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Versions: 00 01 draft-ietf-appsawg-media-type-regs

Network Working Group                                           N. Freed
Internet-Draft                                                    Oracle
Obsoletes: 4288 (if approved)                                 J. Klensin
Expires: March 8, 2012
                                                               T. Hansen
                                                       AT&T Laboratories
                                                       September 5, 2011


         Media Type Specifications and Registration Procedures
                     draft-freed-media-type-regs-01

Abstract

   This document defines procedures for the specification and
   registration of media types for use in MIME and other Internet
   protocols.

Historical Note

   The media type registration process was initially defined for
   registering media types for use in the context of the asynchronous
   Internet mail environment.  In this mail environment there is a need
   to limit the number of possible media types, to increase the
   likelihood of interoperability when the capabilities of the remote
   mail system are not known.  As media types are used in new
   environments in which the proliferation of media types is not a
   hindrance to interoperability, the original procedure proved
   excessively restrictive and had to be generalized.  This was
   initially done in [RFC2048], but the procedure defined there was
   still part of the MIME document set.  The media type specification
   and registration procedure has now been moved to this 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
   revision attempts for the first time to incorporate such restrictions
   into media type registrations in a systematic way.  See Section 4.9
   for additional discussion.

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-



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   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 March 8, 2012.

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.




























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Media Type Registration Preliminaries  . . . . . . . . . . . .  5
   3.  Registration Trees and Subtype Names . . . . . . . . . . . . .  5
     3.1.  Standards Tree . . . . . . . . . . . . . . . . . . . . . .  6
     3.2.  Vendor Tree  . . . . . . . . . . . . . . . . . . . . . . .  6
     3.3.  Personal or Vanity Tree  . . . . . . . . . . . . . . . . .  7
     3.4.  Special x. Tree  . . . . . . . . . . . . . . . . . . . . .  7
     3.5.  Additional Registration Trees  . . . . . . . . . . . . . .  8
   4.  Registration Requirements  . . . . . . . . . . . . . . . . . .  8
     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 . . . . . . . . . . . . . . 11
       4.2.8.  Structured Syntax Name Suffixes  . . . . . . . . . . . 12
     4.3.  Parameter Requirements . . . . . . . . . . . . . . . . . . 12
     4.4.  Canonicalization and Format Requirements . . . . . . . . . 13
     4.5.  Interchange Recommendations  . . . . . . . . . . . . . . . 14
     4.6.  Security Requirements  . . . . . . . . . . . . . . . . . . 14
     4.7.  Requirements specific to XML media types . . . . . . . . . 15
     4.8.  Encoding Requirements  . . . . . . . . . . . . . . . . . . 15
     4.9.  Usage and Implementation Non-requirements  . . . . . . . . 16
     4.10. Publication Requirements . . . . . . . . . . . . . . . . . 17
     4.11. Additional Information . . . . . . . . . . . . . . . . . . 17
   5.  Media Type Registration Procedures . . . . . . . . . . . . . . 18
     5.1.  Preliminary Community Review . . . . . . . . . . . . . . . 18
     5.2.  Review and Approval  . . . . . . . . . . . . . . . . . . . 19
     5.3.  IANA Registration  . . . . . . . . . . . . . . . . . . . . 19
     5.4.  Media Types Reviewer . . . . . . . . . . . . . . . . . . . 19
     5.5.  Comments on Media Type Registrations . . . . . . . . . . . 20
     5.6.  Location of Registered Media Type List . . . . . . . . . . 20
     5.7.  IANA Procedures for Registering Media Types  . . . . . . . 20
     5.8.  Change Procedures  . . . . . . . . . . . . . . . . . . . . 21
     5.9.  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  . . . . . . . . . . . . . . . . . . . . . 25
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 25



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     10.2. Informative References . . . . . . . . . . . . . . . . . . 26
   Appendix A.  Grandfathered Media Types . . . . . . . . . . . . . . 26
   Appendix B.  Changes Since RFC 4288  . . . . . . . . . . . . . . . 27
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27















































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1.  Introduction

   Recent Internet protocols have been carefully designed to be easily
   extensible in certain areas.  In particular, many protocols,
   including but not limited to MIME [RFC2045], are capable of carrying
   arbitrary labeled content.  A mechanism is needed to label such
   content and a registration process is needed for these labels, to
   ensure that the set of such values is developed in an orderly, well-
   specified, and public manner.

