[dispatch] IANA Registry for parameters for the MIME header field "Content-Type" ?

[Daniel Kahn Gillmor <[e-mail]>]

Hey IETF folks--

While polishing draft-ietf-lamps-header-protection, i noticed that there
is no IANA registry for parameters for the Content-Type MIME header
field.

Some of these are pretty common, like "boundary" (for distinguishing
subparts of any multipart MIME part) and "charset" (for identifying the
encoding used in a text part), and others are more obscure.

Scanning a reasonably large mail corpus, i found a range of parameters
used:

  - boundary
  - charset
  - delsp
  - format
  - markup
  - micalg
  - name
  - protected-headers
  - protocol
  - reply-type
  - report-type
  - smime-type
  - type

I note that there are also some comparably-structured "parameter" fields
for the Content-Disposition header (e.g. "filename"), though i doubt
that there are so many as there are for Content-Type.

It seems like it might be worthwhile to try to establish a registry for
these parameters (at least for Content-Type, so that there is at least a
stable reference that can be used by a MUA that wants to handle the
parts appropriately..

Any thoughts about the right place to do this work on e-mail in the
IETF?

        --dkg

PS to be clear, it is not the intent of this message to:

 - create any new document dependency that might block
   draft-ietf-lamps-protected-headers

 - define any new parameters for Content-Type