| draft-ietf-httpbis-p6-cache-11.txt |  | draft-ietf-httpbis-p6-cache-12.txt |
--- | --- | --- | --- | ---
| HTTPbis Working Group R. Fielding, Ed. |  | HTTPbis Working Group R. Fielding, Ed. |
| Internet-Draft Day Software |  | Internet-Draft Day Software |
| 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 5, 2011 J. Mogul |  | Expires: April 28, 2011 J. Mogul |
| HP |  | HP |
| H. Frystyk |  | H. Frystyk |
| Microsoft |  | Microsoft |
| L. Masinter |  | L. Masinter |
| Adobe Systems |  | Adobe Systems |
| P. Leach |  | P. Leach |
| Microsoft |  | Microsoft |
| T. Berners-Lee |  | T. Berners-Lee |
| W3C/MIT |  | W3C/MIT |
| Y. Lafon, Ed. |  | Y. Lafon, Ed. |
| W3C |  | W3C |
| M. Nottingham, Ed. |  | M. Nottingham, Ed. |
| J. Reschke, Ed. |  | J. Reschke, Ed. |
| greenbytes |  | greenbytes |
| August 4, 2010 |  | October 25, 2010 |
| HTTP/1.1, part 6: Caching |  | HTTP/1.1, part 6: Caching |
| draft-ietf-httpbis-p6-cache-11 |  | draft-ietf-httpbis-p6-cache-12 |
| Abstract |  | Abstract |
| The Hypertext Transfer Protocol (HTTP) is an application-level |  | The Hypertext Transfer Protocol (HTTP) is an application-level |
| protocol for distributed, collaborative, hypermedia information |  | protocol for distributed, collaborative, hypermedia information |
| systems. This document is Part 6 of the seven-part specification |  | systems. This document is Part 6 of the seven-part specification |
| that defines the protocol referred to as "HTTP/1.1" and, taken |  | that defines the protocol referred to as "HTTP/1.1" and, taken |
| together, obsoletes RFC 2616. Part 6 defines requirements on HTTP |  | together, obsoletes RFC 2616. Part 6 defines requirements on HTTP |
| caches and the associated header fields that control cache behavior |  | caches and the associated header fields that control cache behavior |
| or indicate cacheable response messages. |  | or indicate cacheable response messages. |
| Editorial Note (To be removed by RFC Editor) |  | Editorial Note (To be removed by RFC Editor) |
| 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). The current issues list is |  | group mailing list (ietf-http-wg@w3.org). The current issues list is |
| at <http://tools.ietf.org/wg/httpbis/trac/report/3> and related |  | at <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.12. |  | The changes in this draft are summarized in Appendix C.13. |
| 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 5, 2011. |  | This Internet-Draft will expire on April 28, 2011. |
| Copyright Notice |  | Copyright Notice |
| Copyright (c) 2010 IETF Trust and the persons identified as the |  | Copyright (c) 2010 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 3, line 17 |  | skipping to change at page 3, line 17 |
| Specification . . . . . . . . . . . . . . . . . . . . 7 |  | Specification . . . . . . . . . . . . . . . . . . . . 7 |
| 2. Cache Operation . . . . . . . . . . . . . . . . . . . . . . . 7 |  | 2. Cache Operation . . . . . . . . . . . . . . . . . . . . . . . 7 |
| 2.1. Response Cacheability . . . . . . . . . . . . . . . . . . 7 |  | 2.1. Response Cacheability . . . . . . . . . . . . . . . . . . 7 |
| 2.1.1. Storing Partial and Incomplete Responses . . . . . . . 8 |  | 2.1.1. Storing Partial and Incomplete Responses . . . . . . . 8 |
| 2.2. Constructing Responses from Caches . . . . . . . . . . . . 9 |  | 2.2. Constructing Responses from Caches . . . . . . . . . . . . 9 |
| 2.3. Freshness Model . . . . . . . . . . . . . . . . . . . . . 10 |  | 2.3. Freshness Model . . . . . . . . . . . . . . . . . . . . . 10 |
| 2.3.1. Calculating Freshness Lifetime . . . . . . . . . . . . 11 |  | 2.3.1. Calculating Freshness Lifetime . . . . . . . . . . . . 11 |
| 2.3.2. Calculating Age . . . . . . . . . . . . . . . . . . . 12 |  | 2.3.2. Calculating Age . . . . . . . . . . . . . . . . . . . 12 |
| 2.3.3. Serving Stale Responses . . . . . . . . . . . . . . . 13 |  | 2.3.3. Serving Stale Responses . . . . . . . . . . . . . . . 13 |
| 2.4. Validation Model . . . . . . . . . . . . . . . . . . . . . 14 |  | 2.4. Validation Model . . . . . . . . . . . . . . . . . . . . . 14 |
| 2.5. Request Methods that Invalidate . . . . . . . . . . . . . 14 |  | 2.5. Request Methods that Invalidate . . . . . . . . . . . . . 15 |
| 2.6. Shared Caching of Authenticated Responses . . . . . . . . 15 |  | 2.6. Shared Caching of Authenticated Responses . . . . . . . . 15 |
| 2.7. Caching Negotiated Responses . . . . . . . . . . . . . . . 16 |  | 2.7. Caching Negotiated Responses . . . . . . . . . . . . . . . 16 |
| 2.8. Combining Responses . . . . . . . . . . . . . . . . . . . 16 |  | 2.8. Combining Responses . . . . . . . . . . . . . . . . . . . 17 |
| 3. Header Field Definitions . . . . . . . . . . . . . . . . . . . 17 |  | 3. Header Field Definitions . . . . . . . . . . . . . . . . . . . 17 |
| 3.1. Age . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 |  | 3.1. Age . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 |
| 3.2. Cache-Control . . . . . . . . . . . . . . . . . . . . . . 18 |  | 3.2. Cache-Control . . . . . . . . . . . . . . . . . . . . . . 18 |
| 3.2.1. Request Cache-Control Directives . . . . . . . . . . . 18 |  | 3.2.1. Request Cache-Control Directives . . . . . . . . . . . 19 |
| 3.2.2. Response Cache-Control Directives . . . . . . . . . . 20 |  | 3.2.2. Response Cache-Control Directives . . . . . . . . . . 20 |
| 3.2.3. Cache Control Extensions . . . . . . . . . . . . . . . 22 |  | 3.2.3. Cache Control Extensions . . . . . . . . . . . . . . . 23 |
| 3.3. Expires . . . . . . . . . . . . . . . . . . . . . . . . . 24 |  | 3.3. Expires . . . . . . . . . . . . . . . . . . . . . . . . . 24 |
| 3.4. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . . 24 |  | 3.4. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . . 25 |
| 3.5. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 |  | 3.5. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 |
| 3.6. Warning . . . . . . . . . . . . . . . . . . . . . . . . . 26 |  | 3.6. Warning . . . . . . . . . . . . . . . . . . . . . . . . . 26 |
| 4. History Lists . . . . . . . . . . . . . . . . . . . . . . . . 28 |  | 4. History Lists . . . . . . . . . . . . . . . . . . . . . . . . 29 |
| 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 |  | 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 |
| 5.1. Cache Directive Registry . . . . . . . . . . . . . . . . . 28 |  | 5.1. Cache Directive Registry . . . . . . . . . . . . . . . . . 29 |
| 5.2. Header Field Registration . . . . . . . . . . . . . . . . 29 |  | 5.2. Header Field Registration . . . . . . . . . . . . . . . . 30 |
| 6. Security Considerations . . . . . . . . . . . . . . . . . . . 29 |  | 6. Security Considerations . . . . . . . . . . . . . . . . . . . 30 |
| 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 30 |  | 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 30 |
| 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30 |  | 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30 |
| 8.1. Normative References . . . . . . . . . . . . . . . . . . . 30 |  | 8.1. Normative References . . . . . . . . . . . . . . . . . . . 30 |
| 8.2. Informative References . . . . . . . . . . . . . . . . . . 31 |  | 8.2. Informative References . . . . . . . . . . . . . . . . . . 31 |
| Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 31 |  | Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 32 |
| Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 31 |  | Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 32 |
| Appendix C. Change Log (to be removed by RFC Editor before |  | Appendix C. Change Log (to be removed by RFC Editor before |
| publication) . . . . . . . . . . . . . . . . . . . . 33 |  | publication) . . . . . . . . . . . . . . . . . . . . 33 |
| C.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 33 |  | C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 34 |
| C.2. Since draft-ietf-httpbis-p6-cache-00 . . . . . . . . . . . 33 |  | C.2. Since draft-ietf-httpbis-p6-cache-00 . . . . . . . . . . . 34 |
| C.3. Since draft-ietf-httpbis-p6-cache-01 . . . . . . . . . . . 34 |  | C.3. Since draft-ietf-httpbis-p6-cache-01 . . . . . . . . . . . 34 |
| C.4. Since draft-ietf-httpbis-p6-cache-02 . . . . . . . . . . . 34 |  | C.4. Since draft-ietf-httpbis-p6-cache-02 . . . . . . . . . . . 35 |
| C.5. Since draft-ietf-httpbis-p6-cache-03 . . . . . . . . . . . 34 |  | C.5. Since draft-ietf-httpbis-p6-cache-03 . . . . . . . . . . . 35 |
| C.6. Since draft-ietf-httpbis-p6-cache-04 . . . . . . . . . . . 34 |  | C.6. Since draft-ietf-httpbis-p6-cache-04 . . . . . . . . . . . 35 |
| C.7. Since draft-ietf-httpbis-p6-cache-05 . . . . . . . . . . . 35 |  | C.7. Since draft-ietf-httpbis-p6-cache-05 . . . . . . . . . . . 35 |
| C.8. Since draft-ietf-httpbis-p6-cache-06 . . . . . . . . . . . 35 |  | C.8. Since draft-ietf-httpbis-p6-cache-06 . . . . . . . . . . . 36 |
| C.9. Since draft-ietf-httpbis-p6-cache-07 . . . . . . . . . . . 35 |  | C.9. Since draft-ietf-httpbis-p6-cache-07 . . . . . . . . . . . 36 |
| C.10. Since draft-ietf-httpbis-p6-cache-08 . . . . . . . . . . . 36 |  | C.10. Since draft-ietf-httpbis-p6-cache-08 . . . . . . . . . . . 36 |
| C.11. Since draft-ietf-httpbis-p6-cache-09 . . . . . . . . . . . 36 |  | C.11. Since draft-ietf-httpbis-p6-cache-09 . . . . . . . . . . . 37 |
| C.12. Since draft-ietf-httpbis-p6-cache-10 . . . . . . . . . . . 37 |  | C.12. Since draft-ietf-httpbis-p6-cache-10 . . . . . . . . . . . 37 |
| Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 |  | C.13. Since draft-ietf-httpbis-p6-cache-11 . . . . . . . . . . . 38 |
|  |  | Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 |
| 1. Introduction |  | 1. Introduction |
| HTTP is typically used for distributed information systems, where |  | HTTP is typically used for distributed information systems, where |
| performance can be improved by the use of response caches. This |  | performance can be improved by the use of response caches. This |
