RFC 1495 (rfc1495) - Page 2 of 11

Mapping between X

RFC 1495            MHS/RFC-822 Message Body Mapping         August 1993


   document, STD-11, RFC-822 [1], which defines the standard format for
   the exchange of messages.  RFC-822 has proven immensely popular; in
   fact, the 822-connected Internet, is larger than the scope of the
   IP-connected Internet.

   The framework provided by RFC-822 allows for memo-based textual
   messages.  Each message consists of two parts:  the headers and the
   body.  The headers are analogous to the structured fields found in an
   inter-office memo, whilst the body is free-form.  Both parts are
   encoded using ASCII.

   Recently, the Internet Engineering Task Force (IETF) has developed an
   document called,

      Multipurpose Internet Mail Extensions

   or MIME RFC-1341.  The title is actually misleading.  MIME defines
   structure for Internet message bodies.  It is not an extension to
   RFC-822.

   Independently of this, the International standards community
   developed a different framework in 1984 (some say that's the
   problem).  This framework is known as the OSI Message Handling System
   (MHS) or sometimes X.400.

   Since the introduction of X.400(84), there has been work ongoing for
   defining mappings between MHS and RFC-822.  The most recent work in
   this area is RFC-1327 [3], which focuses primarily on translation of
   envelope and headers.  This document is complimentary to RFC-1327 as
   it focuses on translation of the message body.  The mappings defined
   are largely symmetrical with respect to MIME and MHS structuring
   semantics, although the MIME semantics are somewhat richer.  In order
   to provide for reversible transformations, MHS heading extensions are
   used to carry the additional MIME semantics.

   Please send comments to the MIME-MHS mailing list:
   [email protected]>.

2.  Approach

   The mappings have been specifically designed to provide optimal
   behavior for three different scenarios:

   (1) Allow a MIME user and an MHS user to exchange an arbitrary binary
       content;

   (2) Allow MIME content-types to "tunnel" through an MHS relay that
       is, two MIME users can exchange content-types without loss



Alvestrand, Kille, Miles, Rose & Thompson