Re: [tcpm] [EXTERNAL] WGLC for draft-ietf-tcpm-rack-08

Praveen Balasubramanian <pravb@microsoft.com> Mon, 06 April 2020 22:54 UTC

Return-Path: <pravb@microsoft.com>
X-Original-To: tcpm@ietfa.amsl.com
Delivered-To: tcpm@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 198EE3A0E22 for <tcpm@ietfa.amsl.com>; Mon, 6 Apr 2020 15:54:49 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.268
X-Spam-Level:
X-Spam-Status: No, score=-2.268 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.168, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=microsoft.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id SjR2PbFMfZva for <tcpm@ietfa.amsl.com>; Mon, 6 Apr 2020 15:54:47 -0700 (PDT)
Received: from NAM06-BL2-obe.outbound.protection.outlook.com (mail-eopbgr650116.outbound.protection.outlook.com [40.107.65.116]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 4F46E3A0E21 for <tcpm@ietf.org>; Mon, 6 Apr 2020 15:54:47 -0700 (PDT)
ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=gVTsjLE1O+FOI1RTWZCj8j8P960I5XhFyM3YuQ6JUhzbLth89sVZvv5QnFVhdhjIcEoohYdWZurtdKsl8Y67a8UBgMc0uje5D18Cy+s8ftAd1SJhH3yIy6LIWehxua5kFQcFDXNpRySgpiIsiO6IrBCQIJL2MIybgQAycTz4QCeKbeyoVkkvpHNAn9t38hDM8bVuhz8FhJLV5kODmePxaemcTjuuu9WMfRQYxfhoTk1Gsl6PMNZYksDzBbvjlcTSGjI6vHfNXhMLEQsJWyyIMNjFnFE0MaS1BzWG1D5TQCQdPcExng3GG7Mn8Mc4znUdLpsok+iaoqZvFsvqt8ePng==
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=serDD2O4k5A8+6XGIuRn10b8gU+BVAATXFPMnL8+Q9A=; b=ajpuUjGVvdKCoPhYvbqfE0B3sD/B+SpSJV9eX4AoRizH+vJzrqUHBIC8OCA3NVfxqN03kwKGofaic+X4tQbQtkpbB5Iezei8xPaRnvpxaqKALJlRpEdEFpXo1Qh/K9CG6+EKblftJF6eDugxPHmzF9rE7ekVRD16RidGcuw47Sh25MlWBFDTChP1H8q4EK8dnxtU/zbo4FmdPkMy88PGRwWq9zFPoVRe07uwFFG57uMxvC4r5HycsG87Jyc6O95SX4lb2oIWYz3IvJojGbzmRz49oACt5LHoAi1f+ggmqzeGfXxVgTDxVLeH5R365UVwdCdpbmt7mRgtIuC2/Z2Mzg==
ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=microsoft.com; dmarc=pass action=none header.from=microsoft.com; dkim=pass header.d=microsoft.com; arc=none
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=serDD2O4k5A8+6XGIuRn10b8gU+BVAATXFPMnL8+Q9A=; b=Oay5h+7TC6cqHJn5uDdHtjYKAJIha62Q4vHAFfHWNHCw+jLut5m/YKmSPNsdmuArHDOm1G/j58fc4mQKlWFSfSxGeLylqKgdY9caFCkO2WXnvTPV3afZYNFTWVpceOXm2Nx2a7HSMR4ZJZZvZwjqUByTtcsFPm9szqb9XPrwqV0=
Received: from CO2PR00MB0181.namprd00.prod.outlook.com (2603:10b6:102:15::22) by MW2PR00MB0299.namprd00.prod.outlook.com (2603:10b6:302:8::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2923.0; Mon, 6 Apr 2020 22:54:45 +0000
Received: from CO2PR00MB0181.namprd00.prod.outlook.com ([fe80::41b0:e003:becf:c63]) by CO2PR00MB0181.namprd00.prod.outlook.com ([fe80::41b0:e003:becf:c63%4]) with mapi id 15.20.2928.000; Mon, 6 Apr 2020 22:54:45 +0000
From: Praveen Balasubramanian <pravb@microsoft.com>
To: Michael Tuexen <tuexen@fh-muenster.de>, tcpm IETF list <tcpm@ietf.org>
Thread-Topic: [EXTERNAL] [tcpm] WGLC for draft-ietf-tcpm-rack-08
Thread-Index: AQHWBuKUegmSdEwkOUCkCzJgctSQTqhsulqg
Date: Mon, 6 Apr 2020 22:54:44 +0000
Message-ID: <CO2PR00MB01810A38E6F23DEE3BD81B77B6C20@CO2PR00MB0181.namprd00.prod.outlook.com>
References: <3D4D034B-7A72-4313-8FB6-CB689A167E91@fh-muenster.de>