| document defines aspects of HTTP/1.1 related to caching and reusing |  | document defines aspects of HTTP/1.1 related to caching and reusing |
| response messages. |  | response messages. |
| 1.1. Purpose |  | 1.1. Purpose |
| skipping to change at page 8, line 8 |  | skipping to change at page 8, line 8 |
| 2.1. Response Cacheability |  | 2.1. Response Cacheability |
| A cache MUST NOT store a response to any request, unless: |  | A cache MUST NOT store a response to any request, unless: |
| o The request method is understood by the cache and defined as being |  | o The request method is understood by the cache and defined as being |
| cacheable, and |  | cacheable, and |
| o the response status code is understood by the cache, and |  | o the response status code is understood by the cache, and |
| o the "no-store" cache directive (see Section 3.2) does not appear |  | o the "no-store" cache directive (see Section 3.2) does not appear |
| in request or response headers, and |  | in request or response header fields, and |
| o the "private" cache response directive (see Section 3.2.2 does not |  | o the "private" cache response directive (see Section 3.2.2 does not |
| appear in the response, if the cache is shared, and |  | appear in the response, if the cache is shared, and |
| o the "Authorization" header (see Section 3.1 of [Part7]) does not |  | o the "Authorization" header field (see Section 4.1 of [Part7]) does |
| appear in the request, if the cache is shared, unless the response |  | not appear in the request, if the cache is shared, unless the |
| explicitly allows it (see Section 2.6), and |  | response explicitly allows it (see Section 2.6), and |
| o the response either: |  | o the response either: |
| * contains an Expires header (see Section 3.3), or |  | * contains an Expires header field (see Section 3.3), or |
| * contains a max-age response cache directive (see |  | * contains a max-age response cache directive (see |
| Section 3.2.2), or |  | Section 3.2.2), or |
| * contains a s-maxage response cache directive and the cache is |  | * contains a s-maxage response cache directive and the cache is |
| shared, or |  | shared, or |
| * contains a Cache Control Extension (see Section 3.2.3) that |  | * contains a Cache Control Extension (see Section 3.2.3) that |
| allows it to be cached, or |  | allows it to be cached, or |
| skipping to change at page 8, line 47 |  | skipping to change at page 8, line 47 |
| content (see Section 2.1.1). |  | content (see Section 2.1.1). |
| Note that in normal operation, most caches will not store a response |  | Note that in normal operation, most caches will not store a response |
| that has neither a cache validator nor an explicit expiration time, |  | that has neither a cache validator nor an explicit expiration time, |
| as such responses are not usually useful to store. However, caches |  | as such responses are not usually useful to store. However, caches |
| are not prohibited from storing such responses. |  | are not prohibited from storing such responses. |
| 2.1.1. Storing Partial and Incomplete Responses |  | 2.1.1. Storing Partial and Incomplete Responses |
| A cache that receives an incomplete response (for example, with fewer |  | A cache that receives an incomplete response (for example, with fewer |
| bytes of data than specified in a Content-Length header) can store |  | bytes of data than specified in a Content-Length header field) can |
| the response, but MUST treat it as a partial response [Part5]. |  | store the response, but MUST treat it as a partial response [Part5]. |
| Partial responses can be combined as described in Section 4 of |  | Partial responses can be combined as described in Section 4 of |
| [Part5]; the result might be a full response or might still be |  | [Part5]; the result might be a full response or might still be |
| partial. A cache MUST NOT return a partial response to a client |  | partial. A cache MUST NOT return a partial response to a client |
| without explicitly marking it as such using the 206 (Partial Content) |  | without explicitly marking it as such using the 206 (Partial Content) |
| status code. |  | status code. |
| A cache that does not support the Range and Content-Range headers |  | A cache that does not support the Range and Content-Range header |
| MUST NOT store incomplete or partial responses. |  | fields MUST NOT store incomplete or partial responses. |
| 2.2. Constructing Responses from Caches |  | 2.2. Constructing Responses from Caches |
| For a presented request, a cache MUST NOT return a stored response, |  | For a presented request, a cache MUST NOT return a stored response, |
| unless: |  | unless: |
| o The presented effective request URI (Section 4.3 of [Part1]) and |  | o The presented effective request URI (Section 4.3 of [Part1]) and |
| that of the stored response match, and |  | that of the stored response match, and |
| o the request method associated with the stored response allows it |  | o the request method associated with the stored response allows it |
| to be used for the presented request, and |  | to be used for the presented request, and |
| o selecting request-headers nominated by the stored response (if |  | o selecting request-header fields nominated by the stored response |
| any) match those presented (see Section 2.7), and |  | (if any) match those presented (see Section 2.7), and |
| o the presented request and stored response are free from directives |  | o the presented request and stored response are free from directives |
| that would prevent its use (see Section 3.2 and Section 3.4), and |  | that would prevent its use (see Section 3.2 and Section 3.4), and |
| o the stored response is either: |  | o the stored response is either: |
| * fresh (see Section 2.3), or |  | * fresh (see Section 2.3), or |
| * allowed to be served stale (see Section 2.3.3), or |  | * allowed to be served stale (see Section 2.3.3), or |
| skipping to change at page 9, line 48 |  | skipping to change at page 9, line 48 |
| Requests with methods that are unsafe (Section 7.1.1 of [Part2]) MUST |  | Requests with methods that are unsafe (Section 7.1.1 of [Part2]) MUST |
| be written through the cache to the origin server; i.e., a cache must |  | be written through the cache to the origin server; i.e., a cache must |
| not reply to such a request before having forwarded the request and |  | not reply to such a request before having forwarded the request and |
| having received a corresponding response. |  | having received a corresponding response. |
| Also, note that unsafe requests might invalidate already stored |  | Also, note that unsafe requests might invalidate already stored |
| responses; see Section 2.5. |  | responses; see Section 2.5. |
| Caches MUST use the most recent response (as determined by the Date |  | Caches MUST use the most recent response (as determined by the Date |
| header) when more than one suitable response is stored. They can |  | header field) when more than one suitable response is stored. They |
| also forward a request with "Cache-Control: max-age=0" or "Cache- |  | can also forward a request with "Cache-Control: max-age=0" or "Cache- |
| Control: no-cache" to disambiguate which response to use. |  | Control: no-cache" to disambiguate which response to use. |
|  |  | An HTTP implementation without a clock MUST NOT used stored responses |
|  |  | without revalidating them on every use. An HTTP cache, especially a |
|  |  | shared cache, SHOULD use a mechanism, such as NTP [RFC1305], to |
|  |  | synchronize its clock with a reliable external standard. |
| 2.3. Freshness Model |  | 2.3. Freshness Model |
| When a response is "fresh" in the cache, it can be used to satisfy |  | When a response is "fresh" in the cache, it can be used to satisfy |
| subsequent requests without contacting the origin server, thereby |  | subsequent requests without contacting the origin server, thereby |
| improving efficiency. |  | improving efficiency. |
| The primary mechanism for determining freshness is for an origin |  | The primary mechanism for determining freshness is for an origin |
| server to provide an explicit expiration time in the future, using |  | server to provide an explicit expiration time in the future, using |
| either the Expires header (Section 3.3) or the max-age response cache |  | either the Expires header field (Section 3.3) or the max-age response |
| directive (Section 3.2.2). Generally, origin servers will assign |  | cache directive (Section 3.2.2). Generally, origin servers will |
| future explicit expiration times to responses in the belief that the |  | assign future explicit expiration times to responses in the belief |
| representation is not likely to change in a semantically significant |  | that the representation is not likely to change in a semantically |
| way before the expiration time is reached. |  | significant way before the expiration time is reached. |
| If an origin server wishes to force a cache to validate every |  | If an origin server wishes to force a cache to validate every |
| request, it can assign an explicit expiration time in the past to |  | request, it can assign an explicit expiration time in the past to |
| indicate that the response is already stale. Compliant caches will |  | indicate that the response is already stale. Compliant caches will |
| validate the cached response before reusing it for subsequent |  | validate the cached response before reusing it for subsequent |
| requests. |  | requests. |
| Since origin servers do not always provide explicit expiration times, |  | Since origin servers do not always provide explicit expiration times, |
| HTTP caches MAY assign heuristic expiration times when explicit times |  | HTTP caches MAY assign heuristic expiration times when explicit times |
| are not specified, employing algorithms that use other header values |  | are not specified, employing algorithms that use other heade field |
| (such as the Last-Modified time) to estimate a plausible expiration |  | values (such as the Last-Modified time) to estimate a plausible |
