Individual Submission J. Snell Internet-Draft December 7, 2007 Expires: June 9, 2008 Prefer Header for HTTP draft-snell-http-prefer-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on June 9, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This specification defines a new HTTP header that can be used by a client to request that certain behaviors be implemented by a server while processing a request. Snell Expires June 9, 2008 [Page 1]
Internet-Draft HTTP Prefer December 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. The Prefer Request Header . . . . . . . . . . . . . . . . . . . 3 3. The "return-no-content" Preference . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 6. Normative References . . . . . . . . . . . . . . . . . . . . . 4 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 4 Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . . 5 Appendix C. Notes to RFC Editor . . . . . . . . . . . . . . . . . 5 Appendix D. Editorial Notes . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . . . 6 Snell Expires June 9, 2008 [Page 2]
Internet-Draft HTTP Prefer December 2007 1. Introduction This specification defines a new HTTP header that can be used by a client to request that certain behaviors be implemented by a server while processing a request. In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in [RFC2119]. 2. The Prefer Request Header The Prefer request-header is used to indicate that particular server behaviors are preferred, but not required, by the client. Prefer is similar in nature to the Expect header defined by [RFC2616] with the exception that servers are allowed to ignore a clients stated preferences. Prefer = "Prefer" ":" 1#preference preference = "return-no-content" | preference-extension preference-extension = token [ "=" ( token | quoted-string ) *prefer-params ] prefer-params = ";" token [ "=" ( token | quoted-string ) ] This header is defined with an extensible syntax to allow for future extensions. A server that does not understand or is unable to comply with any of the preference values in the Prefer field of a request MUST ignore those values and MUST NOT stop processing or signal an error. Comparison of preference values is case-insensitive for unquoted tokens and is case-sensitive for quoted-string preference-extensions. The Prefer mechanism is hop-by-hop: that is, an HTTP proxy MAY choose to honor a preference even if the origin server does not. However, the Prefer request-header itself is end-to-end; it MUST be forwarded if the request is forwarded. 3. The "return-no-content" Preference The "return-no-content" token indicates that the client prefers that the server not include an entity in the response to a successful request. Typically, such responses would use the 204 No Content status code as defined in Section 10.2.5 of [RFC2616], but other status codes can be used as appropriate. Snell Expires June 9, 2008 [Page 3]
Internet-Draft HTTP Prefer December 2007 4. IANA Considerations The 'Prefer' request header should be added to the permanent registry (see [RFC3864]). Header field name: Prefer Applicable Protocol: HTTP Status: standard Author/Change controller: IETF Specification document: this specification 5. Security Considerations Specific preferences requested by a client can introduce security considerations and concerns beyond those discussed in [RFC2616]. Implementors must refer to the specifications and descriptions of those preferences to determine the security considerations relevant to each. 6. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004. Appendix A. Acknowledgements The author greatfully acknowledges the input from the IETF HTTP mailing list on the development of this document. Snell Expires June 9, 2008 [Page 4]
Internet-Draft HTTP Prefer December 2007 Appendix B. Changes TODO Appendix C. Notes to RFC Editor The RFC Editor should remove this section and the Changes section. Appendix D. Editorial Notes We need to determine how new preference codes are created/registered Author's Address James M Snell Phone: Email: jasnell@gmail.com URI: http://www.snellspace.com Snell Expires June 9, 2008 [Page 5]
Internet-Draft HTTP Prefer December 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Snell Expires June 9, 2008 [Page 6]