| draft-ietf-httpbis-p4-conditional-16.txt |  | draft-ietf-httpbis-p4-conditional-17.txt |
--- | --- | --- | --- | ---
| HTTPbis Working Group R. Fielding, Ed. |  | HTTPbis Working Group R. Fielding, Ed. |
| Internet-Draft Adobe |  | Internet-Draft Adobe |
| Obsoletes: 2616 (if approved) J. Gettys |  | Obsoletes: 2616 (if approved) J. Gettys |
| Intended status: Standards Track Alcatel-Lucent |  | Intended status: Standards Track Alcatel-Lucent |
| Expires: February 25, 2012 J. Mogul |  | Expires: May 3, 2012 J. Mogul |
| HP |  | HP |
| H. Frystyk |  | H. Frystyk |
| Microsoft |  | Microsoft |
| L. Masinter |  | L. Masinter |
| Adobe |  | Adobe |
| P. Leach |  | P. Leach |
| Microsoft |  | Microsoft |
| T. Berners-Lee |  | T. Berners-Lee |
| W3C/MIT |  | W3C/MIT |
| Y. Lafon, Ed. |  | Y. Lafon, Ed. |
| W3C |  | W3C |
| J. Reschke, Ed. |  | J. Reschke, Ed. |
| greenbytes |  | greenbytes |
| August 24, 2011 |  | October 31, 2011 |
| HTTP/1.1, part 4: Conditional Requests |  | HTTP/1.1, part 4: Conditional Requests |
| draft-ietf-httpbis-p4-conditional-16 |  | draft-ietf-httpbis-p4-conditional-17 |
| Abstract |  | Abstract |
| The Hypertext Transfer Protocol (HTTP) is an application-level |  | The Hypertext Transfer Protocol (HTTP) is an application-level |
| protocol for distributed, collaborative, hypertext information |  | protocol for distributed, collaborative, hypertext information |
| systems. HTTP has been in use by the World Wide Web global |  | systems. HTTP has been in use by the World Wide Web global |
| information initiative since 1990. This document is Part 4 of the |  | information initiative since 1990. This document is Part 4 of the |
| seven-part specification that defines the protocol referred to as |  | seven-part specification that defines the protocol referred to as |
| "HTTP/1.1" and, taken together, obsoletes RFC 2616. |  | "HTTP/1.1" and, taken together, obsoletes RFC 2616. |
| skipping to change at page 1, line 49 |  | skipping to change at page 1, line 49 |
| Discussion of this draft should take place on the HTTPBIS working |  | Discussion of this draft should take place on the HTTPBIS working |
| group mailing list (ietf-http-wg@w3.org), which is archived at |  | group mailing list (ietf-http-wg@w3.org), which is archived at |
| <http://lists.w3.org/Archives/Public/ietf-http-wg/>. |  | <http://lists.w3.org/Archives/Public/ietf-http-wg/>. |
| The current issues list is at |  | The current issues list is at |
| <http://tools.ietf.org/wg/httpbis/trac/report/3> and related |  | <http://tools.ietf.org/wg/httpbis/trac/report/3> and related |
| documents (including fancy diffs) can be found at |  | documents (including fancy diffs) can be found at |
| <http://tools.ietf.org/wg/httpbis/>. |  | <http://tools.ietf.org/wg/httpbis/>. |
| The changes in this draft are summarized in Appendix C.17. |  | The changes in this draft are summarized in Appendix C.18. |
| Status of This Memo |  | Status of This Memo |
| This Internet-Draft is submitted in full conformance with the |  | This Internet-Draft is submitted in full conformance with the |
| provisions of BCP 78 and BCP 79. |  | provisions of BCP 78 and BCP 79. |
| Internet-Drafts are working documents of the Internet Engineering |  | Internet-Drafts are working documents of the Internet Engineering |
| Task Force (IETF). Note that other groups may also distribute |  | Task Force (IETF). Note that other groups may also distribute |
| working documents as Internet-Drafts. The list of current Internet- |  | working documents as Internet-Drafts. The list of current Internet- |
| Drafts is at http://datatracker.ietf.org/drafts/current/. |  | Drafts is at http://datatracker.ietf.org/drafts/current/. |
| Internet-Drafts are draft documents valid for a maximum of six months |  | Internet-Drafts are draft documents valid for a maximum of six months |
| and may be updated, replaced, or obsoleted by other documents at any |  | and may be updated, replaced, or obsoleted by other documents at any |
| time. It is inappropriate to use Internet-Drafts as reference |  | time. It is inappropriate to use Internet-Drafts as reference |
| material or to cite them other than as "work in progress." |  | material or to cite them other than as "work in progress." |