| time. The HTTP/1.1 specification does not provide specific |  | expiration time. The HTTP/1.1 specification does not provide |
| algorithms, but does impose worst-case constraints on their results. |  | specific algorithms, but does impose worst-case constraints on their |
|  |  | results. |
| The calculation to determine if a response is fresh is: |  | The calculation to determine if a response is fresh is: |
| response_is_fresh = (freshness_lifetime > current_age) |  | response_is_fresh = (freshness_lifetime > current_age) |
| The freshness_lifetime is defined in Section 2.3.1; the current_age |  | The freshness_lifetime is defined in Section 2.3.1; the current_age |
| is defined in Section 2.3.2. |  | is defined in Section 2.3.2. |
| Additionally, clients might need to influence freshness calculation. |  | Additionally, clients might need to influence freshness calculation. |
| They can do this using several request cache directives, with the |  | They can do this using several request cache directives, with the |
| skipping to change at page 11, line 16 |  | skipping to change at page 11, line 20 |
| A cache can calculate the freshness lifetime (denoted as |  | A cache can calculate the freshness lifetime (denoted as |
| freshness_lifetime) of a response by using the first match of: |  | freshness_lifetime) of a response by using the first match of: |
| o If the cache is shared and the s-maxage response cache directive |  | o If the cache is shared and the s-maxage response cache directive |
| (Section 3.2.2) is present, use its value, or |  | (Section 3.2.2) is present, use its value, or |
| o If the max-age response cache directive (Section 3.2.2) is |  | o If the max-age response cache directive (Section 3.2.2) is |
| present, use its value, or |  | present, use its value, or |
| o If the Expires response header (Section 3.3) is present, use its |  | o If the Expires response header field (Section 3.3) is present, use |
| value minus the value of the Date response header, or |  | its value minus the value of the Date response header field, or |
| o Otherwise, no explicit expiration time is present in the response. |  | o Otherwise, no explicit expiration time is present in the response. |
| A heuristic freshness lifetime might be applicable; see |  | A heuristic freshness lifetime might be applicable; see |
| Section 2.3.1.1. |  | Section 2.3.1.1. |
| Note that this calculation is not vulnerable to clock skew, since all |  | Note that this calculation is not vulnerable to clock skew, since all |
| of the information comes from the origin server. |  | of the information comes from the origin server. |
| 2.3.1.1. Calculating Heuristic Freshness |  | 2.3.1.1. Calculating Heuristic Freshness |
| If no explicit expiration time is present in a stored response that |  | If no explicit expiration time is present in a stored response that |
| has a status code whose definition allows heuristic freshness to be |  | has a status code whose definition allows heuristic freshness to be |
| used (including the following in Section 8 of [Part2]: 200, 203, 206, |  | used (including the following in Section 8 of [Part2]: 200, 203, 206, |
| 300, 301 and 410), a heuristic expiration time MAY be calculated. |  | 300, 301 and 410), a heuristic expiration time MAY be calculated. |
| Heuristics MUST NOT be used for response status codes that do not |  | Heuristics MUST NOT be used for response status codes that do not |
| explicitly allow it. |  | explicitly allow it. |
| When a heuristic is used to calculate freshness lifetime, the cache |  | When a heuristic is used to calculate freshness lifetime, the cache |
| SHOULD attach a Warning header with a 113 warn-code to the response |  | SHOULD attach a Warning header field with a 113 warn-code to the |
| if its current_age is more than 24 hours and such a warning is not |  | response if its current_age is more than 24 hours and such a warning |
| already present. |  | is not already present. |
| Also, if the response has a Last-Modified header (Section 6.6 of |  | Also, if the response has a Last-Modified header field (Section 6.6 |
| [Part4]), the heuristic expiration value SHOULD be no more than some |  | of [Part4]), the heuristic expiration value SHOULD be no more than |
| fraction of the interval since that time. A typical setting of this |  | some fraction of the interval since that time. A typical setting of |
| fraction might be 10%. |  | this fraction might be 10%. |
| Note: RFC 2616 ([RFC2616], Section 13.9) required that caches do |  | Note: RFC 2616 ([RFC2616], Section 13.9) required that caches do |
| not calculate heuristic freshness for URLs with query components |  | not calculate heuristic freshness for URLs with query components |
| (i.e., those containing '?'). In practice, this has not been |  | (i.e., those containing '?'). In practice, this has not been |
| widely implemented. Therefore, servers are encouraged to send |  | widely implemented. Therefore, servers are encouraged to send |
| explicit directives (e.g., Cache-Control: no-cache) if they wish |  | explicit directives (e.g., Cache-Control: no-cache) if they wish |
| to preclude caching. |  | to preclude caching. |
| 2.3.2. Calculating Age |  | 2.3.2. Calculating Age |
| HTTP/1.1 uses the Age response-header to convey the estimated age of |  | HTTP/1.1 uses the Age response-header field to convey the estimated |
| the response message when obtained from a cache. The Age field value |  | age of the response message when obtained from a cache. The Age |
| is the cache's estimate of the amount of time since the response was |  | field value is the cache's estimate of the amount of time since the |
| generated or validated by the origin server. In essence, the Age |  | response was generated or validated by the origin server. In |
| value is the sum of the time that the response has been resident in |  | essence, the Age value is the sum of the time that the response has |
| each of the caches along the path from the origin server, plus the |  | been resident in each of the caches along the path from the origin |
| amount of time it has been in transit along network paths. |  | server, plus the amount of time it has been in transit along network |
|  |  | paths. |
| The following data is used for the age calculation: |  | The following data is used for the age calculation: |
| age_value |  | age_value |
| The term "age_value" denotes the value of the Age header |  | The term "age_value" denotes the value of the Age header field |
| (Section 3.1), in a form appropriate for arithmetic operation; or |  | (Section 3.1), in a form appropriate for arithmetic operation; or |
| 0, if not available. |  | 0, if not available. |
| date_value |  | date_value |
| HTTP/1.1 requires origin servers to send a Date header, if |  | HTTP/1.1 requires origin servers to send a Date header field, if |
| possible, with every response, giving the time at which the |  | possible, with every response, giving the time at which the |
| response was generated. The term "date_value" denotes the value |  | response was generated. The term "date_value" denotes the value |
| of the Date header, in a form appropriate for arithmetic |  | of the Date header field, in a form appropriate for arithmetic |
| operations. See Section 9.3 of [Part1] for the definition of the |  | operations. See Section 9.3 of [Part1] for the definition of the |
| Date header, and for requirements regarding responses without a |  | Date header field, and for requirements regarding responses |
| Date response header. |  | without it. |
| now |  | now |
| The term "now" means "the current value of the clock at the host |  | The term "now" means "the current value of the clock at the host |
| performing the calculation". Hosts that use HTTP, but especially |  | performing the calculation". Hosts that use HTTP, but especially |
| hosts running origin servers and caches, SHOULD use NTP |  | hosts running origin servers and caches, SHOULD use NTP |
| ([RFC1305]) or some similar protocol to synchronize their clocks |  | ([RFC1305]) or some similar protocol to synchronize their clocks |
| to a globally accurate time standard. |  | to a globally accurate time standard. |
| request_time |  | request_time |
| skipping to change at page 13, line 48 |  | skipping to change at page 14, line 7 |
| explicit in-protocol directive (e.g., by a "no-store" or "no-cache" |  | explicit in-protocol directive (e.g., by a "no-store" or "no-cache" |
| cache directive, a "must-revalidate" cache-response-directive, or an |  | cache directive, a "must-revalidate" cache-response-directive, or an |
| applicable "s-maxage" or "proxy-revalidate" cache-response-directive; |  | applicable "s-maxage" or "proxy-revalidate" cache-response-directive; |
| see Section 3.2.2). |  | see Section 3.2.2). |
| Caches SHOULD NOT return stale responses unless they are disconnected |  | Caches SHOULD NOT return stale responses unless they are disconnected |
| (i.e., it cannot contact the origin server or otherwise find a |  | (i.e., it cannot contact the origin server or otherwise find a |
| forward path) or otherwise explicitly allowed (e.g., the max-stale |  | forward path) or otherwise explicitly allowed (e.g., the max-stale |
| request directive; see Section 3.2.1). |  | request directive; see Section 3.2.1). |
| Stale responses SHOULD have a Warning header with the 110 warn-code |  | Stale responses SHOULD have a Warning header field with the 110 warn- |
| (see Section 3.6). Likewise, the 112 warn-code SHOULD be sent on |  | code (see Section 3.6). Likewise, the 112 warn-code SHOULD be sent |
| stale responses if the cache is disconnected. |  | on stale responses if the cache is disconnected. |
| If a cache receives a first-hand response (either an entire response, |  | If a cache receives a first-hand response (either an entire response, |
| or a 304 (Not Modified) response) that it would normally forward to |  | or a 304 (Not Modified) response) that it would normally forward to |
