| draft-ietf-httpbis-p6-cache-17.txt |  | draft-ietf-httpbis-p6-cache-18.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: May 3, 2012 J. Mogul |  | Expires: July 7, 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 |
| M. Nottingham, Ed. |  | M. Nottingham, Ed. |
| Rackspace |  | Rackspace |
| J. Reschke, Ed. |  | J. Reschke, Ed. |
| greenbytes |  | greenbytes |
| October 31, 2011 |  | January 4, 2012 |
| HTTP/1.1, part 6: Caching |  | HTTP/1.1, part 6: Caching |
| draft-ietf-httpbis-p6-cache-17 |  | draft-ietf-httpbis-p6-cache-18 |
| 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 6 of the |  | information initiative since 1990. This document is Part 6 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 2, line 6 |  | skipping to change at page 2, line 6 |
| 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.18. |  | The changes in this draft are summarized in Appendix C.19. |
| 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 May 3, 2012. |  | This Internet-Draft will expire on July 7, 2012. |
| Copyright Notice |  | Copyright Notice |
| Copyright (c) 2011 IETF Trust and the persons identified as the |  | Copyright (c) 2012 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 |
| carefully, as they describe your rights and restrictions with respect |  | carefully, as they describe your rights and restrictions with respect |
| to this document. Code Components extracted from this document must |  | to this document. Code Components extracted from this document must |
| include Simplified BSD License text as described in Section 4.e of |  | include Simplified BSD License text as described in Section 4.e of |
| the Trust Legal Provisions and are provided without warranty as |  | the Trust Legal Provisions and are provided without warranty as |
| skipping to change at page 3, line 19 |  | skipping to change at page 3, line 19 |
| 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 |  | 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 |
| 1.3. Conformance and Error Handling . . . . . . . . . . . . . . 7 |  | 1.3. Conformance and Error Handling . . . . . . . . . . . . . . 7 |
| 1.4. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7 |  | 1.4. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7 |
| 1.4.1. Core Rules . . . . . . . . . . . . . . . . . . . . . . 8 |  | 1.4.1. Core Rules . . . . . . . . . . . . . . . . . . . . . . 8 |
| 1.4.2. ABNF Rules defined in other Parts of the |  | 1.4.2. ABNF Rules defined in other Parts of the |
| Specification . . . . . . . . . . . . . . . . . . . . 8 |  | Specification . . . . . . . . . . . . . . . . . . . . 8 |
| 1.5. Delta Seconds . . . . . . . . . . . . . . . . . . . . . . 8 |  | 1.5. Delta Seconds . . . . . . . . . . . . . . . . . . . . . . 8 |
| 2. Cache Operation . . . . . . . . . . . . . . . . . . . . . . . 8 |  | 2. Cache Operation . . . . . . . . . . . . . . . . . . . . . . . 8 |
| 2.1. Response Cacheability . . . . . . . . . . . . . . . . . . 9 |  | 2.1. Response Cacheability . . . . . . . . . . . . . . . . . . 9 |
| 2.2. Constructing Responses from Caches . . . . . . . . . . . . 10 |  | 2.2. Constructing Responses from Caches . . . . . . . . . . . . 10 |
| 2.3. Freshness Model . . . . . . . . . . . . . . . . . . . . . 11 |  | 2.3. Freshness Model . . . . . . . . . . . . . . . . . . . . . 12 |
| 2.3.1. Calculating Freshness Lifetime . . . . . . . . . . . . 12 |  | 2.3.1. Calculating Freshness Lifetime . . . . . . . . . . . . 13 |
| 2.3.2. Calculating Age . . . . . . . . . . . . . . . . . . . 13 |  | 2.3.2. Calculating Age . . . . . . . . . . . . . . . . . . . 14 |
| 2.3.3. Serving Stale Responses . . . . . . . . . . . . . . . 15 |  | 2.3.3. Serving Stale Responses . . . . . . . . . . . . . . . 16 |
| 2.4. Validation Model . . . . . . . . . . . . . . . . . . . . . 16 |  | 2.4. Validation Model . . . . . . . . . . . . . . . . . . . . . 16 |
| 2.4.1. Freshening Responses . . . . . . . . . . . . . . . . . 17 |  | 2.4.1. Freshening Responses . . . . . . . . . . . . . . . . . 17 |