| This Internet-Draft will expire on February 25, 2012. |  | This Internet-Draft will expire on May 3, 2012. |
| Copyright Notice |  | Copyright Notice |
| Copyright (c) 2011 IETF Trust and the persons identified as the |  | Copyright (c) 2011 IETF Trust and the persons identified as the |
| document authors. All rights reserved. |  | document authors. All rights reserved. |
| This document is subject to BCP 78 and the IETF Trust's Legal |  | This document is subject to BCP 78 and the IETF Trust's Legal |
| Provisions Relating to IETF Documents |  | Provisions Relating to IETF Documents |
| (http://trustee.ietf.org/license-info) in effect on the date of |  | (http://trustee.ietf.org/license-info) in effect on the date of |
| publication of this document. Please review these documents |  | publication of this document. Please review these documents |
| skipping to change at page 2, line 52 |  | skipping to change at page 2, line 52 |
| Without obtaining an adequate license from the person(s) controlling |  | Without obtaining an adequate license from the person(s) controlling |
| the copyright in such materials, this document may not be modified |  | the copyright in such materials, this document may not be modified |
| outside the IETF Standards Process, and derivative works of it may |  | outside the IETF Standards Process, and derivative works of it may |
| not be created outside the IETF Standards Process, except to format |  | not be created outside the IETF Standards Process, except to format |
| it for publication as an RFC or to translate it into languages other |  | it for publication as an RFC or to translate it into languages other |
| than English. |  | than English. |
| Table of Contents |  | Table of Contents |
| 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 |  | 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 |
| 1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 5 |  | 1.1. Conformance and Error Handling . . . . . . . . . . . . . . 5 |
| 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 6 |  | 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 6 |
| 2. Validators . . . . . . . . . . . . . . . . . . . . . . . . . . 6 |  | 2. Validators . . . . . . . . . . . . . . . . . . . . . . . . . . 6 |
| 2.1. Weak versus Strong . . . . . . . . . . . . . . . . . . . . 6 |  | 2.1. Weak versus Strong . . . . . . . . . . . . . . . . . . . . 6 |
| 2.2. Last-Modified . . . . . . . . . . . . . . . . . . . . . . 8 |  | 2.2. Last-Modified . . . . . . . . . . . . . . . . . . . . . . 8 |
| 2.2.1. Generation . . . . . . . . . . . . . . . . . . . . . . 8 |  | 2.2.1. Generation . . . . . . . . . . . . . . . . . . . . . . 8 |
| 2.2.2. Comparison . . . . . . . . . . . . . . . . . . . . . . 9 |  | 2.2.2. Comparison . . . . . . . . . . . . . . . . . . . . . . 9 |
| 2.3. ETag . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 |  | 2.3. ETag . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 |
| 2.3.1. Generation . . . . . . . . . . . . . . . . . . . . . . 11 |  | 2.3.1. Generation . . . . . . . . . . . . . . . . . . . . . . 11 |
| 2.3.2. Comparison . . . . . . . . . . . . . . . . . . . . . . 11 |  | 2.3.2. Comparison . . . . . . . . . . . . . . . . . . . . . . 11 |
| 2.3.3. Example: Entity-tags varying on Content-Negotiated |  | 2.3.3. Example: Entity-tags varying on Content-Negotiated |
| Resources . . . . . . . . . . . . . . . . . . . . . . 12 |  | Resources . . . . . . . . . . . . . . . . . . . . . . 12 |
| 2.4. Rules for When to Use Entity-tags and Last-Modified |  | 2.4. Rules for When to Use Entity-tags and Last-Modified |
| Dates . . . . . . . . . . . . . . . . . . . . . . . . . . 13 |  | Dates . . . . . . . . . . . . . . . . . . . . . . . . . . 13 |
| 3. Precondition Header Fields . . . . . . . . . . . . . . . . . . 14 |  | 3. Precondition Header Fields . . . . . . . . . . . . . . . . . . 14 |
| 3.1. If-Match . . . . . . . . . . . . . . . . . . . . . . . . . 14 |  | 3.1. If-Match . . . . . . . . . . . . . . . . . . . . . . . . . 15 |
| 3.2. If-None-Match . . . . . . . . . . . . . . . . . . . . . . 15 |  | 3.2. If-None-Match . . . . . . . . . . . . . . . . . . . . . . 15 |
| 3.3. If-Modified-Since . . . . . . . . . . . . . . . . . . . . 17 |  | 3.3. If-Modified-Since . . . . . . . . . . . . . . . . . . . . 17 |
