Internet Engineering Task Force (IETF) N. Freed Request for Comments: 6838 Oracle BCP: 13 J. Klensin Obsoletes: 4288 Category: Best Current Practice T. Hansen ISSN: 2070-1721 AT&T Laboratories January 2013 Media Type Specifications and Registration Procedures
AbstractThis document defines procedures for the specification and registration of media types for use in HTTP, MIME, and other Internet protocols. Status of This Memo This memo documents an Internet Best Current Practice. 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 BCPs 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/rfc6838. Copyright Notice Copyright (c) 2013 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.
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Historical Note . . . . . . . . . . . . . . . . . . . . . 3 1.2. Conventions Used in This Document . . . . . . . . . . . . 4 2. Media Type Registration Preliminaries . . . . . . . . . . . . 4 3. Registration Trees and Subtype Names . . . . . . . . . . . . . 4 3.1. Standards Tree . . . . . . . . . . . . . . . . . . . . . . 4 3.2. Vendor Tree . . . . . . . . . . . . . . . . . . . . . . . 6 3.3. Personal or Vanity Tree . . . . . . . . . . . . . . . . . 6 3.4. Unregistered x. Tree . . . . . . . . . . . . . . . . . . . 7 3.5. Additional Registration Trees . . . . . . . . . . . . . . 7 4. Registration Requirements . . . . . . . . . . . . . . . . . . 7 4.1. Functionality Requirement . . . . . . . . . . . . . . . . 8 4.2. Naming Requirements . . . . . . . . . . . . . . . . . . . 8 4.2.1. Text Media Types . . . . . . . . . . . . . . . . . . . 9 4.2.2. Image Media Types . . . . . . . . . . . . . . . . . . 10 4.2.3. Audio Media Types . . . . . . . . . . . . . . . . . . 10 4.2.4. Video Media Types . . . . . . . . . . . . . . . . . . 10 4.2.5. Application Media Types . . . . . . . . . . . . . . . 11 4.2.6. Multipart and Message Media Types . . . . . . . . . . 11 4.2.7. Additional Top-Level Types . . . . . . . . . . . . . . 12 4.2.8. Structured Syntax Name Suffixes . . . . . . . . . . . 12 4.2.9. Deprecated Aliases . . . . . . . . . . . . . . . . . . 13 4.3. Parameter Requirements . . . . . . . . . . . . . . . . . . 13 4.4. Canonicalization and Format Requirements . . . . . . . . . 14 4.5. Interchange Recommendations . . . . . . . . . . . . . . . 15 4.6. Security Requirements . . . . . . . . . . . . . . . . . . 15 4.7. Requirements Specific to XML Media Types . . . . . . . . . 16 4.8. Encoding Requirements . . . . . . . . . . . . . . . . . . 16 4.9. Usage and Implementation Non-Requirements . . . . . . . . 17 4.10. Publication Requirements . . . . . . . . . . . . . . . . . 18 4.11. Fragment Identifier Requirements . . . . . . . . . . . . . 18 4.12. Additional Information . . . . . . . . . . . . . . . . . . 19 5. Media Type Registration Procedures . . . . . . . . . . . . . . 19 5.1. Preliminary Community Review . . . . . . . . . . . . . . . 19 5.2. Submit Request to IANA . . . . . . . . . . . . . . . . . . 20 5.2.1. Provisional Registrations . . . . . . . . . . . . . . 20 5.3. Review and Approval . . . . . . . . . . . . . . . . . . . 21 5.4. Comments on Media Type Registrations . . . . . . . . . . . 21 5.5. Change Procedures . . . . . . . . . . . . . . . . . . . . 21 5.6. Registration Template . . . . . . . . . . . . . . . . . . 22 6. Structured Syntax Suffix Registration Procedures . . . . . . . 23 6.1. Change Procedures . . . . . . . . . . . . . . . . . . . . 24 6.2. Structured Syntax Suffix Registration Template . . . . . . 24 7. Security Considerations . . . . . . . . . . . . . . . . . . . 25 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27 10.1. Normative References . . . . . . . . . . . . . . . . . . . 27 10.2. Informative References . . . . . . . . . . . . . . . . . . 28 Appendix A. Grandfathered Media Types . . . . . . . . . . . . . . 30 Appendix B. Changes since RFC 4288 . . . . . . . . . . . . . . . 30 RFC2616] and MIME [RFC2045], are capable of carrying arbitrary labeled content. The mechanism used to label such content is a media type, consisting of a top-level type and a subtype, which is further structured into trees. Optionally, media types can define companion data, known as parameters. A registration process is needed for these labels, so that the set of such values are defined in a reasonably orderly, well-specified, and public manner. This document specifies the criteria for media type registrations and defines the procedures to be used to register media types (Section 5) as well as media type structured suffixes (Section 6) in the Internet Assigned Numbers Authority (IANA) central registry. The location of the media type registry managed by these procedures is: http://www.iana.org/assignments/media-types/ RFC2048], but the procedure defined there was still part of the MIME document set. The media type specification and registration procedure is now a separate document, to make it clear that it is independent of MIME.
