Internet DRAFT - draft-reschke-http-status-308
draft-reschke-http-status-308
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
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Internet-Drafts are draft documents valid for a maximum of six months
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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.
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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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