| 3.4. If-Unmodified-Since . . . . . . . . . . . . . . . . . . . 18 |  | 3.4. If-Unmodified-Since . . . . . . . . . . . . . . . . . . . 18 |
| 3.5. If-Range . . . . . . . . . . . . . . . . . . . . . . . . . 19 |  | 3.5. If-Range . . . . . . . . . . . . . . . . . . . . . . . . . 19 |
| 4. Status Code Definitions . . . . . . . . . . . . . . . . . . . 19 |  | 4. Status Code Definitions . . . . . . . . . . . . . . . . . . . 19 |
| 4.1. 304 Not Modified . . . . . . . . . . . . . . . . . . . . . 19 |  | 4.1. 304 Not Modified . . . . . . . . . . . . . . . . . . . . . 19 |
| 4.2. 412 Precondition Failed . . . . . . . . . . . . . . . . . 20 |  | 4.2. 412 Precondition Failed . . . . . . . . . . . . . . . . . 20 |
| 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 |  | 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 |
| 5.1. Status Code Registration . . . . . . . . . . . . . . . . . 20 |  | 5.1. Status Code Registration . . . . . . . . . . . . . . . . . 20 |
| 5.2. Header Field Registration . . . . . . . . . . . . . . . . 20 |  | 5.2. Header Field Registration . . . . . . . . . . . . . . . . 20 |
| skipping to change at page 3, line 42 |  | skipping to change at page 3, line 42 |
| 8.1. Normative References . . . . . . . . . . . . . . . . . . . 21 |  | 8.1. Normative References . . . . . . . . . . . . . . . . . . . 21 |
| 8.2. Informative References . . . . . . . . . . . . . . . . . . 21 |  | 8.2. Informative References . . . . . . . . . . . . . . . . . . 21 |
| Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 22 |  | Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 22 |
| Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 22 |  | Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 22 |
| Appendix C. Change Log (to be removed by RFC Editor before |  | Appendix C. Change Log (to be removed by RFC Editor before |
| publication) . . . . . . . . . . . . . . . . . . . . 23 |  | publication) . . . . . . . . . . . . . . . . . . . . 23 |
| C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 23 |  | C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 23 |
| C.2. Since draft-ietf-httpbis-p4-conditional-00 . . . . . . . . 23 |  | C.2. Since draft-ietf-httpbis-p4-conditional-00 . . . . . . . . 23 |
| C.3. Since draft-ietf-httpbis-p4-conditional-01 . . . . . . . . 23 |  | C.3. Since draft-ietf-httpbis-p4-conditional-01 . . . . . . . . 23 |
| C.4. Since draft-ietf-httpbis-p4-conditional-02 . . . . . . . . 23 |  | C.4. Since draft-ietf-httpbis-p4-conditional-02 . . . . . . . . 23 |
| C.5. Since draft-ietf-httpbis-p4-conditional-03 . . . . . . . . 23 |  | C.5. Since draft-ietf-httpbis-p4-conditional-03 . . . . . . . . 24 |
| C.6. Since draft-ietf-httpbis-p4-conditional-04 . . . . . . . . 24 |  | C.6. Since draft-ietf-httpbis-p4-conditional-04 . . . . . . . . 24 |
| C.7. Since draft-ietf-httpbis-p4-conditional-05 . . . . . . . . 24 |  | C.7. Since draft-ietf-httpbis-p4-conditional-05 . . . . . . . . 24 |
| C.8. Since draft-ietf-httpbis-p4-conditional-06 . . . . . . . . 24 |  | C.8. Since draft-ietf-httpbis-p4-conditional-06 . . . . . . . . 24 |
| C.9. Since draft-ietf-httpbis-p4-conditional-07 . . . . . . . . 24 |  | C.9. Since draft-ietf-httpbis-p4-conditional-07 . . . . . . . . 24 |
| C.10. Since draft-ietf-httpbis-p4-conditional-08 . . . . . . . . 24 |  | C.10. Since draft-ietf-httpbis-p4-conditional-08 . . . . . . . . 25 |
| C.11. Since draft-ietf-httpbis-p4-conditional-09 . . . . . . . . 25 |  | C.11. Since draft-ietf-httpbis-p4-conditional-09 . . . . . . . . 25 |
| C.12. Since draft-ietf-httpbis-p4-conditional-10 . . . . . . . . 25 |  | C.12. Since draft-ietf-httpbis-p4-conditional-10 . . . . . . . . 25 |
| C.13. Since draft-ietf-httpbis-p4-conditional-11 . . . . . . . . 25 |  | C.13. Since draft-ietf-httpbis-p4-conditional-11 . . . . . . . . 25 |
| C.14. Since draft-ietf-httpbis-p4-conditional-12 . . . . . . . . 25 |  | C.14. Since draft-ietf-httpbis-p4-conditional-12 . . . . . . . . 25 |
| C.15. Since draft-ietf-httpbis-p4-conditional-13 . . . . . . . . 25 |  | C.15. Since draft-ietf-httpbis-p4-conditional-13 . . . . . . . . 25 |
| C.16. Since draft-ietf-httpbis-p4-conditional-14 . . . . . . . . 26 |  | C.16. Since draft-ietf-httpbis-p4-conditional-14 . . . . . . . . 26 |
| C.17. Since draft-ietf-httpbis-p4-conditional-15 . . . . . . . . 26 |  | C.17. Since draft-ietf-httpbis-p4-conditional-15 . . . . . . . . 26 |