| 2.5. Request Methods that Invalidate . . . . . . . . . . . . . 18 |  | 2.5. Request Methods that Invalidate . . . . . . . . . . . . . 18 |
| 2.6. Shared Caching of Authenticated Responses . . . . . . . . 18 |  | 2.6. Shared Caching of Authenticated Responses . . . . . . . . 18 |
| 2.7. Caching Negotiated Responses . . . . . . . . . . . . . . . 19 |  | 2.7. Caching Negotiated Responses . . . . . . . . . . . . . . . 19 |
| 2.8. Combining Partial Content . . . . . . . . . . . . . . . . 20 |  | 2.8. Combining Partial Content . . . . . . . . . . . . . . . . 20 |
| 3. Header Field Definitions . . . . . . . . . . . . . . . . . . . 20 |  | 3. Header Field Definitions . . . . . . . . . . . . . . . . . . . 20 |
| 3.1. Age . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 |  | 3.1. Age . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 |
| 3.2. Cache-Control . . . . . . . . . . . . . . . . . . . . . . 21 |  | 3.2. Cache-Control . . . . . . . . . . . . . . . . . . . . . . 21 |
| 3.2.1. Request Cache-Control Directives . . . . . . . . . . . 21 |  | 3.2.1. Request Cache-Control Directives . . . . . . . . . . . 21 |
| 3.2.2. Response Cache-Control Directives . . . . . . . . . . 23 |  | 3.2.2. Response Cache-Control Directives . . . . . . . . . . 23 |
| 3.2.3. Cache Control Extensions . . . . . . . . . . . . . . . 26 |  | 3.2.3. Cache Control Extensions . . . . . . . . . . . . . . . 26 |
| 3.3. Expires . . . . . . . . . . . . . . . . . . . . . . . . . 27 |  | 3.3. Expires . . . . . . . . . . . . . . . . . . . . . . . . . 27 |
| 3.4. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . . 28 |  | 3.4. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . . 28 |
| 3.5. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 |  | 3.5. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 |
| 3.6. Warning . . . . . . . . . . . . . . . . . . . . . . . . . 29 |  | 3.6. Warning . . . . . . . . . . . . . . . . . . . . . . . . . 29 |
| 4. History Lists . . . . . . . . . . . . . . . . . . . . . . . . 32 |  | 3.6.1. 110 Response is Stale . . . . . . . . . . . . . . . . 31 |
| 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 |  | 3.6.2. 111 Revalidation Failed . . . . . . . . . . . . . . . 31 |
| 5.1. Cache Directive Registry . . . . . . . . . . . . . . . . . 32 |  | 3.6.3. 112 Disconnected Operation . . . . . . . . . . . . . . 31 |
| 5.2. Header Field Registration . . . . . . . . . . . . . . . . 33 |  | 3.6.4. 113 Heuristic Expiration . . . . . . . . . . . . . . . 31 |
| 6. Security Considerations . . . . . . . . . . . . . . . . . . . 33 |  | 3.6.5. 199 Miscellaneous Warning . . . . . . . . . . . . . . 31 |
| 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 33 |  | 3.6.6. 214 Transformation Applied . . . . . . . . . . . . . . 31 |
| 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 33 |  | 3.6.7. 299 Miscellaneous Persistent Warning . . . . . . . . . 31 |
| 8.1. Normative References . . . . . . . . . . . . . . . . . . . 33 |  | 3.6.8. Warn Code Extensions . . . . . . . . . . . . . . . . . 32 |
| 8.2. Informative References . . . . . . . . . . . . . . . . . . 34 |  | 3.7. History Lists . . . . . . . . . . . . . . . . . . . . . . 32 |
|  |  | 3.8. IANA Considerations . . . . . . . . . . . . . . . . . . . 32 |
|  |  | 3.8.1. Cache Directive Registry . . . . . . . . . . . . . . . 32 |
|  |  | 3.8.2. Warn Code Registry . . . . . . . . . . . . . . . . . . 33 |
|  |  | 3.9. Header Field Registration . . . . . . . . . . . . . . . . 33 |
|  |  | 4. Security Considerations . . . . . . . . . . . . . . . . . . . 34 |
|  |  | 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 34 |
|  |  | 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 34 |
|  |  | 6.1. Normative References . . . . . . . . . . . . . . . . . . . 34 |
|  |  | 6.2. Informative References . . . . . . . . . . . . . . . . . . 35 |
| Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 35 |  | Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 35 |
| Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 35 |  | Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 36 |