   This document defines media type specification and registration
   procedures that use the Internet Assigned Numbers Authority (IANA) as
   a central registry.

1.1.  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].

   This specification makes use of the Augmented Backus-Naur Form (ABNF)
   [RFC4234] notation, including the core rules defined in Appendix A of
   that document.


2.  Media Type Registration Preliminaries

   Registration of a new media type or types starts with the
   construction of a registration proposal.  Registration may occur
   within several different registration trees that have different
   requirements, as discussed below.  In general, a new registration
   proposal is circulated and reviewed in a fashion appropriate to the
   tree involved.  The media type is then registered if the proposal is
   acceptable.  The following sections describe the requirements and
   procedures used for each of the different registration trees.


3.  Registration Trees and Subtype Names

   In order to increase the efficiency and flexibility of the
   registration process, different structures of subtype names may be
   registered to accommodate the different natural requirements for,
   e.g., a subtype that will be recommended for wide support and
   implementation by the Internet community, or a subtype that is used
   to move files associated with proprietary software.  The following
   subsections define registration "trees" that are distinguished by the
   use of faceted names, e.g., names of the form
   "tree.subtree...subtype".  Note that some media types defined prior



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   to this document do not conform to the naming conventions described
   below.  See Appendix A for a discussion of them.

3.1.  Standards Tree

   The standards tree is intended for types of general interest to the
   Internet community.  Registrations in the standards tree MUST be
   either:

   1.  approved directly by the IESG, or

   2.  registered using the "Specification Required" IANA registration
       policy [RFC5226] (which implies Expert Review).

   The former procedure is used for registering 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.  In the
   latter case the IESG makes the decision on whether the registration
   submitter represents a recognized Standards Body; after that a Media
   Types Reviewer (Designated Expert or a group of Designated Experts)
   performs the expert review as specified in this document.

   In the case of registration for the IETF itself, the registration
   proposal MUST be published as an IETF Consensus RFC.

   Registrations published in non-IETF RFC streams are allowed and
   require IESG approval.

   Standards-tree registration RFCs can either be standalone
   "registration only" RFCs, or they can be incorporated into a more
   general specification of some sort.

   Media types in the standards tree are normally denoted by names that
   are not explicitly faceted, i.e., do not contain period (".", full
   stop) characters.

   The "owner" of a media type registration in the standards tree is
   assumed to be the standards body itself.  Modification or alteration
   of the specification requires the same level of processing (e.g., a
   registration submitted on Standards Track can be revised in another
   Standards Track RFC, but can't be revised in an Informational RFC)
   required for the initial registration.

3.2.  Vendor Tree

   The vendor tree is used for media types associated with commercially
   available products.  "Vendor" or "producer" are construed as



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   equivalent and very broadly in this context.

   A registration may be placed in the vendor tree by anyone who needs
   to interchange files associated with the particular product.
   However, the registration formally belongs to the vendor or
   organization producing the software or file format being registered.
   Changes to the specification will be made at their request, as
   discussed in subsequent sections.

   Registrations in the vendor tree 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 is not required, using the ietf-types@iana.org
   mailing list for review is strongly 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.

3.3.  Personal or Vanity Tree

   Registrations for media types created experimentally or as part of
   products that are not distributed commercially may be registered in
   the personal or vanity tree.  The registrations are distinguished by
   the leading facet "prs.".

   The owner of "personal" registrations and associated specifications
   is the person or entity making the registration, or one to whom
   responsibility has been transferred as described below.

   While public exposure and review of media types to be registered in
   the personal tree is not required, using the ietf-types list for
   review is strongly 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.

3.4.  Special x. Tree

   For convenience and symmetry with this registration scheme, subtype
   names with "x." as the first facet may be used for the same purposes
   for which names starting in "x-" are used.  These types are
   unregistered, experimental, and for use only with the active
   agreement of the parties exchanging them.



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   However, with the simplified registration procedures described above
   for vendor and personal trees, it should rarely, if ever, be
   necessary to use unregistered experimental types.  Therefore, use of
   both "x-" and "x." forms is discouraged.

   Types in this tree MUST NOT be registered.  If a generally useful and
   widely deployed type incorrectly ends up with an "x." or "x-" name
   prefix, it MAY be registered using its current name in an alternate
   tree by following the procedure defined in Appendix A.

