Internet DRAFT - draft-ietf-httpbis-rfc7238bis
draft-ietf-httpbis-rfc7238bis
HTTPbis Working Group J. Reschke
Internet-Draft greenbytes
Obsoletes: 7238 (if approved) February 5, 2015
Intended status: Standards Track
Expires: August 9, 2015
The Hypertext Transfer Protocol Status Code 308 (Permanent Redirect)
draft-ietf-httpbis-rfc7238bis-03
Abstract
This document specifies the additional Hypertext Transfer Protocol
(HTTP) status code 308 (Permanent Redirect).
Status of This Memo
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This Internet-Draft will expire on August 9, 2015.
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Copyright (c) 2015 IETF Trust and the persons identified as the
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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 . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
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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 6.4 of [RFC7231], 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 6.4.7 of [RFC7231] states that it does not define a permanent
variant of status code 307; this specification adds the status code
308, defining this missing variant (Section 3).
This specification contains no technical changes from the
experimental RFC 7238, which it obsoletes.
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 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 [RFC7230]) to
one or more of the new references sent by the server, where possible.
The server SHOULD generate a Location header field ([RFC7231],
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).
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A 308 response is cacheable by default; i.e., unless otherwise
indicated by the method definition or explicit cache controls (see
[RFC7234], Section 4.2.2).
Note: This status code is similar to 301 (Moved Permanently)
([RFC7231], Section 6.4.2), except that it does not allow changing
the request method from POST to GET.
4. Deployment Considerations
Section 6 of [RFC7231] requires recipients to treat unknown 3xx
status codes the same way as status code 300 Multiple Choices
([RFC7231], 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, the use of status code 308 is restricted to cases where
the server has sufficient confidence in the client's 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 code that is both hard to maintain and hard to debug and
would also require special attention to caching (i.e., setting a
"Vary" response header field, as defined in Section 7.1.4 of
[RFC7231]).
Note that many existing HTML-based user agents will emulate a refresh
when encountering an HTML <meta> refresh directive ([HTML], Section
4.2.5.3). 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: 356
<!DOCTYPE HTML>
<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 [RFC7231]).
Unsecured communication over the Internet is subject to man in the
middle modification of messages, including changing status codes or
redirect targets. Use of TLS is one way to mitigate those attacks.
See Section 9 of [RFC7230] for related attacks on authority and
message integrity.
6. IANA Considerations
The "Hypertext Transfer Protocol (HTTP) Status Code Registry"
(defined in Section 8.2 of [RFC7231] and located at
<http://www.iana.org/assignments/http-status-codes>) needs to be
updated with the registration below:
+-------+--------------------+---------------------------------+
| Value | Description | Reference |
+-------+--------------------+---------------------------------+
| 308 | Permanent Redirect | Section 3 of this specification |
+-------+--------------------+---------------------------------+
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7. Acknowledgements
The definition for the new status code 308 reuses text from the
HTTP/1.1 definitions of status codes 301 and 307.
Furthermore, thanks to Ben Campbell, Cyrus Daboo, Adrian Farrell,
Eran Hammer-Lahav, Bjoern Hoehrmann, Barry Leiba, Subramanian
Moonesamy, Kathleen Moriarty, Peter Saint-Andre, Robert Sparks, and
Roy Fielding 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.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, June 2014.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
June 2014.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, June 2014.
8.2. Informative References
[HTML] Hickson, I., Berjon, R., Faulkner, S., Leithead, T., Doyle
Navara, E., O'Connor, E., and S. Pfeiffer, "HTML5", W3C
Recommendation REC-html5-20141028, October 2014,
<http://www.w3.org/TR/2014/REC-html5-20141028/>.
Latest version available at <http://www.w3.org/TR/html5/>.
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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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