| Appendix C. Change Log (to be removed by RFC Editor before |  | Appendix C. Change Log (to be removed by RFC Editor before |
| publication) . . . . . . . . . . . . . . . . . . . . 36 |  | publication) . . . . . . . . . . . . . . . . . . . . 37 |
| C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 36 |  | C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 37 |
| C.2. Since draft-ietf-httpbis-p6-cache-00 . . . . . . . . . . . 37 |  | C.2. Since draft-ietf-httpbis-p6-cache-00 . . . . . . . . . . . 37 |
| C.3. Since draft-ietf-httpbis-p6-cache-01 . . . . . . . . . . . 37 |  | C.3. Since draft-ietf-httpbis-p6-cache-01 . . . . . . . . . . . 38 |
| C.4. Since draft-ietf-httpbis-p6-cache-02 . . . . . . . . . . . 38 |  | C.4. Since draft-ietf-httpbis-p6-cache-02 . . . . . . . . . . . 38 |
| C.5. Since draft-ietf-httpbis-p6-cache-03 . . . . . . . . . . . 38 |  | C.5. Since draft-ietf-httpbis-p6-cache-03 . . . . . . . . . . . 39 |
| C.6. Since draft-ietf-httpbis-p6-cache-04 . . . . . . . . . . . 38 |  | C.6. Since draft-ietf-httpbis-p6-cache-04 . . . . . . . . . . . 39 |
| C.7. Since draft-ietf-httpbis-p6-cache-05 . . . . . . . . . . . 38 |  | C.7. Since draft-ietf-httpbis-p6-cache-05 . . . . . . . . . . . 39 |
| C.8. Since draft-ietf-httpbis-p6-cache-06 . . . . . . . . . . . 39 |  | C.8. Since draft-ietf-httpbis-p6-cache-06 . . . . . . . . . . . 40 |
| C.9. Since draft-ietf-httpbis-p6-cache-07 . . . . . . . . . . . 39 |  | C.9. Since draft-ietf-httpbis-p6-cache-07 . . . . . . . . . . . 40 |
| C.10. Since draft-ietf-httpbis-p6-cache-08 . . . . . . . . . . . 39 |  | C.10. Since draft-ietf-httpbis-p6-cache-08 . . . . . . . . . . . 40 |
| C.11. Since draft-ietf-httpbis-p6-cache-09 . . . . . . . . . . . 40 |  | C.11. Since draft-ietf-httpbis-p6-cache-09 . . . . . . . . . . . 41 |
| C.12. Since draft-ietf-httpbis-p6-cache-10 . . . . . . . . . . . 40 |  | C.12. Since draft-ietf-httpbis-p6-cache-10 . . . . . . . . . . . 41 |
| C.13. Since draft-ietf-httpbis-p6-cache-11 . . . . . . . . . . . 41 |  | C.13. Since draft-ietf-httpbis-p6-cache-11 . . . . . . . . . . . 41 |
| C.14. Since draft-ietf-httpbis-p6-cache-12 . . . . . . . . . . . 41 |  | C.14. Since draft-ietf-httpbis-p6-cache-12 . . . . . . . . . . . 42 |
| C.15. Since draft-ietf-httpbis-p6-cache-13 . . . . . . . . . . . 41 |  | C.15. Since draft-ietf-httpbis-p6-cache-13 . . . . . . . . . . . 42 |
| C.16. Since draft-ietf-httpbis-p6-cache-14 . . . . . . . . . . . 41 |  | C.16. Since draft-ietf-httpbis-p6-cache-14 . . . . . . . . . . . 42 |
| C.17. Since draft-ietf-httpbis-p6-cache-15 . . . . . . . . . . . 42 |  | C.17. Since draft-ietf-httpbis-p6-cache-15 . . . . . . . . . . . 42 |
| C.18. Since draft-ietf-httpbis-p6-cache-16 . . . . . . . . . . . 42 |  | C.18. Since draft-ietf-httpbis-p6-cache-16 . . . . . . . . . . . 43 |
| Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 |  | C.19. Since draft-ietf-httpbis-p6-cache-17 . . . . . . . . . . . 43 |
|  |  | Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 |
| 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 11, line 11 |  | skipping to change at page 11, line 11 |
| 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 header fields nominated by the stored response (if any) |  | o selecting header fields nominated by the stored response (if any) |
| match those presented (see Section 2.7), and |  | match those presented (see Section 2.7), and |
| o the presented request and stored response are free from directives |  | o the presented request does not contain the no-cache pragma |
| that would prevent its use (see Section 3.2 and Section 3.4), and |  | (Section 3.4), nor the no-cache cache directive (Section 3.2.1), |
|  |  | unless the stored response is successfully validated |
|  |  | (Section 2.4), and |
|  |  | o the stored response does not contain the no-cache cache directive |
|  |  | (Section 3.2.2), unless it is successfully validated |
|  |  | (Section 2.4), 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 |
| * successfully validated (see Section 2.4). |  | * successfully validated (see Section 2.4). |