| the requesting client, and the received response is no longer fresh, |  | the requesting client, and the received response is no longer fresh, |
| the cache SHOULD forward it to the requesting client without adding a |  | the cache SHOULD forward it to the requesting client without adding a |
| new Warning (but without removing any existing Warning headers). A |  | new Warning (but without removing any existing Warning header |
| cache SHOULD NOT attempt to validate a response simply because that |  | fields). A cache SHOULD NOT attempt to validate a response simply |
| response became stale in transit. |  | because that response became stale in transit. |
| 2.4. Validation Model |  | 2.4. Validation Model |
| When a cache has one or more stored responses for a requested URI, |  | When a cache has one or more stored responses for a requested URI, |
| but cannot serve any of them (e.g., because they are not fresh, or |  | but cannot serve any of them (e.g., because they are not fresh, or |
| one cannot be selected; see Section 2.7), it can use the conditional |  | one cannot be selected; see Section 2.7), it can use the conditional |
| request mechanism [Part4] in the forwarded request to give the origin |  | request mechanism [Part4] in the forwarded request to give the origin |
| server an opportunity to both select a valid stored response to be |  | server an opportunity to both select a valid stored response to be |
| used, and to update it. This process is known as "validating" or |  | used, and to update it. This process is known as "validating" or |
| "revalidating" the stored response. |  | "revalidating" the stored response. |
| When sending such a conditional request, the cache SHOULD add an If- |  | When sending such a conditional request, the cache SHOULD add an If- |
| Modified-Since header whose value is that of the Last-Modified header |  | Modified-Since header field whose value is that of the Last-Modified |
| from the selected (see Section 2.7) stored response, if available. |  | header field from the selected (see Section 2.7) stored response, if |
|  |  | available. |
| Additionally, the cache SHOULD add an If-None-Match header whose |  | Additionally, the cache SHOULD add an If-None-Match header field |
| value is that of the ETag header(s) from all responses stored for the |  | whose value is that of the ETag header field(s) from all responses |
| requested URI, if present. However, if any of the stored responses |  | stored for the requested URI, if present. However, if any of the |
| contains only partial content, its entity-tag SHOULD NOT be included |  | stored responses contains only partial content, its entity-tag SHOULD |
| in the If-None-Match header field unless the request is for a range |  | NOT be included in the If-None-Match header field unless the request |
| that would be fully satisfied by that stored response. |  | is for a range that would be fully satisfied by that stored response. |
| A 304 (Not Modified) response status code indicates that the stored |  | A 304 (Not Modified) response status code indicates that the stored |
| response can be updated and reused; see Section 2.8. |  | response can be updated and reused; see Section 2.8. |
| A full response (i.e., one with a response body) indicates that none |  | A full response (i.e., one with a response body) indicates that none |
| of the stored responses nominated in the conditional request is |  | of the stored responses nominated in the conditional request is |
| suitable. Instead, the full response SHOULD be used to satisfy the |  | suitable. Instead, the full response SHOULD be used to satisfy the |
| request and MAY replace the stored response. |  | request and MAY replace the stored response. |
| If a cache receives a 5xx response while attempting to validate a |  | If a cache receives a 5xx response while attempting to validate a |
| skipping to change at page 15, line 7 |  | skipping to change at page 15, line 14 |
| case, it MAY return a previously stored response (see Section 2.3.3). |  | case, it MAY return a previously stored response (see Section 2.3.3). |
| 2.5. Request Methods that Invalidate |  | 2.5. Request Methods that Invalidate |
| Because unsafe methods (Section 7.1.1 of [Part2]) have the potential |  | Because unsafe methods (Section 7.1.1 of [Part2]) have the potential |
| for changing state on the origin server, intervening caches can use |  | for changing state on the origin server, intervening caches can use |
| them to keep their contents up-to-date. |  | them to keep their contents up-to-date. |
| The following HTTP methods MUST cause a cache to invalidate the |  | The following HTTP methods MUST cause a cache to invalidate the |
| effective Request URI (Section 4.3 of [Part1]) as well as the URI(s) |  | effective Request URI (Section 4.3 of [Part1]) as well as the URI(s) |
| in the Location and Content-Location headers (if present): |  | in the Location and Content-Location header fields (if present): |
| o PUT |  | o PUT |
| o DELETE |  | o DELETE |
| o POST |  | o POST |
| An invalidation based on a URI from a Location or Content-Location |  | An invalidation based on a URI from a Location or Content-Location |
| header MUST NOT be performed if the host part of that URI differs |  | header field MUST NOT be performed if the host part of that URI |
| from the host part in the effective request URI (Section 4.3 of |  | differs from the host part in the effective request URI (Section 4.3 |
| [Part1]). This helps prevent denial of service attacks. |  | of [Part1]). This helps prevent denial of service attacks. |
| A cache that passes through requests for methods it does not |  | A cache that passes through requests for methods it does not |
| understand SHOULD invalidate the effective request URI (Section 4.3 |  | understand SHOULD invalidate the effective request URI (Section 4.3 |
| of [Part1]). |  | of [Part1]). |
| Here, "invalidate" means that the cache will either remove all stored |  | Here, "invalidate" means that the cache will either remove all stored |
| responses related to the effective request URI, or will mark these as |  | responses related to the effective request URI, or will mark these as |
| "invalid" and in need of a mandatory validation before they can be |  | "invalid" and in need of a mandatory validation before they can be |
| returned in response to a subsequent request. |  | returned in response to a subsequent request. |
| Note that this does not guarantee that all appropriate responses are |  | Note that this does not guarantee that all appropriate responses are |
| invalidated. For example, the request that caused the change at the |  | invalidated. For example, the request that caused the change at the |
| origin server might not have gone through the cache where a response |  | origin server might not have gone through the cache where a response |
| is stored. |  | is stored. |
| 2.6. Shared Caching of Authenticated Responses |  | 2.6. Shared Caching of Authenticated Responses |
| Shared caches MUST NOT use a cached response to a request with an |  | Shared caches MUST NOT use a cached response to a request with an |
| Authorization header (Section 3.1 of [Part7]) to satisfy any |  | Authorization header field (Section 4.1 of [Part7]) to satisfy any |
| subsequent request unless a cache directive that allows such |  | subsequent request unless a cache directive that allows such |
| responses to be stored is present in the response. |  | responses to be stored is present in the response. |
| In this specification, the following Cache-Control response |  | In this specification, the following Cache-Control response |
| directives (Section 3.2.2) have such an effect: must-revalidate, |  | directives (Section 3.2.2) have such an effect: must-revalidate, |
| public, s-maxage. |  | public, s-maxage. |
| Note that cached responses that contain the "must-revalidate" and/or |  | Note that cached responses that contain the "must-revalidate" and/or |
| "s-maxage" response directives are not allowed to be served stale |  | "s-maxage" response directives are not allowed to be served stale |
| (Section 2.3.3) by shared caches. In particular, a response with |  | (Section 2.3.3) by shared caches. In particular, a response with |
| either "max-age=0, must-revalidate" or "s-maxage=0" cannot be used to |  | either "max-age=0, must-revalidate" or "s-maxage=0" cannot be used to |
| satisfy a subsequent request without revalidating it on the origin |  | satisfy a subsequent request without revalidating it on the origin |
| server. |  | server. |
| 2.7. Caching Negotiated Responses |  | 2.7. Caching Negotiated Responses |
| When a cache receives a request that can be satisfied by a stored |  | When a cache receives a request that can be satisfied by a stored |
| response that has a Vary header field (Section 3.5), it MUST NOT use |  | response that has a Vary header field (Section 3.5), it MUST NOT use |
| that response unless all of the selecting request-headers nominated |  | that response unless all of the selecting request-header fields |
| by the Vary header match in both the original request (i.e., that |  | nominated by the Vary header field match in both the original request |
| associated with the stored response), and the presented request. |  | (i.e., that associated with the stored response), and the presented |
|  |  | request. |
| The selecting request-headers from two requests are defined to match |  | The selecting request-header fields from two requests are defined to |
| if and only if those in the first request can be transformed to those |  | match if and only if those in the first request can be transformed to |
| in the second request by applying any of the following: |  | those in the second request by applying any of the following: |
| o adding or removing whitespace, where allowed in the header's |  | o adding or removing whitespace, where allowed in the header field's |
