Network Working Group N. Freed Internet-Draft Sun Microsystems Obsoletes: 2048 (if approved) J. Klensin Expires: February 17, 2005 August 17, 2004 Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures draft-freed-mime-p4-05.txt Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 15, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document specifies IANA registration procedures for MIME external body access types and content-transfer-encodings. Freed & Klensin Expires February 15, 2005 [Page 1] Internet-Draft MIME Registration Procedures August 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Conventions Used In This Document . . . . . . . . . . . . 3 2. External Body Access Types . . . . . . . . . . . . . . . . . . 4 2.1 Registration Requirements . . . . . . . . . . . . . . . . 4 2.1.1 Naming Requirements . . . . . . . . . . . . . . . . . 4 2.1.2 Mechanism Specification Requirements . . . . . . . . . 4 2.1.3 Publication Requirements . . . . . . . . . . . . . . . 4 2.1.4 Security Requirements . . . . . . . . . . . . . . . . 4 2.2 Registration Procedure . . . . . . . . . . . . . . . . . . 5 2.2.1 Present the Access Type to the Community . . . . . . . 5 2.2.2 Access Type Reviewer . . . . . . . . . . . . . . . . . 5 2.2.3 IANA Registration . . . . . . . . . . . . . . . . . . 5 2.3 Location of Registered Access Type List . . . . . . . . . 5 2.4 IANA Procedures for Registering Access Types . . . . . . . 5 3. Transfer Encodings . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Transfer Encoding Requirements . . . . . . . . . . . . . . 7 3.1.1 Naming Requirements . . . . . . . . . . . . . . . . . 7 3.1.2 Algorithm Specification Requirements . . . . . . . . . 7 3.1.3 Input Domain Requirements . . . . . . . . . . . . . . 8 3.1.4 Output Range Requirements . . . . . . . . . . . . . . 8 3.1.5 Data Integrity and Generality Requirements . . . . . . 8 3.1.6 New Functionality Requirements . . . . . . . . . . . . 8 3.1.7 Security Requirements . . . . . . . . . . . . . . . . 8 3.2 Transfer Encoding Definition Procedure . . . . . . . . . . 8 3.3 IANA Procedures for Transfer Encoding Registration . . . . 9 3.4 Location of Registered Transfer Encodings List . . . . . . 9 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1 Normative References . . . . . . . . . . . . . . . . . . . . 13 7.2 Informative References . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13 A. Changes made since RFC 2048 . . . . . . . . . . . . . . . . . 14 Intellectual Property and Copyright Statements . . . . . . . . 15 Freed & Klensin Expires February 15, 2005 [Page 2] Internet-Draft MIME Registration Procedures August 2004 1. Introduction Recent Internet protocols have been carefully designed to be easily extensible in certain areas. In particular, MIME [RFC2045] is an open-ended framework and can accommodate additional object types, charsets, and access methods without any changes to the basic protocol. A registration process is needed, however, to ensure that the set of such values is developed in an orderly, well-specified, and public manner. This document defines registration procedures which use the Internet Assigned Numbers Authority (IANA) as a central registry for such values. Note Registration of media types and charsets for use in MIME are now specified in separate documents and are no longer addressed here. 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]. Freed & Klensin Expires February 15, 2005 [Page 3] Internet-Draft MIME Registration Procedures August 2004 2. External Body Access Types [RFC2046] defines the message/external-body media type, whereby a MIME entity can act as pointer to the actual body data in lieu of including the data directly in the entity body. Each message/ external-body reference specifies an access type, which determines the mechanism used to retrieve the actual body data. RFC 2046 defines an initial set of access types, but allows for the registration of additional access types to accommodate new retrieval mechanisms. 2.1 Registration Requirements New access type specifications MUST conform to a number of requirements as described below. 2.1.1 Naming Requirements Each access type MUST have a unique name. This name appears in the access-type parameter in the message/external-body content-type header field, and MUST conform to MIME content type parameter syntax. 2.1.2 Mechanism Specification Requirements All of the protocols, transports, and procedures used by a given access type MUST be described, either in the specification of the access type itself or in some other publicly available specification, in sufficient detail for the access type to be implemented by any competent implementor. Use of secret and/or proprietary methods in access types is expressly prohibited. The restrictions imposed by [RFC2026] on the standardization of patented algorithms must be respected as well. 2.1.3 Publication Requirements All access types MUST be described by an RFC. The RFC may be informational rather than standards-track, although standard-track review and approval are encouraged for all access types. 2.1.4 Security Requirements Any known security issues that arise from the use of the access type MUST be completely and fully described. It is not required that the access type be secure or that it be free from risks, but that the known risks be identified. Publication of a new access type does not require an exhaustive security review, and the security considerations section is subject to continuing evaluation. Additional security considerations SHOULD be addressed by publishing Freed & Klensin Expires February 15, 2005 [Page 4] Internet-Draft MIME Registration Procedures August 2004 revised versions of the access type specification. 