Re: [core] Chair's review of draft-ietf-core-hop-limit-02.txt

<> Mon, 25 February 2019 07:22 UTC

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To: Carsten Bormann <>, Jim Schaad <>
CC: core <>, "" <>
Thread-Topic: [core] Chair's review of draft-ietf-core-hop-limit-02.txt
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Date: Mon, 25 Feb 2019 07:22:23 +0000
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Subject: Re: [core] Chair's review of draft-ietf-core-hop-limit-02.txt
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Hi Carsten, Jim, all,

I do agree with Jim that it is early to have a “SHOULD deploy” level. At least that is not the intent of the text which triggered the comment. 

The intent is to allow for a configurable behavior of proxies which support the option. That wording can be updated to avoid misinterpretation, e.g.,:

   If a CoAP proxy receives a request which does not include a Hop-Limit
   option, it SHOULD insert a Hop-Limit option when relaying the request
   to a next hop (absent explicit policy/configuration otherwise). 

   A CoAP proxy MAY be instructed, using a configuration parameter, to
   insert a Hop-Limit option when relaying a request which do not
   include the Hop-Limit option.


> -----Message d'origine-----
> De : Carsten Bormann []
> Envoyé : samedi 23 février 2019 06:58
> À : Jim Schaad
> Cc : BOUCADAIR Mohamed TGI/OLN; core;
> Objet : Re: [core] Chair's review of draft-ietf-core-hop-limit-02.txt
> On Feb 22, 2019, at 22:47, Jim Schaad <> wrote:
> >
> > My gut feeling is that the answer should be yes it should become a
> recommended option for all CoAP proxies.  I am not sure that this is the time
> for that to happen.  I think that in the next couple of years there may be a
> larger need to develop some BCPs for proxies and that would be the time to
> make the recommendation.
> Right.  So the specific question for the WG is:
> Are we ready to strongly recommend (on a “SHOULD deploy” level) hop-limit as
> our proxy loop mitigation technique now?
> Or should we wait with such a recommendation until we have had a broader view
> at proxy requirements?  (E.g., then, MAYBE we might want to go for Via-like
> loop prevention instead — very big MAYBE, as Via is expensive with IPv6.)
> I don’t have a strong opinion either way and therefore would like some more
> feedback from the WG.
> In any case, the place in DOTS where it says how CoAP is used for DOTS should
> also say “please do deploy hop-limit where proxies are used” in the strength
> that the DOTS people are comfortable with.
> While the hop-limit draft is not heavily associated with DOTS, maybe it would
> be useful to add some “not just for DOTS” language as well (after all, that
> was the point of splitting it out).
> Grüße, Carsten