RFC 2157 (rfc2157) - Page 3 of 49

Mapping between X

RFC 2157                X.400/MIME Body Mapping             January 1998


1.1.  Glossary

   The following terms are defined in this document:

   Body part
      Part of a message that has a unique type. This term comes from
      X.400; the corresponding term in MIME (RFC 2046) is limited to use
      in parts of a multipart message; the term "body" may correspond
      better.

   Content-type
      Type information indicating what the content of a body part
      actually is. This term comes from MIME; the corresponding X.400
      term is "body part type".

   Mapping
      (noun): A description of how to transform an X.400 body part into
      a MIME body part, or how to transform a MIME body part into an
      X.400 body part.

   Equivalence
      A set of two mappings that taken together provide a lossless
      conversion between an X.400 body part and a MIME body part

   Encapsulation
      The process of wrapping something from one of the mail systems in
      such a way that it can be carried inside the other mail system.
      When encapsulating, it is not expected that the other mail system
      can make reasonable sense of the body part, but a gateway back
      into the first system will always be able to convert the body part
      without loss back to its original format.

   HARPOON encapsulation
      The encapsulating of a MIME body part by putting it inside an IA5
      body with all headers and encoding intact. First described in RFC
      1496 [HARPOON].

   Tunneling
      What happens when one gateway encapsulates a message and sends it
      to another gateway that decapsulates it.  The hope is that this
      will cause minimal damage to the message in transit.

   DISCUSSION
      At many points in this document, the author has found it useful to
      include material that explains part of the reasoning behind the
      specification. These sections all start with DISCUSSION: and
      continue to the next numbered section heading; they do not dictate
      any additional requirements on a gateway.



Alvestrand                  Standards Track