It may be desirable to restrict the use of media types to specific environments or to prohibit their use in other environments. This specification incorporates such restrictions into media type registrations in a systematic way. See Section 4.9 for additional discussion. RFC2119] when they appear in ALL CAPS. They may also appear in lower or mixed case as plain English words, without any normative meaning. This specification makes use of the Augmented Backus-Naur Form (ABNF) [RFC5234] notation, including the core rules defined in Appendix B of that document. Appendix A for a discussion of them.
1. in the case of registrations associated with IETF specifications, approved directly by the IESG, or 2. registered by a recognized standards-related organization using the "Specification Required" IANA registration policy [RFC5226] (which implies Expert Review). The first procedure is used for registrations from IETF Consensus documents, or in rare cases when registering a grandfathered (see Appendix A) and/or otherwise incomplete registration is in the interest of the Internet community. The registration proposal MUST be published as an RFC. When the registration RFC is in the IETF stream, it must have IETF Consensus, which can be attained with a status of Standards Track, BCP, Informational, or Experimental. Registrations published in non-IETF RFC streams are also allowed and require IESG approval. A registration can be either in a stand-alone "registration only" RFC or incorporated into a more general specification of some sort. In the second case, the IESG makes a one-time decision on whether the registration submitter represents a recognized standards-related organization; after that, a Media Types Reviewer (Designated Expert or a group of Designated Experts) performs the Expert Review as specified in this document. Subsequent submissions from the same source do not involve the IESG. The format MUST be described by a formal standards specification produced by the submitting standards- related organization. Media types in the standards tree MUST NOT have faceted names, unless they are grandfathered in using the process described in Appendix A. The "owner" of a media type registered in the standards tree is assumed to be the standards-related organization itself. Modification or alteration of the specification uses the same level of processing (e.g., a registration submitted on Standards Track can be revised in another Standards Track RFC, but cannot be revised in an Informational RFC) required for the initial registration. Standards-tree registrations from recognized standards-related organizations are submitted directly to the IANA, where they will undergo Expert Review [RFC5226] prior to approval. In this case, the Expert Reviewer(s) will, among other things, ensure that the required specification provides adequate documentation.
Section 5.5 for additional information. When a third party registers a type on behalf of someone else, both entities SHOULD be noted in the Change Controller field in the registration. One possible format for this would be "Foo, on behalf of Bar". Vendor-tree registrations will be distinguished by the leading facet "vnd.". That may be followed, at the discretion of the registrant, by either a media subtype name from a well-known producer (e.g., "vnd.mudpie") or by an IANA-approved designation of the producer's name that is followed by a media type or product designation (e.g., vnd.bigcompany.funnypictures). While public exposure and review of media types to be registered in the vendor tree are not required, using the firstname.lastname@example.org mailing list for review is encouraged, to improve the quality of those specifications. Registrations in the vendor tree may be submitted directly to the IANA, where they will undergo Expert Review [RFC5226] prior to approval.
While public exposure and review of media types to be registered in the personal tree are not required, using the email@example.com mailing list (see Section 5.1) for review is encouraged, to improve the quality of those specifications. Registrations in the personal tree may be submitted directly to the IANA, where they will undergo Expert Review [RFC5226] prior to approval. RFC6648]). Also note that if a generally useful and widely deployed type incorrectly ends up with an "x-" name prefix, it MAY be registered using its current name in an alternative tree by following the procedure defined in Appendix A.