3.5.  Additional Registration Trees

   From time to time and as required by the community, the IANA may, by
   and with the advice and consent of the IESG, create new top-level
   registration trees.  It is explicitly assumed that these trees may be
   created for external registration and management by well-known
   permanent bodies; for example, scientific societies may register
   media types specific to the sciences they cover.  In general, the
   quality of review of specifications for one of these additional
   registration trees is expected to be equivalent to registrations in
   the standards tree.  Establishment of these new trees MUST be done
   with a Standards Track RFC.


4.  Registration Requirements

   Media type registration proposals are all expected to conform to
   various requirements laid out in the following sections.  Note that
   requirement specifics sometimes vary depending on the registration
   tree, again as detailed in the following sections.

4.1.  Functionality Requirement

   Media types MUST function as an actual media format.  Registration of
   things that are better thought of as a transfer encoding, as a
   charset, or as a collection of separate entities of another type, is
   not allowed.  For example, although applications exist to decode the
   base64 transfer encoding [RFC2045], base64 cannot be registered as a
   media type.

   This requirement applies regardless of the registration tree
   involved.

4.2.  Naming Requirements

   All registered media types MUST be assigned type and subtype names.
   The combination of these names serves to uniquely identify the media
   type, and the format of the subtype name identifies the registration



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   tree.  Both type and subtype names are case-insensitive.

   Type and subtype names beginning with "X-" are reserved for
   experimental use and MUST NOT be registered.  This parallels the
   restriction on the x. tree, as discussed in Section 3.4.

   Type and subtype names MUST conform to the following ABNF:

       type-name = reg-name
       subtype-name = reg-name

       reg-name = 1*127reg-name-chars
       reg-name-chars = ALPHA / DIGIT / "!" /
                        "#" / "$" / "&" / "." /
                        "+" / "-" / "^" / "_"

   Note that this syntax is somewhat more restrictive than what is
   allowed by the ABNF in [RFC2045].

   Although the name syntax treates "+" as equivalent to any other
   character, it is used in media type names to introduce a structured
   syntax specificer 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 name 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 MIME, MAY impose additional restrictions
   on the media types they can transport.  (See [RFC2046] for additional
   information on the restrictions MIME imposes.)

4.2.1.  Text Media Types

   The "text" media type is intended for sending material that is
   principally textual in form.  A "charset" parameter MAY be used to
   indicate the charset of the body text for "text" subtypes, notably
   including the subtype "text/plain", which is a generic subtype for
   plain text defined in [RFC2046].  If defined, a text "charset"
   parameter MUST be used to specify a charset name defined in



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   accordance to the procedures laid out in [RFC2978].

   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 opposite 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 should be
   represented using subtypes of "text".

4.2.2.  Image Media Types

   A media type of "image" indicates that the content specifies one or
   more separate images that require appropriate hardware to display.
   The subtype names the specific image format.

4.2.3.  Audio Media Types

   A media type of "audio" indicates that the content contains audio
   data.

4.2.4.  Video Media Types

   A media type of "video" indicates that the content specifies a time-
   varying-picture image, possibly with color and coordinated sound.
   The term 'video' is used in its most generic sense, rather than with
   reference to any particular technology or format, and is not meant to
   preclude subtypes such as animated drawings encoded compactly.

   Note that although in general this document strongly discourages the
   mixing of multiple media in a single body, it is recognized that many
   so-called video formats include a representation for synchronized
   audio and/or text, and this is explicitly permitted for subtypes of
   "video".





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4.2.5.  Application Media Types

   The "application" media type is to be used for discrete data that do
   not fit in any of the media types, and particularly for data to be
   processed by some type of application program.  This is information
   that must be processed by an application before it is viewable or
   usable by a user.  Expected uses for the "application" media type
   include but are not limited to file transfer, spreadsheets,
   presentations, scheduling data, and languages for "active"
   (computational) material.  (The latter, in particular, can pose
   security problems that must be understood by implementors, and are
   considered in detail in the discussion of the "application/
   PostScript" media type in [RFC2046].)

   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" media type.

   The subtype of "application" will often be either 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 be
   used freely as a subtype of "application".

4.2.6.  Multipart and Message Media Types

   Multipart and message are composite types, that is, they provide a
   means of encapsulating zero or more objects, each labeled with its
   own media type.

   All subtypes of multipart and message MUST conform to the syntax
   rules and other requirements specified in [RFC2046].

