Re: [core] [Anima] constrained resources at root for debugging connectivity

Carsten Bormann <cabo@tzi.org> Thu, 22 July 2021 08:43 UTC

Return-Path: <cabo@tzi.org>
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 3B0823A3E63; Thu, 22 Jul 2021 01:43:46 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.899
X-Spam-Level:
X-Spam-Status: No, score=-1.899 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
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 QOn6IR7GOCZP; Thu, 22 Jul 2021 01:43:40 -0700 (PDT)
Received: from gabriel-smtp.zfn.uni-bremen.de (gabriel-smtp.zfn.uni-bremen.de [IPv6:2001:638:708:32::15]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id D87363A3E58; Thu, 22 Jul 2021 01:43:34 -0700 (PDT)
Received: from [192.168.217.118] (p548dcc89.dip0.t-ipconnect.de [84.141.204.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by gabriel-smtp.zfn.uni-bremen.de (Postfix) with ESMTPSA id 4GVmFK1YFKz31Lw; Thu, 22 Jul 2021 10:43:33 +0200 (CEST)
Content-Type: text/plain; charset=utf-8
Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.7\))
From: Carsten Bormann <cabo@tzi.org>
In-Reply-To: <25674.1626896178@localhost>
Date: Thu, 22 Jul 2021 10:43:32 +0200
Cc: Esko Dijk <esko.dijk@iotconsultancy.nl>, "anima@ietf.org" <anima@ietf.org>, "core@ietf.org" <core@ietf.org>
X-Mao-Original-Outgoing-Id: 648636212.862666-8d6445ef3d0b09f09ae679c47ceaf0d6
Content-Transfer-Encoding: quoted-printable
Message-Id: <7C073EC6-1335-454F-9E34-C60DD8E94167@tzi.org>
References: <AM8P190MB097901225CE72EF7973ADCC4FD139@AM8P190MB0979.EURP190.PROD.OUTLOOK.COM> <AM8P190MB09791181A1D8F74ECDC6F04FFD129@AM8P190MB0979.EURP190.PROD.OUTLOOK.COM> <d2da849f46f57a410d28f47d4ed32f97@bbhmail.nl> <AM8P190MB0979B2CB8DEDB7E9FDCF9C73FDE19@AM8P190MB0979.EURP190.PROD.OUTLOOK.COM> <6b1b6fc38752b6f0598d4289c7cfeb31@bbhmail.nl> <AM8P190MB0979C689144DE6989C5D33E7FDE29@AM8P190MB0979.EURP190.PROD.OUTLOOK.COM> <8c3348a5adb2b2c0d0a4b615cadc75a6@bbhmail.nl> <AM8P190MB0979EC82DA418ECF74440BA9FDE29@AM8P190MB0979.EURP190.PROD.OUTLOOK.COM> <57da5e79b97eeca3967da119a60b0ed6@bbhmail.nl> <AM8P190MB0979EBF594EA31877BFBED5DFDE29@AM8P190MB0979.EURP190.PROD.OUTLOOK.COM> <18975.1626788349@localhost> <AM8P190MB097925B04E575071242002CFFDE39@AM8P190MB0979.EURP190.PROD.OUTLOOK.COM> <25674.1626896178@localhost>
To: Michael Richardson <mcr+ietf@sandelman.ca>
X-Mailer: Apple Mail (2.3608.120.23.2.7)
Archived-At: <https://mailarchive.ietf.org/arch/msg/core/hML-Iz_eudyxw6-vgKJtQku4HCM>
Subject: Re: [core] [Anima] constrained resources at root for debugging connectivity
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: Thu, 22 Jul 2021 08:43:56 -0000


> On 2021-07-21, at 21:36, Michael Richardson <mcr+ietf@sandelman.ca> wrote:
> 
> Signed PGP part
> 
> Esko Dijk <esko.dijk@iotconsultancy.nl> wrote:
>> There is already a "CoAP ping" described in RFC 7252 that can be
>> used. It does not access any resource, just the CoAP server endpoint at
>> CoAP message layer. As a side effect of this ping your DTLS stack will
>> set up the connection which is handy.
> 
> I recalled that later in the day that CoAP "ping" is not connected to CoAP
> "echo" :-)

The Echo option is not an echo in the sense of an ICMP echo.
(Maybe we should fix the name to “cookie”.)

> I think that there is also potentially a need for a way to debug possible MTU
> issues.

Good point, CoAP Ping (empty CON messages) cannot do that.

Actually, the fact that it was possible to set up DTLS should give one considerable confidence; the CoAP Ping is not needed to verify pure presence.  Verifying that that server actually speaks a specific protocol would need to be part of that protocol though.

Also, cough, cough, https://datatracker.ietf.org/doc/html/rfc6520 gives you a nice way to ping a DTLS server with different MTU sizes.
(Ignoring the fact that an incorrect implementation led to the biggest TLS, er, “event” we ever had.)

Grüße, Carsten