|  |  | C.18. Since draft-ietf-httpbis-p4-conditional-16 . . . . . . . . 26 |
| Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 |  | Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 |
| 1. Introduction |  | 1. Introduction |
| This document defines the HTTP/1.1 conditional request mechanisms, |  | This document defines the HTTP/1.1 conditional request mechanisms, |
| including both metadata for indicating/observing changes in resource |  | including both metadata for indicating/observing changes in resource |
| representations and request header fields that specify preconditions |  | representations and request header fields that specify preconditions |
| on that metadata be checked before performing the request method. |  | on that metadata be checked before performing the request method. |
| Conditional GET requests are the most efficient mechanism for HTTP |  | Conditional GET requests are the most efficient mechanism for HTTP |
| cache updates [Part6]. Conditionals can also be applied to state- |  | cache updates [Part6]. Conditionals can also be applied to state- |
| skipping to change at page 5, line 36 |  | skipping to change at page 5, line 36 |
| harm will result when the precondition evaluates to false. |  | harm will result when the precondition evaluates to false. |
| We use the term "selected representation" to refer to the current |  | We use the term "selected representation" to refer to the current |
| representation of the target resource that would have been selected |  | representation of the target resource that would have been selected |
| in a successful response if the same request had used the method GET |  | in a successful response if the same request had used the method GET |
| and had excluded all of the conditional request header fields. The |  | and had excluded all of the conditional request header fields. The |
| conditional request preconditions are evaluated by comparing the |  | conditional request preconditions are evaluated by comparing the |
| values provided in the request header fields to the current metadata |  | values provided in the request header fields to the current metadata |
| for the selected representation. |  | for the selected representation. |
| 1.1. Requirements |  | 1.1. Conformance and Error Handling |
| The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", |  | The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", |
| "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this |  | "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this |
| document are to be interpreted as described in [RFC2119]. |  | document are to be interpreted as described in [RFC2119]. |
| An implementation is not compliant if it fails to satisfy one or more |  | This document defines conformance criteria for several roles in HTTP |
| of the "MUST" or "REQUIRED" level requirements for the protocols it |  | communication, including Senders, Recipients, Clients, Servers, User- |
| implements. An implementation that satisfies all the "MUST" or |  | Agents, Origin Servers, Intermediaries, Proxies and Gateways. See |
| "REQUIRED" level and all the "SHOULD" level requirements for its |  | Section 2 of [Part1] for definitions of these terms. |
| protocols is said to be "unconditionally compliant"; one that |  |  |
| satisfies all the "MUST" level requirements but not all the "SHOULD" |  | An implementation is considered conformant if it complies with all of |
| level requirements for its protocols is said to be "conditionally |  | the requirements associated with its role(s). Note that SHOULD-level |
| compliant". |  | requirements are relevant here, unless one of the documented |
|  |  | exceptions is applicable. |
|  |  | This document also uses ABNF to define valid protocol elements |
|  |  | (Section 1.2). In addition to the prose requirements placed upon |
|  |  | them, Senders MUST NOT generate protocol elements that are invalid. |
|  |  | Unless noted otherwise, Recipients MAY take steps to recover a usable |
|  |  | protocol element from an invalid construct. However, HTTP does not |
|  |  | define specific error handling mechanisms, except in cases where it |
|  |  | has direct impact on security. This is because different uses of the |
|  |  | protocol require different error handling strategies; for example, a |