RFC2045], base64 cannot be registered as a media type. This requirement applies regardless of the registration tree involved. Section 5.1 of [RFC2045] or Section 4.2 of [RFC4288]. Also note that while this syntax allows names of up to 127 characters, implementation limits may make such long names problematic. For this reason, <type-name> and <subtype-name> SHOULD be limited to 64 characters. Although the name syntax treats "." as equivalent to any other character, characters before any initial "." always specify the registration facet. Note that this means that facet-less standards- tree registrations cannot use periods in the subtype name.
Similarly, the final "+" in a subtype name introduces a structured syntax specifier suffix. Structured syntax suffix requirements are specified in Section 4.2.8. While it is possible for a given media type to be assigned additional names, the use of different names to identify the same media type is discouraged. These requirements apply regardless of the registration tree involved. The choice of top-level type MUST take into account the nature of media type involved. New subtypes of top-level types MUST conform to the restrictions of the top-level type, if any. The following sections describe each of the initial set of top-level types and their associated restrictions. Additionally, various protocols, including but not limited to HTTP and MIME, MAY impose additional restrictions on the media types they can transport. (See [RFC2046] for additional information on the restrictions MIME imposes.) RFC2046], define a "charset" parameter. If a "charset" parameter is defined for a particular subtype of text, it MUST be used to specify a charset name defined in accordance to the procedures laid out in [RFC2978]. As specified in [RFC6657], a "charset" parameter SHOULD NOT be specified when charset information is transported inside the payload (e.g., as in "text/xml"). If a "charset" parameter is specified, it SHOULD be a required parameter, eliminating the options of specifying a default value. If there is a strong reason for the parameter to be optional despite this advice, each subtype MAY specify its own default value, or alternatively, it MAY specify that there is no default value. Finally, the "UTF-8" charset [RFC3629] SHOULD be selected as the default. See [RFC6657] for additional information on the use of "charset" parameters in conjunction with subtypes of text. Regardless of what approach is chosen, all new text/* registrations MUST clearly specify how the charset is determined; relying on the US-ASCII default defined in Section 4.1.2 of [RFC2046] is no longer
permitted. If explanatory text is needed, this SHOULD be placed in the additional information section of the registration. Plain text does not provide for or allow formatting commands, font attribute specifications, processing instructions, interpretation directives, or content markup. Plain text is seen simply as a linear sequence of characters, possibly interrupted by line breaks or page breaks. Plain text MAY allow the stacking of several characters in the same position in the text. Plain text in scripts like Arabic and Hebrew may also include facilities that allow the arbitrary mixing of text segments with different writing directions. Beyond plain text, there are many formats for representing what might be known as "rich text". An interesting characteristic of many such representations is that they are to some extent readable even without the software that interprets them. It is useful to distinguish them, at the highest level, from such unreadable data as images, audio, or text represented in an unreadable form. In the absence of appropriate interpretation software, it is reasonable to present subtypes of "text" to the user, while it is not reasonable to do so with most non-textual data. Such formatted textual data can be represented using subtypes of "text". RFC2046], it is recognized that many video formats include a representation for synchronized audio and/or text, and this is explicitly permitted for subtypes of "video".
RFC2046] provides a good example of how to handle these issues.) For example, a meeting scheduler might define a standard representation for information about proposed meeting dates. An intelligent user agent would use this information to conduct a dialog with the user, and might then send additional material based on that dialog. More generally, there have been several "active" languages developed in which programs in a suitably specialized language are transported to a remote location and automatically run in the recipient's environment. Such applications may be defined as subtypes of the "application" top-level type. The subtype of "application" will often either be the name or include part of the name of the application for which the data are intended. This does not mean, however, that any application program name may simply be used freely as a subtype of "application"; the subtype needs to be registered. RFC2046] and amended by Section 3.5 of [RFC6532].
RFC3023] defined the first such augmentation to the media type definition to additionally specify the underlying structure of that media type. To quote: This document also standardizes a convention (using the suffix '+xml') for naming media types ... when those media types represent XML MIME (Multipurpose Internet Mail Extensions) entities. That is, it specified a suffix (in that case, "+xml") to be appended to the base subtype name. Since this was published, the de facto practice has arisen for using this suffix convention for other well-known structuring syntaxes. In particular, media types have been registered with suffixes such as "+der", "+fastinfoset", and "+json". This specification formalizes this practice and sets up a registry for structured type name suffixes. The primary guideline for whether a structured type name suffix is registrable is that it be described by a readily available description, preferably within a document published by an established standards-related organization, and for which there's a reference that can be used in a Normative References section of an RFC. Media types that make use of a named structured syntax SHOULD use the appropriate registered "+suffix" for that structured syntax when they are registered. By the same token, media types MUST NOT be given names incorporating suffixes for structured syntaxes they do not actually employ. "+suffix" constructs for as-yet unregistered structured syntaxes SHOULD NOT be used, given the possibility of conflicts with future suffix definitions.