| Note that any of the requirements listed above can be overridden by a |  | Note that any of the requirements listed above can be overridden by a |
| skipping to change at page 12, line 34 |  | skipping to change at page 12, line 40 |
| expiration time. This specification does not provide specific |  | expiration time. This specification does not provide specific |
| algorithms, but does impose worst-case constraints on their results. |  | 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 can influence freshness calculation -- either |
| They can do this using several request cache directives, with the |  | constraining it relaxing it -- by using the max-age and min-fresh |
| effect of either increasing or loosening constraints on freshness. |  | request cache directives. See Section 3.2.1 for details. |
| See Section 3.2.1. |  |  |
| Note that freshness applies only to cache operation; it cannot be |  | Note that freshness applies only to cache operation; it cannot be |
| used to force a user agent to refresh its display or reload a |  | used to force a user agent to refresh its display or reload a |
| resource. See Section 4 for an explanation of the difference between |  | resource. See Section 3.7 for an explanation of the difference |
| caches and history mechanisms. |  | between caches and history mechanisms. |
| 2.3.1. Calculating Freshness Lifetime |  | 2.3.1. Calculating Freshness Lifetime |
| 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 |
| skipping to change at page 15, line 10 |  | skipping to change at page 15, line 20 |
| 2. the "corrected_age_value", if all of the caches along the |  | 2. the "corrected_age_value", if all of the caches along the |
| response path implement HTTP/1.1. A cache MUST interpret this |  | response path implement HTTP/1.1. A cache MUST interpret this |
| value relative to the time the request was initiated, not the |  | value relative to the time the request was initiated, not the |
| time that the response was received. |  | time that the response was received. |
| apparent_age = max(0, response_time - date_value); |  | apparent_age = max(0, response_time - date_value); |
| response_delay = response_time - request_time; |  | response_delay = response_time - request_time; |
| corrected_age_value = age_value + response_delay; |  | corrected_age_value = age_value + response_delay; |
| These are combined as |  | These SHOULD be combined as |
| corrected_initial_age = max(apparent_age, corrected_age_value); |  | corrected_initial_age = max(apparent_age, corrected_age_value); |
|  |  | unless the cache is confident in the value of the Age header (e.g., |
|  |  | because there are no HTTP/1.0 hops in the Via header), in which case |
|  |  | the corrected_age_value MAY be used as the corrected_initial_age. |
| The current_age of a stored response can then be calculated by adding |  | The current_age of a stored response can then be calculated by adding |
| the amount of time (in seconds) since the stored response was last |  | the amount of time (in seconds) since the stored response was last |
| validated by the origin server to the corrected_initial_age. |  | validated by the origin server to the corrected_initial_age. |
| resident_time = now - response_time; |  | resident_time = now - response_time; |
| current_age = corrected_initial_age + resident_time; |  | current_age = corrected_initial_age + resident_time; |
| Additionally, to avoid common problems in date parsing: |  | Additionally, to avoid common problems in date parsing: |
| o HTTP/1.1 clients and caches SHOULD assume that an RFC-850 date |  | o HTTP/1.1 clients and caches SHOULD assume that an RFC-850 date |
| skipping to change at page 31, line 12 |  | skipping to change at page 31, line 12 |
| warn-date, and that warn-date is different from the Date value in the |  | warn-date, and that warn-date is different from the Date value in the |
| response, then that warning-value MUST be deleted from the message |  | response, then that warning-value MUST be deleted from the message |
| before storing, forwarding, or using it. (preventing the consequences |  | before storing, forwarding, or using it. (preventing the consequences |
