AVT Working Group Internet Draft P. Jones <draft-jones-avt-audio-t38-00.txt> Cisco Systems, Inc. Expires: January 2004 August 2003 Real-Time Facsimile (T.38) - audio/t38 MIME Sub-type Registration Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. 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 and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document defines the MIME sub-type audio/t38. The packetization and usage of this MIME type, which is intended for use within SDP [2] and H.248 [3] systems, is specified within ITU-T Recommendation T.38 [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 RFC 2119. Table of Contents 1. Introduction...................................................2 2. audio/t38 Usage................................................2 3. IANA Registration..............................................2 4. Security Considerations........................................3 Jones Expires - February 2004 [Page 1]
MIME Sub-Type audio/t38 August 2003 5. References.....................................................3 6. Acknowledgments................................................4 7. Author's Addresses.............................................4 1. Introduction ITU-T Recommendation T.38 defines the Internet Facsimile Protocol (IFP) and packetization of that protocol for carriage over IP networks. As one option, IFP packets may be carried within an RTP stream, either as the only content within the media stream or switched along with other audio payload types. Utilizing RTP for the carriage of facsimile signals over IP networks allows devices to take advantage of the forward error correction, redundancy, and security mechanisms designed for RTP. In addition, RTCP provides valuable statistics including packet loss and jitter, which may be utilized to improve service quality. Switching between payload types, such as audio and IFP, allows devices such as media gateways to transition between audio and fax relay very gracefully. It should be noted that in the context of a media gateway, the IFP encoding is merely an alternative encoding of the audio channel and the main driver for introducing the carriage of facsimile via RTP. 2. audio/t38 Usage The usage of audio/t38 for SDP and H.248-based systems is defined in Annexes D and E of Recommendation T.38, respectively. This media sub-type registration is not intended for use with e-mail. 3. IANA Registration To: ietf-types@iana.org Subject: Registration of Standard MIME media type audio/t38 MIME media type name: audio MIME subtype name: t38 Require parameters: none Optional parameters: none Encoding considerations: binary Security considerations: Jones Expires - February 2004 [Page 2]
MIME Sub-Type audio/t38 August 2003 The IFP packets carried via RTP do not carry any particular security risks in and of themselves. However, as with other audio packets, there is the potential for unauthorized eavesdropping on facsimile transmissions if the media stream is not properly secured. Interoperability considerations: ITU-T Recommendation T.38 defines the procedures, syntax, and parameters for the carriage of T.38 over RTP within the context of H.323 [4], SIP [5], and H.248 [3] systems. Published specification: ITU-T Recommendation T.38, "Procedures for real-time Group 3 facsimile communication over IP networks", with Amendment TBD, January 2004. Applications which use this media type: Real-time facsimile (fax) Additional information: Magic number(s): File extension(s): Macintosh File Type Code(s): Person & email address to contact for further information: Paul E. Jones paulej@packetizer.com Intended usage: COMMON Author/Change controller: Paul E. Jones 4. Security Considerations The IFP packets carried via RTP do not carry any particular security risks in and of themselves. However, as with other audio packets, there is the potential for unauthorized eavesdropping or manipulation of facsimile transmissions if the media stream is not properly secured. 5. References [1] ITU-T Recommendation T.38, "Procedures for real-time Group 3 facsimile communication over IP networks", March 2002. Jones Expires - February 2004 [Page 3]
MIME Sub-Type audio/t38 August 2003 [2] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998. [3] ITU-T Recommendation H.248, "Gateway Control Protocol", May 2002. [4] ITU-T Recommendation H.323, "Packet-based multimedia communications systems", May 2003. [5] 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. 6. Author's Addresses Paul E. Jones Cisco Systems, Inc. 7025 Kit Creek Rd. Research Triangle Park, NC 27709 Phone: +1 919 392 6948 Email: paulej@packetizer.com Jones Expires - February 2004 [Page 4]