4.2.7.  Additional Top-level Types

   In some cases a new media type may not "fit" under any currently
   defined top-level content type.  Such cases are expected to be quite
   rare.  However, if such a case does arise a new top-level type can be
   defined to accommodate it.  Such a definition MUST be done via
   standards-track RFC; no other mechanism can be used to define
   additional top-level content types.





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4.2.8.  Structured Syntax Name Suffixes

   [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 media type name.

   Since this was published, the defacto 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
   should be registerable is that it be) described by a readily-
   available description, preferably within a document published by an
   established standards organization, and for which there's a reference
   that can be used in a 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 be used with care, given the possibility
   of conflicts with future suffix definitions.

4.3.  Parameter Requirements

   Media types MAY elect to use one or more media type parameters, or
   some parameters may be automatically made available to the media type
   by virtue of being a subtype of a content type that defines a set of
   parameters applicable to any of its subtypes.  In either case, the
   names, values, and meanings of any parameters MUST be fully specified
   when a media type is registered in the standards tree, and SHOULD be
   specified as completely as possible when media types are registered
   in the vendor or personal trees.

   Parameter names have the syntax as media type names and values:

       parameter-name = reg-name



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   Note that this syntax is somewhat more restrictive than what is
   allowed by the ABNF in [RFC2045] and amended by [RFC2231].

   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 should be taken to limit the use of potentially problematic
   syntaxes; e.g., pure binary valued parameters, while permitted in
   some protocols, probably should be avoided.

   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.

4.4.  Canonicalization and Format Requirements

   All registered media types MUST employ a single, canonical data
   format, regardless of registration tree.

   A precise and openly available specification of the format of each
   media type MUST exist for all types registered in the standards tree
   and MUST at a minimum be referenced by, if it isn't actually included
   in, the media type registration proposal itself.

   The specifications of format and processing particulars may or may
   not be publicly available for media types registered in the vendor
   tree, and such registration proposals are explicitly permitted to
   limit specification to which software and version produce or process
   such media types.  References to or inclusion of format
   specifications in registration proposals is encouraged but not
   required.

   Format specifications are still required for registration in the
   personal tree, but may be either published as RFCs or otherwise
   deposited with the IANA.  The deposited specifications will meet the
   same criteria as those required to register a well-known TCP port
   and, in particular, need not be made public.

   Some media types involve the use of patented technology.  The
   registration of media types involving patented technology is
   specifically permitted.  However, the restrictions set forth in
   [RFC2026] on the use of patented technology in IETF standards-track
   protocols must be respected when the specification of a media type is



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   part of a standards-track protocol.  In addition, other standards
   bodies making use of the standards tree may have their own rules
   regarding intellectual property that must be observed in their
   registrations.

4.5.  Interchange Recommendations

   Media types SHOULD interoperate across as many systems and
   applications as possible.  However, some media types will inevitably
   have problems interoperating across different platforms.  Problems
   with different versions, byte ordering, and specifics of gateway
   handling can and will arise.

   Universal interoperability of media types is not required, but known
   interoperability issues SHOULD be identified whenever possible.
   Publication of a media type does not require an exhaustive review of
   interoperability, and the interoperability considerations section is
   subject to continuing evaluation.

   These recommendations apply regardless of the registration tree
   involved.

4.6.  Security Requirements

   An analysis of security issues MUST be done for all types registered
   in the standards Tree.  A similar analysis for media types registered
   in the vendor or personal trees is encouraged but not required.
   However, regardless of what security analysis has or has not been
   done, all descriptions of security issues MUST be as accurate as
   possible regardless of registration tree.  In particular, a statement
   that there are "no security issues associated with this type" MUST
   NOT be confused with "the security issues associates with this type
   have not been assessed".

   There is absolutely no requirement that media types registered in any
   tree be secure or completely free from risks.  Nevertheless, all
   known security risks MUST be identified in the registration of a
   media type, again regardless of registration tree.

   The security considerations section of all registrations is subject
   to continuing evaluation and modification, and in particular MAY be
   extended by use of the "comments on media types" mechanism described
   in Section 5.5 below.

   Some of the issues that should be looked at in a security analysis of
   a media type are:





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   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
      should be described in a media type registration.

   o  All registrations MUST state whether or not they employ such
      "active content", and if they do, they MUST state what steps have
      been taken 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, and 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 not provide the necessary security
      mechanisms themselves.  For example, a media type could be defined
      for storage of confidential medical information that in turn
      requires an external confidentiality service, or which is designed
      for use only within a secure environment.