|  |  | Web browser may wish to transparently recover from a response where |
|  |  | the Location header field doesn't parse according to the ABNF, |
|  |  | whereby in a systems control protocol using HTTP, this type of error |
|  |  | recovery could lead to dangerous consequences. |
| 1.2. Syntax Notation |  | 1.2. Syntax Notation |
| This specification uses the ABNF syntax defined in Section 1.2 of |  | This specification uses the ABNF syntax defined in Section 1.2 of |
| [Part1] (which extends the syntax defined in [RFC5234] with a list |  | [Part1] (which extends the syntax defined in [RFC5234] with a list |
| rule). Appendix B shows the collected ABNF, with the list rule |  | rule). Appendix B shows the collected ABNF, with the list rule |
| expanded. |  | expanded. |
| The following core rules are included by reference, as defined in |  | The following core rules are included by reference, as defined in |
| [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF |  | [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF |
| (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), |  | (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), |
| HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any 8-bit |  | HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any 8-bit |
| sequence of data), SP (space), VCHAR (any visible USASCII character), |  | sequence of data), SP (space), and VCHAR (any visible US-ASCII |
| and WSP (whitespace). |  | character). |
| The ABNF rules below are defined in [Part1]: |  | The ABNF rules below are defined in [Part1] and [Part2]: |
| OWS = <OWS, defined in [Part1], Section 1.2.2> |  | OWS = <OWS, defined in [Part1], Section 1.2.2> |
| quoted-string = <quoted-string, defined in [Part1], Section 3.2.3> |  | quoted-string = <quoted-string, defined in [Part1], Section 3.2.3> |
| HTTP-date = <HTTP-date, defined in [Part1], Section 6.1> |  | HTTP-date = <HTTP-date, defined in [Part2], Section 8> |
| 2. Validators |  | 2. Validators |
| This specification defines two forms of metadata that are commonly |  | This specification defines two forms of metadata that are commonly |
| used to observe resource state and test for preconditions: |  | used to observe resource state and test for preconditions: |
| modification dates and opaque entity tags. Additional metadata that |  | modification dates and opaque entity tags. Additional metadata that |
| reflects resource state has been defined by various extensions of |  | reflects resource state has been defined by various extensions of |
| HTTP, such as WebDAV [RFC4918], that are beyond the scope of this |  | HTTP, such as WebDAV [RFC4918], that are beyond the scope of this |
| specification. A resource metadata value is referred to as a |  | specification. A resource metadata value is referred to as a |
| "validator" when it is used within a precondition. |  | "validator" when it is used within a precondition. |
| skipping to change at page 9, line 15 |  | skipping to change at page 9, line 29 |
| response is generated. |  | response is generated. |
| An origin server with a clock MUST NOT send a Last-Modified date that |  | An origin server with a clock MUST NOT send a Last-Modified date that |
| is later than the server's time of message origination (Date). If |  | is later than the server's time of message origination (Date). If |
| the last modification time is derived from implementation-specific |  | the last modification time is derived from implementation-specific |
| metadata that evaluates to some time in the future, according to the |  | metadata that evaluates to some time in the future, according to the |
| origin server's clock, then the origin server MUST replace that value |  | origin server's clock, then the origin server MUST replace that value |
| with the message origination date. This prevents a future |  | with the message origination date. This prevents a future |
| modification date from having an adverse impact on cache validation. |  | modification date from having an adverse impact on cache validation. |
|  |  | An origin server without a clock MUST NOT assign Last-Modified values |
|  |  | to a response unless these values were associated with the resource |
|  |  | by some other system or user with a reliable clock. |
