Network Working GroupJ. Reschke
Internet-Draftgreenbytes
Intended status: ExperimentalApril 6, 2014
Expires: October 8, 2014

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

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 October 8, 2014.

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Table of Contents

Issues list

IdTypeStatusDateRaised By
consistencychangeclosed2013-10-03julian.reschke@greenbytes.de
editeditopen2011-04-15julian.reschke@greenbytes.de
 I  edit   (type: edit, status: open)
julian.reschke@greenbytes.de2011-04-15 Umbrella issue for editorial fixes/enhancements.
Associated changes in this document: 4, 4, 8.1, A, 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 6.4 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:

PermanentTemporary
Allows changing the request method from POST to GET301302
Does not allow changing the request method from POST to GET-307

Section 6.4.7 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

 I  consistency   (type: change, status: closed)
julian.reschke@greenbytes.de2013-10-03 This text was written to be consistent with the other redirect definitions in the httpbis spec; back when -19 was current. It needs to be updated to be consistent with what gets approved.
Resolution:Done.
Associated changes in this document: 3.
 I  

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 4.2.2) 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 7.1.2). A response payload can contain a short hypertext note with a hyperlink to the new URI(s).

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. 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 sent by the server, where possible.

The server SHOULD generate a Location header field ([draft-ietf-httpbis-p2-semantics], 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 [draft-ietf-httpbis-p6-cache], Section 4.2.2).

Note: This status code is similar to 301 (Moved Permanently) ([draft-ietf-httpbis-p2-semantics], Section 6.4.2), except that it does not allow changing the request method from POST to GET.

4. Deployment Considerations

 I Section 4 of [draft-ietf-httpbis-p2-semantics]Section 6 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 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 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  I Section 3.5 of [draft-ietf-httpbis-p6-cache]Section 7.1.4 of [draft-ietf-httpbis-p2-semantics]).

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

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

6. IANA Considerations

The registration below shall be added to the HTTP Status Code Registry (defined in Section 8.2 of [draft-ietf-httpbis-p2-semantics] and located at <http://www.iana.org/assignments/http-status-codes>):

ValueDescriptionReference
308Permanent RedirectSection 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, Bjoern Hoehrmann, Subramanian Moonesamy, Peter Saint-Andre, and Robert Sparks for feedback on this document.

8. References

8.1 Normative References

[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”, Internet-Draft 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”, Internet-Draft 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”, Internet-Draft draft-ietf-httpbis-p6-cache-19 (work in progress), March 2012.
[draft-ietf-httpbis-p1-messaging]Fielding, R., Ed. and J. Reschke, Ed., “Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing”, Internet-Draft draft-ietf-httpbis-p1-messaging-26 (work in progress), February 2014.
[draft-ietf-httpbis-p2-semantics]Fielding, R., Ed. and J. Reschke, Ed., “Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content”, Internet-Draft draft-ietf-httpbis-p2-semantics-26 (work in progress), February 2014.
[draft-ietf-httpbis-p6-cache]Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, Ed., “Hypertext Transfer Protocol (HTTP/1.1): Caching”, Internet-Draft draft-ietf-httpbis-p6-cache-26 (work in progress), February 2014.
[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.

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>.

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/

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:  I now in "nightly" builds, scheduled for release inimplemented as of 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.

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.

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.

 I  

B.8 Since draft-reschke-http-status-308-07

Update HTTPbis references. Update Firefox implementation status. Added and resolved issue "consistency".