4.7.  Requirements specific to XML media types

   There are a number of additional requirements specific to the
   registration of XML media types.  These requirements are specified in
   [RFC3023].

4.8.  Encoding Requirements

   Some transports impose restrictions on the type of data they can
   carry.  For example, Internet mail traditionally was limited to 7bit
   US-ASCII text.  Encoding schemes are often used to work around such
   transport limitations.

   It is therefore useful to note what sort of data a media type can



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   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 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 [RFC3555].

   Additional restrictions on 7bit and 8bit text are given in [RFC2046].

4.9.  Usage and Implementation Non-requirements

   In the asynchronous mail environment, where information on the
   capabilities of the remote mail agent is frequently not available to
   the sender, maximum interoperability is attained by restricting the
   media types used to those "common" formats expected to be widely
   implemented.  This was asserted in the past as a reason to limit the
   number of possible media types, and resulted in a registration
   process with a significant hurdle and delay for those registering
   media types.

   However, the need for "common" media types does not require limiting
   the registration of new media types.  If a limited set of media types
   is recommended for a particular application, that should be asserted
   by a separate applicability statement specific for the application
   and/or environment.

   Therefore, universal support and implementation of a media type is
   NOT a requirement for registration.  However, if a media type is
   explicitly intended for limited use, this MUST be noted in its
   registration.  The "Restrictions on Usage" field is provided for this



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   purpose.

4.10.  Publication Requirements

   Proposals for media types registered in the standards tree by the
   IETF itself MUST be published as RFCs.  RFC publication of vendor and
   personal media type proposals is encouraged but not required.  In all
   cases the IANA will retain copies of all media type proposals and
   "publish" them as part of the media types registration tree itself.

   As stated previously, standards tree registrations for media types
   defined in documents produced by other standards bodies MUST be
   described by a formal standards specification produced by that body.
   Such specifications MUST contain an appropriate media type
   registration template taken from Section 5.9.  Additionally, the
   copyright on the registration template MUST allow the IANA to copy it
   into the IANA registry.

   Other than IETF registrations in the standards tree, the registration
   of a data type does not imply endorsement, approval, or
   recommendation by the IANA or the IETF or even certification that the
   specification is adequate.  To become Internet Standards, a protocol
   or data object must go through the IETF standards process.  This is
   too difficult and too lengthy a process for the convenient
   registration of media types.

   The standards tree exists for media types that do require a
   substantive review and approval process in a recognized standards
   body.  The vendor and personal trees exist for those media types that
   do not require such a process.  It is expected that applicability
   statements for particular applications will be published from time to
   time in the IETF, recommending implementation of, and support for,
   media types that have proven particularly useful in those contexts.

   As discussed above, registration of a top-level type requires
   standards-track processing in the IETF and, hence, RFC publication.

4.11.  Additional Information

   Various sorts of optional information SHOULD be included in the
   specification of a media type if it is available:

   o  Magic number(s) (length, octet values).  Magic numbers are byte
      sequences that are always present at a given place in the file and
      thus can be used to identify entities as being of a given media
      type.





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   o  File name extension(s) commonly used on one or more platforms to
      indicate that some file contains a given media type.

   o  Mac OS File Type code(s) (4 octets) used to label files containing
      a given media type.

   o  Information about how fragment/anchor identifiers [RFC3986] are
      constructed for use in conjunction with this media type.

   In the case of a registration in the standards tree, this additional
   information MAY be provided in the formal specification of the media
   type.  It is suggested that this be done by incorporating the IANA
   media type registration form into the specification itself.


5.  Media Type Registration Procedures

   The media type registration procedure is not a formal standards
   process, but rather an administrative procedure intended to allow
   community comment and sanity checking without excessive time delay.

   The normal IETF processes should be followed for all IETF
   registrations in the standards tree.  The posting of an Internet
   Draft is a necessary first step, followed by posting to the
   ietf-types@iana.org list as discussed below.

   Registrations in the vendor and personal tree should be submitted
   directly to the IANA, ideally after first posting to the
   ietf-types@iana.org list for review.

   Proposed registrations in the standards tree by other standards
   bodies MUST be communicated to both the IESG (at iesg@ietf.org) and
   to the ietf-types list (at ietf-types@iana.org).  Prior posting as an
   Internet Draft is not required for these registrations, but may be
   helpful to the IESG and is encouraged.

