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Versions: 00 01 02 03 04 05 06 07 RFC 7238

Network Working Group                                         J. Reschke
Internet-Draft                                                greenbytes
Intended status: Experimental                             March 26, 2012
Expires: September 27, 2012


   The Hypertext Transfer Protocol (HTTP) Status Code 308 (Permanent
                               Redirect)
                    draft-reschke-http-status-308-07

Abstract

   This document specifies the additional HyperText Transfer Protocol
   (HTTP) Status Code 308 (Permanent Redirect).

Editorial Note (To be removed by RFC Editor before publication)

   Distribution of this document is unlimited.  Although this is not a
   work item of the HTTPbis Working Group, comments should be sent to
   the Hypertext Transfer Protocol (HTTP) mailing list at
   ietf-http-wg@w3.org [1], which may be joined by sending a message
   with subject "subscribe" to ietf-http-wg-request@w3.org [2].

   Discussions of the HTTPbis Working Group are archived at
   <http://lists.w3.org/Archives/Public/ietf-http-wg/>.

   XML versions, latest edits, and the issues list for this document are
   available from
   <http://greenbytes.de/tech/webdav/#draft-reschke-http-status-308>.

   Test cases related to redirection in general and the status code 308
   in particular can be found at
   <http://greenbytes.de/tech/tc/httpredirects/#l-308>.

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-
   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."



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   This Internet-Draft will expire on September 27, 2012.

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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . . . 3
   3.  308 Permanent Redirect  . . . . . . . . . . . . . . . . . . . . 3
   4.  Deployment Considerations . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Appendix A.  Implementations (to be removed by RFC Editor
                before publication)  . . . . . . . . . . . . . . . . . 7
   Appendix B.  Change Log (to be removed by RFC Editor before
                publication) . . . . . . . . . . . . . . . . . . . . . 7
     B.1.  Since draft-reschke-http-status-308-00  . . . . . . . . . . 7
     B.2.  Since draft-reschke-http-status-308-01  . . . . . . . . . . 7
     B.3.  Since draft-reschke-http-status-308-02  . . . . . . . . . . 7
     B.4.  Since draft-reschke-http-status-308-03  . . . . . . . . . . 7
     B.5.  Since draft-reschke-http-status-308-04  . . . . . . . . . . 7
     B.6.  Since draft-reschke-http-status-308-05  . . . . . . . . . . 8
     B.7.  Since draft-reschke-http-status-308-06  . . . . . . . . . . 8
   Appendix C.  Resolved issues (to be removed by RFC Editor
                before publication)  . . . . . . . . . . . . . . . . . 8
     C.1.  consistency307  . . . . . . . . . . . . . . . . . . . . . . 8
     C.2.  sniffing  . . . . . . . . . . . . . . . . . . . . . . . . . 8
   Appendix D.  Open issues (to be removed by RFC Editor prior to
                publication) . . . . . . . . . . . . . . . . . . . . . 8
     D.1.  edit  . . . . . . . . . . . . . . . . . . . . . . . . . . . 8




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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 7.3 of
   [draft-ietf-httpbis-p2-semantics], 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 7.3.7 of [draft-ietf-httpbis-p2-semantics] 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 target resource has been assigned a new permanent URI and any
   future references to this resource SHOULD use one of the returned
   URIs.  Clients with link editing capabilities ought to automatically
   re-link references to the effective request URI (Section 5.5 of
   [draft-ietf-httpbis-p1-messaging]) to one or more of the new
   references returned by the server, where possible.

   Caches MAY use a heuristic (see [draft-ietf-httpbis-p6-cache],
   Section 2.3.1.1) to determine freshness for 308 responses.

   The new permanent URI SHOULD be given by the Location field in the
   response ([draft-ietf-httpbis-p2-semantics], Section 10.5).  A
   response payload can contain a short hypertext note with a hyperlink
   to the new URI(s).



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      Note: This status code is similar to 301 Moved Permanently
      (Section 7.3.2 of [draft-ietf-httpbis-p2-semantics]), except that
      it does not allow rewriting the request method from POST to GET.

4.  Deployment Considerations

   Section 4 of [draft-ietf-httpbis-p2-semantics] requires recipients to
   treat unknown 3xx status codes the same way as status code 300
   Multiple Choices ([draft-ietf-httpbis-p2-semantics], Section 7.3.1).
   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 clients
   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 both hard to maintain and hard to debug code
   and would also require special attention to caching (i.e., setting a
   "Vary" response header field, as defined in Section 3.5 of
   [draft-ietf-httpbis-p6-cache]).