| 2.2.2. Comparison |  | 2.2.2. Comparison |
| A Last-Modified time, when used as a validator in a request, is |  | A Last-Modified time, when used as a validator in a request, is |
| implicitly weak unless it is possible to deduce that it is strong, |  | implicitly weak unless it is possible to deduce that it is strong, |
| using the following rules: |  | using the following rules: |
| o The validator is being compared by an origin server to the actual |  | o The validator is being compared by an origin server to the actual |
| current validator for the representation and, |  | current validator for the representation and, |
| o That origin server reliably knows that the associated |  | o That origin server reliably knows that the associated |
| skipping to change at page 13, line 21 |  | skipping to change at page 13, line 24 |
| Vary: Accept-Encoding |  | Vary: Accept-Encoding |
| Content-Type: text/plain |  | Content-Type: text/plain |
| Content-Encoding: gzip |  | Content-Encoding: gzip |
| ...binary data... |  | ...binary data... |
| Note: Content codings are a property of the representation, so |  | Note: Content codings are a property of the representation, so |
| therefore an entity-tag of an encoded representation must be |  | therefore an entity-tag of an encoded representation must be |
| distinct from an unencoded representation to prevent conflicts |  | distinct from an unencoded representation to prevent conflicts |
| during cache updates and range requests. In contrast, transfer |  | during cache updates and range requests. In contrast, transfer |
| codings (Section 6.2 of [Part1]) apply only during message |  | codings (Section 5.1 of [Part1]) apply only during message |
| transfer and do not require distinct entity-tags. |  | transfer and do not require distinct entity-tags. |
| 2.4. Rules for When to Use Entity-tags and Last-Modified Dates |  | 2.4. Rules for When to Use Entity-tags and Last-Modified Dates |
| We adopt a set of rules and recommendations for origin servers, |  | We adopt a set of rules and recommendations for origin servers, |
| clients, and caches regarding when various validator types ought to |  | clients, and caches regarding when various validator types ought to |
| be used, and for what purposes. |  | be used, and for what purposes. |
| HTTP/1.1 origin servers: |  | HTTP/1.1 origin servers: |
| skipping to change at page 19, line 27 |  | skipping to change at page 19, line 27 |
| received and would have resulted in a 200 (OK) response if it were |  | received and would have resulted in a 200 (OK) response if it were |
| not for the fact that the condition has evaluated to false. In other |  | not for the fact that the condition has evaluated to false. In other |
| words, there is no need for the server to transfer a representation |  | words, there is no need for the server to transfer a representation |
| of the target resource because the client's request indicates that it |  | of the target resource because the client's request indicates that it |
| already has a valid representation, as indicated by the 304 response |  | already has a valid representation, as indicated by the 304 response |
| header fields, and is therefore redirecting the client to make use of |  | header fields, and is therefore redirecting the client to make use of |
| that stored representation as if it were the payload of a 200 |  | that stored representation as if it were the payload of a 200 |
| response. The 304 response MUST NOT contain a message-body, and thus |  | response. The 304 response MUST NOT contain a message-body, and thus |
| is always terminated by the first empty line after the header fields. |  | is always terminated by the first empty line after the header fields. |
| A 304 response MUST include a Date header field (Section 9.3 of |  | A 304 response MUST include a Date header field (Section 9.2 of |
| [Part1]) unless its omission is required by Section 9.3.1 of [Part1]. |  | [Part2]) unless the origin server does not have a clock that can |
| If a 200 response to the same request would have included any of the |  | provide a reasonable approximation of the current time. If a 200 |
| header fields Cache-Control, Content-Location, ETag, Expires, Last- |  | response to the same request would have included any of the header |