| of naive caching of Warning header fields.) If all of the warning- |  | of naive caching of Warning header fields.) If all of the warning- |
| values are deleted for this reason, the Warning header field MUST be |  | values are deleted for this reason, the Warning header field MUST be |
| deleted as well. |  | 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 |  | 3.6.1. 110 Response is Stale |
| A cache SHOULD include this whenever the returned response is |  | A cache SHOULD include this whenever the returned response is stale. |
| stale. |  |  |
| 111 Revalidation failed |  | 3.6.2. 111 Revalidation Failed |
| A cache SHOULD include this when returning a stale response |  | A cache SHOULD include this when returning a stale response because |
| because an attempt to validate the response failed, due to an |  | an attempt to validate the response failed, due to an inability to |
| inability to reach the server. |  | reach the server. |
| 112 Disconnected operation |  | 3.6.3. 112 Disconnected Operation |
| A cache SHOULD include this if it is intentionally disconnected |  | A cache SHOULD include this if it is intentionally disconnected from |
| from the rest of the network for a period of time. |  | the rest of the network for a period of time. |
| 113 Heuristic expiration |  | 3.6.4. 113 Heuristic Expiration |
| A cache SHOULD include this if it heuristically chose a freshness |  | A cache SHOULD include this if it heuristically chose a freshness |
| lifetime greater than 24 hours and the response's age is greater |  | lifetime greater than 24 hours and the response's age is greater than |
| than 24 hours. |  | 24 hours. |
| 199 Miscellaneous warning |  | 3.6.5. 199 Miscellaneous Warning |
| The warning text can include arbitrary information to be presented |  | The warning text can include arbitrary information to be presented to |
| to a human user, or logged. A system receiving this warning MUST |  | a human user, or logged. A system receiving this warning MUST NOT |
| NOT take any automated action, besides presenting the warning to |  | take any automated action, besides presenting the warning to the |
| the user. |  | user. |
| 214 Transformation applied |  | 3.6.6. 214 Transformation Applied |
| MUST be added by a proxy if it applies any transformation to the |  | MUST be added by a proxy if it applies any transformation to the |
| representation, such as changing the content-coding, media-type, |  | representation, such as changing the content-coding, media-type, or |
| or modifying the representation data, unless this Warning code |  | modifying the representation data, unless this Warning code already |
| already appears in the response. |  | appears in the response. |
| 299 Miscellaneous persistent warning |  | 3.6.7. 299 Miscellaneous Persistent Warning |
| The warning text can include arbitrary information to be presented |  | The warning text can include arbitrary information to be presented to |
| to a human user, or logged. A system receiving this warning MUST |  | a human user, or logged. A system receiving this warning MUST NOT |
| NOT take any automated action. |  | take any automated action. |
| 4. History Lists |  | 3.6.8. Warn Code Extensions |
|  |  | The HTTP Warn Code Registry defines the name space for warn codes. |
|  |  | A registration MUST include the following fields: |
|  |  | o Warn Code (3 digits) |
|  |  | o Short Description |
|  |  | o Pointer to specification text |
|  |  | Values to be added to this name space are subject to IETF review |
|  |  | ([RFC5226], Section 4.1). |
|  |  | The registry itself is maintained at |
|  |  | <http://www.iana.org/assignments/http-warn-codes>. |
|  |  | 3.7. History Lists |
| User agents often have history mechanisms, such as "Back" buttons and |  | User agents often have history mechanisms, such as "Back" buttons and |
| history lists, that can be used to redisplay a representation |  | history lists, that can be used to redisplay a representation |
