Date: Tue, 27 Jul 93 12:51:44 -0400
From: Greg Vaudreuil <gvaudre(_at_)CNRI(_dot_)Reston(_dot_)VA(_dot_)US>
Comments on the Schiller MIME/PEM Proposal
1) RFC1421 PEM allows for multiple PEM objects in a single PEM
message. A message with multiple PEM objects will be returned to
MIME in a format that is not easily manipulated, i.e., the
individual objects are not distinct. Note that this condition can
occur both for content-domains RFC822 and MIME if multiple MIME
objects are PEMed together.
Two solutions come to mind. The first is to prohibit multiple PEM
objects in a single Application/PEM-1421, and the other is to
specify some post-processing rules by which the multiple PEM
objects are returned in a MIME multipart format.
I prefer the "prohibit multiple PEM objects" approach. I'll hunt for
some appropriate words to express this.
2) PEM provides (via the RFC 934 mechanism) for nested PEMed
objects. This is useful for forwarding PEMed messages and attached
comments. Because the nesting rules of RFC934 and MIME are quite
different, this is where most of the complexity of MIME/PEM
integration exists.
I will have to double check the exact wording of RFC1421. My take on
this is that if Content-Domain is RFC822, then the RFC934 mechanism
should be followed within the PEM body. However if Content-Domain
MIME is in effect, then MIME mechanisms should be used to nest
items within the PEM body.
An example of a nested PEM object in the MIME context similar to
the one provided in the Crocker, Freed, Galvin, Rose draft would be
very helpful in understanding how these message structuring issues
would be addressed.
OK, I'll put one together.
-Jeff