In-Reply-To: <3D4D034B-7A72-4313-8FB6-CB689A167E91@fh-muenster.de>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=True; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Owner=pravb@ntdev.microsoft.com; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SetDate=2020-04-06T22:53:38.3152583Z; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Name=General; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Application=Microsoft Azure Information Protection; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ActionId=1cad61a8-76c7-4549-828f-401dc3a2b3d2; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Extended_MSFT_Method=Automatic
authentication-results: spf=none (sender IP is ) smtp.mailfrom=pravb@microsoft.com;
x-originating-ip: [2001:4898:80e8:0:95d8:3f73:f682:d302]
x-ms-publictraffictype: Email
x-ms-office365-filtering-ht: Tenant
x-ms-office365-filtering-correlation-id: 4a194db8-1199-4689-672c-08d7da7d8010
x-ms-traffictypediagnostic: MW2PR00MB0299:|MW2PR00MB0299:
x-ms-exchange-transport-forked: True
x-microsoft-antispam-prvs: <MW2PR00MB029902F14751AEE2798414A8B6C20@MW2PR00MB0299.namprd00.prod.outlook.com>
x-ms-oob-tlc-oobclassifiers: OLM:10000;
x-forefront-prvs: 0365C0E14B
x-forefront-antispam-report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:CO2PR00MB0181.namprd00.prod.outlook.com; PTR:; CAT:NONE; SFTY:; SFS:(10019020)(4636009)(346002)(376002)(366004)(136003)(396003)(39860400002)(10290500003)(966005)(82960400001)(82950400001)(478600001)(110136005)(8990500004)(54906003)(81166006)(53546011)(7696005)(86362001)(6506007)(8936002)(81156014)(2906002)(8676002)(66446008)(66556008)(66476007)(316002)(52536014)(66946007)(64756008)(107886003)(186003)(33656002)(4326008)(9686003)(5660300002)(71200400001)(55016002)(76116006); DIR:OUT; SFP:1102;
received-spf: None (protection.outlook.com: microsoft.com does not designate permitted sender hosts)
x-ms-exchange-senderadcheck: 1
x-microsoft-antispam: BCL:0;
x-microsoft-antispam-message-info: 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
x-ms-exchange-antispam-messagedata: qW1IFsdmJA5k2QYSPIMMv35mzDlOpQlMUDttybqmuEN2BcZXRJaz8niKAtcU15CHzGO3YLzrrrnJ7+73U1ONI8XefhosfpZdJGmh24QZc9nHvhSJ2koiTn1GsUSotX5yWu9SeWB3SvaYLjda0HoM8KBB2dDg03mluLHLQCWfBkHg/Dp/b5DsrxVlUsVRHHYmuV8/7Zejgw4pmtJzRoCm9Q==
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-OriginatorOrg: microsoft.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 4a194db8-1199-4689-672c-08d7da7d8010
X-MS-Exchange-CrossTenant-originalarrivaltime: 06 Apr 2020 22:54:44.9820 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: vs2rQQ2g6IR2xmuuSqEXev6XXzEgxZhq9AdlUJI/aJs2zoms02Iz0lFWcZUXRZ6vrkZItl5jtWluBK0TOMJCvr/EjpHY48M9aCmmYHYUAyg=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR00MB0299
Archived-At: <https://mailarchive.ietf.org/arch/msg/tcpm/3QNtb82NuGuygz-DVWj0Aqg9uYw>
Subject: Re: [tcpm] [EXTERNAL] WGLC for draft-ietf-tcpm-rack-08
X-BeenThere: tcpm@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: TCP Maintenance and Minor Extensions Working Group <tcpm.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/tcpm>, <mailto:tcpm-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/tcpm/>
List-Post: <mailto:tcpm@ietf.org>
List-Help: <mailto:tcpm-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/tcpm>, <mailto:tcpm-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 06 Apr 2020 22:54:49 -0000