| retrieved earlier in a session. |  | retrieved earlier in a session. |
| The freshness model (Section 2.3) does not necessarily apply to |  | The freshness model (Section 2.3) does not necessarily apply to |
| history mechanisms. I.e., a history mechanism can display a previous |  | history mechanisms. I.e., a history mechanism can display a previous |
| representation even if it has expired. |  | representation even if it has expired. |
| This does not prohibit the history mechanism from telling the user |  | This does not prohibit the history mechanism from telling the user |
| that a view might be stale, or from honoring cache directives (e.g., |  | that a view might be stale, or from honoring cache directives (e.g., |
| Cache-Control: no-store). |  | Cache-Control: no-store). |
| 5. IANA Considerations |  | 3.8. IANA Considerations |
| 5.1. Cache Directive Registry |  | 3.8.1. Cache Directive Registry |
| The registration procedure for HTTP Cache Directives is defined by |  | The registration procedure for HTTP Cache Directives is defined by |
| Section 3.2.3 of this document. |  | Section 3.2.3 of this document. |
| The HTTP Cache Directive Registry shall be created at |  | The HTTP Cache Directive Registry shall be created at |
| <http://www.iana.org/assignments/http-cache-directives> and be |  | <http://www.iana.org/assignments/http-cache-directives> and be |
| populated with the registrations below: |  | populated with the registrations below: |
| +------------------------+------------------------------+ |  | +------------------------+------------------------------+ |
| | Cache Directive | Reference | |  | | Cache Directive | Reference | |
| skipping to change at page 33, line 5 |  | skipping to change at page 33, line 24 |
| | no-transform | Section 3.2.1, Section 3.2.2 | |  | | no-transform | Section 3.2.1, Section 3.2.2 | |
| | only-if-cached | Section 3.2.1 | |  | | only-if-cached | Section 3.2.1 | |
| | private | Section 3.2.2 | |  | | private | Section 3.2.2 | |
| | proxy-revalidate | Section 3.2.2 | |  | | proxy-revalidate | Section 3.2.2 | |
| | public | Section 3.2.2 | |  | | public | Section 3.2.2 | |
| | s-maxage | Section 3.2.2 | |  | | s-maxage | Section 3.2.2 | |
| | stale-if-error | [RFC5861], Section 4 | |  | | stale-if-error | [RFC5861], Section 4 | |
| | stale-while-revalidate | [RFC5861], Section 3 | |  | | stale-while-revalidate | [RFC5861], Section 3 | |
| +------------------------+------------------------------+ |  | +------------------------+------------------------------+ |
| 5.2. Header Field Registration |  | 3.8.2. Warn Code Registry |
|  |  | The registration procedure for HTTP Warn Codes is defined by |
|  |  | Section 3.6.8 of this document. |
|  |  | The HTTP Warn Code Registry shall be created at |
|  |  | <http://www.iana.org/assignments/http-cache-directives> and be |
|  |  | populated with the registrations below: |
|  |  | +-----------+----------------------------------+---------------+ |
|  |  | | Warn Code | Short Description | Reference | |
|  |  | +-----------+----------------------------------+---------------+ |
|  |  | | 110 | Response is Stale | Section 3.6.1 | |
|  |  | | 111 | Revalidation Failed | Section 3.6.2 | |
|  |  | | 112 | Disconnected Operation | Section 3.6.3 | |
|  |  | | 113 | Heuristic Expiration | Section 3.6.4 | |
|  |  | | 199 | Miscellaneous Warning | Section 3.6.5 | |
|  |  | | 214 | Transformation Applied | Section 3.6.6 | |
|  |  | | 299 | Miscellaneous Persistent Warning | Section 3.6.7 | |
|  |  | +-----------+----------------------------------+---------------+ |
|  |  | 3.9. Header Field Registration |
| The Message Header Field Registry located at <http://www.iana.org/ |  | The Message Header Field Registry located at <http://www.iana.org/ |
| assignments/message-headers/message-header-index.html> shall be |  | assignments/message-headers/message-header-index.html> shall be |
| updated with the permanent registrations below (see [RFC3864]): |  | updated with the permanent registrations below (see [RFC3864]): |
