RFC 6466
IANA Registration of the 'image' Media Type for the Session Description Protocol (SDP)
RFC 6466: IANA Registration of the 'image' Media Type for the Session Description Protocol (SDP) 🎀
Okay bestie, this one is a Standards Track doc from December 2011 (ISSN 2070-1721) by Gonzalo Salgueiro at Cisco Systems. Its header doesn't list anything it obsoletes or updates. It's all about getting the 'image' media type officially registered for SDP so T.38 fax streams can be negotiated. 📠✨
Abstract ✨
Okay so this doc explains how the 'image' media type gets used and registers it with IANA as a top-level media type for SDP. The main job is letting SDP negotiate and set up T.38 media streams. It's giving organization 💅
Status of This Memo 📜
This is an Internet Standards Track document. 🌸
It's a product of the Internet Engineering Task Force (IETF), it represents the consensus of the IETF community, it got public review, and the Internet Engineering Steering Group (IESG) approved it for publication. For more on Internet Standards, check Section 2 of RFC 5741. 🔥
For the current status, errata, and feedback info, go to 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, since 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. 🫶
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 . . . . . . . . . . . . . . . . . . 51. Overview 🌈
Okay so in an earlier version of the SDP spec [RFC2327], packetized media types like the ones used with the Real-time Transport Protocol (RTP) [RFC3550] shared a namespace with the Multipurpose Internet Mail Extensions (MIME) media types registry [RFC4288] [RFC4289], aka "MIME media types." The newest SDP spec [RFC4566] went a different way and asked IANA to create and maintain an SDP-specific media type registry. The top-level SDP media content types RFC 4566 [RFC4566] registered are 'audio', 'video', 'text', 'application', and 'message'. The big glaring omission? 'image' 👀
'image' is already an existing top-level MIME media type, and it's super widely used in SDP for setting up T.38 Real-Time Facsimile [T38] streams. Tons of examples in ITU-T T.38 [T38] and Standards Track docs like RFC 4145 [RFC4145] use it. Here's the media description of a T.38 stream you'd usually see in a Session Initiation Protocol (SIP) [RFC3261] INVITE. It's an SDP offer for T.38 over both UDP Transport Layer (UDPTL) and TCP. Just the SDP body is shown, to keep it short. 📞
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:localTCFSo the whole point of this doc is registering 'image' with IANA as a top-level SDP media type. That keeps everything consistent with docs already using the 'image' MIME media type and the earlier-registered sub-types like 'image/t38' [RFC3362], which are used as SDP media descriptors for T.38 [T38]. 💖
This doc follows the request in Section 8.2.1 of RFC 4566 [RFC4566], which says:
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 registered an 'image' token in the media sub-registry of the Session Description Protocols (SDP) Parameters registry. The registration has the required information elements from the SDP registration procedure in Section 8.2.8 of RFC 4566 [RFC4566]. Here's the whole registration, verbatim:
(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 64664. Security Considerations 🔥
The 'image' media type registered by this doc in the SDP parameters registry (maintained by IANA) is mainly for the offer/answer model of the Session Description Protocol [RFC3264], to negotiate and establish T.38 [T38] media streams using SIP [RFC3261]. This extra SDP media type does not add any security considerations beyond the ones in Section 7 of RFC 4566 [RFC4566]. 🔐
Now the serious part 🚨 The security vulnerabilities in T.38 [T38] and its transport protocols (TCP [RFC0793], UDP [RFC0768], and RTP [RFC3550]) are well documented in each of their own specs. Also, being able to exchange images other than T.38 can expose the recipient to potentially malicious executable code. Be careful out there, bestie 💀
5. Acknowledgements 🫶
Huge thanks to the chairs of the IETF Multiparty Multimedia Session Control (MMUSIC) working group, Miguel A. Garcia and Flemming Andreasen, for their guidance, encouragement, and for creating the media type registry. Extra special thanks to Miguel A. Garcia for his thorough and insightful review of the many draft revisions. 👑
This doc also benefited from the discussion and review of the MMUSIC working group, especially the detailed and thoughtful comments and corrections from Keith Drage, Yasubumi Chimura, Kevin P. Fleming, Bert Greevenbosch, and Gonzalo Camarillo. 💜
The author also wants to acknowledge the big efforts of Kevin P. Fleming and the members of the Fax-over-IP (FoIP) TG in the SIP Forum. They contributed to the new revision of the ITU-T T.38 Recommendation, which is why the 'image' media type for SDP needed registering. 📠🌸
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.
[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.comThat's the whole RFC, slay 🌈💖
📦 where this page comes from
- ietf: rfc6466 2011-12
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms