Network Working Group G. Parsons Request for Comments: 3362 Nortel Networks Category: Standards Track August 2002
Real-time Facsimile (T.38) - image/t38 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 (C) The Internet Society (2002). All Rights Reserved.
This document describes the registration of the MIME sub-type image/t38. The encoding is defined by ITU Recommendation T.38 and is intended for use as an Session Description Protocol (SDP) media descriptor.
1. Conventions used in this document
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].
This document describes the registration of the MIME sub-type image/t38. The encoding is defined by [T.38] and is intended for use as an SDP media descriptor.
3. T.38 Definition
ITU-T Recommendation T.38 [T.38] describes the technical features necessary to transfer facsimile documents in real-time between two standard Group 3 facsimile terminals over the Internet or other networks using IP protocols. The Recommendation allows the use of either TCP or UDP depending on the service environment.
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ITU-T Recommendation T.38 [T.38] Annex D describes system level requirements and procedures for internet aware facsimile implementations and internet aware facsimile gateways conforming to ITU-T T.38 to establish calls with other ITU-T T.38 implementations using the procedures defined in IETF RFC 2543 [SIP-99] and IETF RFC 2327 [SDP].
Note that ITU-T T.38 Recommendation T.38 (04/02) [T.38] is an aggregation of the original ITU-T Recommendation T.38 (06/98) [T.38- 98] and all of the subsequent Amendments and Corrigendum including [T.38D-00]. While [T.38] and [T.38D-00] describe SIP procedures per [SIP-99], the procedures can also be applied to the revised Session Initiation Protocol specification [SIP].
3.1 image/t38 Usage
Annex D of [T.38] describes that the image/t38 media type is intended to indicate a T.38 media stream in SDP.
This media type registration is not intended for email usage.
4. IANA Registration
To: firstname.lastname@example.org Subject: Registration of Standard MIME media type image/t38
MIME media type name: image
MIME subtype name: t38
Required parameters: none
Optional parameters: none
Encoding considerations: Binary
This content denotes a facsimile bit stream that may or may not be encrypted.
Interoperability considerations :
This MIME media subtype is intended to be used as a parameter by SDP in SIP call setup for T.38 as described in ITU-T Rec. T.38 Annex D. Any use of this media type by email applications is not defined and as a result is not guaranteed to interoperate with a T.38 stream.
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ITU-T Recommendation T.38, 'Procedures for real-time Group 3 facsimile communication over IP networks', April 2002.
A copy of the T.38 specifications can be found at:
Applications which use this media type:
Real-time facsimile (fax)
Magic number(s): II (little-endian): MM (big-endian): File extension(s): .T38 Macintosh File Type Code(s): T38
Person & email address to contact for further information:
Glenn W. Parsons email@example.com
Intended usage: COMMON
Change controller: Glenn Parsons
5. Security Considerations
Security considerations for this media type are discussed in the MIME type registration that appears in section 4.
[REQ] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[MIME4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996.
Parsons Standards Track [Page 3] RFC 3362 MIME Sub-type image/t38 August 2002
[SDP] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998.
[SIP] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002.
[SIP-99] Handley, M., Schulzrinne, H., Schooler, E. and J. Rosenberg, "SIP: Session Initiation Protocol", RFC 2543, March 1999.
[T.38] ITU-T Recommendation T.38, 'Procedures for real-time Group 3 facsimile communication over IP networks', April 2002.
[T.38-98] ITU-T Recommendation T.38, 'Procedures for real-time Group 3 facsimile communication over IP networks', June 1998.
[T.38D-00] ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', February 2000.
7. Authors' Address
Glenn W. Parsons Nortel Networks P.O. Box 3511, Station C Ottawa, ON K1Y 4H7 Canada
Phone: +1-613-763-7582 Fax: +1-613-763-2697 EMail: firstname.lastname@example.org
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8. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
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