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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MMUSIC G. Salgueiro 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track October 10, 2011 5 Expires: April 12, 2012 7 IANA Registration of the 'image' Media Type 8 for the Session Description Protocol (SDP) 9 draft-salgueiro-mmusic-image-iana-registration-09 11 Abstract 13 This document describes the usage of the 'image' media type and 14 registers it with IANA as a top-level media type for the Session 15 Description Protocol (SDP). This media type is primarily used by SDP 16 to negotiate and establish T.38 media streams. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on April 12, 2012. 35 Copyright Notice 37 Copyright (c) 2011 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Conventions Used in This Document . . . . . . . . . . . . . . . 3 53 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 55 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 56 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 57 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 58 6.1. Normative References . . . . . . . . . . . . . . . . . . . 5 59 6.2. Informative References . . . . . . . . . . . . . . . . . . 6 60 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 62 1. Conventions Used in This Document 64 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 65 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 66 document are to be interpreted as described in RFC 2119 [RFC2119]. 68 2. Overview 70 In an earlier version of the SDP specification [RFC2327] packetized 71 media types, such as those used with the Real-Time Transport Protocol 72 (RTP) [RFC3550], share the namespace with Multipurpose Internet Mail 73 Extensions (MIME) media types registry [RFC4288] [RFC4289] (i.e. 74 "MIME media types"). This is in contrast to the latest version of 75 the SDP specification [RFC4566] which requested that an SDP-specific 76 media type registry be created and maintained by IANA. The top-level 77 SDP media content types registered by RFC 4566 [RFC4566] are "audio", 78 "video", "text", "application", and "message". A glaring omission 79 from this list is the "image" media type. 81 The 'image' media type is an existing top-level MIME media type and 82 is widely used in SDP implementations for setting up T.38 Real-Time 83 Facsimile [T38] media streams. This media type is extensively 84 referenced by examples in ITU-T T.38 [T38] and IETF standards like 85 RFC 4145 [RFC4145]. The following example shows the media 86 description of a T.38 media stream as commonly found in a Session 87 Initiation Protocol (SIP) [RFC3261] INVITE; it contains an SDP offer 88 for T.38 over both UDP Transport Layer (UDPTL) and TCP. For the sake 89 of brevity, only the SDP body of the SIP INVITE request is displayed 90 in this example. 92 v=0 93 o=alice 53655765 2353687637 IN IP4 pc33.example.com 94 s=SDP image example 95 c=IN IP4 192.0.2.2 96 t=0 0 97 m=image 49170 udptl t38 98 a=T38FaxVersion:0 99 a=T38MaxBitRate:14400 100 a=T38FaxRateManagement:transferredTCF 101 a=T38FaxMaxBuffer:262 102 a=T38FaxMaxDatagram:90 103 a=T38FaxUdpEC:t38UDPRedundancy 104 a=sendrecv 105 m=image 49172 tcp t38 106 a=T38FaxRateManagement:localTCF 108 The purpose of this document is to register with IANA the 'image' 109 media type as a top-level SDP media type. This ensures seamless 110 continuity with documentation that uses the 'image' MIME media type 111 and the previously registered MIME media sub-types like 'image/t38' 112 [RFC3362] that are used as SDP media descriptors for T.38 [T38]. 114 This document complies with the request of section 8.2.1 of RFC 4566 115 [RFC4566] that indicates: 117 "The same rules should apply for media names as for top-level 118 media content types, and where possible the same name should be 119 registered for SDP as for MIME. For media other than existing 120 top-level media content types, a Standards Track RFC MUST be 121 produced for a new top-level content type to be registered, and 122 the registration MUST provide good justification why no existing 123 media name is appropriate." 125 3. IANA Considerations 127 This document instructs IANA to register an 'image' token in the 128 media sub-registry of the Session Description Protocols (SDP) 129 Parameters registry. This registration contains the required 130 information elements outlined in the SDP registration procedure 131 defined in Section 8.2.8 of RFC 4566 [RFC4566]. 