[MMUSIC] File transfer issue 49: multipart/mixed or multipart/related

[Miguel Garcia <Miguel.Garcia at nsn.com>]

During the last IETF meeting there was a comment with respect the 
relation of SDP bodies and icon bodies.

When the two bodies appear together, the draft says they need to be 
wrapped in a MIME multipart/mixed container. Adam commented that it 
should be multipart/related instead.

RFC 2387 defines the multipart/related MIME wrapper:

   The Multipart/Related media type is intended for compound objects
   consisting of several inter-related body parts.  For a
   Multipart/Related object, proper display cannot be achieved by
   individually displaying the constituent body parts.

RFC 2046 defines the multipart/mixed MIME wrapper:

   The "mixed" subtype of "multipart" is intended for use when the body
   parts are independent and need to be bundled in a particular order.
   Any "multipart" subtypes that an implementation does not recognize
   must be treated as being of subtype "mixed".


The difference between both is subtle, in my opinion. The 
multipart/related definition says that "proper display cannot be 
achieved by individually displayign the constituent body parts", which 
is not entirely true: SDP will be meaningful in the absence of an icon; 
the icon is also meaningful isolated, although it is not linked to any 
file descriptor.

The multipart/mixed definition speaks about "independent parts that need 
to be bundled in a particular order", which is probably true, because 
although the SDP and the icon are independent, the SDP should be read first.

While I don't have a strong opinion, I would suggest to leave the draft 
with the current indication of multipart/mixed.

Comments?

/Migel
--
Miguel A. Garcia           tel:+358-50-4804586
Nokia Siemens Networks     Espoo, Finland


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