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+Internet Engineering Task Force (IETF) G. Salgueiro
+Request for Comments: 6466 Cisco Systems
+Category: Standards Track December 2011
+ISSN: 2070-1721
+
+
+ IANA Registration of the 'image' Media Type
+ for the Session Description Protocol (SDP)
+
+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 is an Internet Standards Track document.
+
+ This document is a product of the Internet Engineering Task Force
+ (IETF). It represents the consensus of the IETF community. It has
+ received public review and has been approved for publication by the
+ Internet Engineering Steering Group (IESG). Further information on
+ Internet Standards is available in Section 2 of RFC 5741.
+
+ Information about the current status of this document, any errata,
+ and how to provide feedback on it may be obtained at
+ http://www.rfc-editor.org/info/rfc6466.
+
+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 Standards Track [Page 1]
+
+RFC 6466 'image' Media Type Registration December 2011
+
+
+Table of Contents
+
+ 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 2. Conventions Used in This Document . . . . . . . . . . . . . . . 3
+ 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
+ 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
+ 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4
+ 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
+ 6.1. Normative References . . . . . . . . . . . . . . . . . . . 5
+ 6.2. Informative References . . . . . . . . . . . . . . . . . . 5
+
+1. Overview
+
+ In an earlier version of the SDP specification [RFC2327] of
+ 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
+ [RFC4288] [RFC4289] (i.e., "MIME media 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 media 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 Track
+ documents 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) [RFC3261] INVITE; it contains an
+ SDP offer for T.38 over both UDP Transport Layer (UDPTL) and TCP.
+ For the sake of brevity, only the SDP body of the SIP INVITE request
+ is displayed in this example.
+
+
+
+
+
+
+
+
+
+
+
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+Salgueiro Standards Track [Page 2]
+
+RFC 6466 'image' Media Type Registration December 2011
+
+
+ v=0
+ o=alice 53655765 2353687637 IN IP4 pc33.example.com
+ s=SDP image example
+ c=IN IP4 192.0.2.2
+ t=0 0
+ m=image 49170 udptl t38
+ a=T38FaxVersion:0
+ a=T38MaxBitRate:14400
+ a=T38FaxRateManagement:transferredTCF
+ a=T38FaxMaxBuffer:262
+ a=T38FaxMaxDatagram:90
+ a=T38FaxUdpEC:t38UDPRedundancy
+ a=sendrecv
+ m=image 49172 tcp t38
+ a=T38FaxRateManagement:localTCF
+
+ 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 media type
+ and the previously registered MIME media sub-types like 'image/t38'
+ [RFC3362] that are used as SDP media descriptors for T.38 [T38].
+
+ 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
+ the registration MUST provide good justification why no existing
+ media name is appropriate.
+
+2. 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].
+
+3. IANA Considerations
+
+ IANA has registered an 'image' token in the media sub-registry of the
+ Session Description Protocols (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].
+
+
+
+
+
+Salgueiro Standards Track [Page 3]
+
+RFC 6466 'image' Media Type Registration December 2011
+
+
+ (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 'image' media type for the Session Description Protocol
+ is used to describe a media stream whose content consists of
+ one or more separate images that require appropriate hardware
+ to display. The media subtype further describes the specific
+ format of the image. Currently, the 'image' media type for
+ SDP is used ubiquitously by the SIP control protocol to
+ establish T.38 media streams.
+
+ (6) Specification for the registered name: RFC 6466
+
+4. Security Considerations
+
+ The 'image' media type registered by this document in the SDP
+ parameters registry maintained by 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
+ 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. The
+ ability to exchange images other than T.38 can expose the recipient
+ to potentially malicious executable code.
+
+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
+
+
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+Salgueiro Standards Track [Page 4]
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+RFC 6466 'image' Media Type Registration December 2011
+
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+ media type registry. Special thanks to Miguel A. Garcia for his
+ thorough and insightful review of the many draft revisions of this
+ document.
+
+ 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, Kevin P. Fleming,
+ Bert Greevenbosch, and Gonzalo Camarillo.
+
+ The author would also like to acknowledge the considerable efforts of
+ Kevin P. Fleming and the members of the Fax-over-IP (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.
+
+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.
+
+ [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.
+
+
+
+
+Salgueiro Standards Track [Page 5]
+
+RFC 6466 'image' Media Type Registration December 2011
+
+
+ [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.
+
+ [RFC4289] Freed, N. and J. Klensin, "Multipurpose Internet Mail
+ Extensions (MIME) Part Four: Registration Procedures",
+ BCP 13, RFC 4289, December 2005.
+
+ [T38] International Telecommunication Union, "Procedures for
+ real-time Group 3 facsimile communication over IP
+ Networks", ITU-T Recommendation T.38 (Pre-Published),
+ September 2010,
+ <http://www.itu.int/rec/T-REC-T.38-201009-P/en>.
+
+Author's Address
+
+ Gonzalo Salgueiro
+ Cisco Systems
+ 7200-12 Kit Creek Road
+ Research Triangle Park, NC 27709
+ US
+
+ EMail: gsalguei@cisco.com
+
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