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+Internet Engineering Task Force (IETF)                        J. Reschke
+Request for Comments: 7238                                    greenbytes
+Category: Experimental                                         June 2014
+ISSN: 2070-1721
+
+
+  The Hypertext Transfer Protocol Status Code 308 (Permanent Redirect)
+
+Abstract
+
+   This document specifies the additional Hypertext Transfer Protocol
+   (HTTP) status code 308 (Permanent Redirect).
+
+Status of This Memo
+
+   This document is not an Internet Standards Track specification; it is
+   published for examination, experimental implementation, and
+   evaluation.
+
+   This document defines an Experimental Protocol for the Internet
+   community.  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).  Not
+   all documents approved by the IESG are a candidate for any level of
+   Internet Standard; see 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/rfc7238.
+
+Copyright Notice
+
+   Copyright (c) 2014 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                       Experimental                      [Page 1]
+
+RFC 7238                  HTTP Status Code 308                 June 2014
+
+
+Table of Contents
+
+   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
+   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . . . 2
+   3.  308 Permanent Redirect  . . . . . . . . . . . . . . . . . . . . 2
+   4.  Deployment Considerations . . . . . . . . . . . . . . . . . . . 3
+   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
+   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
+   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
+   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
+     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
+     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
+
+1.  Introduction
+
+   HTTP defines a set of status codes for the purpose of redirecting a
+   request to a different URI ([RFC3986]).  The history of these status
+   codes is summarized in Section 6.4 of [RFC7231], which also
+   classifies the existing status codes into four categories.
+
+   The first of these categories contains the status codes 301 (Moved
+   Permanently), 302 (Found), and 307 (Temporary Redirect), which can be
+   classified as below:
+
+   +-------------------------------------------+-----------+-----------+
+   |                                           | Permanent | Temporary |
+   +-------------------------------------------+-----------+-----------+
+   | Allows changing the request method from   | 301       | 302       |
+   | POST to GET                               |           |           |
+   | Does not allow changing the request       | -         | 307       |
+   | method from POST to GET                   |           |           |
+   +-------------------------------------------+-----------+-----------+
+
+   Section 6.4.7 of [RFC7231] states that HTTP does not define a
+   permanent variant of status code 307; this specification adds the
+   status code 308, defining this missing variant (Section 3).
+
+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].
+
+3.  308 Permanent Redirect
+
+   The 308 (Permanent Redirect) status code indicates that the target
+   resource has been assigned a new permanent URI and any future
+   references to this resource ought to use one of the enclosed URIs.
+
+
+
+Reschke                       Experimental                      [Page 2]
+
+RFC 7238                  HTTP Status Code 308                 June 2014
+
+
+   Clients with link editing capabilities ought to automatically re-link
+   references to the effective request URI (Section 5.5 of [RFC7230]) to
+   one or more of the new references sent by the server, where possible.
+
+   The server SHOULD generate a Location header field ([RFC7231],
+   Section 7.1.2) in the response containing a preferred URI reference
+   for the new permanent URI.  The user agent MAY use the Location field
+   value for automatic redirection.  The server's response payload
+   usually contains a short hypertext note with a hyperlink to the new
+   URI(s).
+
+   A 308 response is cacheable by default; i.e., unless otherwise
+   indicated by the method definition or explicit cache controls (see
+   [RFC7234], Section 4.2.2).
+
+      Note: This status code is similar to 301 (Moved Permanently)
+      ([RFC7231], Section 6.4.2), except that it does not allow changing
+      the request method from POST to GET.
+
+4.  Deployment Considerations
+
+   Section 6 of [RFC7231] requires recipients to treat unknown 3xx
+   status codes the same way as status code 300 Multiple Choices
+   ([RFC7231], Section 6.4.1).  Thus, servers will not be able to rely
+   on automatic redirection happening similar to status codes 301, 302,
+   or 307.
