Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters
RFC 5987

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Internet Engineering Task Force (IETF)                        J. Reschke
Request for Comments: 5987                                    greenbytes
Category: Standards Track                                    August 2010
ISSN: 2070-1721

                Character Set and Language Encoding for
       Hypertext Transfer Protocol (HTTP) Header Field Parameters

Abstract

   By default, message header field parameters in Hypertext Transfer
   Protocol (HTTP) messages cannot carry characters outside the ISO-
   8859-1 character set.  RFC 2231 defines an encoding mechanism for use
   in Multipurpose Internet Mail Extensions (MIME) headers.  This
   document specifies an encoding suitable for use in HTTP header fields
   that is compatible with a profile of the encoding defined in RFC
   2231.

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/rfc5987.

Copyright Notice

   Copyright (c) 2010 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.

Reschke                      Standards Track                    [Page 1]
RFC 5987            Charset/Language Encoding in HTTP        August 2010

Table of Contents

   1. Introduction ....................................................2
   2. Notational Conventions ..........................................2
   3. Comparison to RFC 2231 and Definition of the Encoding ...........3
      3.1. Parameter Continuations ....................................3
      3.2. Parameter Value Character Set and Language Information .....3
           3.2.1. Definition ..........................................3
           3.2.2. Examples ............................................6
      3.3. Language Specification in Encoded Words ....................6
   4. Guidelines for Usage in HTTP Header Field Definitions ...........7
      4.1. When to Use the Extension ..................................7
      4.2. Error Handling .............................................7
   5. Security Considerations .........................................8
   6. Acknowledgements ................................................8
   7. References ......................................................8
      7.1. Normative References .......................................8
      7.2. Informative References .....................................9

1.  Introduction

   By default, message header field parameters in HTTP ([RFC2616])
   messages cannot carry characters outside the ISO-8859-1 character set
   ([ISO-8859-1]).  RFC 2231 ([RFC2231]) defines an encoding mechanism
   for use in MIME headers.  This document specifies an encoding
   suitable for use in HTTP header fields that is compatible with a
   profile of the encoding defined in RFC 2231.

      Note: in the remainder of this document, RFC 2231 is only
      referenced for the purpose of explaining the choice of features
      that were adopted; they are therefore purely informative.

      Note: this encoding does not apply to message payloads transmitted
      over HTTP, such as when using the media type "multipart/form-data"
      ([RFC2388]).

2.  Notational Conventions

   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 uses the ABNF (Augmented Backus-Naur Form)
   notation defined in [RFC5234].  The following core rules are included
   by reference, as defined in [RFC5234], Appendix B.1: ALPHA (letters),
   DIGIT (decimal 0-9), HEXDIG (hexadecimal 0-9/A-F/a-f), and LWSP
   (linear whitespace).

Reschke                      Standards Track                    [Page 2]
RFC 5987            Charset/Language Encoding in HTTP        August 2010

   Note that this specification uses the term "character set" for
   consistency with other IETF specifications such as RFC 2277 (see