| syntax |  | syntax |
| o combining multiple message-header fields with the same field name |  | o combining multiple message-header fields with the same field name |
| (see Section 3.2 of [Part1]) |  | (see Section 3.2 of [Part1]) |
| o normalizing both header values in a way that is known to have |  | o normalizing both header field values in a way that is known to |
| identical semantics, according to the header's specification |  | have identical semantics, according to the header field's |
| (e.g., re-ordering field values when order is not significant; |  | specification (e.g., re-ordering field values when order is not |
| case-normalization, where values are defined to be case- |  | significant; case-normalization, where values are defined to be |
| insensitive) |  | case-insensitive) |
| If (after any normalization that might take place) a header field is |  | If (after any normalization that might take place) a header field is |
| absent from a request, it can only match another request if it is |  | absent from a request, it can only match another request if it is |
| also absent there. |  | also absent there. |
| A Vary header field-value of "*" always fails to match, and |  | A Vary header field-value of "*" always fails to match, and |
| subsequent requests to that resource can only be properly interpreted |  | subsequent requests to that resource can only be properly interpreted |
| by the origin server. |  | by the origin server. |
| The stored response with matching selecting request-headers is known |  | The stored response with matching selecting request-header fields is |
| as the selected response. |  | known as the selected response. |
| If no selected response is available, the cache MAY forward the |  | If no selected response is available, the cache MAY forward the |
| presented request to the origin server in a conditional request; see |  | presented request to the origin server in a conditional request; see |
| Section 2.4. |  | Section 2.4. |
| 2.8. Combining Responses |  | 2.8. Combining Responses |
| When a cache receives a 304 (Not Modified) response or a 206 (Partial |  | When a cache receives a 304 (Not Modified) response or a 206 (Partial |
| Content) response (in this section, the "new" response"), it needs to |  | Content) response (in this section, the "new" response"), it needs to |
| created an updated response by combining the stored response with the |  | created an updated response by combining the stored response with the |
| skipping to change at page 17, line 13 |  | skipping to change at page 17, line 23 |
| If the new response contains an ETag, it identifies the stored |  | If the new response contains an ETag, it identifies the stored |
| response to use. [[TODO-mention-CL: might need language about |  | response to use. [[TODO-mention-CL: might need language about |
| Content-Location here]][[TODO-select-for-combine: Shouldn't this be |  | Content-Location here]][[TODO-select-for-combine: Shouldn't this be |
| the selected response?]] |  | the selected response?]] |
| If the new response's status code is 206 (partial content), both the |  | If the new response's status code is 206 (partial content), both the |
| stored and new responses MUST have validators, and those validators |  | stored and new responses MUST have validators, and those validators |
| MUST match using the strong comparison function (see Section 4 of |  | MUST match using the strong comparison function (see Section 4 of |
| [Part4]). Otherwise, the responses MUST NOT be combined. |  | [Part4]). Otherwise, the responses MUST NOT be combined. |
| The stored response headers are used as those of the updated |  | The stored response header fields are used as those of the updated |
| response, except that |  | response, except that |
| o any stored Warning headers with warn-code 1xx (see Section 3.6) |  | o any stored Warning header fields with warn-code 1xx (see |
| MUST be deleted. |  | Section 3.6) MUST be deleted. |
| o any stored Warning headers with warn-code 2xx MUST be retained. |  | o any stored Warning header fields with warn-code 2xx MUST be |
|  |  | retained. |
| o any other headers provided in the new response MUST replace all |  | o any other header fields provided in the new response MUST replace |
| instances of the corresponding headers from the stored response. |  | all instances of the corresponding header fields from the stored |
|  |  | response. |
| The updated response headers MUST be used to replace those of the |  | The updated response header fields MUST be used to replace those of |
| stored response in cache (unless the stored response is removed from |  | the stored response in cache (unless the stored response is removed |
| cache). In the case of a 206 response, the combined representation |  | from cache). In the case of a 206 response, the combined |
| MAY be stored. |  | representation MAY be stored. |
| 3. Header Field Definitions |  | 3. Header Field Definitions |
| This section defines the syntax and semantics of HTTP/1.1 header |  | This section defines the syntax and semantics of HTTP/1.1 header |
| fields related to caching. |  | fields related to caching. |
| 3.1. Age |  | 3.1. Age |
| The "Age" response-header field conveys the sender's estimate of the |  | The "Age" response-header field conveys the sender's estimate of the |
| amount of time since the response was generated or successfully |  | amount of time since the response was generated or successfully |
| skipping to change at page 17, line 51 |  | skipping to change at page 18, line 15 |
| Age = "Age" ":" OWS Age-v |  | Age = "Age" ":" OWS Age-v |
| Age-v = delta-seconds |  | Age-v = delta-seconds |
| Age field-values are non-negative integers, representing time in |  | Age field-values are non-negative integers, representing time in |
| seconds. |  | seconds. |
| delta-seconds = 1*DIGIT |  | delta-seconds = 1*DIGIT |
| If a cache receives a value larger than the largest positive integer |  | If a cache receives a value larger than the largest positive integer |
| it can represent, or if any of its age calculations overflows, it |  | it can represent, or if any of its age calculations overflows, it |
| MUST transmit an Age header with a field-value of 2147483648 (2^31). |  | MUST transmit an Age header field with a field-value of 2147483648 |
|  |  | (2^31). Caches SHOULD use an arithmetic type of at least 31 bits of |
| Caches SHOULD use an arithmetic type of at least 31 bits of range. |  | range. |
| The presence of an Age header field in a response implies that a |  | The presence of an Age header field in a response implies that a |
| response is not first-hand. However, the converse is not true, since |  | response is not first-hand. However, the converse is not true, since |
| HTTP/1.0 caches might not implement the Age header field. |  | HTTP/1.0 caches might not implement the Age header field. |
| 3.2. Cache-Control |  | 3.2. Cache-Control |
| The "Cache-Control" general-header field is used to specify |  | The "Cache-Control" general-header field is used to specify |
| directives for caches along the request/response chain. Such cache |  | directives for caches along the request/response chain. Such cache |
| directives are unidirectional in that the presence of a directive in |  | directives are unidirectional in that the presence of a directive in |
| skipping to change at page 20, line 9 |  | skipping to change at page 20, line 18 |
| The min-fresh request directive indicates that the client is |  | The min-fresh request directive indicates that the client is |
| willing to accept a response whose freshness lifetime is no less |  | willing to accept a response whose freshness lifetime is no less |
| than its current age plus the specified time in seconds. That is, |  | than its current age plus the specified time in seconds. That is, |
| the client wants a response that will still be fresh for at least |  | the client wants a response that will still be fresh for at least |
| the specified number of seconds. |  | the specified number of seconds. |
| no-transform |  | no-transform |
| The no-transform request directive indicates that an intermediate |  | The no-transform request directive indicates that an intermediate |
| cache or proxy MUST NOT change the Content-Encoding, Content-Range |  | cache or proxy MUST NOT change the Content-Encoding, Content-Range |
| or Content-Type request headers, nor the request representation. |  | or Content-Type request header fields, nor the request |
|  |  | representation. |
| only-if-cached |  | only-if-cached |
| The only-if-cached request directive indicates that the client |  | The only-if-cached request directive indicates that the client |
| only wishes to return a stored response. If it receives this |  | only wishes to return a stored response. If it receives this |
| directive, a cache SHOULD either respond using a stored response |  | directive, a cache SHOULD either respond using a stored response |
| that is consistent with the other constraints of the request, or |  | that is consistent with the other constraints of the request, or |
| respond with a 504 (Gateway Timeout) status code. If a group of |  | respond with a 504 (Gateway Timeout) status code. If a group of |
| caches is being operated as a unified system with good internal |  | caches is being operated as a unified system with good internal |
| connectivity, such a request MAY be forwarded within that group of |  | connectivity, such a request MAY be forwarded within that group of |
| skipping to change at page 20, line 41 |  | skipping to change at page 20, line 51 |
| / "proxy-revalidate" |  | / "proxy-revalidate" |
| / "max-age" "=" delta-seconds |  | / "max-age" "=" delta-seconds |
| / "s-maxage" "=" delta-seconds |  | / "s-maxage" "=" delta-seconds |
| / cache-extension |  | / cache-extension |
| public |  | public |
| The public response directive indicates that the response MAY be |  | The public response directive indicates that the response MAY be |
