MMUSIC G. Salgueiro Internet-Draft Cisco Systems Intended status: Standards Track May 25, 2011 Expires: November 26, 2011 IANA Registration of the 'image' Media Type for the Session Description Protocol (SDP) draft-salgueiro-mmusic-image-iana-registration-05 Abstract This document describes the usage of the 'image' media type and registers it with IANA as a top-level media type for the Session Description Protocol (SDP). This 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/. 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Salgueiro Expires November 26, 2011 [Page 1] Internet-Draft 'image' Media Type Registration May 2011 Table of Contents 1. Conventions Used in This Document . . . . . . . . . . . . . . . 3 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 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 November 26, 2011 [Page 2] Internet-Draft 'image' Media Type Registration May 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 RFC 2119 [RFC2119]. 2. Overview In an earlier version of the SDP specification [RFC2327] packetized media types, such as those used with the Real-Time Transport Protocol (RTP) [RFC3550], share the namespace with 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] which requested that an SDP-specific media type registry be created and maintained by IANA. The top-level SDP media content types registered by RFC 4566 [RFC4566] are "audio", "video", "text", "application", and "message". A glaring omission from this list is the "image" media type. The 'image' media type is an existing top-level MIME type and is widely used in SDP implementations 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 RFC 4145 [RFC4145]. The following example shows the media description of a T.38 media stream as commonly found in a Session Initiation Protocol (SIP) INVITE; it contains an SDP offer for T.38 over both UDPTL and TCP. For the sake of brevity, the main portion of the session description is omitted in this example, which only shows 'm' lines and their attributes (including 'c' lines). c=IN IP4 192.0.2.2 m=image 49170 udptl t38 a=T38FaxRateManagement:transferredTCF a=T38FaxUdpEC:t38UDPFEC m=image 49172 tcp t38 a=T38FaxRateManagement:localTCF This document complies with the request of section 8.2.1 of RFC 4566 [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 Salgueiro Expires November 26, 2011 [Page 3] Internet-Draft 'image' Media Type Registration May 2011 the registration MUST provide good justification why no existing media name is appropriate." The purpose of this document is to register with IANA the 'image' media type as a top-level SDP media type. This ensures seamless continuity with documentation that uses the 'image' MIME type and 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 in the Session Description Protocol (SDP) Parameters registry. This registration contains the REQUIRED information elements outlined in the SDP registration procedure defined in Section 8.2.8 of RFC 4566 [RFC4566]. (1) Contact Information: Name: Gonzalo Salgueiro Email: gsalguei@cisco.com Telephone Number: (919) 392-3266 (2) Name being registered (as it will appear in SDP): image (3) Long-form name in English: image (4) Type of name ('media', 'proto', 'fmt', 'bwtype', 'nettype', or 'addrtype'): media (5) Purpose of the registered name: The currently registered list of SDP media types ('audio', 'video', 'text', 'application', and 'message') does not include one suitable for real-time facsimile (fax) applications. The 'image' media type for the Session Description Protocol (SDP) is primarily intended to be utilized as a parameter by SDP [RFC4566] in SIP [RFC3261] to establish T.38 [T38] media streams. (6) Specification for the registered name: RFC XXXX [This document] Salgueiro Expires November 26, 2011 [Page 4] Internet-Draft 'image' Media Type Registration May 2011 4. Security Considerations The 'image' media type registered by this document in the SDP parameters registry maintained by IANA [SDP-IANA] is primarily for use by the offer/answer model of the Session Description Protocol [RFC3264] for the negotiation and establishment of T.38 [T38] media streams using the Session Initiation Protocol (SIP) [RFC3261]. This additional SDP media type does not introduce any security considerations beyond those detailed in Section 7 of RFC 4566 [RFC4566]. The security vulnerabilities in T.38 [T38] and its associated transport protocols (TCP [RFC0793], UDP [RFC0768], and RTP [RFC3550]) are well documented in each of their respective specifications. 5. Acknowledgements Thanks go 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. Special thanks to Miguel A. Garcia for his thorough and insightful review of the early revisions of the draft. This document has benefited from the discussion and review of the MMUSIC working group, especially the detailed and thoughtful comments and corrections of Keith Drage, Yasubumi Chimura, and Kevin P. Fleming. The author would also like to acknowledge the considerable efforts of Kevin P. 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 November 26, 2011 [Page 5] Internet-Draft 'image' Media Type Registration May 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. [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, 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. [T38] International Telecommunications Union, "Procedures for real-time Group 3 facsimile communication over IP Networks", ITU-T Recommendation T.38, October 2010. Salgueiro Expires November 26, 2011 [Page 6] Internet-Draft 'image' Media Type Registration May 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 November 26, 2011 [Page 7]