Re: [core] Adam Roach's No Objection on draft-ietf-core-hop-limit-06: (with COMMENT)

Carsten Bormann <> Thu, 17 October 2019 10:10 UTC

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From: Carsten Bormann <>
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Date: Thu, 17 Oct 2019 12:10:27 +0200
Cc: Adam Roach <>, The IESG <>, "" <>, Jaime Jimenez <>, "" <>, "" <>
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Subject: Re: [core] Adam Roach's No Objection on draft-ietf-core-hop-limit-06: (with COMMENT)
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I seem to remember that for a short time during the development of OSCORE we thought about defining an HTTP header field “CoAP-Option” (not sure that was the actual name) that can be used for tunneling any kind of CoAP Options through HTTP segments of a proxy path.
I forget why we eventually decided we didn’t need this, but the idea of course can be revived; CoAP’s option types are stylized enough that this can be made to work in general.
I wouldn’t necessarily put this into this draft; an update of RFC 8075 might be a good receptacle.

Grüße, Carsten

> On Oct 17, 2019, at 09:28, <> <> wrote:
> Hi Adam, 
> It was raised in the WG whether we want to fix this or only record the issue. I'm not convinced it is worth to request a new HTTP header to address a specific case, e.g., two COAP realms connected via an HTTP leg. For such loop to happen, this means that CoAP nodes are able to communicate natively using CoAP without crossing the proxies. The natural question is why then these proxies are deployed. 
> I do think that the current approach in the draft is the right one: record a potential issue without speculating on how the issue is critical given that we don't have arguments.
> Please note also that Section 10 of RFC7252 only discusses CoAP-to-HTTP proxy and vice-versa, and does not discuss CoAP-to-HTTP-to-CoAP schemes. May be an item to clarify in 7252-bis.
> Thank you. 
> Cheers,
> Med
>> -----Message d'origine-----
>> De : Adam Roach via Datatracker []
>> Envoyé : mercredi 16 octobre 2019 06:03
>> À : The IESG
>> Cc :; Jaime Jimenez; core-
>> Objet : Adam Roach's No Objection on draft-ietf-core-hop-limit-06: (with
>> Adam Roach has entered the following ballot position for
>> draft-ietf-core-hop-limit-06: No Objection
>> When responding, please keep the subject line intact and reply to all
>> email addresses included in the To and CC lines. (Feel free to cut this
>> introductory paragraph, however.)
>> Please refer to
>> for more information about IESG DISCUSS and COMMENT positions.
>> The document, along with other ballot positions, can be found here:
>> ----------------------------------------------------------------------
>> ----------------------------------------------------------------------
>> Thanks to everyone who worked on this document.
>> I'm a little surprised that the treatment of loops that go between HTTP and
>> CoAP networks involves a simple observation that detection of such cases
>> simply
>> won't work, without any attempt at mitigation.
>> I'm sympathetic to the observation during WGLC that directly interworking
>> with
>> RFC 8586 isn't feasible, but surprised that more primitive approaches to at
>> least preserving the CoAP Hop-Count as it crossed the HTTP network weren't
>> considered. There are aesthetic discussions to be had around, e.g.,
>> defining an
>> HTTP "Hop-Count" header field (which isn't acted on by the HTTP network,
>> but
>> serves the purpose of preserving the value during transit) or overloading
>> the
>> semantics (but not really the meaning) of the HTTP "Max-Forwards" header
>> field,
>> or (in extremis) squirreling the Hop-Count away in the `pseudonym` portion
>> of
>> the inserted HTTP Via header field.  But I think the high order bit here is
>> that preserving the Hop-Count value through the HTTP network would be
>> trivial,
>> and would prevent the identified shortcoming of the current mechanism.