| Modified, or Vary, then those same header fields MUST be sent in a |  | fields Cache-Control, Content-Location, ETag, Expires, Last-Modified, |
| 304 response. |  | or Vary, then those same header fields MUST be sent in a 304 |
|  |  | response. |
| Since the goal of a 304 response is to minimize information transfer |  | Since the goal of a 304 response is to minimize information transfer |
| when the recipient already has one or more cached representations, |  | when the recipient already has one or more cached representations, |
| the response SHOULD NOT include representation metadata other than |  | the response SHOULD NOT include representation metadata other than |
| the above listed fields unless said metadata exists for the purpose |  | the above listed fields unless said metadata exists for the purpose |
| of guiding cache updates (e.g., future HTTP extensions). |  | of guiding cache updates (e.g., future HTTP extensions). |
| If the recipient of a 304 response does not have a cached |  | If the recipient of a 304 response does not have a cached |
| representation corresponding to the entity-tag indicated by the 304 |  | representation corresponding to the entity-tag indicated by the 304 |
| response, then the recipient MUST NOT use the 304 to update its own |  | response, then the recipient MUST NOT use the 304 to update its own |
| skipping to change at page 21, line 7 |  | skipping to change at page 21, line 7 |
| The change controller is: "IETF (iesg@ietf.org) - Internet |  | The change controller is: "IETF (iesg@ietf.org) - Internet |
| Engineering Task Force". |  | Engineering Task Force". |
| 6. Security Considerations |  | 6. Security Considerations |
| No additional security considerations have been identified beyond |  | No additional security considerations have been identified beyond |
| those applicable to HTTP in general [Part1]. |  | those applicable to HTTP in general [Part1]. |
| 7. Acknowledgments |  | 7. Acknowledgments |
| See Section 12 of [Part1]. |  | See Section 11 of [Part1]. |
| 8. References |  | 8. References |
| 8.1. Normative References |  | 8.1. Normative References |
| [Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |  | [Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |
| Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., |  | Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., |
| and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections, |  | and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections, |
| and Message Parsing", draft-ietf-httpbis-p1-messaging-16 |  | and Message Parsing", draft-ietf-httpbis-p1-messaging-17 |
| (work in progress), August 2011. |  | (work in progress), October 2011. |
|  |  | [Part2] 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", draft-ietf-httpbis-p2-semantics-17 (work in |
|  |  | progress), October 2011. |
| [Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |  | [Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |
| Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., |  | Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., |
| and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload |  | and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload |
| and Content Negotiation", draft-ietf-httpbis-p3-payload-16 |  | and Content Negotiation", draft-ietf-httpbis-p3-payload-17 |
| (work in progress), August 2011. |  | (work in progress), October 2011. |
| [Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |  | [Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |
| Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., |  | Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., |
| and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and |  | and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and |
| Partial Responses", draft-ietf-httpbis-p5-range-16 (work |  | Partial Responses", draft-ietf-httpbis-p5-range-17 (work |
| in progress), August 2011. |  | in progress), October 2011. |
| [Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |  | [Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |
| Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., |  | Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., |
| Nottingham, M., Ed., and J. Reschke, Ed., "HTTP/1.1, part |  | Nottingham, M., Ed., and J. Reschke, Ed., "HTTP/1.1, part |
