HTTP Representation Variants
draft-ietf-httpbis-variants-05
HTTP M. Nottingham
Internet-Draft Fastly
Updates: 7234 (if approved) March 25, 2019
Intended status: Standards Track
Expires: September 26, 2019
HTTP Representation Variants
draft-ietf-httpbis-variants-05
Abstract
This specification introduces an alternative way to communicate a
secondary cache key for a HTTP resource, using the HTTP "Variants"
and "Variant-Key" response header fields. Its aim is to make HTTP
proactive content negotiation more cache-friendly.
Note to Readers
_RFC EDITOR: please remove this section before publication_
Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/ [1].
Working Group information can be found at https://httpwg.github.io/
[2]; source code and issues list for this draft can be found at
https://github.com/httpwg/http-extensions/labels/variants [3].
There is a prototype implementation of the algorithms herein at
https://github.com/mnot/variants-toy [4].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 26, 2019.
Nottingham Expires September 26, 2019 [Page 1]
Internet-Draft HTTP Representation Variants March 2019
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. The "Variants" HTTP Header Field . . . . . . . . . . . . . . 5
2.1. Relationship to Vary . . . . . . . . . . . . . . . . . . 7
3. The "Variant-Key" HTTP Header Field . . . . . . . . . . . . . 7
4. Cache Behaviour . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Compute Possible Keys . . . . . . . . . . . . . . . . . . 10
4.2. Check Vary . . . . . . . . . . . . . . . . . . . . . . . 11
4.3. Example of Cache Behaviour . . . . . . . . . . . . . . . 11
4.3.1. A Variant Missing From the Cache . . . . . . . . . . 12
4.3.2. Variants That Don't Overlap the Client's Request . . 13
5. Origin Server Behaviour . . . . . . . . . . . . . . . . . . . 13
5.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1.1. Single Variant . . . . . . . . . . . . . . . . . . . 14
5.1.2. Multiple Variants . . . . . . . . . . . . . . . . . . 15
5.1.3. Partial Coverage . . . . . . . . . . . . . . . . . . 15
6. Defining Content Negotiation Using Variants . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . 18
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Appendix A. Variants for Existing Content Negotiation Mechanisms 19
A.1. Accept . . . . . . . . . . . . . . . . . . . . . . . . . 19
A.2. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 20
A.3. Accept-Language . . . . . . . . . . . . . . . . . . . . . 20
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 21
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 21
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