| cached, even if it would normally be non-cacheable or cacheable |  | cached, even if it would normally be non-cacheable or cacheable |
| only within a non-shared cache. (See also Authorization, Section |  | only within a non-shared cache. (See also Authorization, Section |
| 3.1 of [Part7], for additional details.) |  | 4.1 of [Part7], for additional details.) |
| private |  | private |
| The private response directive indicates that the response message |  | The private response directive indicates that the response message |
| is intended for a single user and MUST NOT be stored by a shared |  | is intended for a single user and MUST NOT be stored by a shared |
| cache. A private (non-shared) cache MAY store the response. |  | cache. A private (non-shared) cache MAY store the response. |
| If the private response directive specifies one or more field- |  | If the private response directive specifies one or more field- |
| names, this requirement is limited to the field-values associated |  | names, this requirement is limited to the field-values associated |
| with the listed response headers. That is, the specified field- |  | with the listed response header fields. That is, the specified |
| names(s) MUST NOT be stored by a shared cache, whereas the |  | field-names(s) MUST NOT be stored by a shared cache, whereas the |
| remainder of the response message MAY be. |  | remainder of the response message MAY be. |
| Note: This usage of the word private only controls where the |  | Note: This usage of the word private only controls where the |
| response can be stored; it cannot ensure the privacy of the |  | response can be stored; it cannot ensure the privacy of the |
| message content. Also, private response directives with field- |  | message content. Also, private response directives with field- |
| names are often handled by implementations as if an unqualified |  | names are often handled by implementations as if an unqualified |
| private directive was received; i.e., the special handling for the |  | private directive was received; i.e., the special handling for the |
| qualified form is not widely implemented. |  | qualified form is not widely implemented. |
| no-cache |  | no-cache |
| The no-cache response directive indicates that the response MUST |  | The no-cache response directive indicates that the response MUST |
| NOT be used to satisfy a subsequent request without successful |  | NOT be used to satisfy a subsequent request without successful |
| validation on the origin server. This allows an origin server to |  | validation on the origin server. This allows an origin server to |
| prevent a cache from using it to satisfy a request without |  | prevent a cache from using it to satisfy a request without |
| contacting it, even by caches that have been configured to return |  | contacting it, even by caches that have been configured to return |
| stale responses. |  | stale responses. |
| If the no-cache response directive specifies one or more field- |  | If the no-cache response directive specifies one or more field- |
| names, this requirement is limited to the field-values associated |  | names, this requirement is limited to the field-values associated |
| with the listed response headers. That is, the specified field- |  | with the listed response header fields. That is, the specified |
| name(s) MUST NOT be sent in the response to a subsequent request |  | field-name(s) MUST NOT be sent in the response to a subsequent |
| without successful validation on the origin server. This allows |  | request without successful validation on the origin server. This |
| an origin server to prevent the re-use of certain header fields in |  | allows an origin server to prevent the re-use of certain header |
| a response, while still allowing caching of the rest of the |  | fields in a response, while still allowing caching of the rest of |
| response. |  | the response. |
| Note: Most HTTP/1.0 caches will not recognize or obey this |  | Note: Most HTTP/1.0 caches will not recognize or obey this |
| directive. Also, no-cache response directives with field-names |  | directive. Also, no-cache response directives with field-names |
| are often handled by implementations as if an unqualified no-cache |  | are often handled by implementations as if an unqualified no-cache |
| directive was received; i.e., the special handling for the |  | directive was received; i.e., the special handling for the |
| qualified form is not widely implemented. |  | qualified form is not widely implemented. |
| no-store |  | no-store |
| The no-store response directive indicates that a cache MUST NOT |  | The no-store response directive indicates that a cache MUST NOT |
| skipping to change at page 22, line 39 |  | skipping to change at page 22, line 48 |
| The max-age response directive indicates that response is to be |  | The max-age response directive indicates that response is to be |
| considered stale after its age is greater than the specified |  | considered stale after its age is greater than the specified |
| number of seconds. |  | number of seconds. |
| s-maxage |  | s-maxage |
| The s-maxage response directive indicates that, in shared caches, |  | The s-maxage response directive indicates that, in shared caches, |
| the maximum age specified by this directive overrides the maximum |  | the maximum age specified by this directive overrides the maximum |
| age specified by either the max-age directive or the Expires |  | age specified by either the max-age directive or the Expires |
| header. The s-maxage directive also implies the semantics of the |  | header field. The s-maxage directive also implies the semantics |
| proxy-revalidate response directive. |  | of the proxy-revalidate response directive. |
| no-transform |  | no-transform |
| The no-transform response directive indicates that an intermediate |  | The no-transform response directive indicates that an intermediate |
| cache or proxy MUST NOT change the Content-Encoding, Content-Range |  | cache or proxy MUST NOT change the Content-Encoding, Content-Range |
| or Content-Type response headers, nor the response representation. |  | or Content-Type response header fields, nor the response |
|  |  | representation. |
| 3.2.3. Cache Control Extensions |  | 3.2.3. Cache Control Extensions |
| The Cache-Control header field can be extended through the use of one |  | The Cache-Control header field can be extended through the use of one |
| or more cache-extension tokens, each with an optional value. |  | or more cache-extension tokens, each with an optional value. |
| Informational extensions (those that do not require a change in cache |  | Informational extensions (those that do not require a change in cache |
| behavior) can be added without changing the semantics of other |  | behavior) can be added without changing the semantics of other |
| directives. Behavioral extensions are designed to work by acting as |  | directives. Behavioral extensions are designed to work by acting as |
| modifiers to the existing base of cache directives. Both the new |  | modifiers to the existing base of cache directives. Both the new |
| directive and the standard directive are supplied, such that |  | directive and the standard directive are supplied, such that |
| skipping to change at page 25, line 41 |  | skipping to change at page 26, line 6 |
| validation; see Section 2.7. |  | validation; see Section 2.7. |
| In uncacheable or stale responses, the Vary field value advises the |  | In uncacheable or stale responses, the Vary field value advises the |
| user agent about the criteria that were used to select the |  | user agent about the criteria that were used to select the |
| representation. |  | representation. |
| Vary = "Vary" ":" OWS Vary-v |  | Vary = "Vary" ":" OWS Vary-v |
| Vary-v = "*" / 1#field-name |  | Vary-v = "*" / 1#field-name |
| The set of header fields named by the Vary field value is known as |  | The set of header fields named by the Vary field value is known as |
| the selecting request-headers. |  | the selecting request-header fields. |
| Servers SHOULD include a Vary header field with any cacheable |  | Servers SHOULD include a Vary header field with any cacheable |
| response that is subject to server-driven negotiation. Doing so |  | response that is subject to server-driven negotiation. Doing so |
| allows a cache to properly interpret future requests on that resource |  | allows a cache to properly interpret future requests on that resource |
| and informs the user agent about the presence of negotiation on that |  | and informs the user agent about the presence of negotiation on that |
| resource. A server MAY include a Vary header field with a non- |  | resource. A server MAY include a Vary header field with a non- |
| cacheable response that is subject to server-driven negotiation, |  | cacheable response that is subject to server-driven negotiation, |
| since this might provide the user agent with useful information about |  | since this might provide the user agent with useful information about |
| the dimensions over which the response varies at the time of the |  | the dimensions over which the response varies at the time of the |
| response. |  | response. |
| A Vary field value of "*" signals that unspecified parameters not |  | A Vary field value of "*" signals that unspecified parameters not |
| limited to the request-headers (e.g., the network address of the |  | limited to the request-header fields (e.g., the network address of |
| client), play a role in the selection of the response representation; |  | the client), play a role in the selection of the response |
| therefore, a cache cannot determine whether this response is |  | representation; therefore, a cache cannot determine whether this |
| appropriate. The "*" value MUST NOT be generated by a proxy server. |  | response is appropriate. The "*" value MUST NOT be generated by a |
|  |  | proxy server. |
