Re: [core] Opsdir last call review of draft-ietf-core-hop-limit-05

Thomas Fossati <Thomas.Fossati@arm.com> Wed, 02 October 2019 16:31 UTC

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From: Thomas Fossati <Thomas.Fossati@arm.com>
To: Carsten Bormann <cabo@tzi.org>
CC: "core@ietf.org" <core@ietf.org>, Thomas Fossati <Thomas.Fossati@arm.com>
Thread-Topic: [core] Opsdir last call review of draft-ietf-core-hop-limit-05
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Date: Wed, 02 Oct 2019 16:31:17 +0000
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Archived-At: <https://mailarchive.ietf.org/arch/msg/core/tg_m_NuzP4usxz6unNyUxJb6iEk>
Subject: Re: [core] Opsdir last call review of draft-ietf-core-hop-limit-05
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Hi Carsten,

[trimming the CC list to CoRE only]

On 02/10/2019, 16:47, "core on behalf of Carsten Bormann" <core-bounces@ietf.org on behalf of cabo@tzi.org> wrote:
> In the CoRE Virtual Interim we just had (minutes to be posted), we
> said that the WG wouldn’t have a problem with changing the “are
> expected to” (implement and default-enable) in Section 1.1 into a
> stronger MUST.  This would still leave the option for a Proxy operator
> to turn off the use of the Option, i.e., a receiver cannot rely on
> actually receiving it.  Let’s wait for the ADs to chime in on that…

Having thought a bit more on the specific change that was discussed
during the interim:

   CoAP proxies that do not have specific knowledge that proxy
   forwarding loops are avoided in some other way, MUST
   implement this option and have it enabled by default.

I think this should be tweaked further.

How I read the sentence is: "You can't deploy a proxy box that can
potentially be part of a forwarding loop, if that box is not able to
understand and process the option."

Trouble is that the conditional clause looks implausible in general - it
seems to presume divination skills.

If we want this option to be part of the future CoAP ecosystem (which I
think is a good thing), we should just say something like:

   Newly deployed CoAP proxies MUST implement this option and have it
   enabled by default.

One of the good properties about this option IIUC is that even one
implementer can make a difference -- i.e., you don't need fork-lift
upgrades to start getting some benefit.

Cheers, t


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