133 (1) Contact Information: 135 Name: Gonzalo Salgueiro 136 Email: gsalguei@cisco.com 137 Telephone Number: (919) 392-3266 139 (2) Name being registered (as it will appear in SDP): image 141 (3) Long-form name in English: image 143 (4) Type of name ('media', 'proto', 'fmt', 'bwtype', 'nettype', or 144 'addrtype'): media 146 (5) Purpose of the registered name: 148 The 'image' media type for the Session Description Protocol 149 is used to describes a media stream that represents a still 150 image. The media subtype further describes the specific 151 format of the image. Currently, the 'image' media type for 152 SDP is used ubiquitously by the SIP control protocol to 153 establish T.38 media streams. 155 (6) Specification for the registered name: RFC XXXX [This document] 157 4. Security Considerations 159 The 'image' media type registered by this document in the SDP 160 parameters registry maintained by IANA is primarily for use by the 161 offer/answer model of the Session Description Protocol [RFC3264] for 162 the negotiation and establishment of T.38 [T38] media streams using 163 the Session Initiation Protocol (SIP) [RFC3261]. This additional SDP 164 media type does not introduce any security considerations beyond 165 those detailed in Section 7 of RFC 4566 [RFC4566]. 167 The security vulnerabilities in T.38 [T38] and its associated 168 transport protocols (TCP [RFC0793], UDP [RFC0768], and RTP [RFC3550]) 169 are well documented in each of their respective specifications. The 170 ability to exchange images other than T.38 can expose the recipient 171 to potentially malicious executable code. 173 5. Acknowledgements 175 Thanks go to the chairs of the IETF Multiparty Multimedia Session 176 Control (MMUSIC) working group (Miguel A. Garcia and Flemming 177 Andreasen) for their guidance, encouragement, and the creation of the 178 media type registry. Special thanks to Miguel A. Garcia for his 179 thorough and insightful review of the many revisions of the draft. 181 This document has benefited from the discussion and review of the 182 MMUSIC working group, especially the detailed and thoughtful comments 183 and corrections of Keith Drage, Yasubumi Chimura, Kevin P. Fleming, 184 Bert Greevenbosch, and Gonzalo Camarillo. 186 The author would also like to acknowledge the considerable efforts of 187 Kevin P. Fleming and the members of the FoIP TG in the SIP Forum that 188 contributed to the new revision of the ITU-T T.38 Recommendation that 189 prompted the need to register the 'image' media type for SDP. 191 6. References 193 6.1. Normative References 195 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 196 Requirement Levels", BCP 14, RFC 2119, March 1997. 198 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 199 Description Protocol", RFC 4566, July 2006. 201 6.2. Informative References 203 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 204 August 1980. 206 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, 207 RFC 793, September 1981. 209 [RFC2327] Handley, M. and V. Jacobson, "SDP: Session Description 210 Protocol", RFC 2327, April 1998. 212 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 213 A., Peterson, J., Sparks, R., Handley, M., and E. 214 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 215 June 2002. 217 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 218 with Session Description Protocol (SDP)", RFC 3264, 219 June 2002. 221 [RFC3362] Parsons, G., "Real-time Facsimile (T.38) - image/t38 MIME 222 Sub-type Registration", RFC 3362, August 2002. 224 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 225 Jacobson, "RTP: A Transport Protocol for Real-Time 226 Applications", STD 64, RFC 3550, July 2003. 228 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in 229 the Session Description Protocol (SDP)", RFC 4145, 230 September 2005. 232 [RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and 233 Registration Procedures", BCP 13, RFC 4288, December 2005. 235 [RFC4289] Freed, N. and J. Klensin, "Multipurpose Internet Mail 236 Extensions (MIME) Part Four: Registration Procedures", 237 BCP 13, RFC 4289, December 2005. 239 [T38] International Telecommunications Union, "Procedures for 240 real-time Group 3 facsimile communication over IP 241 Networks", ITU-T Recommendation T.38, October 2010. 243 Author's Address 245 Gonzalo Salgueiro 246 Cisco Systems 247 7200-12 Kit Creek Road 248 Research Triangle Park, NC 27709 249 US 251 Email: gsalguei@cisco.com