RFC2045] and amended by [RFC2231]. Parameter names are case-insensitive and no meaning is attached to the order in which they appear. It is an error for a specific parameter to be specified more than once. There is no defined syntax for parameter values. Therefore, registrations MUST specify parameter value syntax. Additionally, some transports impose restrictions on parameter value syntax, so care needs be taken to limit the use of potentially problematic syntaxes; e.g., pure binary valued parameters, while permitted in some protocols, are best avoided. Note that a protocol can impose further restrictions on parameter value syntax, depending on how it chooses to represent parameters. Both MIME [RFC2045] [RFC2231] and HTTP [RFC2045] [RFC5987] allow binary parameters as well as parameter values expressed in a specific charset, but other protocols may be less flexible. New parameters SHOULD NOT be defined as a way to introduce new functionality in types registered in the standards tree, although new parameters MAY be added to convey additional information that does
not otherwise change existing functionality. An example of this would be a "revision" parameter to indicate a revision level of an external specification such as JPEG. Similar behavior is encouraged for media types registered in the vendor or personal trees, but is not required. Changes to parameters (including the introduction of new ones) is managed in the same manner as other changes to the media type; see Section 5.5. RFC3979] and BCP 78 [RFC5378] on the use of patented technology in IETF Standards Track protocols must be respected when the specification of a media type is part of a Standards Track protocol. In addition, other standards-related organizations making use of the standards tree may have their own rules regarding intellectual property that must be observed in their registrations. Intellectual Property Rights (IPR) disclosures for registrations in the vendor and personal trees are encouraged but not required.
Section 5.4 below. Some of the issues that need to be examined and described in a security analysis of a media type are: o Complex media types may include provisions for directives that institute actions on a recipient's files or other resources. In many cases, provision is made for originators to specify arbitrary actions in an unrestricted fashion that may then have devastating effects. See the registration of the application/postscript media
type in [RFC2046] for an example of such directives and how they can be described in a media type registration. o Any security analysis MUST state whether or not they employ such "active content"; if they do, they MUST state what steps have been taken, or MUST be taken by applications of the media type, to protect users of the media type from harm. o Complex media types may include provisions for directives that institute actions that, while not directly harmful to the recipient, may result in disclosure of information that either facilitates a subsequent attack or else violates a recipient's privacy in some way. Again, the registration of the application/ postscript media type illustrates how such directives can be handled. o A media type that employs compression may provide an opportunity for sending a small amount of data that, when received and evaluated, expands enormously to consume all of the recipient's resources. All media types SHOULD state whether or not they employ compression; if they do, they SHOULD discuss what steps need to be taken to avoid such attacks. o A media type might be targeted for applications that require some sort of security assurance but don't provide the necessary security mechanisms themselves. For example, a media type could be defined for storage of sensitive medical information that in turn requires external confidentiality and integrity protection services, or which is designed for use only within a secure environment. Types SHOULD always document whether or not they need such services in their security considerations. RFC3023].
It is therefore useful to note what sort of data a media type can consist of as part of its registration. An "encoding considerations" field is provided for this purpose. Possible values of this field are: 7bit: The content of the media type consists solely of CRLF- delimited 7bit US-ASCII text. 8bit: The content of the media type consists solely of CRLF- delimited 8bit text. binary: The content consists of an unrestricted sequence of octets. framed: The content consists of a series of frames or packets without internal framing or alignment indicators. Additional out- of-band information is needed to interpret the data properly, including but not necessarily limited to knowledge of the boundaries between successive frames and knowledge of the transport mechanism. Note that media types of this sort cannot simply be stored in a file or transported as a simple stream of octets; therefore, such media types are unsuitable for use in many traditional protocols. A commonly used transport with framed encoding is the Real-time Transport Protocol, RTP. Additional rules for framed encodings defined for transport using RTP are given in [RFC4855]. Additional restrictions on 7bit and 8bit text are given in Section 4.1.1 of [RFC2046].
explicitly intended for limited use, this MUST be noted in its registration. The "Restrictions on Usage" field is provided for this purpose. Section 3.5 of [RFC3986]) associated with the media type.
