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Network Working Group
Request for Comments: 3950
Obsoletes: 3250
Category: Standards Track
L. McIntyre
Consultant
G. Parsons
Nortel Networks
J. Rafferty
Brooktrout Technology
February 2005

Tag Image File Format Fax eXtended (TIFF-FX) - image/tiff-fx

MIME Sub-type Registration

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 Notice

Copyright © The Internet Society (2005).

Abstract

This document describes the registration of the MIME sub-type image/tiff-fx. The encodings are defined by File Format for Internet Fax and its extensions.

1. Introduction

This document describes the registration of the MIME sub-type image/tiff-fx. The encodings are defined by File Format for Internet Fax [TIFF-FX] and its extensions.

This document is a product of the IETF Internet Fax Working Group.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [REQ].

2. TIFF-FX Definition

Tag Image File Format Fax eXtended (TIFF-FX), is defined in detail by RFC 3949, "File Format for Internet Fax" [TIFF-FX].

While a brief scope and feature description is provided in this section as background information, the reader is directed to the original TIFF-FX specification (File Format for Internet Fax) to obtain complete feature and technical details.

2.1. TIFF-FX Scope

This document defines a TIFF-based file format specification for enabling standardized messaging-based fax over the Internet. It specifies the TIFF fields and field values required for compatibility with the existing ITU-T Recommendations for Group 3 black-and-white, grayscale and color facsimile. TIFF has historically been used for handling fax image files in applications such as store-and-forward messaging. Implementations that support this file format specification for import/export may elect to support it as a native format. This document recommends a TIFF file structure that is compatible with low-memory and page-level streaming implementations.

Unless otherwise noted, the current TIFF specification [TIFF] and selected TIFF Technical Notes [TTN1, TTN2] are the primary references for describing TIFF and defining TIFF fields. This document is the primary reference for defining TIFF field values for fax applications.

2.2. TIFF-FX Features

Some of the features of TIFF-FX are: 

   -  TIFF-FX is capable of describing bilevel, grayscale, palette-
   
      color, full-color and mixed content image data.
  • TIFF-FX includes a number of compression schemes that allow developers to choose the best space or time tradeoff for their applications.
  • TIFF-FX is designed to be extensible and to evolve gracefully as new needs arise.

3. MIME Definition

This document defines the image/tiff-fx MIME sub-type to refer to TIFF-FX Profiles J, C, L and M encoded image data and any future TIFF-FX extensions, or a subset. The image/tiff-fx content type MAY be used when black-and-white image data is encoded using TIFF-FX Profiles S or F, or a subset, however, the image/tiff content type SHOULD be used.

4. IANA Registration

   To: ietf-types@iana.org
   Subject: Registration of Standard MIME media type image/tiff-fx

MIME media type name: image

MIME subtype name: tiff-fx 

   Required parameters: none
   
   Optional parameters: none

Encoding Considerations:

This media type consists of binary data. The base64 encoding should be used on transports that cannot accommodate binary data directly.

Security considerations:

TIFF-FX utilizes a structure which can store image data and attributes of this image data. The fields defined in the TIFF-FX specification are of a descriptive nature and provide information that is useful to facilitate viewing and rendering of images by a recipient. As such, the fields currently defined in the TIFF-FX specification do not in themselves create additional security risks, since the fields are not used to induce any particular behavior by the recipient application.

TIFF-FX has an extensible structure, so that it is theoretically possible that fields could be defined in the future which could be used to induce particular actions on the part of the recipient, thus presenting additional security risks, but this type of capability is not supported in the referenced TIFF-FX specification. Indeed, the definition of fields which would include such processing instructions is inconsistent with the goals and spirit of the TIFF-FX specification.

The MIME type and file extension defined by this document MUST NOT be used to blindly select a processing program. It is up to the implementation to determine the application (if necessary) and render the image to the user.

Interoperability considerations:

The ability of implementations to handle all the defined applications (or profiles within applications) of TIFF-FX may not be ubiquitous. As a result, implementations may decode and attempt to display the encoded TIFF-FX image data only to determine that the image cannot be rendered.