2.2 Registration Procedure Registration of a new access type starts with the the publication of the specification as an internet-draft. 2.2.1 Present the Access Type to the Community Send a proposed access type specification to the "ietf-types@iana.org" mailing list for a two week review period. This mailing list has been established for the purpose of reviewing proposed access and media types. Proposed access types are not formally registered and must not be used. The intent of the public posting is to solicit comments and feedback on the access type specification and a review of any security considerations. 2.2.2 Access Type Reviewer When the two week period has passed, the access type reviewer, who is appointed by the IETF Applications Area Director(s), either forwards the request to iana@iana.org, or rejects it because of significant objections raised on the list. Decisions made by the reviewer must be posted to the ietf-types mailing list within 14 days. Decisions made by the reviewer may be appealed to the IESG as specified in [RFC2026]. 2.2.3 IANA Registration Provided that the access type has either passed review or has been successfully appealed to the IESG, the IANA will register the access type and make the registration available to the community. The specification of the access type must also be published as an RFC. 2.3 Location of Registered Access Type List Access type registrations are listed by the IANA on the web page: http://www.iana.org/assignments/access-types 2.4 IANA Procedures for Registering Access Types The identity of the access type reviewer is communicated to the IANA by the IESG. The IANA then only acts in response to access type Freed & Klensin Expires February 15, 2005 [Page 5] Internet-Draft MIME Registration Procedures August 2004 definitions that either are approved by the access type reviewer and forwarded by the reviewer to the IANA for registration, or in response to a communication from the IESG that an access type definition appeal has overturned the access type reviewer's ruling. Freed & Klensin Expires February 15, 2005 [Page 6] Internet-Draft MIME Registration Procedures August 2004 3. Transfer Encodings Transfer encodings are tranformations applied to MIME media types after conversion to the media type's canonical form. Transfer encodings are used for several purposes: o Many transports, especially message transports, can only handle data consisting of relatively short lines of text. There can also be severe restrictions on what characters can be used in these lines of text -- some transports are restricted to a small subset of US-ASCII and others cannot handle certain character sequences. Transfer encodings are used to transform binary data into textual form that can survive such transports. Examples of this sort of transfer encoding include the base64 and quoted-printable transfer encodings defined in [RFC2045]. o Image, audio, video, and even application entities are sometimes quite large. Compression algorithms are often quite effective in reducing the size of large entities. Transfer encodings can be used to apply general-purpose non-lossy compression algorithms to MIME entities. o Transport encodings can be defined as a means of representing existing encoding formats in a MIME context. IMPORTANT: The standardization of a large numbers of different transfer encodings is seen as a significant barrier to widespread interoperability and is expressely discouraged. Nevertheless, the following procedure has been defined to provide a means of defining additional transfer encodings, should standardization actually be justified. 3.1 Transfer Encoding Requirements Transfer encoding specifications MUST conform to a number of requirements as described below. 3.1.1 Naming Requirements Each transfer encoding MUST have a unique name. This name appears in the Content-Transfer-Encoding header field and MUST conform to the syntax of that field. 3.1.2 Algorithm Specification Requirements All of the algorithms used in a transfer encoding (e.g., conversion to printable form, compression) MUST be described in their entirety in the transfer encoding specification. Use of secret and/or proprietary algorithms in standardized transfer encodings is expressly prohibited. The restrictions imposed by [RFC2026] on the standardization of patented algorithms MUST be respected as well. Freed & Klensin Expires February 15, 2005 [Page 7] Internet-Draft MIME Registration Procedures August 2004 3.1.3 Input Domain Requirements All transfer encodings MUST be applicable to an arbitrary sequence of octets of any length. Dependence on particular input forms is not allowed. It should be noted that the 7bit and 8bit encodings do not conform to this requirement. Aside from the undesireability of having specialized encodings, the intent here is to forbid the addition of additional encodings similar to or redundant with 7bit and 8bit. 3.1.4 Output Range Requirements There is no requirement that a particular tranfer encoding produce a particular form of encoded output. However, the output format for each transfer encoding MUST be fully and completely documented. In particular, each specification MUST clearly state whether the output format always lies within the confines of 7bit data, 8bit data, or is simply pure binary data. 3.1.5 Data Integrity and Generality Requirements All transfer encodings MUST be fully invertible on any platform; it MUST be possible for anyone to recover the original data by performing the corresponding decoding operation. Note that this requirement effectively excludes all forms of lossy compression as well as all forms of encryption from use as a transfer encoding. 