| +-------------------+----------+----------+-------------+ |  | +-------------------+----------+----------+-------------+ |
| | Header Field Name | Protocol | Status | Reference | |  | | Header Field Name | Protocol | Status | Reference | |
| +-------------------+----------+----------+-------------+ |  | +-------------------+----------+----------+-------------+ |
| | Age | http | standard | Section 3.1 | |  | | Age | http | standard | Section 3.1 | |
| | Cache-Control | http | standard | Section 3.2 | |  | | Cache-Control | http | standard | Section 3.2 | |
| | Expires | http | standard | Section 3.3 | |  | | Expires | http | standard | Section 3.3 | |
| | Pragma | http | standard | Section 3.4 | |  | | Pragma | http | standard | Section 3.4 | |
| | Vary | http | standard | Section 3.5 | |  | | Vary | http | standard | Section 3.5 | |
| | Warning | http | standard | Section 3.6 | |  | | Warning | http | standard | Section 3.6 | |
| +-------------------+----------+----------+-------------+ |  | +-------------------+----------+----------+-------------+ |
| 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 |  | 4. Security Considerations |
| Caches expose additional potential vulnerabilities, since the |  | Caches expose additional potential vulnerabilities, since the |
| contents of the cache represent an attractive target for malicious |  | contents of the cache represent an attractive target for malicious |
| exploitation. Because cache contents persist after an HTTP request |  | exploitation. Because cache contents persist after an HTTP request |
| is complete, an attack on the cache can reveal information long after |  | is complete, an attack on the cache can reveal information long after |
| a user believes that the information has been removed from the |  | a user believes that the information has been removed from the |
| network. Therefore, cache contents need to be protected as sensitive |  | network. Therefore, cache contents need to be protected as sensitive |
| information. |  | information. |
| 7. Acknowledgments |  | 5. Acknowledgments |
| See Section 11 of [Part1]. |  | See Section 11 of [Part1]. |
| 8. References |  | 6. References |
| 8.1. Normative References |  | 6.1. 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-17 |  | and Message Parsing", draft-ietf-httpbis-p1-messaging-18 |
| (work in progress), October 2011. |  | (work in progress), January 2012. |
| [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-17 (work in |  | Semantics", draft-ietf-httpbis-p2-semantics-18 (work in |
| progress), October 2011. |  | progress), January 2012. |
| [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-17 (work in |  | Requests", draft-ietf-httpbis-p4-conditional-18 (work in |
| progress), October 2011. |  | progress), January 2012. |
| [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-17 (work |  | Partial Responses", draft-ietf-httpbis-p5-range-18 (work |
| in progress), October 2011. |  | in progress), January 2012. |
| [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-17 (work in progress), |  | draft-ietf-httpbis-p7-auth-18 (work in progress), |
| October 2011. |  | January 2012. |
| [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 |  | 6.2. Informative References |
| [RFC1305] Mills, D., "Network Time Protocol (Version 3) |  | [RFC1305] Mills, D., "Network Time Protocol (Version 3) |
| Specification, Implementation", RFC 1305, March 1992. |  | Specification, Implementation", RFC 1305, March 1992. |
| [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., |  | [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., |
| Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext |  | Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext |
| Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. |  | Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. |
| [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration |  | [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration |
| Procedures for Message Header Fields", BCP 90, RFC 3864, |  | Procedures for Message Header Fields", BCP 90, RFC 3864, |