Published specification:

TIFF-FX (Tag Image File Format Fax eXtended) is defined in: 

      RFC 3949, "File Format for Internet Fax", February 2005, Buckley,
      R., Venable, D., McIntyre, L., Parsons, G., and J. Rafferty.

Applications which use this media type: 

      Imaging, fax, messaging and multi-media

Additional information: 

      Magic number(s):
           II (little-endian):  49 49 2A 00 hex
           MM (big-endian):     4D 4D 00 2A hex
      File extension(s): .TFX
      Macintosh File Type Code(s): TFX

Person & email address to contact for further information:

Lloyd McIntyre
Lloyd_McIntyre@Dell.com

Glenn W. Parsons
gparsons@nortelnetworks.com

James Rafferty
jraff@brooktrout.com 

   Intended usage: COMMON

Change controller: Lloyd McIntyre

5. Security Considerations

TIFF-FX utilizes a structure which can store image data and attributes of this image data. The fields defined in the TIFF-FX specification are of a descriptive nature and provide information that is useful to facilitate viewing and rendering of images by a recipient. As such, the fields currently defined in the TIFF-FX specification do not in themselves create additional security risks, since the fields are not used to induce any particular behavior by the recipient application.

TIFF-FX has an extensible structure, so that it is theoretically possible that fields could be defined in the future which could be used to induce particular actions on the part of the recipient, thus presenting additional security risks, but this type of capability is not supported in the referenced TIFF-FX specification. Indeed, the definition of fields which would include such processing instructions is inconsistent with the goals and spirit of the TIFF-FX specification.

The MIME type and file extension defined by this document MUST NOT be used to blindly select a processing program. It is up to the implementation to determine the application (if necessary) and render the image to the user.

6. References

6.1. Normative References

[TIFF-FX] Buckley, R., Venable, D., McIntyre, L., Parsons, G., and J.

Rafferty, "File Format for Internet Fax", RFC 3949, February 2005.

6.2. Informative References

   [TIFF]    Adobe Developers Association, TIFF (TM) Revision 6.0 -
             Final, June 3, 1992.
   
   [REQ]     Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.
   
   [TTN1]    Adobe PageMaker 6.0 TIFF Technical Notes, Sept. 14, 1995,
             http://partners.adobe.com/asn/developer/pdfs/tn/TIFFPM6.pdf
   
   [TTN2]    Adobe Photoshop TIFF Technical Notes, Replacement TIFF/JPEG
             specification, March 22, 2002,
             http://partners.adobe.com/asn/developer/pdfs/tn/
             TIFFphotoshop.pdf

Annex A. List of edits to RFC 3250

   +----+---------+-------------------------------------------------+
   | No.| Section |                  Edit                           |
   +----+---------+-------------------------------------------------+
   | 1. | All     | Updated references from RFC 2301 to             |
   |    |         | draft-ietf-fax-tiff-fx-13.txt                   |
   +----+---------+-------------------------------------------------+
   | 2. | 5       | MIME Definition - added a "SHOULD" statement to |
   |    |         | stress that image/tiff is the preferred content |
   |    |         | type when representing Profiles S and/or F.     |
   +----+---------+-------------------------------------------------+
   | 3. | 7       | Revise security considerations.                 |
   +----+---------+-------------------------------------------------+
   | 4. | 3       | Merged sections 2 & 3 and renumbered.           |
   +----+---------+-------------------------------------------------+

Authors' Addresses

Lloyd McIntyre
10328 S. Stelling Road
Cupertino, CA 95014 USA 

   Phone: +1-408-725-1624
   EMail: lloyd10328@pacbell.net or
   
          Lloyd_McIntyre@Dell.com
   
   Glenn W. Parsons
   Nortel Networks
   P.O. Box 3511, Station C
   Ottawa, ON  K1Y 4H7
   Canada
   
   Phone: +1-613-763-7582
   Fax:   +1-613-967-5060
   EMail: gparsons@nortel.com
   
   James Rafferty
   Brooktrout Technology
   410 First Avenue
   Needham, MA  02494
   USA
   
   Phone: +1-781-433-9462
   Fax:   +1-781-433-9268
   EMail: jraff@brooktrout.com

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