| 6: Caching", draft-ietf-httpbis-p6-cache-16 (work in |  | 6: Caching", draft-ietf-httpbis-p6-cache-17 (work in |
| progress), August 2011. |  | progress), October 2011. |
| [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate |  | [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate |
| Requirement Levels", BCP 14, RFC 2119, March 1997. |  | Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax |  | [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax |
| Specifications: ABNF", STD 68, RFC 5234, January 2008. |  | Specifications: ABNF", STD 68, RFC 5234, January 2008. |
| 8.2. Informative References |  | 8.2. Informative References |
| [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., |  | [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., |
| skipping to change at page 22, line 20 |  | skipping to change at page 22, line 25 |
| Allow weak entity-tags in all requests except range requests |  | Allow weak entity-tags in all requests except range requests |
| (Sections 2.1 and 3.2). |  | (Sections 2.1 and 3.2). |
| Change ABNF productions for header fields to only define the field |  | Change ABNF productions for header fields to only define the field |
| value. (Section 3) |  | value. (Section 3) |
| Appendix B. Collected ABNF |  | Appendix B. Collected ABNF |
| ETag = entity-tag |  | ETag = entity-tag |
| HTTP-date = <HTTP-date, defined in [Part1], Section 6.1> |  | HTTP-date = <HTTP-date, defined in [Part2], Section 8> |
| If-Match = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS |  | If-Match = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS |
| entity-tag ] ) ) |  | entity-tag ] ) ) |
| If-Modified-Since = HTTP-date |  | If-Modified-Since = HTTP-date |
| If-None-Match = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS |  | If-None-Match = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS |
| entity-tag ] ) ) |  | entity-tag ] ) ) |
| If-Unmodified-Since = HTTP-date |  | If-Unmodified-Since = HTTP-date |
| Last-Modified = HTTP-date |  | Last-Modified = HTTP-date |
| skipping to change at page 26, line 17 |  | skipping to change at page 26, line 20 |
| None. |  | None. |
| C.17. Since draft-ietf-httpbis-p4-conditional-15 |  | C.17. Since draft-ietf-httpbis-p4-conditional-15 |
| Closed issues: |  | Closed issues: |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/304>: "If-Range |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/304>: "If-Range |
| should be listed when dicussing contexts where L-M can be |  | should be listed when dicussing contexts where L-M can be |
| considered strong" |  | considered strong" |
|  |  | C.18. Since draft-ietf-httpbis-p4-conditional-16 |
|  |  | Closed issues: |
|  |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/186>: "Document |
|  |  | HTTP's error-handling philosophy" |
| Index |  | Index |
| 3 |  | 3 |
| 304 Not Modified (status code) 19 |  | 304 Not Modified (status code) 19 |
| 4 |  | 4 |
| 412 Precondition Failed (status code) 20 |  | 412 Precondition Failed (status code) 20 |
| E |  | E |
| ETag header field 10 |  | ETag header field 10 |
| skipping to change at page 26, line 43 |  | skipping to change at page 27, line 4 |
| If-Modified-Since 17 |  | If-Modified-Since 17 |
| If-None-Match 16 |  | If-None-Match 16 |
| If-Unmodified-Since 18 |  | If-Unmodified-Since 18 |
| Last-Modified 8 |  | Last-Modified 8 |
| opaque-tag 10 |  | opaque-tag 10 |
| weak 10 |  | weak 10 |
| H |  | H |
| Header Fields |  | Header Fields |
| ETag 10 |  | ETag 10 |
| If-Match 14 |  | If-Match 15 |
| If-Modified-Since 17 |  | If-Modified-Since 17 |
| If-None-Match 15 |  | If-None-Match 15 |
| If-Unmodified-Since 18 |  | If-Unmodified-Since 18 |
| Last-Modified 8 |  | Last-Modified 8 |
| I |  | I |
| If-Match header field 14 |  | If-Match header field 15 |
| If-Modified-Since header field 17 |  | If-Modified-Since header field 17 |
| If-None-Match header field 15 |  | If-None-Match header field 15 |
| If-Unmodified-Since header field 18 |  | If-Unmodified-Since header field 18 |
| L |  | L |
| Last-Modified header field 8 |  | Last-Modified header field 8 |
| M |  | M |
| metadata 6 |  | metadata 6 |
End of changes. 27 change blocks.
| 41 lines changed or deleted |  | 75 lines changed or added |
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