MMUSIC G. Salgueiro Internet-Draft Cisco Systems Intended status: Standards Track April 20, 2011 Expires: October 22, 2011 The 'image' Media Type for the Session Description Protocol (SDP) draft-gsalguei-image-media-type-00 Abstract This document describes the registration of 'image' as a top-level media type for the Session Description Protocol (SDP). The 'image' media type is primarily used by SDP to negotiate and establish T.38 media streams. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on October 22, 2011. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Salgueiro Expires October 22, 2011 [Page 1] Internet-Draft 'image' Media Type Registration April 2011 Table of Contents 1. Conventions Used in This Document . . . . . . . . . . . . . . . 3 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6.1. Normative References . . . . . . . . . . . . . . . . . . . 5 6.2. Informative References . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Salgueiro Expires October 22, 2011 [Page 2] Internet-Draft 'image' Media Type Registration April 2011 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 [RFC2119]. 2. Overview In the previous version of the SDP specification [RFC2327] packetized media types, such as those shared by RTP, share the same namespace used by the Multipurpose Internet Mail Extensions (MIME) media types registry [RFC2048] (i.e. "MIME types"). This is in contrast to the latest version of the SDP specification [RFC4566] where an SDP- specific media type registry is created. The top-level SDP media content types registered by [RFC4566] are "audio", "video", "text", "application", and "message". A glaring omission on this list is the 'image' media type. The 'image' media type is an existing top-level MIME type and is widely used by SDP for setting up T.38 Real-Time Facsimile [T38] media streams. This media type is extensively referenced by examples in ITU-T T.38 [T38] and IETF standards like [RFC4145]. This document complies with the request of section 8.2.1 of [RFC4566] that indicates: "The same rules should apply for media names as for top-level media content types, and where possible the same name should be registered for SDP as for MIME. For media other than existing top-level media content types, a Standards Track RFC MUST be produced for a new top-level content type to be registered, and the registration MUST provide good justification why no existing media name is appropriate." The registration of 'image' as a top-level SDP media type ensures seamless continuity with documentation that uses the 'image' MIME type. This also simplifies the usage of previously registered MIME sub-types like 'image/t38' [RFC3362] that are used as SDP media descriptors for T.38 [T38]. 3. IANA Considerations This document registers with IANA the 'image' media type as a top- level media content type in accordance with the "Standards Action" policy defined in Section 4.1 of [RFC5226]. This registration follows the procedures described in BCP 13 [RFC4288]. Salgueiro Expires October 22, 2011 [Page 3] Internet-Draft 'image' Media Type Registration April 2011 To: ietf-types@iana.org Subject: Registration of 'image' media type for the Session Description Protocol (SDP) Type name: image Subtype name: Required parameters: None Optional parameters: None Encoding considerations: Binary encoding as defined in ITU-T Recommendation T.38 [T38]. Security considerations: Refer to Section 4 Interoperability considerations: This media type is primarily intended to be utilized as a parameter by SDP [RFC4566] in SIP [RFC3261] to establish T.38 [T38] media streams. Published specification: RFC 4566 Applications that 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: Gonzalo Salgueiro gsalguei@cisco.com Intended usage: COMMON Restrictions on usage: None Salgueiro Expires October 22, 2011 [Page 4] Internet-Draft 'image' Media Type Registration April 2011 Author: Gonzalo Salgueiro Change controller: The IESG 4. Security Considerations The 'image' media type registered by this document to the IANA registry for SDP [SDP-IANA] is primarily for use by the offer/answer model of the Session Description Protocol [RFC4566] for the negotiation and establishment of T.38 [T38] media streams using the Session Initiation Protocol [RFC3261]. This additional SDP parameter does not introduce any new security considerations beyond those detailed in Section 7 of [RFC4566]. The security vulnerabilities in T.38 [T38] and its associated transport protocols (TCP [RFC0793], UDP [RFC0768], or RTP [RFC3550]) are well documented in each of their respective specifications. 5. Acknowledgements Thanks goes to the chairs of the IETF Multiparty Multimedia Session Control (MMUSIC) working group (Miguel A. Garcia and Flemming Andreasen) for their guidance, encouragement, and the creation of the media type registry. The author would also like to acknowledge the considerable efforts of Kevin Fleming and the members of the FoIP TG in the SIP Forum that contributed to the new revision of the ITU-T T.38 Recommendation that prompted the need to register the 'image' media type for SDP. 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. [SDP-IANA] IANA, "Session Description Protocol (SDP) Parameters", http://www.iana.org/assignments/sdp-parameters , 2011. Salgueiro Expires October 22, 2011 [Page 5] Internet-Draft 'image' Media Type Registration April 2011 6.2. Informative References [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. [RFC2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996. [RFC2327] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998. [RFC3261] 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. [RFC3362] Parsons, G., "Real-time Facsimile (T.38) - image/t38 MIME Sub-type Registration", RFC 3362, August 2002. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in the Session Description Protocol (SDP)", RFC 4145, September 2005. [RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and Registration Procedures", BCP 13, RFC 4288, December 2005. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. [T38] International Telecommunications Union, "Procedures for real-time Group 3 facsimile communication over IP Networks", ITU-T Recommendation T.38, 2010. Salgueiro Expires October 22, 2011 [Page 6] Internet-Draft 'image' Media Type Registration April 2011 Author's Address Gonzalo Salgueiro Cisco Systems 7200-12 Kit Creek Road Research Triangle Park, NC 27709 US Email: gsalguei@cisco.com Salgueiro Expires October 22, 2011 [Page 7]