| skipping to change at page 42, line 22 |  | skipping to change at page 43, line 15 |
| C.18. Since draft-ietf-httpbis-p6-cache-16 |  | C.18. Since draft-ietf-httpbis-p6-cache-16 |
| Closed issues: |  | Closed issues: |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/186>: "Document |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/186>: "Document |
| HTTP's error-handling philosophy" |  | HTTP's error-handling philosophy" |
| o <http://tools.ietf.org/wg/httpbis/trac/ticket/317>: "Cache-Control |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/317>: "Cache-Control |
| directive case sensitivity" |  | directive case sensitivity" |
|  |  | C.19. Since draft-ietf-httpbis-p6-cache-17 |
|  |  | Closed issues: |
|  |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/293>: "Interaction |
|  |  | of request and response Cache-Control" |
|  |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/212>: "Refining age |
|  |  | for 1.1 proxy chains" |
|  |  | o <http://tools.ietf.org/wg/httpbis/trac/ticket/274>: "warn-code |
|  |  | registry" |
| Index |  | Index |
|  |  | 1 |
|  |  | 110 Response is Stale (warn code) 31 |
|  |  | 111 Revalidation Failed (warn code) 31 |
|  |  | 112 Disconnected Operation (warn code) 31 |
|  |  | 113 Heuristic Expiration (warn code) 31 |
|  |  | 199 Miscellaneous Warning (warn code) 31 |
|  |  | 2 |
|  |  | 214 Transformation Applied (warn code) 31 |
|  |  | 299 Miscellaneous Persistent Warning (warn code) 31 |
| A |  | A |
| age 6 |  | age 6 |
| Age header field 20 |  | Age header field 20 |
| C |  | C |
| cache 5 |  | cache 5 |
| Cache Directives |  | Cache Directives |
| max-age 22, 25 |  | max-age 22, 25 |
| max-stale 22 |  | max-stale 22 |
| min-fresh 22 |  | min-fresh 22 |
| must-revalidate 25 |  | must-revalidate 25 |
| no-cache 21, 24 |  | no-cache 22, 24 |
| no-store 22, 24 |  | no-store 22, 24 |
| no-transform 23, 25 |  | no-transform 23, 25 |
| only-if-cached 23 |  | only-if-cached 23 |
| private 23 |  | private 23 |
| proxy-revalidate 25 |  | proxy-revalidate 25 |
| public 23 |  | public 23 |
| s-maxage 25 |  | s-maxage 25 |
| cache entry 8 |  | cache entry 8 |
| cache key 8 |  | cache key 8 |
| Cache-Control header field 21 |  | Cache-Control header field 21 |
| skipping to change at page 43, line 50 |  | skipping to change at page 45, line 19 |
| Cache Directive 22, 25 |  | Cache Directive 22, 25 |
| max-stale |  | max-stale |
| Cache Directive 22 |  | Cache Directive 22 |
| min-fresh |  | min-fresh |
| Cache Directive 22 |  | Cache Directive 22 |
| must-revalidate |  | must-revalidate |
| Cache Directive 25 |  | Cache Directive 25 |
| N |  | N |
| no-cache |  | no-cache |
| Cache Directive 21, 24 |  | Cache Directive 22, 24 |
| no-store |  | no-store |
| Cache Directive 22, 24 |  | Cache Directive 22, 24 |
| no-transform |  | no-transform |
| Cache Directive 23, 25 |  | Cache Directive 23, 25 |
| O |  | O |
| only-if-cached |  | only-if-cached |
| Cache Directive 23 |  | Cache Directive 23 |
| P |  | P |
| skipping to change at page 44, line 35 |  | skipping to change at page 46, line 4 |
| shared cache 5 |  | shared cache 5 |
| stale 6 |  | stale 6 |
| strong validator 7 |  | strong validator 7 |
| V |  | V |
| validator 6 |  | validator 6 |
| strong 7 |  | strong 7 |
| Vary header field 28 |  | Vary header field 28 |
| W |  | W |
|  |  | Warn Codes |
|  |  | 110 Response is Stale 31 |
|  |  | 111 Revalidation Failed 31 |
|  |  | 112 Disconnected Operation 31 |
|  |  | 113 Heuristic Expiration 31 |
|  |  | 199 Miscellaneous Warning 31 |
|  |  | 214 Transformation Applied 31 |
|  |  | 299 Miscellaneous Persistent Warning 31 |
| Warning header field 29 |  | Warning header field 29 |
| Authors' Addresses |  | Authors' Addresses |
| Roy T. Fielding (editor) |  | Roy T. Fielding (editor) |
| Adobe Systems Incorporated |  | Adobe Systems Incorporated |
| 345 Park Ave |  | 345 Park Ave |
| San Jose, CA 95110 |  | San Jose, CA 95110 |
| USA |  | USA |
End of changes. 52 change blocks.
| 94 lines changed or deleted |  | 183 lines changed or added |
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