3.1.6 New Functionality Requirements All transfer encodings MUST provide some sort of new functionality. Some degree of functionality overlap with previously defined transfer encodings is acceptable, but any new transfer encoding MUST also offer something no other transfer encoding provides. 3.1.7 Security Requirements To the greatest extent possible transfer encodings SHOULD NOT contain known security issues. Regardless, any known security issues that arise from the use of the transfer encoding MUST be completely and fully described. If additional security issues come to light after initial publication and registration they SHOULD be addressed by publishing revised versions of the transfer encoding pecification. 3.2 Transfer Encoding Definition Procedure Definition of a new transfer encoding starts with the the publication of the specification as an internet-draft. The draft MUST define the Freed & Klensin Expires February 15, 2005 [Page 8] Internet-Draft MIME Registration Procedures August 2004 transfer encoding precisely and completely, and MUST also provide substantial justification for defining and standardizing a new transfer encoding. This specification MUST then be presented to the IESG for consideration. The IESG can o reject the specification outright as being inappropriate for standardization, o assign the specification to an existing IETF working group for further work, o approve the formation of an IETF working group to work on the specification in accordance with IETF procedures, or, o accept the specification as-is for processing as an individual standards track submission. Transfer encoding specifications on the standards track follow normal IETF rules for standards track documents. A transfer encoding is considered to be defined and available for use once it is on the standards track. 3.3 IANA Procedures for Transfer Encoding Registration There is no need for a special procedure for registering Transfer Encodings with the IANA. All legitimate transfer encoding registrations MUST appear as a standards-track RFC, so it is the IESG's responsibility to notify the IANA when a new transfer encoding has been approved. 3.4 Location of Registered Transfer Encodings List The list of transfer encoding registrations can be found at: http://www.iana.org/assignments/transfer-encodings Freed & Klensin Expires February 15, 2005 [Page 9] Internet-Draft MIME Registration Procedures August 2004 4. Security Considerations Security requirements for access types are discussed in Section 2.1.4. Security requirements for transfer encodings are discussed in Section 3.1.7. Freed & Klensin Expires February 15, 2005 [Page 10] Internet-Draft MIME Registration Procedures August 2004 5. IANA Considerations The sole purpose of this document is to define IANA registries for access types and transfer encodings. The IANA procedures for these registries are specified in Section 2.4 and Section 3.3 respectively. Freed & Klensin Expires February 15, 2005 [Page 11] Internet-Draft MIME Registration Procedures August 2004 6. 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. We hope that the current version is one with which he would have agreed but, since it is impossible to verify that agreement, we have regretfully removed his name as a co-author. Freed & Klensin Expires February 15, 2005 [Page 12] Internet-Draft MIME Registration Procedures August 2004 7. References 7.1 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. [RFC3023] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001. 7.2 Informative References [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. Authors' Addresses Ned Freed Sun Microsystems 1050 Lakes Drive West Covina, CA 91790 USA EMail: ned.freed@mrochek.com John C Klensin 1770 Massachusetts Ave, #322 Cambridge, MA 02140 EMail: klensin@jck.com Freed & Klensin Expires February 15, 2005 [Page 13] Internet-Draft MIME Registration Procedures August 2004 Appendix A. Changes made since RFC 2048 o Media type registration procedures are now described in a separate document. o The various URLs and addresses in this document have been changed so they all refer to iana.org rather than isi.edu. Additionally, many of the URLs have been changed to use HTTP; formerly they used FTP. o Much of the document has been clarified in the light of operational experience with these procedures. o Several of the references in this document have been updated to refer to current versions of the relevant specifications. o The option of assigning the task of working on a new transfer encoding to an existing working group has been added to the list of possible actions the IESG can take. o Security considerations and IANA considerations sections have been added. Freed & Klensin Expires February 15, 2005 [Page 14] Internet-Draft MIME Registration Procedures August 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Freed & Klensin Expires February 15, 2005 [Page 15]