Re: [core] Tsvart last call review of draft-ietf-core-too-many-reqs-04

Ari Keränen <ari.keranen@ericsson.com> Sun, 21 October 2018 18:50 UTC

Return-Path: <ari.keranen@ericsson.com>
X-Original-To: core@ietfa.amsl.com
Delivered-To: core@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 80D9D130E9E for <core@ietfa.amsl.com>; Sun, 21 Oct 2018 11:50:42 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -3.386
X-Spam-Level:
X-Spam-Status: No, score=-3.386 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.064, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FROM_EXCESS_BASE64=0.979, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001] autolearn=unavailable autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=ericsson.com header.b=DSjdIY3i; dkim=fail (1024-bit key) reason="fail (body has been altered)" header.d=ericsson.com header.b=A+WzyBFa
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 kxgWAm-_FcBc for <core@ietfa.amsl.com>; Sun, 21 Oct 2018 11:50:35 -0700 (PDT)
Received: from sessmg23.ericsson.net (sessmg23.ericsson.net [193.180.251.45]) (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 0A0F3130E7E for <core@ietf.org>; Sun, 21 Oct 2018 11:50:34 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; d=ericsson.com; s=mailgw201801; c=relaxed/simple; q=dns/txt; i=@ericsson.com; t=1540147833; x=1542739833; h=From:Sender:Reply-To:Subject:Date:Message-ID:To:CC:MIME-Version:Content-Type: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=KMyxUhz0TE+BHWZGGpGM7dyV1zpFh9PrPF8D6mZ9c5Y=; b=DSjdIY3ihVWfbxTpWRwDMPBuuK937AFWyJqPtOBsuY0/DgKICMJPyoPJYjK/OtxE U7euJuqlbaWHXU1Co6vZomzXeTNV9volQneWvp5XZ1cOFZzOZ25TURQeY/TlKbFb /D4hbYIhxyGBxoivOYm4mw71ZEuYDzvZHIlKDM+Mv3A=;
X-AuditID: c1b4fb2d-fb3d09e000003a27-4d-5bccca79f0b8
Received: from ESESSMB501.ericsson.se (Unknown_Domain [153.88.183.119]) by sessmg23.ericsson.net (Symantec Mail Security) with SMTP id DD.37.14887.97ACCCB5; Sun, 21 Oct 2018 20:50:33 +0200 (CEST)
Received: from ESESBMB504.ericsson.se (153.88.183.171) by ESESSMB501.ericsson.se (153.88.183.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1466.3; Sun, 21 Oct 2018 20:50:32 +0200
Received: from EUR02-AM5-obe.outbound.protection.outlook.com (153.88.183.157) by ESESBMB504.ericsson.se (153.88.183.171) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1466.3 via Frontend Transport; Sun, 21 Oct 2018 20:50:32 +0200
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ericsson.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=ngFSeowesLUvEjiqHUAw2x1YXCagQ/QWwPUc0DBcsRc=; b=A+WzyBFaHVLbkPA+RsNC4XuSBwkNRpYsB8jVAWwJpQhpmU9fF2J0WKnGMEb5M8kpRnxQBNiO1KDm/ukCmq8ZK7aahFeBv81K18guRMvQqSWzBaVfo/4BVO38VweEoB+gj1OpuEYk7aD2HHubuXQ2q4UwHT4mF0PZN2DA4oHoeXY=
Received: from HE1PR07MB4236.eurprd07.prod.outlook.com (20.176.166.145) by HE1PR07MB3243.eurprd07.prod.outlook.com (10.170.246.22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.1273.15; Sun, 21 Oct 2018 18:50:31 +0000
Received: from HE1PR07MB4236.eurprd07.prod.outlook.com ([fe80::b074:afe2:469c:dd95]) by HE1PR07MB4236.eurprd07.prod.outlook.com ([fe80::b074:afe2:469c:dd95%2]) with mapi id 15.20.1273.014; Sun, 21 Oct 2018 18:50:31 +0000
