The Hypertext Transfer Protocol (HTTP) Status Code 308 (Permanent Redirect)

This document specifies the additional HyperText Transfer Protocol (HTTP) Status Codes 308 (Permanent Redirect).¶

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/.¶

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This Internet-Draft will expire on June 21, 2012.¶

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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.¶

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 this status code (Section 3).¶

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.¶

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]).¶

The definition for the new status code 308 re-uses text from the HTTP/1.1 definitions of status codes 301 and 307.¶

8. Normative References

[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.