+
+   Therefore, initial use of status code 308 will be restricted to cases
+   where the server has sufficient confidence in the client's
+   understanding the new code or when a fallback to the semantics of
+   status code 300 is not problematic.  Server implementers are advised
+   not to vary the status code based on characteristics of the request,
+   such as the User-Agent header field ("User-Agent Sniffing") -- doing
+   so usually results in code that is both hard to maintain and hard to
+   debug and would also require special attention to caching (i.e.,
+   setting a "Vary" response header field, as defined in Section 7.1.4
+   of [RFC7231]).
+
+   Note that many existing HTML-based user agents will emulate a refresh
+   when encountering an HTML <meta> refresh directive ([HTML]).  This
+   can be used as another fallback.  For example:
+
+   Client request:
+
+     GET / HTTP/1.1
+     Host: example.com
+
+
+
+
+
+Reschke                       Experimental                      [Page 3]
+
+RFC 7238                  HTTP Status Code 308                 June 2014
+
+
+   Server response:
+
+     HTTP/1.1 308 Permanent Redirect
+     Content-Type: text/html; charset=UTF-8
+     Location: http://example.com/new
+     Content-Length: 454
+
+     <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+                           "http://www.w3.org/TR/html4/strict.dtd">
+     <html>
+        <head>
+           <title>Permanent Redirect</title>
+           <meta http-equiv="refresh"
+                 content="0; url=http://example.com/new">
+        </head>
+        <body>
+           <p>
+              The document has been moved to
+              <a href="http://example.com/new"
+              >http://example.com/new</a>.
+           </p>
+        </body>
+     </html>
+
+5.  Security Considerations
+
+   All security considerations that apply to HTTP redirects apply to the
+   308 status code as well (see Section 9 of [RFC7231]).
+
+6.  IANA Considerations
+
+   The registration below has been added to the "Hypertext Transfer
+   Protocol (HTTP) Status Code Registry" (defined in Section 8.2 of
+   [RFC7231] and located at
+   <http://www.iana.org/assignments/http-status-codes>):
+
+   +-------+--------------------+---------------------------------+
+   | Value | Description        | Reference                       |
+   +-------+--------------------+---------------------------------+
+   | 308   | Permanent Redirect | Section 3 of this specification |
+   +-------+--------------------+---------------------------------+
+
+
+
+
+
+
+
+
+
+
+Reschke                       Experimental                      [Page 4]
+
+RFC 7238                  HTTP Status Code 308                 June 2014
+
+
+7.  Acknowledgements
+
+   The definition for the new status code 308 reuses text from the
+   HTTP/1.1 definitions of status codes 301 and 307.
+
+   Furthermore, thanks to Ben Campbell, Cyrus Daboo, Eran Hammer-Lahav,
+   Bjoern Hoehrmann, Subramanian Moonesamy, Peter Saint-Andre, and
+   Robert Sparks for feedback on this document.
+
+8.  References
+
+8.1.  Normative References
+
+   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
+              Resource Identifier (URI): Generic Syntax", STD 66,
+              RFC 3986, January 2005.
+
+   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
+              Protocol (HTTP/1.1): Message Syntax and Routing",
+              RFC 7230, June 2014.
+
+   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
+              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
+              June 2014.
+
+   [RFC7234]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
+              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
+              RFC 7234, June 2014.
+
+8.2.  Informative References
+
+   [HTML]     Raggett, D., Le Hors, A., and I. Jacobs, "HTML 4.01
+              Specification", W3C Recommendation REC-html401-19991224,
+              December 1999,
+              <http://www.w3.org/TR/1999/REC-html401-19991224>.
+
+              Latest version available at
+              <http://www.w3.org/TR/html401>.
+
+
+
+
+
+
+
+
+
+
+Reschke                       Experimental                      [Page 5]
+
+RFC 7238                  HTTP Status Code 308                 June 2014
+
+
+Author's Address
+
+   Julian F. Reschke
+   greenbytes GmbH
+   Hafenweg 16
+   Muenster, NW  48155
+   Germany
+
+   EMail: julian.reschke@greenbytes.de
+   URI:   http://greenbytes.de/tech/webdav/
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+Reschke                       Experimental                      [Page 6]
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