[core] "No Content" CoAP option (was Re: "Too Many Requests Response Code for CoAP" draft (draft-keranen-core-too-many-reqs-00))

[Ari Keränen <[e-mail]>]

> On 5 Mar 2018, at 19.51, Klaus Hartke <[e-mail]> wrote:
> 
> Michael Koster wrote:
>> We are proposing a code in Pub/Sub for the case of a broker where the topic
>> exists but there is not a valid data value.
> 
> This sounds strangely familiar:
> https://tools.ietf.org/html/draft-hartke-core-pending-02

The 2.05 "Content Pending" has indeed quite similar semantics to our proposal and should work for pub/sub too.

But the dual use of the "X" vs. "X pending" was a bit unclear in the draft now. Maybe it's worth clarifying already in the intro that it's the new payload format that indicates this difference. Could also mention explicitly that these are not new Response Codes, since that's probably what most readers would expect this  draft to specify.

>> We thought that an equivalent to the HTTP 204 "No Content" could be used but
>> the code conflicts with 2.04 in CoAP, so we propose 2.07
> 
> We had that in the -01 version of the draft, but that didn't seem to
> gain traction, so we've switched to a new content-format to indicate
> this status. Would this work for pub/sub?

Do you remember what was the reason for lack of traction? 

Implementation-wise it seems slightly simpler to handle different "error/pending" cases just by looking at the response code and not having to bother about the payload type, but I don't have a strong opinion on this (or an implementation, at least yet).


Cheers,
Ari