HTTP Link Hints
draft-nottingham-link-hint-02

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Network Working Group                                      M. Nottingham
Internet-Draft                                             March 4, 2020
Intended status: Informational
Expires: September 5, 2020

                            HTTP Link Hints
                     draft-nottingham-link-hint-02

Abstract

   This memo specifies "HTTP Link Hints", a mechanism for annotating Web
   links to HTTP(S) resources with information that otherwise might be
   discovered by interacting with them.

Note to Readers

   _RFC EDITOR: please remove this section before publication_

   The issues list for this draft can be found at
   https://github.com/mnot/I-D/labels/link-hint [1].

   The most recent (often, unpublished) draft is at
   https://mnot.github.io/I-D/link-hint/ [2].

   Recent changes are listed at https://github.com/mnot/I-D/commits/gh-
   pages/link-hint [3].

   See also the draft's current status in the IETF datatracker, at
   https://datatracker.ietf.org/doc/draft-nottingham-link-hint/ [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
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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 5, 2020.

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Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  HTTP Link Hints . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Pre-Defined HTTP Link Hints . . . . . . . . . . . . . . . . .   4
     3.1.  allow . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  formats . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  links . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  accept-post . . . . . . . . . . . . . . . . . . . . . . .   6
     3.5.  accept-patch  . . . . . . . . . . . . . . . . . . . . . .   7
     3.6.  accept-ranges . . . . . . . . . . . . . . . . . . . . . .   7
     3.7.  accept-prefer . . . . . . . . . . . . . . . . . . . . . .   7
     3.8.  precondition-req  . . . . . . . . . . . . . . . . . . . .   8
     3.9.  auth-schemes  . . . . . . . . . . . . . . . . . . . . . .   8
     3.10. status  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  HTTP Link Hint Registry . . . . . . . . . . . . . . . . .   9
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  11
     6.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .  12
   Appendix A.  Representing Link Hints in Link Headers  . . . . . .  12
   Appendix B.  Acknowledgements . . . . . . . . . . . . . . . . . .  13
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   HTTP [RFC7230] clients can discover a variety of information about a
   resource by interacting with it.  For example, the methods supported
   can be learned through the Allow response header field, and the need

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   for authentication is conveyed with a 401 Authentication Required
   status code.

   Often, it can be beneficial to know this information before
   interacting with the resource; not only can such knowledge save time
   (through reduced round trips), but it can also affect the choices
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