MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations (RFC2231)
Original Publication Date: 1997-Nov-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
N. Freed: AUTHOR [+2]
This memo defines extensions to the RFC 2045 media type and RFC 2183 disposition parameter value mechanisms to provide
Network Working Group N. Freed
Request for Comments: 2231 Innosoft
Updates: 2045, 2047, 2183 K. Moore
Obsoletes: 2184 University of Tennessee
Category: Standards Track November 1997
MIME Parameter Value and Encoded Word Extensions:
Character Sets, Languages, and Continuations
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1997). All Rights Reserved.
This memo defines extensions to the RFC 2045 media type and RFC 2183
disposition parameter value mechanisms to provide
(1) a means to specify parameter values in character sets
other than US-ASCII,
(2) to specify the language to be used should the value be
(3) a continuation mechanism for long parameter values to
avoid problems with header line wrapping.
This memo also defines an extension to the encoded words defined in
RFC 2047 to allow the specification of the language to be used for
display as well as the character set.
The Multipurpose Internet Mail Extensions, or MIME [RFC-2045, RFC-
2046, RFC-2047, RFC-2048, RFC-2049], define a message format that
(1) textual message bodies in character sets other than
(2) non-textual message bodies,
(3) multi-part message bodies, and
(4) textual header information in character sets other than
MIME is now widely deployed and is used by a variety of Internet
protocols, including, of course, Internet email. However, MIME's
success has resulted in the need for additional mechanisms that were
not provided in the original protocol specification.
In particular, existing MIME mechanisms provide for named media type
(content-type field) parameters as well as named disposition
(content-disposition field). A MIME media type may specify any
number of parameters associated with all of its subtypes, and any
specific subtype may specify additional parameters for its own use. A
MIME disposition value may specify any number of associated
parameters, the most important of which is probably the attachment
disposition's filename parameter.
These parameter names and values end up appearing in the content-type
and content-disposition header fields in Internet email. This
inherently imposes three crucial limitations:
(1) Lines in Internet email header fields are folded
according to RFC 822 folding rules. This ma...