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 <gsalguei@cisco.com>
Change controller:
The IESG <iesg@ietf.org>
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]