From: =?utf-8?B?QXJpIEtlcsOkbmVu?= <ari.keranen@ericsson.com>
To: Jana Iyengar <jri.ietf@gmail.com>
CC: "tsv-art@ietf.org" <tsv-art@ietf.org>, "draft-ietf-core-too-many-reqs.all@ietf.org" <draft-ietf-core-too-many-reqs.all@ietf.org>, "ietf@ietf.org" <ietf@ietf.org>, "core@ietf.org" <core@ietf.org>
Thread-Topic: Tsvart last call review of draft-ietf-core-too-many-reqs-04
Thread-Index: AQHUZ0al/vYbOEm8REOs/MI8MHZ8N6UqD1MA
Date: Sun, 21 Oct 2018 18:50:31 +0000
Message-ID: <5C4D6ED9-4EA8-4113-BFC3-2FE22FA2BEE1@ericsson.com>
References: <153991061080.22113.5687839428927498383@ietfa.amsl.com>
In-Reply-To: <153991061080.22113.5687839428927498383@ietfa.amsl.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach: yes
X-MS-TNEF-Correlator:
authentication-results: spf=none (sender IP is ) smtp.mailfrom=ari.keranen@ericsson.com;
x-originating-ip: [2001:14bb:180:9de9:c917:11cd:c0cb:e1a5]
x-ms-publictraffictype: Email
x-microsoft-exchange-diagnostics: 1; HE1PR07MB3243; 6:5ybSz/nykfDsdX4OtwRGKj4SJy2ZJHNHf3jLPPz8PQqchLfRkpd3rEaxIZWxcRXOjwpO/uqFduzy/kwfi502qIGNiDgPGRfdrXfe5vT3mKaj0Y1tG389H4rHwA45dXaurjV1yyqxTGxA9jmi33hANVVbOBMucfK7RMH2ka7uf8NBi85RlTnnnUQgfYBNyIdt/rsc2qKA7LDA1cr7JEZXyAXaTpbMe3wdKQ6g4i75vMGxoGUNA3B1G+bzses0DDU5o5/drZrEYZf25FvMiThIIbdd31GNWC7AcQCbLL9Z8mKVUsPVD4FKGXoI2fc452Nzk8H0QDyR+rdrZFeT248PCvBP9XP1H0In+ASwpwmsMORgp/GeG2mki1Ct503e4F1FxSRL/7nzW72hrqXTQql48fzwjG/+JZ7eAjWJKfNO8XvwGQNmQhs6EWoE54qLjdxU1gbr/0P2TnMlUc3wstnvAw==; 5:HuQCSPRTzxYr9Z8Y1BhzcrYhf16JxFLCAGcDQuLLBDKUAvacomd8BNY19CsLqkFwqPhrsp/Fwmiw3bXY2vv1ATLKh/bxapDC09xN9h6OOAzMX3S8DxKSRMWwzjBytFoSN10NBhmeiPzo45Y6IV3MtS3RVQgBt3HWSJ7Fj5/y0l4=; 7:8DfuKOQtt/jT+GdYivP7AZLBKq+2oEFV2paUXEemWM1zKlPRfRwf+Q+tC+UgRvviNQ2aFivMyUN0TMTubOynquN680n3TfC3Vp/SvtQlqXgDK2+X1oUpZJiLGcUmYOO6JijefBpT4Lc5ebhoYeX1Aw==
x-ms-exchange-antispam-srfa-diagnostics: SOS;
x-ms-office365-filtering-correlation-id: 92f57117-576b-4db3-9914-08d637861395
x-microsoft-antispam: BCL:0; PCL:0; RULEID:(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600074)(711020)(2017052603328)(7153060)(49563074)(7193020); SRVR:HE1PR07MB3243;
x-ms-traffictypediagnostic: HE1PR07MB3243:
x-microsoft-antispam-prvs: <HE1PR07MB3243104EC4203246FFCA9D2A85FB0@HE1PR07MB3243.eurprd07.prod.outlook.com>
x-exchange-antispam-report-test: UriScan:(158342451672863)(85827821059158);
x-ms-exchange-senderadcheck: 1
x-exchange-antispam-report-cfa-test: BCL:0; PCL:0; RULEID:(8211001083)(102415395)(6040522)(2401047)(8121501046)(5005006)(3002001)(3231355)(944501410)(4983020)(52105095)(10201501046)(93006095)(93001095)(148016)(149066)(150057)(6041310)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(20161123558120)(20161123562045)(20161123564045)(20161123560045)(201708071742011)(7699051)(76991095); SRVR:HE1PR07MB3243; BCL:0; PCL:0; RULEID:; SRVR:HE1PR07MB3243;
x-forefront-prvs: 083289FD26