   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




















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   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 12 of
   [draft-ietf-httpbis-p2-semantics]).

6.  IANA Considerations

   The registration below shall be added to the HTTP Status Code
   Registry (defined in Section 4.2 of [draft-ietf-httpbis-p2-semantics]
   and located at <http://www.iana.org/assignments/http-status-codes>):

   +-------+--------------------+---------------------------------+
   | Value | Description        | Reference                       |
   +-------+--------------------+---------------------------------+
   | 308   | Permanent Redirect | Section 3 of this specification |
   +-------+--------------------+---------------------------------+

7.  Acknowledgements

   The definition for the new status code 308 re-uses text from the
   HTTP/1.1 definitions of status codes 301 and 307.

   Furthermore, thanks to Ben Campbell, Cyrus Daboo, Eran Hammer-Lahav,



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   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.

   [draft-ietf-httpbis-p1-messaging]  Fielding, R., Ed., Lafon, Y., Ed.,
                                      and J. Reschke, Ed., "HTTP/1.1,
                                      part 1: URIs, Connections, and
                                      Message Parsing",
                                      draft-ietf-httpbis-p1-messaging-19
                                      (work in progress), March 2012.

   [draft-ietf-httpbis-p2-semantics]  Fielding, R., Ed., Lafon, Y., Ed.,
                                      and J. Reschke, Ed., "HTTP/1.1,
                                      part 2: Message Semantics",
                                      draft-ietf-httpbis-p2-semantics-19
                                      (work in progress), March 2012.

   [draft-ietf-httpbis-p6-cache]      Fielding, R., Ed., Lafon, Y., Ed.,
                                      Nottingham, M., Ed., and J.
                                      Reschke, Ed., "HTTP/1.1, part 6:
                                      Caching",
                                      draft-ietf-httpbis-p6-cache-19
                                      (work in progress), March 2012.

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>.



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URIs

   [1]  <mailto:ietf-http-wg@w3.org>

   [2]  <mailto:ietf-http-wg-request@w3.org?subject=subscribe>

Appendix A.  Implementations (to be removed by RFC Editor before
             publication)

   Chrome: Feature requested in Chromium Issue 109012
   (<http://code.google.com/p/chromium/issues/detail?id=109012>).

   Curl (the library): no change was needed (test case:
   <https://github.com/bagder/curl/blob/master/tests/data/test1325>).

   Firefox: now in "nightly" builds, scheduled for release in Firefox 14
   (see <https://bugzilla.mozilla.org/show_bug.cgi?id=714302>).

   Safari: automatically redirects 3xx status codes when a Location
   header field is present, but does not preserve the request method.

Appendix B.  Change Log (to be removed by RFC Editor before publication)

B.1.  Since draft-reschke-http-status-308-00

   Updated HTTPbis reference.  Added Appendix A.  Added and resolved
   issue "refresh".

B.2.  Since draft-reschke-http-status-308-01

   Added URI spec reference.

B.3.  Since draft-reschke-http-status-308-02

   Tune HTML example.  Expand "Implementations" section.  Added and
   resolved issue "respformat" (align with new proposed text for 307 in
   HTTPbis P2).

B.4.  Since draft-reschke-http-status-308-03

   Added and resolved issue "uaconfirm".

B.5.  Since draft-reschke-http-status-308-04

   Added and resolved issue "missingconsiderations".  Added request
   message to example.  Updated the Safari implementation note.





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B.6.  Since draft-reschke-http-status-308-05

   Add informative HTML reference.  Update HTTPbis references.

B.7.  Since draft-reschke-http-status-308-06

   Added and resolved issues "consistency307" and "sniffing".  Updated
   Firefox implementation status.

Appendix C.  Resolved issues (to be removed by RFC Editor before
             publication)

   Issues that were either rejected or resolved in this version of this
   document.

C.1.  consistency307

   In Section 3:

   Type: edit

   ben@nostrum.com (2012-03-16): The 307 definition includes an explicit
   post about that behavior not being allowed.  Section 3 of this doc
   does neither.

   Resolution: Import (part of the) note from status code 307
   description.

C.2.  sniffing

   In Section 4:

   Type: edit

   rjsparks@nostrum.com (2012-03-15): Would it be worth adding something
   to the draft explicitily discouraging UA sniffing?  A reference to
   something that already explores why that's not a good idea perhaps?

   Resolution: Add advice not to attempt UA sniffing.

Appendix D.  Open issues (to be removed by RFC Editor prior to
             publication)

D.1.  edit

   Type: edit

   julian.reschke@greenbytes.de (2011-04-15): Umbrella issue for



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   editorial fixes/enhancements.

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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