|Network Working Group||J. Reschke|
|Intended status: Experimental||December 19, 2011|
|Expires: June 21, 2012|
The Hypertext Transfer Protocol (HTTP) Status Code 308 (Permanent Redirect)
This document specifies the additional HyperText Transfer Protocol (HTTP) Status Codes 308 (Permanent Redirect).
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 email@example.com, which may be joined by sending a message with subject "subscribe" to firstname.lastname@example.org.
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HTTP defines a set of status codes for the purpose of redirecting a request to a different URI. 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:
|Allows changing the request method from POST to GET||301||302|
|Does not allow changing the request method from POST to GET||-||307|
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].
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. Unless the request method was HEAD, the representation of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s), since most user agents do not understand the 308 status code yet. Therefore, the note SHOULD contain the information necessary for a user to repeat the original request on the new URI.
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.
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 a fallback to the semantics of status code 300 is not problematic.
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>):
|308||Permanent Redirect||Section 3|
The definition for the new status code 308 re-uses text from the HTTP/1.1 definitions of status codes 301 and 307.
|[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-17 (work in progress), October 2011.|
|[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-17 (work in progress), October 2011.|
|[RFC2119]||Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels”, BCP 14, RFC 2119, March 1997.|