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This Internet-Draft will expire on August 4, 2012.
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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. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Appendix A. Implementations (to be removed by RFC Editor
before publication) . . . . . . . . . . . . . . . . . 6
Appendix B. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . 6
B.1. Since draft-reschke-http-status-308-00 . . . . . . . . . . 6
B.2. Since draft-reschke-http-status-308-01 . . . . . . . . . . 6
B.3. Since draft-reschke-http-status-308-02 . . . . . . . . . . 6
Appendix C. Resolved issues (to be removed by RFC Editor
before publication) . . . . . . . . . . . . . . . . . 7
C.1. respformat . . . . . . . . . . . . . . . . . . . . . . . . 7
Appendix D. Open issues (to be removed by RFC Editor prior to
publication) . . . . . . . . . . . . . . . . . . . . . 7
D.1. edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
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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 7.3.8 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)..
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
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[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 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
Permanent Redirect
The document has been moved to
http://example.com/new.
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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 ):
+-------+--------------------+-----------+
| 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
[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., 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",
draft-ietf-httpbis-p1-messaging-18
(work in progress), January 2012.
[draft-ietf-httpbis-p2-semantics] Fielding, R., Ed., Gettys, J.,
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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",
draft-ietf-httpbis-p2-semantics-18
(work in progress), January 2012.
[1]
[2]
Appendix A. Implementations (to be removed by RFC Editor before
publication)
Chrome: Feature requested in Chromium Issue 109012
().
Curl (the library): no change was needed (test case:
).
Firefox: Feature requested in Bugzilla bug 714302
(), patch
available.
Safari: Safari automatically redirects 3xx status codes when a
Location header field is present, thus no change is needed.
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).
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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. respformat
Type: change
derhoermi@gmx.net (2012-01-14): "The fallback requirement (...)
strikes me as a bad idea. It's a transient problem so it should be
con- ditioned and how widely supported this is, and it's only useful
if you have some HTML implementation on the other end or an
interactive user; a web service not meant for interactive use where
you can be sure that the code is supported, because, say, you control
the client, is unaffected, and if you add that as another exception
you basically end up saying you can do this so your site works better
with legacy clients in some situ- ations and making your site work
good is probably a good idea, so I'd prefer just saying that. I
don't really want to ponder whether I should send this hypertext
response in response to an OPTIONS request in 2015, just because your
specification says I should."
julian.reschke@greenbytes.de (2012-01-29): See related HTTPbis issue
http://trac.tools.ietf.org/wg/httpbis/trac/ticket/332 -- we should
fix this in the base spec, then copy over the new text to this
document. Proposal: use final text from HTTPbis.
Resolution (2012-01-31): The spec has been aligned with HTTPbis,
relaxing the requirement.
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
editorial fixes/enhancements.
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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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