x-forefront-antispam-report: SFV:NSPM; SFS:(10009020)(979002)(366004)(346002)(396003)(376002)(39860400002)(136003)(189003)(199004)(46003)(25786009)(6486002)(54906003)(97736004)(4326008)(36756003)(478600001)(68736007)(2906002)(6436002)(186003)(99286004)(85182001)(305945005)(83716004)(82746002)(86362001)(99936001)(5660300001)(6916009)(7736002)(71200400001)(316002)(71190400001)(6506007)(345774005)(53936002)(14454004)(81166006)(14444005)(76176011)(6512007)(81156014)(2616005)(11346002)(486006)(106356001)(85202003)(105586002)(6246003)(476003)(8676002)(256004)(33656002)(5250100002)(6116002)(2900100001)(102836004)(8936002)(446003)(39060400002)(229853002)(969003)(989001)(999001)(1009001)(1019001); DIR:OUT; SFP:1101; SCL:1; SRVR:HE1PR07MB3243; H:HE1PR07MB4236.eurprd07.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; MX:1; A:1;
received-spf: None (protection.outlook.com: ericsson.com does not designate permitted sender hosts)
x-microsoft-antispam-message-info: PgEHTzoLwUXvvEwoziAhMoA+FOdfHI+lyE18jeT+mAeAMYTNu+aLZl0AjNLgkhgLsLIeCe7XRkwU+VCIDanFoO8qsDK6Iju3BRgMa0/X0A4kyY2z5uf4U+5BVq/B9urhmOXKNYFIGWjoEhXTjSRKeUyWjYgQQy+e+NmNtga0DNU62/2qqJ0BeORIVtIb+Hyva638A9SOp9+qnphBX4hZADGr37b2FTvBAkxp9YFbvwWdA2Ha9xXBToL2TadU/ZdBBA+HM4hOB+OD/Z2DZeKVJvOT6awwMsBCw1XqidTJwdXYmEXbgyNsC+RYiiOeEW+qaQ66r/41FiCuNgrcgu1/B/khVWaF6rhhpDhdW+l5qkQ=
spamdiagnosticoutput: 1:99
spamdiagnosticmetadata: NSPM
Content-Type: multipart/signed; boundary=Apple-Mail-31347275-E6CD-4D23-B467-AF0062337057; protocol="application/pkcs7-signature"; micalg=sha1
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 92f57117-576b-4db3-9914-08d637861395
X-MS-Exchange-CrossTenant-originalarrivaltime: 21 Oct 2018 18:50:31.1814 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 92e84ceb-fbfd-47ab-be52-080c6b87953f
X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR07MB3243
X-OriginatorOrg: ericsson.com
X-Brightmail-Tracker: H4sIAAAAAAAAA02SfyzUYRzHe77f7919XW6+ncOnK8mV6ceoyHZT6Sp/aIitf8ytH1e+Qzh1 30NIu6ZWO7OEa7nJYbdqJyul1JQbi0WXUNKI5pImWbQwU8p5rs1/r+fzeT3P5/08e2hS3MmT 0slqLatRq1JlfCFVFteQFZDdYVNuv7EgljdN3CPlRaYqnny0zkTJL/dUkHLjs2pKwYt4ahwU RJjNc0QsES/cncCmJmeymm1hx4VJk4MXiNMLMWftF68KdOhjtB650MDsBGuzFemRkBYzrQjq bd8pvJhB8GPayHNYYsZMQHWhwtGgmCISftoqSWyVElBR1UJiy46gQr/PwXxmD4xcalraLWH8 wJjfiRxMMjYEN28JHezORMC1OSsfOwfh451mJwdBQ2O/QI/oxWl+MNCpdZRFzF542DDkDHQA 2j/1Eg52YcLhxdumpQiI8YTZjrsEHuUF/SMmAl9TAsPdr/iYPWDs8wIP+0r41tEuwPVQMAy9 IzF7Q4+pYOlZgHnPh+n6Eh5uBMCkwUA6sgETDV/bg7HTjWBi0kJhZwtcn3jEw04K9PZ64HIk 6GabnRnWgaVwmCpC243LohoXjyKZEgR9fSbKuHTnVdBeNkJhaTNYC2472RdKC4YFmHfBXLkd YQ6B8dYptNypRLQFeXAsx6UlBgUHsprkkxyXrg5Us9oHaPFnNdfPBzxBNeP7WhBDI5mraLTW phTzVJlcdloL2rh4jv1+TReSUup0NSuTiIwvXynFogRVdg6rST+myUhluRa0hqZkXqJAy7N4 MZOo0rIpLHua1fzvErSLVIe8k9jyttw83YcTeaPPN4SuNBT/sfpmPV7vz76OUgxKlfsbPBdC JHVhmecPdZmvTM0HSyyubjF1jbkDV+cUwlhxrOsn77FffdtmDq8Ij9Q+2mQ+Yt9KnbOeyonK jxKt/XvE3cdNkuZ/PMNn3HY0TgO1CkP35zL290jEl7Yzb1YXD8koLkm1Ywup4VT/AIvqNMRh AwAA
Archived-At: <https://mailarchive.ietf.org/arch/msg/core/rD0yuLDw8gGssreVVVBzk47o1Mc>
Subject: Re: [core] Tsvart last call review of draft-ietf-core-too-many-reqs-04
X-BeenThere: core@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Constrained RESTful Environments \(CoRE\) Working Group list" <core.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/core>, <mailto:core-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/core/>
List-Post: <mailto:core@ietf.org>
List-Help: <mailto:core-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/core>, <mailto:core-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sun, 21 Oct 2018 18:50:42 -0000

