Re: [Ace] ace-coap-est-08: using /skg with Accept Option set to TBD287

[Klaus Hartke <[e-mail]>]

Esko Dijk wrote:
> So the client asks for 286, but gets 62 (which has 286
> embedded in it as one of the parts). At first sight this
> appears incompatible with CoAP RFC7252 logic.
>
> A strict server implementation might return 4.06 Not
> Acceptable since the server code has registered the
> response type to be 62; and the client asks something
> different.

 RFC 7252 is quite strict about this:

   If the preferred Content-
   Format cannot be returned, then a 4.06 "Not Acceptable" MUST be sent
   as a response, unless another error code takes precedence for this
   response.

That's a MUST, not a SHOULD.

Since a client might actually support multiple formats, it might make
sense to indicate all supported formats in order of preference e.g. as
query parameters:

Client:
  POST /.well-known/est/skg?ct=TBD287&ct=281
    Accept: 62
    ...

Server:
  2.04
  Content-Format: 62
  Payload: (multipart containing TBD287)

Klaus