5.1.  Preliminary Community Review

   Notice of a potential media type registration in the standards tree
   MUST be sent to the "ietf-types@iana.org" mailing list for review.
   This mailing list has been established for the purpose of reviewing
   proposed media and access types.  Registrations in other trees MAY be
   sent to the list for review as well.

   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



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   considerations.  The submitter may submit a revised registration or
   abandon the registration completely and at any time.

5.2.  Review and Approval

   Media types registered in the standards tree MUST either be reviwed
   and approved by the IESG or follow the Specification Required
   process:

   1.  Specification in a permanent and readily available public
       specification

   2.  Review and approval by the Designated Expert for media types

5.3.  IANA Registration

   Provided that the media type meets all of the relevant requirements
   and has obtained whatever approval this specification requires, the
   author may submit the registration request to the IANA.  Registration
   requests can be sent to iana@iana.org.  A web form for registration
   requests is also available:

     http://www.iana.org/cgi-bin/mediatypes.pl

   Sending to ietf-types@iana.org does not constitute submitting the
   registration to the IANA.

   When the registration is either part of an RFC publication request or
   a registration in the standards tree submitted to the IESG, close
   coordination between the IANA and the IESG means IESG approval in
   effect submits the registration to the IANA.  There is no need for an
   additional registration request in such cases.

5.4.  Media Types Reviewer

   Registrations submitted to the IANA will be passed on to the media
   types reviewer.  The media types reviewer, who is appointed by the
   IETF Applications Area Director(s), will review the registration to
   make sure it meets the requirements set forth in this document.
   Registrations that do not meet these requirements will be returned to
   the submitter for revision.

   Decisions made by the media types reviewer may be appealed to the
   IESG using the procedure specified in [RFC2026] section 6.5.4.

   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.



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5.5.  Comments on Media Type Registrations

   Comments on registered media types may be submitted by members of the
   community to the IANA at iana@iana.org.  These comments will be
   reviewed by the media types reviewer and then passed on to the
   "owner" of the media type if possible.  Submitters of comments may
   request that their comment be attached to the media type registration
   itself, and if the IANA approves of this, the comment will be made
   accessible in conjunction with the type registration.

5.6.  Location of Registered Media Type List

   Media type registrations are listed by the IANA at:

     http://www.iana.org/assignments/media-types/

5.7.  IANA Procedures for Registering Media Types

   Upon receipt of a registration request, the IANA will submit the
   request for Expert Review.  The Expert Reviewer will check to see
   that the following minimal conditions are met:

   o  Media types MUST function as an actual media format.  In
      particular, charsets and transfer encodings MUST NOT be registered
      as media types.

   o  All media types MUST have properly formed type and subtype names.
      All type names MUST be defined by a standards-track RFC.  All
      type/subtype name pairs MUST be unique and MUST contain the proper
      tree prefix.

   o  Types registered in the standards and personal trees MUST either
      provide a format specification or a pointer to one.

   o  All media types MUST have a reasonable security considerations
      section.  (It is neither possible nor necessary for the IANA to
      conduct a comprehensive security review of media type
      registrations.  Nevertheless, the IANA has the authority to
      identify obviously incompetent material and return it to the
      submitter for revision.)

   o  Registrations in the standards tree MUST satisfy the additional
      requirement that they originate from the IETF itself or from
      another Standards Body recognized as such by the IETF.

   Registrations in the standards tree MUST satisfy the additional
   requirement that they originate from the IETF itself or from another
   Standards Body recognized as such by the IETF.  The IESG determines



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   whether or not a given organization qualifies as a standards body.

5.8.  Change Procedures

   Once a media type has been published by the IANA, the owner may
   request a change to its definition.  The descriptions of the
   different registration trees above designate the "owners" of each
   type of registration.  The same procedure that would be appropriate
   for the original registration request is used to process a change
   request.

   Changes 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 and the ietf-types list; 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.

   Media type registrations may not be deleted; media types that are no
   longer believed appropriate for use can be declared OBSOLETE by a
   change to their "intended use" field; such media types will be
   clearly marked in the lists published by the IANA.





