| The field-names given are not limited to the set of standard request- |  | The field-names given are not limited to the set of standard request- |
| header fields defined by this specification. Field names are case- |  | header fields defined by this specification. Field names are case- |
| insensitive. |  | insensitive. |
| 3.6. Warning |  | 3.6. Warning |
| The "Warning" general-header field is used to carry additional |  | The "Warning" general-header field is used to carry additional |
| information about the status or transformation of a message that |  | information about the status or transformation of a message that |
| might not be reflected in the message. This information is typically |  | might not be reflected in the message. This information is typically |
| used to warn about possible incorrectness introduced by caching |  | used to warn about possible incorrectness introduced by caching |
| operations or transformations applied to the payload of the message. |  | operations or transformations applied to the payload of the message. |
| Warnings can be used for other purposes, both cache-related and |  | Warnings can be used for other purposes, both cache-related and |
| otherwise. The use of a warning, rather than an error status code, |  | otherwise. The use of a warning, rather than an error status code, |
| distinguishes these responses from true failures. |  | distinguishes these responses from true failures. |
| Warning headers can in general be applied to any message, however |  | Warning header fields can in general be applied to any message, |
| some warn-codes are specific to caches and can only be applied to |  | however some warn-codes are specific to caches and can only be |
| response messages. |  | applied to response messages. |
| Warning = "Warning" ":" OWS Warning-v |  | Warning = "Warning" ":" OWS Warning-v |
| Warning-v = 1#warning-value |  | Warning-v = 1#warning-value |
| warning-value = warn-code SP warn-agent SP warn-text |  | warning-value = warn-code SP warn-agent SP warn-text |
| [SP warn-date] |  | [SP warn-date] |
| warn-code = 3DIGIT |  | warn-code = 3DIGIT |
| warn-agent = ( uri-host [ ":" port ] ) / pseudonym |  | warn-agent = ( uri-host [ ":" port ] ) / pseudonym |
| ; the name or pseudonym of the server adding |  | ; the name or pseudonym of the server adding |
| ; the Warning header, for use in debugging |  | ; the Warning header field, for use in debugging |
| warn-text = quoted-string |  | warn-text = quoted-string |
| warn-date = DQUOTE HTTP-date DQUOTE |  | warn-date = DQUOTE HTTP-date DQUOTE |
| Multiple warnings can be attached to a response (either by the origin |  | Multiple warnings can be attached to a response (either by the origin |
| server or by a cache), including multiple warnings with the same code |  | server or by a cache), including multiple warnings with the same code |
| number, only differing in warn-text. |  | number, only differing in warn-text. |
| When this occurs, the user agent SHOULD inform the user of as many of |  | When this occurs, the user agent SHOULD inform the user of as many of |
| them as possible, in the order that they appear in the response. |  | them as possible, in the order that they appear in the response. |
| Systems that generate multiple Warning headers SHOULD order them with |  | Systems that generate multiple Warning header fields SHOULD order |
| this user agent behavior in mind. New Warning headers SHOULD be |  | them with this user agent behavior in mind. New Warning header |
| added after any existing Warning headers. |  | fields SHOULD be added after any existing Warning headers fields. |
| Warnings are assigned three digit warn-codes. The first digit |  | Warnings are assigned three digit warn-codes. The first digit |
| indicates whether the Warning is required to be deleted from a stored |  | indicates whether the Warning is required to be deleted from a stored |
| response after validation: |  | response after validation: |
| o 1xx Warnings describe the freshness or validation status of the |  | o 1xx Warnings describe the freshness or validation status of the |
| response, and so MUST be deleted by caches after validation. They |  | response, and so MUST be deleted by caches after validation. They |
| can only be generated by a cache when validating a cached entry, |  | can only be generated by a cache when validating a cached entry, |
| and MUST NOT be generated in any other situation. |  | and MUST NOT be generated in any other situation. |
| o 2xx Warnings describe some aspect of the representation that is |  | o 2xx Warnings describe some aspect of the representation that is |
| not rectified by a validation (for example, a lossy compression of |  | not rectified by a validation (for example, a lossy compression of |
| the representation) and MUST NOT be deleted by caches after |  | the representation) and MUST NOT be deleted by caches after |
| validation, unless a full response is returned, in which case they |  | validation, unless a full response is returned, in which case they |
| MUST be. |  | MUST be. |
| If an implementation sends a message with one or more Warning headers |  | If an implementation sends a message with one or more Warning header |
| to a receiver whose version is HTTP/1.0 or lower, then the sender |  | fields to a receiver whose version is HTTP/1.0 or lower, then the |
| MUST include in each warning-value a warn-date that matches the Date |  | sender MUST include in each warning-value a warn-date that matches |
| header in the message. |  | the Date header field in the message. |
| If an implementation receives a message with a warning-value that |  | If an implementation receives a message with a warning-value that |
| includes a warn-date, and that warn-date is different from the Date |  | includes a warn-date, and that warn-date is different from the Date |
| value in the response, then that warning-value MUST be deleted from |  | value in the response, then that warning-value MUST be deleted from |
| the message before storing, forwarding, or using it. (preventing the |  | the message before storing, forwarding, or using it. (preventing the |
| consequences of naive caching of Warning header fields.) If all of |  | consequences of naive caching of Warning header fields.) If all of |
| the warning-values are deleted for this reason, the Warning header |  | the warning-values are deleted for this reason, the Warning header |
| MUST be deleted as well. |  | field MUST be deleted as well. |
| The following warn-codes are defined by this specification, each with |  | The following warn-codes are defined by this specification, each with |
| a recommended warn-text in English, and a description of its meaning. |  | a recommended warn-text in English, and a description of its meaning. |
| 110 Response is stale |  | 110 Response is stale |
| SHOULD be included whenever the returned response is stale. |  | SHOULD be included whenever the returned response is stale. |
| 111 Revalidation failed |  | 111 Revalidation failed |
| skipping to change at page 30, line 21 |  | skipping to change at page 30, line 48 |
| suggestions and comments from individuals including: Shel Kaphan, |  | suggestions and comments from individuals including: Shel Kaphan, |
| Paul Leach, Koen Holtman, David Morris, and Larry Masinter. |  | Paul Leach, Koen Holtman, David Morris, and Larry Masinter. |
| 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-11 |  | and Message Parsing", draft-ietf-httpbis-p1-messaging-12 |
| (work in progress), August 2010. |  | (work in progress), October 2010. |
| [Part2] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |  | [Part2] 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 2: Message |  | and J. Reschke, Ed., "HTTP/1.1, part 2: Message |
| Semantics", draft-ietf-httpbis-p2-semantics-11 (work in |  | Semantics", draft-ietf-httpbis-p2-semantics-12 (work in |
| progress), August 2010. |  | progress), October 2010. |
| [Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |  | [Part4] 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 4: Conditional |  | and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional |
| Requests", draft-ietf-httpbis-p4-conditional-11 (work in |  | Requests", draft-ietf-httpbis-p4-conditional-12 (work in |
| progress), August 2010. |  | progress), October 2010. |
| [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-11 (work |  | Partial Responses", draft-ietf-httpbis-p5-range-12 (work |
| in progress), August 2010. |  | in progress), October 2010. |
| [Part7] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., |  | [Part7] 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 7: Authentication", |  | and J. Reschke, Ed., "HTTP/1.1, part 7: Authentication", |
| draft-ietf-httpbis-p7-auth-11 (work in progress), |  | draft-ietf-httpbis-p7-auth-12 (work in progress), |
| August 2010. |  | October 2010. |
| [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 |
| [RFC1305] Mills, D., "Network Time Protocol (Version 3) |  | [RFC1305] Mills, D., "Network Time Protocol (Version 3) |
| skipping to change at page 31, line 39 |  | skipping to change at page 32, line 18 |
| (Section 2.3.2) |  | (Section 2.3.2) |
| Remove requirement to consider Content-Location in successful |  | Remove requirement to consider Content-Location in successful |
| responses in order to determine the appropriate response to use. |  | responses in order to determine the appropriate response to use. |
| (Section 2.4) |  | (Section 2.4) |
| Clarify denial of service attack avoidance requirement. |  | Clarify denial of service attack avoidance requirement. |
| (Section 2.5) |  | (Section 2.5) |
| Do not mention RFC 2047 encoding and multiple languages in Warning |  | Do not mention RFC 2047 encoding and multiple languages in Warning |
| headers anymore, as these aspects never were implemented. |  | header fields anymore, as these aspects never were implemented. |
| (Section 3.6) |  | (Section 3.6) |
