The Hypertext Transfer Protocol (HTTP) Status Code 308 (Permanent Redirect)
draft-reschke-http-status-308-05

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, which may be joined by sending a message with subject "subscribe" to ietf-http-wg-request@w3.org.

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."

This Internet-Draft will expire on August 15, 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
• 2. Notational Conventions
• 3. 308 Permanent Redirect
• 4. Deployment Considerations
• 5. Security Considerations
• 6. IANA Considerations
• 7. Acknowledgements
• 8. References
• Appendix A. Implementations (to be removed by RFC Editor before publication)
• Appendix B. Change Log (to be removed by RFC Editor before publication)
• Appendix B.1. Since draft-reschke-http-status-308-00
• Appendix B.2. Since draft-reschke-http-status-308-01
• Appendix B.3. Since draft-reschke-http-status-308-02
• Appendix B.4. Since draft-reschke-http-status-308-03
• Appendix B.5. Since draft-reschke-http-status-308-04
• Appendix C. Resolved issues (to be removed by RFC Editor before publication)
• Appendix C.1. missingconsiderations
• Appendix D. Open issues (to be removed by RFC Editor prior to publication)
• Appendix D.1. edit
• Author's Address

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:

Section 7.3.8 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 4.3 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 9.5). A response payload can contain a short hypertext note with a hyperlink to the new URI(s).

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.

Note that many existing HTML-based user agents will emulate a refresh when encountering an HTML <meta> refresh directive. This can be used as another fallback. For example:

Client request:

  GET / HTTP/1.1
  Host: example.com
  
  

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 11 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):

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 Cyrus Daboo, Bjoern Hoehrmann, Subramanian Moonesamy, and Peter Saint-Andre for feedback on this document.

8. References

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: Feature requested in Bugzilla bug 714302 (https://bugzilla.mozilla.org/show_bug.cgi?id=714302), patch available.

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)

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

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

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

Added URI spec reference.

Appendix 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).

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

Added and resolved issue "uaconfirm".

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

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

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.

Appendix C.1. missingconsiderations

In Section 3:

Type: change

stpeter@stpeter.im (2012-02-10): According to HTTPbis Part 2, need to explain the request conditions, interactions with response headers, and implications for caches. If certain default behavior is assumed, it would be good to make that explicit.

Resolution (2012-02-13): Added missing caching considerations.

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

Appendix D.1. edit

Type: edit

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

Author's Address