnwMo++UFgDXREFtJwAf Og5aJoU9e9yS8klB4LEh2t7eJXlL3ALHSXJOBrk4yeAPAtngNSHMmRjRAtIC4IVX mMWGXeYt7W9D3GckBVxBstHDPZ8qB1uqEUt0192+7fBHmeFjpqvQhQ02klDN2LlE Xt6MBh7Sx5CMtmcQVtJ5Mlw9mmLih3Aq9nijf18qfKQlqxQ6noRlMfW4mKRUmSdY S8YlxbAlDqLNcV/9saV66nl8XnYd1ZqEJfR7ibUuOvVUpCLT8IoqUY/O0MCiBjtQ Z+Ogm+0i6vz3Jkobm9OMZxU0XAB7mm4huXQiQyttPE5NWXGkpfbgmil7zcQZU59F hE0zan8Ydpr8lWl49DcYuRbH1et2TUF+05P5jQYDriKctEwAysjw0FlxeXq3Bbof zvCRAOmwgAL3NQ2soHmA6e8JHwYBVF7S3JO1ZSzaLDqLDVwFQ32cmdbvrNcgsvxs 6QO08JE3Z4CwUKxYRnQ8cwEEEtIaWuIRpt6Hl+wwtUX5sCyB9HCcZ2t4HyfJRXWw BHN0kQcnT4phSQqBL9FTDXofNW+ENOXXpDL4NxPj2rDa8w0Nty0= =5zs3 -----END PGP SIGNATURE----- --Apple-Mail=_2638F57F-47AD-41F5-BD24-427D0BEFA8D4--