We reviewed the latest version of RACK as a part of the TCPM WGLC and this is some feedback: 

Section 5 Requirements
>>  For each packet sent, the sender MUST store its most recent transmission time 
It is important to call out that in practice for sends that are batched together in time, an implementation may choose to keep per-send transmission timestamps instead of per-packet. This improves memory efficiency. The way the RFC requirement is worded it seems to exclude such an optimization. 

Section 4 Design Rationale for Reordering Tolerance
>>If RACK becomes widely deployed, the underlying networks may introduce more reordering for higher throughput.
A better word here would be universally deployed because otherwise networks would be unfairly harming TCP stacks that have not deployed RACK. Plus as pointed out, reordering puts other strains on the network including ECMP, RSS, hardware offloads etc. Consider removing any recommendations for networks from this draft to prevent any unintentional relaxing of requirements on networks. This section should ideally only focus on why RACK chooses to relax reordering requirements as they pertain to loss detection and recovery. 

>>temporarily override the reorder window
Nit: Let's consistently call this reordering window throughout the draft.


Section 7.2 Upon receiving an ACK   Step 5.
>>For timely loss detection, the sender MAY install a "reordering settling" timer set to fire at the earliest moment at which it is safe to conclude that some packet is lost.
At least in lab tests this timer seems to make a big difference. Recommend changing this to a SHOULD instead of MAY.

>>This can be implemented by using a seperate doubly-linked list sorted in time order.
Typo separate. We shouldn't recommend a specific data structure. 

Some questions that need more explanation: 
1. What about TLP and its relationship to Limited Transmit? Both of them are techniques trying to solve the same problem. Its important to clarify whether Limited Transmit is left unchanged from RFC 6675. It is also unclear whether Limited Transmit should be upgraded from a MAY to a SHOULD. The non-SACK case might benefit from Limited Transmit? 
2. Why does TLP require SACK? In the case SACK negotiation fails, or SACK blocks are stripped in the network, TLP may still recover faster than an RTO when FlightSize is 1.


-----Original Message-----
From: tcpm <tcpm-bounces@ietf.org> On Behalf Of Michael Tuexen
Sent: Monday, March 30, 2020 3:28 PM
To: tcpm IETF list <tcpm@ietf.org>
Subject: [EXTERNAL] [tcpm] WGLC for draft-ietf-tcpm-rack-08

Dear all,

just a quick reminder:

We are currently running a WGLC for TCP RACK until Tuesday, April 7th 2020.

Please send any comments, including indications to support this document, to the TCMP mailing list by then.

The ID is available at
https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftools.ietf.org%2Fhtml%2Fdraft-ietf-tcpm-rack-08&amp;data=02%7C01%7Cpravb%40microsoft.com%7C0f4389073900466c89c408d7d4f9b460%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637212041259507026&amp;sdata=nQghPe61ph4EBThh4xRYp9LTmfisCp6LZAj96leSpOI%3D&amp;reserved=0

Best regards
Michael