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draft-crocker-headerset-00.txt
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Network Working Group D. Crocker
Internet Draft Silicon Graphics, Inc.
Expiration <4/94> 5 October 1993
MIME Multipart/Header-Set
draft-crocker-headerset-00.txt
STATUS OF THIS MEMO
This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its
Areas, and its Working Groups. (Note that other groups may also
distribute working documents as Internet Drafts).
Internet Drafts are draft documents valid for a maximum of six
months. Internet Drafts may be updated, replaced, or obsolete by
other documents at any time. It is not appropriate is use
Internet Drafts as reference material or to cite them other than
as a "working draft" or "work in progress."
Please check the Internet Draft abstract listing contained in the
IETF Shadow Directories (cd internet-drafts) to learn the current
status of this or any other Internet Draft.
SUMMARY
Data often are aggregated with an initial set of descriptor
information, followed by some number of user data portions. This
specification formalizes the occurrences of such aggregations as
a MIME Multipart Content-type. It is intended that MIME
processors which are aware of the Header-Set construct will be
able to process the user data portions, even when they do not
understand the specific header (or descriptor) information which
begins the set.
D. Crocker 1
Internet Draft Multipart/Header-Set (Expiration: 4/94)
TABLE OF CONTENTS
1. INTRODUCTION
2. Header-Set Content-Subtype Usage in MIME
3. Header-Set Specification
4. Header-Set Examples
7. REFERENCES
8. SECURITY CONSIDERATIONS
9. ACKNOWLEDGMENTS
10. CONTACT
1. INTRODUCTION
Data often are aggregated with an initial set of descriptor
information, followed by some number of user data portions. Such
aggregations derive from a specialized environment, such as a
particular operating system file structure, or a tailored
communication environment, such as privacy enhanced mail. In
particular, one portion of the data contains all of the data
special to that environment and the remainder is regular user-
data, possibly of a type registered within MIME [BORE92].
This specification formalizes the occurrences of such
aggregations as a MIME Multipart Content-type. It dictates that
the descriptor header information shall occur as the first MIME
body-part at the beginning of the Multipart set, and is then
followed by one or more MIME body-parts containing user data.
It is intended that MIME processors which are aware of the Header-
Set construct will be able to process the user data portions,
even when they do not understand the specific header (or
descriptor) information which begins the set. As an example, a
recipient on one operating system may still be able to identify
and process the user-data portion(s) even when the specific
header descriptor is intended for an entirely different and
unrelated operating system. In addition, specifications for MIME
usage which conform to this model will not need to define two
MIME types, one for the Multipart containing "bucket" and one for
the specific Application label to distinguish the portion
containing application-specific data.
D. Crocker 2
Internet Draft Multipart/Header-Set (Expiration: 4/94)
2. Header-Set Content-Subtype Usage in MIME
Header-set information is specified by:
MIME type name: MULTIPART
MIME subtype name: HEADER-SET
Required parameters: Any pertaining to MULTIPART/Mixed
Optional parameters: Any pertaining to MULTIPART/Mixed
Encoding considerations: none
Security considerations: See separate section in the
document.
Published specification: Contained in the following
section.
Rationale:
Permits recipients to process user-data even when they
cannot process the more specialized header descriptor
information. Also, reduces the number of registered MIME
Content-types, since those which conform to this model
need to register only an Application sub-type and are not
also required to register a Multipart subtype.
Contact-info: See Contact section, below.
Detail specific to MIME-based usage:
Provides for a MULTIPART MIME body-part which declares
that the first sub-part in the MULTIPART shall contain a
header which provides descriptive information about the
one or more remaining sub-parts in that MULTIPART. It is
expected that the first sub-part will typically be an
Content-type:Application sub-type.
3. Header-Set Specification
A MIME Content-Type:Multipart/Header-Set body part is a distinct
section of a message and contains two, or more, sub-parts within
in. The first sub-part is the header and any following sub-parts
compose the set of user data associated with that header.
D. Crocker 3
Internet Draft Multipart/Header-Set (Expiration: 4/94)
Typically, the header sub-part will be a registered Content-
Type:Application sub-type, but this is not required.
The Content-Type:Application subtype will declare the "context"
and base of interpretation for processing the MULTIPART body-part
in its entirety. However, the user data body-parts may also be
processed separately, to the extent that the receiver understands
the individual MIME subparts.
4. Header-Set Examples
Assume that a user is sending data from the FOO file system, with
its file-system specific information registered as
Application/Filesys-FOO, and the user data containing US-ASCII
text:
To:
Subject:
From:
Date:
Mime-Version: 1.00
Content-Type: MULTIPART/HEADER-SET; boundary=Boundary-1
--Boundary-1
Content-Type: APPLICATION/Filesys-FOO
(Descriptive information specific to the FOO file system's
storage of the following user data.)
--Boundary-1
Content-Type: TEXT/plain
(Regular text user-data)
--Boundary-1--
7. REFERENCES
[BORE92] Borenstein, N. & Freed, N., "MIME
(Multipurpose Internet Mail Extensions): Mechanisms
for specifying and describing the format of Internet
Message Bodies. March, 1992, Network Information
Center, RFC 1341.
D. Crocker 4
Internet Draft Multipart/Header-Set (Expiration: 4/94)
8. SECURITY CONSIDERATIONS
Specific header parts may contain security-related information.
To the extent that Header-set facilitates the transmission of
operating-system sensitive data, it may open a door for easier
relaxation of security rules than is intended either by the
sender or the administrator of the sender's system.
9. ACKNOWLEDGMENTS
Header-Set developed from the continuing 882ext working group
discussions.
10. CONTACT
name: David H. Crocker;
work <email: dcrocker@sgi.com;
org: Silicon Graphics, Inc.;
street: 2011 N. Shoreline Blvd.;
box: 7311;
geo: Mountain View / CA / US; code: 94039-7311;
phone: +1 415 390 1804; fax: +1 415 962 8404>
D. Crocker 5