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5.9.  Registration Template

   To: ietf-types@iana.org
   Subject: Registration of media type XXX/YYY

   Type name:

   Subtype name:

   Required parameters:

   Optional parameters:

   Encoding considerations:

   Security considerations:

   Interoperability considerations:

   Published specification:

   Applications that use this media type:

   Additional information:

     Magic number(s):
     File extension(s):
     Macintosh file type code(s):
     URI fragment/anchor identifier(s):

   Person & email address to contact for further information:

   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:

   (Any other information that the author deems interesting may be
   added below this line.)

   Some discussion of Macintosh file type codes and their purpose can be



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   found in [MacOSFileTypes].  Additionally, please refrain from writing
   "none" or anything similar when no file extension or Macintosh file
   type is specified, lest "none" be confused with an actual code value.


6.  Structured Syntax Suffix Registration Procedures

   Someone wishing to define a +suffix name for a structured syntax for
   use with a new media type registration SHOULD:

   1.  Check IANA's registry of media type name suffixes to see whether
       or not there is already an entry for that well-defined structured
       syntax.

   2.  If there is no entry for their suffix scheme, fill out the
       template (specified in 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 RFC 3978 [RFC3978].

   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 ietf-types@ietf.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 document containing it) to IANA at iana@iana.org.

   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 a 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.



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   4.  The Designated Expert may request additional review or
       discussion, as necessary.

   5.  If Expert Review recommends registration registration, IANA adds
       the registration to the appropriate registry.

6.1.  Change Procedures

   Registrations may be updated in each registry by the same mechanism
   as required for an initial registration.  In cases where the original
   definition of the scheme is contained in an IESG-approved document,
   update of the specification also requires IESG approval.

6.2.  Structured Syntax Suffix Registration Template

   This template describes the fields that must be supplied in a
   structured syntax sufficx registration request:

   Name
      Full name of the well-defined structured syntax.

   +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.

   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 option of not assessing the security
      considerations is not available for suffix registrations.




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   Contact
      Person (including contact information) to contact for further
      information.

   Author/Change controller.
      Person (including contact information) authorized to change this
      suffix registration.


7.  Security Considerations

   Security requirements for media type registrations are discussed in
   Section 4.6.


8.  IANA Considerations

   The purpose of this document is to define IANA registries for media
   types and structured syntax suffixes.


9.  Acknowledgements

   The current authors would like to acknowledge their debt to the late
   Dr. Jon Postel, whose general model of IANA registration procedures
   and specific contributions shaped the predecessors of this document
   [RFC2048].  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.

   Alexey Melnikov provided many helpful review comments and
   suggestions.


10.  References

10.1.  Normative References

   [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.



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   [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.

   [RFC3555]  Casner, S. and P. Hoschka, "MIME Type Registration of RTP
              Payload Formats", RFC 3555, July 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC4234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

10.2.  Informative References

   [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.

   [RFC3978]  Bradner, S., "IETF Rights in Contributions", RFC 3978,
              March 2005.


Appendix A.  Grandfathered Media Types

   A number of media types with unfaceted names, registered prior to
   1996, would, if registered under the guidelines in this document, be



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   given a faceted name and placed into either the vendor or personal
   trees.  Reregistration of those types to reflect the appropriate
   trees is encouraged but not required.  Ownership and change control
   principles outlined in this document apply to those types as if they
   had been registered in the trees described above.

   From time to time there may also be cases where a media type with an
   unfaceted name has been widely deployed without being registered.  If
   possible such types SHOULD be reregistered with a proper faceted
   name.  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.


Appendix B.  Changes Since RFC 4288

   o  Suffixes to indicate the use of a particular structured syntax are
      now fully specified and a suffix registration process has been
      defined.

   o  Registration of widely deployed unregistered unfaceted type names
      in the vendor or personal trees is now allowed, subject to
      approval by the media types reviewer and the IESG.

   o  The standards tree registration process has been revised to
      include Expert Review and generalized to address cases like media
      types in non-IETF stream documents.

   o  A field for fragment/anchor identifiers has been added to the
      registration template.


Authors' Addresses

   Ned Freed
   Oracle
   800 Royal Oaks
   Monrovia, CA  91016-6347
   USA

   Email: ned+ietf@mrochek.com










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   John C. Klensin
   1770 Massachusetts Ave, #322
   Cambridge, MA  02140
   USA

   Email: klensin+ietf@jck.com


   Tony Hansen
   AT&T Laboratories
   200 Laurel Ave.
   Middletown, NJ  07748
   USA

   Email: tony+mtsuffix@maillennium.att.com




































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