Thank you for the review Jana!

Please see inline.

> On 19 Oct 2018, at 3.57, Jana Iyengar <jri.ietf@gmail.com>; wrote:
> 
> Reviewer: Jana Iyengar
> Review result: Ready with Nits
> 
> I've reviewed this document as part of the transport area review team's ongoing
> effort to review key IETF documents. These comments were written primarily for
> the benefit of the transport area directors. Document editors and WG chairs
> should treat these comments just like any other last call comments.
> 
> This is a simple document that defines a new response code for CoAP servers to
> use when under overload. The response code ("4.29 Too Many Requests") is used
> as a flow control signal to indicate to a client that it needs to stop sending
> more "similar" requests. The amount of time that the client needs to back off
> is encoded in the response.
> 
> This is a straightforward document and I see no major issues, but I have a
> couple of suggestions that might help implementers.
> 
> 1. There should be text suggesting what a server MAY do if the client doesn't
> respect the backoff period indicated in the response. For instance, a server
> MAY drop all incoming requests from a client for an extended period of time if
> the client sends a request without waiting for the duration of the backoff
> period (or some such).

Simply dropping incoming requests results likely in retransmissions, which could be counter-productive for reducing load. I think the best way for the server is to answer with a different error code since if it is a well-behaving client, likely the reason for it to not respect the backoff is that it didn’t simply recognize the error code and understand what to do with Max-Age. 

I’m thinking of adding text in “CoAP server behavior” section along the lines of:

  If a client repeats a request that was answered with 4.29 before Max-Age time has passed, it is possible the client did not recognize the error code and the server MAY respond with a more generic error code (e.g., 5.03).

> 2. There should be some text suggesting that the server does not have to (and
> probably should not) respond to every incoming request during overload with
> this response. Even when the server wants to ask clients to back off, it does
> not need to do that on every incoming request from a client. For instance, a
> server can choose to respond to each client once in every estimated round-trip 
> time.

So this would be mainly for the case when client sends multiple requests before it has a chance to receive the 4.29 to an earlier request? For that once every RTT seems indeed reasonable.

> 3. Is the expectation that the client waits for the back off time starting from
> when the response is received? That seems like the most obvious way to do it,
> but it might be useful to clarify precisely when the client's backoff period
> starts.

RFC7252 says that Max-Age is intended to be current at the time of transmission. But since the precision of Max-Age is at the level of seconds, starting a timer when response is received sounds like a fair approximation. 


Cheers,
Ari