draft-ietf-httpbis-targeted-cache-control-01.txt   draft-ietf-httpbis-targeted-cache-control-latest.txt 
HTTP Working Group S. Ludin HTTP Working Group S. Ludin
Internet-Draft Akamai Internet-Draft Akamai
Intended status: Standards Track M. Nottingham Intended status: Standards Track M. Nottingham
Expires: March 24, 2022 Fastly Expires: March 28, 2022 Fastly
Y. Wu Y. Wu
Cloudflare Cloudflare
September 20, 2021 September 24, 2021
Targeted HTTP Cache Control Targeted HTTP Cache Control
draft-ietf-httpbis-targeted-cache-control-01 draft-ietf-httpbis-targeted-cache-control-latest
Abstract Abstract
This specification defines a convention for HTTP response header This specification defines a convention for HTTP response header
fields that allow directives controlling caching to be targeted at fields that allow directives controlling caching to be targeted at
specific caches or classes of caches. It also defines one such specific caches or classes of caches. It also defines one such
header field, targeted at Content Delivery Network (CDN) caches. header field, targeted at Content Delivery Network (CDN) caches.
Note to Readers Note to Readers
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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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://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 March 24, 2022. This Internet-Draft will expire on March 28, 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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
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age=30;a=b;c=d"), which are ignored unless specified. age=30;a=b;c=d"), which are ignored unless specified.
If a targeted field in a given response is empty, or a parsing error If a targeted field in a given response is empty, or a parsing error
is encountered, that field MUST be ignored by the cache (i.e., it is encountered, that field MUST be ignored by the cache (i.e., it
behaves as if the field were not present, likely falling back to behaves as if the field were not present, likely falling back to
other cache control mechanisms present). other cache control mechanisms present).
2.3. Interaction with HTTP Freshness 2.3. Interaction with HTTP Freshness
HTTP caching has a single, end-to-end freshness model defined in HTTP caching has a single, end-to-end freshness model defined in
Section 4.2 of [I-D.ietf-httpbis-cache]. When additional freshness Section 4.2 of [HTTP-CACHING]. When additional freshness mechanisms
mechanisms are only available to some caches along a request path are only available to some caches along a request path (for example,
(for example, using targeted fields), their interactions need to be using targeted fields), their interactions need to be carefully
carefully considered. In particular, a targeted cache might have considered. In particular, a targeted cache might have longer
longer freshness lifetimes available to it than other caches, causing freshness lifetimes available to it than other caches, causing it to
it to serve responses that appear to be prematurely (or even serve responses that appear to be prematurely (or even immediately)
immediately) stale to them, negatively impacting cache efficiency. stale to them, negatively impacting cache efficiency.
For example, a response stored by a CDN cache might be served with For example, a response stored by a CDN cache might be served with
the following headers: the following headers:
Age: 1800 Age: 1800
Cache-Control: max-age=600 Cache-Control: max-age=600
CDN-Cache-Control: max-age=3600 CDN-Cache-Control: max-age=3600
From the CDN's perspective, this response is still fresh after being From the CDN's perspective, this response is still fresh after being
cached for 30 minutes, while from other caches' standpoint, this cached for 30 minutes, while from other caches' standpoint, this
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[HTTP] Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP [HTTP] Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
Semantics", draft-ietf-httpbis-semantics-19 (work in Semantics", draft-ietf-httpbis-semantics-19 (work in
progress), September 2021. progress), September 2021.
[HTTP-CACHING] [HTTP-CACHING]
Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
Caching", draft-ietf-httpbis-cache-19 (work in progress), Caching", draft-ietf-httpbis-cache-19 (work in progress),
September 2021. September 2021.
[I-D.ietf-httpbis-cache]
Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
Caching", draft-ietf-httpbis-cache-19 (work in progress),
September 2021.
[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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[STRUCTURED-FIELDS] [STRUCTURED-FIELDS]
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