Media types are encouraged to adopt fragment identifier schemes that are used with semantically similar media types. In particular, media types that use a named structured syntax with a registered "+suffix" MUST follow whatever fragment identifier rules are given in the structured syntax suffix registration. MacOSFileTypes]. In the case of a registration in the standards tree, this additional information MAY be provided in the formal specification of the media type format. It is suggested that this be done by incorporating the IANA media type registration form into the format specification itself.
The intent of the public posting to this list is to solicit comments and feedback on the choice of type/subtype name, the unambiguity of the references with respect to versions and external profiling information, and a review of any interoperability or security considerations. The submitter may submit a revised registration proposal or abandon the registration completely and at any time. http://www.iana.org/form/media-types
Section 6.5.4 of [RFC2026]. Once a media type registration has passed review, the IANA will register the media type and make the media type registration available to the community. In the case of standards-tree registrations from other standards- related organizations, IANA will also check that the submitter is in fact a recognized standards-related organization. If the submitter is not currently recognized as such, the IESG will be asked to confirm their status. Recognition from the IESG MUST be obtained before a standards-tree registration can proceed.
Significant changes to a media type's definition should be requested only when there are serious omissions or errors in the published specification. When review is required, a change request may be denied if it renders entities that were valid under the previous definition invalid under the new definition. The owner of a media type may pass responsibility to another person or agency by informing the IANA; this can be done without discussion or review. The IESG may reassign responsibility for a media type. The most common case of this will be to enable changes to be made to types where the author of the registration has died, moved out of contact, or is otherwise unable to make changes that are important to the community.
Intended usage: (One of COMMON, LIMITED USE, or OBSOLETE.) Restrictions on usage: (Any restrictions on where the media type can be used go here.) Author: Change controller: Provisional registration? (standards tree only): (Any other information that the author deems interesting may be added below this line.) "N/A", written exactly that way, can be used in any field if desired to emphasize the fact that it does not apply or that the question was not omitted by accident. Do not use 'none' or other words that could be mistaken for a response. Limited-use media types should also note in the applications list whether or not that list is exhaustive. Section 6.2) and include that with the media type registration. The template may be contained in an Internet Draft, alone or as part of some other protocol specification. The template may also be submitted in some other form (as part of another document or as a stand-alone document), but the contents will be treated as an "IETF Contribution" under the guidelines of BCP 78 [RFC5378]. 3. Send a copy of the template or a pointer to the containing document (with specific reference to the section with the template) to the mailing list firstname.lastname@example.org, requesting
review. This may be combined with a request to review the media type registration. Allow a reasonable time for discussion and comments. 4. Respond to review comments and make revisions to the proposed registration as needed to bring it into line with the guidelines given in this document. 5. Submit the (possibly updated) registration template (or pointer to the document containing it) to IANA at email@example.com. Upon receipt of a structured syntax suffix registration request, 1. IANA checks the submission for completeness; if sections are missing or citations are not correct, IANA rejects the registration request. 2. IANA checks the current registry for an entry with the same name; if such a registry exists, IANA rejects the registration request. 3. IANA requests Expert Review of the registration request against the corresponding guidelines. 4. The Designated Expert may request additional review or discussion, as necessary. 5. If Expert Review recommends registration, IANA adds the registration to the appropriate registry. The initial registry content specification [RFC6839] provides examples of structured syntax suffix registrations.
+suffix Suffix used to indicate conformance to the syntax. References Include full citations for all specifications necessary to understand the structured syntax. Encoding considerations General guidance regarding encoding considerations for any type employing this syntax should be given here. The same requirements for media type encoding considerations given in Section 4.8 apply here. Interoperability considerations Any issues regarding the interoperable use of types employing this structured syntax should be given here. Examples would include the existence of incompatible versions of the syntax, issues combining certain charsets with the syntax, or incompatibilities with other types or protocols. Fragment identifier considerations Generic processing of fragment identifiers for any type employing this syntax should be described here. Security considerations Security considerations shared by media types employing this structured syntax must be specified here. The same requirements for media type security considerations given in Section 4.6 apply here, with the exception that the option of not assessing the security considerations is not available for suffix registrations. Contact Person (including contact information) to contact for further information. Author/Change controller. Person (including contact information) authorized to change this suffix registration. Section 4.6.
