A MIME Body Part for FAX (RFC2159)
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
This document contains the definitions, originally contained in RFC 1494, on how to carry CCITT G3Fax in MIME, and how to translate it to its X.400 representation.
Network Working Group H. Alvestrand
Request for Comments: 2159 UNINETT
Category: Standards Track January 1998
A MIME Body Part for FAX
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 (1998). All Rights Reserved.
This document contains the definitions, originally contained in RFC
1494, on how to carry CCITT G3Fax in MIME, and how to translate it to
its X.400 representation.
NOTE: At the moment, this format does not seem appropriate for a
"general purpose image format for the Internet", if such a beast can
exist. It exists only to carry information that is already in G3 Fax
format, and may be usefully converted to other formats when used in
2. The image/g3fax content-type
This content-type is defined to carry G3 Facsimile byte streams.
In general, a G3Fax image contains 3 pieces of information:
(1) A set of flags indicating the particular coding scheme.
CCITT Recommendation T.30 defines how the flags are
transmitted over telephones. In this medium, the flags are
carried as parameters in the MIME content-type header
(2) A structure that divides the bits into pages. CCITT
recommendation T.4 describes a "return to command mode"
string; this is used here to indicate page breaks.
(3) For each page, a sequence of bits that form the encoding of
the image. CCITT recommendation T.4 defines the bit image
format. This is used without change. The highest bit of
the first byte is the first bit of the T.4 bitstream.
2.1. G3Fax Parameters
The following parameters are defined:
(1) page-length - possible values: A4, B4 and Unlimited
(2) page-width - possible values: A3, A4, B4
(3) encoding - possible values: 1-dimensional, 2-dimensional,
(4) resolution - possible values: Fine, Coarse
(5) DCS - a bit string, represented in Base64.
(6) pages - an integer, giving the number of pages in the
If nothing is specified, the default parameter settings are:
It is possible (but misleading) to view the representation of these
values as single-bit flags. They correspond to the following bits of
the T.30 control string and X.400 G3FacsimileParameters:
Parameter T.30 bit X.400 bit
page-length=A4 no bi...