Update to MIME regarding "charset" Parameter Handling in Textual Media Types
RFC 6657
Document | Type |
RFC - Proposed Standard
(July 2012; No errata)
Updates RFC 2046
|
|
---|---|---|---|
Authors | Alexey Melnikov , Julian Reschke | ||
Last updated | 2015-10-14 | ||
Replaces | draft-melnikov-mime-default-charset | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Murray Kucherawy | ||
Shepherd write-up | Show (last changed 2012-04-21) | ||
IESG | IESG state | RFC 6657 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Barry Leiba | ||
Send notices to | (None) |
Internet Engineering Task Force (IETF) A. Melnikov Request for Comments: 6657 Isode Limited Updates: 2046 J. Reschke Category: Standards Track greenbytes ISSN: 2070-1721 July 2012 Update to MIME regarding "charset" Parameter Handling in Textual Media Types Abstract This document changes RFC 2046 rules regarding default "charset" parameter values for "text/*" media types to better align with common usage by existing clients and servers. Status of This Memo This is an Internet Standards Track document. 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 Internet Standards 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/rfc6657. Copyright Notice Copyright (c) 2012 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. Melnikov & Reschke Standards Track [Page 1] RFC 6657 MIME Charset Default Update July 2012 Table of Contents 1. Introduction and Overview .......................................2 2. Conventions Used in This Document ...............................2 3. New Rules for Default "charset" Parameter Values for "text/*" Media Types ............................................3 4. Default "charset" Parameter Value for "text/plain" Media Type ...4 5. Security Considerations .........................................4 6. IANA Considerations .............................................4 7. References ......................................................4 7.1. Normative References .......................................4 7.2. Informative References .....................................5 Appendix A. Acknowledgements ......................................6 1. Introduction and Overview RFC 2046 specified that the default "charset" parameter (i.e., the value used when the parameter is not specified) is "US-ASCII" (Section 4.1.2 of [RFC2046]). RFC 2616 changed the default for use by HTTP (Hypertext Transfer Protocol) to be "ISO-8859-1" (Section 3.7.1 of [RFC2616]). This encoding is not very common for new "text/*" media types and a special rule in the HTTP specification adds confusion about which specification ([RFC2046] or [RFC2616]) is authoritative in regards to the default charset for "text/*" media types. Many complex text subtypes such as "text/html" [RFC2854] and "text/ xml" [RFC3023] have internal (to their format) means of describing the charset. Many existing User Agents ignore the default of "US- ASCII" rule for at least "text/html" and "text/xml". This document changes RFC 2046 rules regarding default "charset" parameter values for "text/*" media types to better align with common usage by existing clients and servers. It does not change the defaults for any currently registered media type. 2. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Melnikov & Reschke Standards Track [Page 2] RFC 6657 MIME Charset Default Update July 2012 3. New Rules for Default "charset" Parameter Values for "text/*" Media Types Section 4.1.2 of [RFC2046] says: The default character set, which must be assumed in the absence of a charset parameter, is US-ASCII. As explained in the Introduction section, this rule is considered outdated, so this document replaces it with the following set of rules: Each subtype of the "text" media type that uses the "charset" parameter can define its own default value for the "charset" parameter, including the absence of any default.Show full document text