The Hypertext Transfer Protocol (HTTP) 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 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 11, 2012.¶

Copyright Notice

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.¶

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>.¶

Issues list

Id	Type	Status	Date	Raised By
uaconfirm	change	closed	2012-02-03	julian.reschke@greenbytes.de
edit	edit	open	2011-04-15	julian.reschke@greenbytes.de

I edit (type: edit, status: open)
julian.reschke@greenbytes.de	2011-04-15	Umbrella issue for editorial fixes/enhancements.
Associated changes in this document: 3, B.

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 POST to GET	301	302
Does not allow changing the request method from POST to GET	-	307

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.¶

The 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). I ↓. ¶

I uaconfirm (type: change, status: closed)
julian.reschke@greenbytes.de	2012-02-03	The requirement about UA prompts is subject to an open HTTPbis ticket (http://trac.tools.ietf.org/wg/httpbis/trac/ticket/238), and the text should be aligned with whatever the resolution is.
	2012-02-08	Resolution: Align with the proposed fix for the HTTPbis issue by removing the text from the status code definition (in HTTPbis, a relaxed variant is being added to the description of 3xx in general).
Associated changes in this document: 3.

If the 308 status code is received in response to a request method that is known to be "safe", as defined in Section 6.1.1 of [draft-ietf-httpbis-p2-semantics], then the request MAY be automatically redirected by the user agent without confirmation. Otherwise, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

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 existing user agents will emulate a refresh when encountering an HTML <meta> refresh directive. This can be used as another fallback.¶

For example:

HTTP/1.1 308 Permanent Redirect
Content-Type: text/html; charset=UTF-8
Location: http://example.com/new
Content-Length: 443

<!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>):¶

Value	Description	Reference
308	Permanent Redirect	Section 3

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 Bjoern Hoehrmann and Subramanian Moonesamy for feedback on this document.¶

8. Normative References

[draft-ietf-httpbis-p1-messaging]: Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., and J. Reschke, Ed., “HTTP/1.1, part 1: URIs, Connections, and Message Parsing”, Internet-Draft draft-ietf-httpbis-p1-messaging-18 (work in progress), January 2012.
[draft-ietf-httpbis-p2-semantics]: Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., and J. Reschke, Ed., “HTTP/1.1, part 2: Message Semantics”, Internet-Draft draft-ietf-httpbis-p2-semantics-18 (work in progress), January 2012.
[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.

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: Safari automatically redirects 3xx status codes when a Location header field is present, thus no change is needed.¶