Subject: fax-specific fields and MIME parts

From: Dan Wing <[email-masked]>
Date: Thu, 17 Dec 1998 11:41:27 -0800 (PST)

Related to draft-ietf-fax-eifax-11.txt, rfc2305, and the recent
IMC-sponsored FaxConnect event, I have become aware of the following
situation:

  There were apparently several products which generated
  fax-specific headers, such as Fax-From: and Fax-To:, or which generated
  a fax-specific MIME part, such as a text/plain which contained 
  coverpage or human-readable routing information.

Problems:

  1.  Such new header fields (Fax-To and Fax-From) are not standardized
      and will cause interoperability problems with devices, such as
      traditional MUAs, which do not parse or generate such headers.

  1a.  if the 'Fax-to:' and 'Fax-from:' headers are used to _replace_ the
       normal 'From:' and 'To:' headers then information normally required
       by UAs is unavailable.

  1b.  different implementations might use these headers with different
       meaning.

  1c.  applications generating these headers might be assuming that their
       presence triggers some different behaviour than normal mail UAs.

  2.  MIME parts which are intended to be used for coverpage generation
      will cause duplicate coverpage generation (and other
      interoperability issues).

  2a.  multiple ways of generating cover page information which result in
       multiple cover pages would be confusing to a recipient.  

Question to the Working Group:

  Should we add language to RFC2305bis or to draft-ietf-fax-eifax
  to discourage or perhaps standardize such behavior, or are the
  problems described in (1) and (2) above be ignored?
 
At the Orlando IETF, James had mentioned an 'implementors guide', but as
the two problems above relate to interoperability I feel it may be more
appropriate to put them in the standard(s) themselves instead of in a
companion document.
 
Comments?

-Dan Wing

[Thanks to Graham and Larry for helping flesh this out]