Section 5.2.1 for additional information on provisional registrations. IANA has also added the following note at the top of the provisional registry: This registry, unlike some other provisional IANA registries, is only for temporary use. Entries in this registry are either finalized and moved to the main media types registry, or are abandoned and deleted. Entries in this registry are suitable for use for development and test purposes only. The structured syntax name suffix registry has been created as follows: o The name is the "Structured Syntax Suffix" registry. o The registration process is specified in Section 6. o The information required for a registry entry as well as the entry format are specified in Section 6.2. o The initial content of the registry is specified in [RFC6839]. Entries in both the media type and structured suffix registries will be annotated by IANA with both the original registration date as well as the date of the most recent update to the entry. Registrations made prior to the implementation of this specification may, if necessary, be marked as such, rather than with a specific date. Since registration entries can be updated multiple times, IANA will also maintain the history of changes to each registration in such a way that the state of the registration at any given time can be determined.
Finally, per this document, IANA has created a new email address, firstname.lastname@example.org, for the media type review list, which replaces the email@example.com address specified in RFC 4288. firstname.lastname@example.org has been retained as an alias. RFC2048] [RFC4288]. We hope that the current version is one with which he would have agreed but, as it is impossible to verify that agreement, we have regretfully removed his name as a co-author. Randy Bush, Francis Dupont, Bjoern Hoehrmann, Barry Leiba, Murray Kucherawy, Alexey Melnikov, S. Moonesamy, Mark Nottingham, Tom Petch, Peter Saint-Andre, and Jeni Tennison provided many helpful review comments and suggestions. [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2978] Freed, N. and J. Postel, "IANA Charset Registration Procedures", BCP 19, RFC 2978, October 2000. [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types", RFC 3023, January 2001. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [RFC3979] Bradner, S., "Intellectual Property Rights in IETF Technology", BCP 79, RFC 3979, March 2005.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC4855] Casner, S., "Media Type Registration of RTP Payload Formats", RFC 4855, February 2007. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [RFC5378] Bradner, S. and J. Contreras, "Rights Contributors Provide to the IETF Trust", BCP 78, RFC 5378, November 2008. [RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized Email Headers", RFC 6532, February 2012. [RFC6657] Melnikov, A. and J. Reschke, "Update to MIME regarding "charset" Parameter Handling in Textual Media Types", RFC 6657, July 2012. [RFC6839] Hansen, T. and A. Melnikov, "Additional Media Type Structured Syntax Suffixes", RFC 6839, January 2013. [MacOSFileTypes] Apple Computer, Inc., "Mac OS: File Type and Creator Codes, and File Formats", Apple Knowledge Base Article 55381, June 1993, <http://www.info.apple.com/kbnum/n55381>. [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [RFC2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996.
[RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations", RFC 2231, November 1997. [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and Registration Procedures", BCP 13, RFC 4288, December 2005. [RFC5987] Reschke, J., "Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters", RFC 5987, August 2010. [RFC6648] Saint-Andre, P., Crocker, D., and M. Nottingham, "Deprecating the "X-" Prefix and Similar Constructs in Application Protocols", BCP 178, RFC 6648, June 2012.
Section 4.2.9). However, if this is not possible, the type can, subject to approval by both the media types reviewer and the IESG, be registered in the proper tree with its unfaceted name.
o The requirements on changes to registrations have been loosened so minor changes are easier to make. o The registration process has been completely restructured so that with the exception of IETF-generated types in the standards tree, all requests are processed by IANA and not the IESG. o A provisional registration process has been added for early assignment of types in the standards tree. o Many editorial changes have been made throughout the document to make the requirements and processes it describes clearer and easier to follow. o The ability to specify a list of deprecated aliases for a media type has been added. o Types with names beginning with "x-" are no longer considered to be members of the unregistered "x." tree. As with any unfaceted type, special procedures have been added to allow registration of such types in an appropriate tree. o Changes to a type registered by a third party may now be made by the designated change controller even if that isn't the vendor or organization that created the type. However, the vendor or organization may elect to assert ownership and change controller over the type at any time. o Limited-use media types are now asked to note whether or not the supplied list of applications employing the media type is exhaustive. o The ABNF for media type names has been further restricted to require that names begin with an alphanumeric character. o Mailing list review is no longer required prior to registration of media types. Additionally, the address associated with the media type review mailing list has been changed to email@example.com. o The rules for text/* media types have been updated to reflect the changes specified in [RFC6657].