| Appendix B. Collected ABNF |  | Appendix B. Collected ABNF |
| Age = "Age:" OWS Age-v |  | Age = "Age:" OWS Age-v |
| Age-v = delta-seconds |  | Age-v = delta-seconds |
| Cache-Control = "Cache-Control:" OWS Cache-Control-v |  | Cache-Control = "Cache-Control:" OWS Cache-Control-v |
| Cache-Control-v = *( "," OWS ) cache-directive *( OWS "," [ OWS |  | Cache-Control-v = *( "," OWS ) cache-directive *( OWS "," [ OWS |
| cache-directive ] ) |  | cache-directive ] ) |
| skipping to change at page 33, line 20 |  | skipping to change at page 34, line 4 |
| ABNF diagnostics: |  | ABNF diagnostics: |
| ; Age defined but not used |  | ; Age defined but not used |
| ; Cache-Control defined but not used |  | ; Cache-Control defined but not used |
| ; Expires defined but not used |  | ; Expires defined but not used |
| ; Pragma defined but not used |  | ; Pragma defined but not used |
| ; Vary defined but not used |  | ; Vary defined but not used |
| ; Warning defined but not used |  | ; Warning defined but not used |
| Appendix C. Change Log (to be removed by RFC Editor before publication) |  | Appendix C. Change Log (to be removed by RFC Editor before publication) |
|  |  | C.1. Since RFC 2616 |
| C.1. Since RFC2616 |  |  |
| Extracted relevant partitions from [RFC2616]. |  | Extracted relevant partitions from [RFC2616]. |
| C.2. Since draft-ietf-httpbis-p6-cache-00 |  | C.2. Since draft-ietf-httpbis-p6-cache-00 |
| Closed issues: |  | Closed issues: |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/9>: "Trailer" |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/9>: "Trailer" |
| (<http://purl.org/NET/http-errata#trailer-hop>) |  | (<http://purl.org/NET/http-errata#trailer-hop>) |
| skipping to change at page 34, line 33 |  | skipping to change at page 35, line 15 |
| Other changes: |  | Other changes: |
| o Get rid of duplicate BNF rule names ("host" -> "uri-host") (work |  | o Get rid of duplicate BNF rule names ("host" -> "uri-host") (work |
| in progress on <http://tools.ietf.org/wg/httpbis/trac/ticket/36>) |  | in progress on <http://tools.ietf.org/wg/httpbis/trac/ticket/36>) |
| o Add explicit references to BNF syntax and rules imported from |  | o Add explicit references to BNF syntax and rules imported from |
| other parts of the specification. |  | other parts of the specification. |
| C.4. Since draft-ietf-httpbis-p6-cache-02 |  | C.4. Since draft-ietf-httpbis-p6-cache-02 |
| Ongoing work on IANA Message Header Registration |  | Ongoing work on IANA Message Header Field Registration |
| (<http://tools.ietf.org/wg/httpbis/trac/ticket/40>): |  | (<http://tools.ietf.org/wg/httpbis/trac/ticket/40>): |
| o Reference RFC 3984, and update header registrations for headers |  | o Reference RFC 3984, and update header field registrations for |
| defined in this document. |  | header fields defined in this document. |
| C.5. Since draft-ietf-httpbis-p6-cache-03 |  | C.5. Since draft-ietf-httpbis-p6-cache-03 |
| Closed issues: |  | Closed issues: |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/106>: "Vary header |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/106>: "Vary header |
| classification" |  | classification" |
| C.6. Since draft-ietf-httpbis-p6-cache-04 |  | C.6. Since draft-ietf-httpbis-p6-cache-04 |
| Ongoing work on ABNF conversion |  | Ongoing work on ABNF conversion |
| (<http://tools.ietf.org/wg/httpbis/trac/ticket/36>): |  | (<http://tools.ietf.org/wg/httpbis/trac/ticket/36>): |
| o Use "/" instead of "|" for alternatives. |  | o Use "/" instead of "|" for alternatives. |
| o Introduce new ABNF rules for "bad" whitespace ("BWS"), optional |  | o Introduce new ABNF rules for "bad" whitespace ("BWS"), optional |
| whitespace ("OWS") and required whitespace ("RWS"). |  | whitespace ("OWS") and required whitespace ("RWS"). |
| o Rewrite ABNFs to spell out whitespace rules, factor out header |  | o Rewrite ABNFs to spell out whitespace rules, factor out header |
| value format definitions. |  | field value format definitions. |
| C.7. Since draft-ietf-httpbis-p6-cache-05 |  | C.7. Since draft-ietf-httpbis-p6-cache-05 |
| This is a total rewrite of this part of the specification. |  | This is a total rewrite of this part of the specification. |
| Affected issues: |  | Affected issues: |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/54>: "Definition of |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/54>: "Definition of |
| 1xx Warn-Codes" |  | 1xx Warn-Codes" |
| skipping to change at page 35, line 44 |  | skipping to change at page 36, line 26 |
| C.8. Since draft-ietf-httpbis-p6-cache-06 |  | C.8. Since draft-ietf-httpbis-p6-cache-06 |
| Closed issues: |  | Closed issues: |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/161>: "base for |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/161>: "base for |
| numeric protocol elements" |  | numeric protocol elements" |
| Affected issues: |  | Affected issues: |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/37>: Vary and non- |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/37>: WVary and non- |
| existant headers |  | existant headers" |
| C.9. Since draft-ietf-httpbis-p6-cache-07 |  | C.9. Since draft-ietf-httpbis-p6-cache-07 |
| Closed issues: |  | Closed issues: |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/54>: "Definition of |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/54>: "Definition of |
| 1xx Warn-Codes" |  | 1xx Warn-Codes" |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/167>: "Content- |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/167>: "Content- |
| Location on 304 responses" |  | Location on 304 responses" |
| skipping to change at page 37, line 28 |  | skipping to change at page 38, line 13 |
| removing the 'changes from 2068' sections" |  | removing the 'changes from 2068' sections" |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/223>: "Allowing |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/223>: "Allowing |
| heuristic caching for new status codes" |  | heuristic caching for new status codes" |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/223>: "Allowing |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/223>: "Allowing |
| heuristic caching for new status codes" |  | heuristic caching for new status codes" |
| o Clean up TODOs and prose in "Combining Responses." |  | o Clean up TODOs and prose in "Combining Responses." |
|  |  | C.13. Since draft-ietf-httpbis-p6-cache-11 |
|  |  | Closed issues: |
|  |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/204>: "Text about |
|  |  | clock requirement for caches belongs in p6" |
| Index |  | Index |
| A |  | A |
| age 6 |  | age 6 |
| Age header 17 |  | Age header 17 |
| C |  | C |
| cache 5 |  | cache 5 |
| Cache Directives |  | Cache Directives |
| max-age 19, 22 |  | max-age 19, 22 |
| max-stale 19 |  | max-stale 19 |
| min-fresh 19 |  | min-fresh 20 |
| must-revalidate 22 |  | must-revalidate 22 |
| no-cache 19, 21 |  | no-cache 19, 21 |
| no-store 19, 21 |  | no-store 19, 21 |
| no-transform 20, 22 |  | no-transform 20, 23 |
| only-if-cached 20 |  | only-if-cached 20 |
| private 20 |  | private 21 |
| proxy-revalidate 22 |  | proxy-revalidate 22 |
| public 20 |  | public 20 |
| s-maxage 22 |  | s-maxage 22 |
| Cache-Control header 18 |  | Cache-Control header 18 |
| cacheable 5 |  | cacheable 5 |
| E |  | E |
| Expires header 24 |  | Expires header 24 |
| explicit expiration time 5 |  | explicit expiration time 5 |
| F |  | F |
| first-hand 6 |  | first-hand 6 |
| fresh 6 |  | fresh 6 |
| freshness lifetime 6 |  | freshness lifetime 6 |
| G |  | G |
| Grammar |  | Grammar |
| Age 17 |  | Age 18 |
| Age-v 17 |  | Age-v 18 |
| Cache-Control 18 |  | Cache-Control 18 |
| Cache-Control-v 18 |  | Cache-Control-v 18 |
| cache-extension 18 |  | cache-extension 18 |
| cache-request-directive 18 |  | cache-request-directive 19 |
| cache-response-directive 20 |  | cache-response-directive 20 |
| delta-seconds 17 |  | delta-seconds 18 |
| Expires 24 |  | Expires 24 |
| Expires-v 24 |  | Expires-v 24 |
| extension-pragma 24 |  | extension-pragma 25 |
| Pragma 24 |  | Pragma 25 |
| pragma-directive 24 |  | pragma-directive 25 |
| Pragma-v 24 |  | Pragma-v 25 |
| Vary 25 |  | Vary 25 |
| Vary-v 25 |  | Vary-v 25 |
| warn-agent 26 |  | warn-agent 27 |
| warn-code 26 |  | warn-code 27 |
| warn-date 26 |  | warn-date 27 |
| warn-text 26 |  | warn-text 27 |
| Warning 26 |  | Warning 27 |
| Warning-v 26 |  | Warning-v 27 |
| warning-value 26 |  | warning-value 27 |
| H |  | H |
| Headers |  | Headers |
| Age 17 |  | Age 17 |
| Cache-Control 18 |  | Cache-Control 18 |
| Expires 24 |  | Expires 24 |
| Pragma 24 |  | Pragma 25 |
| Vary 25 |  | Vary 25 |
| Warning 26 |  | Warning 26 |
| heuristic expiration time 5 |  | heuristic expiration time 5 |
| M |  | M |
| max-age |  | max-age |
| Cache Directive 19, 22 |  | Cache Directive 19, 22 |
| max-stale |  | max-stale |
| Cache Directive 19 |  | Cache Directive 19 |
| min-fresh |  | min-fresh |
| Cache Directive 19 |  | Cache Directive 20 |
| must-revalidate |  | must-revalidate |
| Cache Directive 22 |  | Cache Directive 22 |
| N |  | N |
| no-cache |  | no-cache |
| Cache Directive 19, 21 |  | Cache Directive 19, 21 |
| no-store |  | no-store |
| Cache Directive 19, 21 |  | Cache Directive 19, 21 |
| no-transform |  | no-transform |
| Cache Directive 20, 22 |  | Cache Directive 20, 23 |
| O |  | O |
| only-if-cached |  | only-if-cached |
| Cache Directive 20 |  | Cache Directive 20 |
| P |  | P |
| Pragma header 24 |  | Pragma header 25 |
| private |  | private |
| Cache Directive 20 |  | Cache Directive 21 |
| proxy-revalidate |  | proxy-revalidate |
| Cache Directive 22 |  | Cache Directive 22 |
| public |  | public |
| Cache Directive 20 |  | Cache Directive 20 |
| S |  | S |
| s-maxage |  | s-maxage |
| Cache Directive 22 |  | Cache Directive 22 |
| stale 6 |  | stale 6 |
End of changes. 91 change blocks.
| 187 lines changed or deleted |  | 208 lines changed or added |
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