Plan-execute on Where ten HTTP header fields are defined

I found the defining RFC and section for all ten header fields. Each section number was checked against the heading text in the RFC page I opened.

How I checked the RFCs are current: I couldn't load the planned status pages (https://www.rfc-editor.org/info/rfc9110, …/rfc9111, …/rfc6797, …/rfc8288); each returned HTTP 404. Instead I read the header block of each full RFC on rfc-editor.org. None of the four shows an "Obsoleted by" line, but that header could be out of date, so this is weaker evidence than the status pages would have been. RFC 9111 says "This document obsoletes RFC 7234" (https://www.rfc-editor.org/rfc/rfc9111.html). RFC 9110 says it "obsoletes RFCs 2818, 7231, 7232, 7233, 7235, 7538, 7615, 7694, and portions of 7230" (https://www.rfc-editor.org/rfc/rfc9110.html). RFC 8288 lists "Obsoletes: 5988" (https://www.rfc-editor.org/rfc/rfc8288.html). So I didn't use the older RFCs 7231, 7232, 7234 or 5988.

Results:

• RFC 9111, HTTP Caching (https://www.rfc-editor.org/rfc/rfc9111.html):

  • Age: §5.1
  • Cache-Control: §5.2
  • Expires: §5.3

• RFC 9110, HTTP Semantics (https://www.rfc-editor.org/rfc/rfc9110.html):

  • Last-Modified: §8.8.2
  • ETag: §8.8.3
  • Location: §10.2.2
  • Retry-After: §10.2.3
  • Vary: §12.5.5

• RFC 6797, HSTS (https://www.rfc-editor.org/rfc/rfc6797.html):

  • Strict-Transport-Security: §6.1, "Strict-Transport-Security HTTP Response Header Field"

• RFC 8288, Web Linking (https://www.rfc-editor.org/rfc/rfc8288.html):

  • Link: §3, "Link Serialisation in HTTP Headers"

The RFC pages break sentences across lines. In the quotes below I joined those line breaks with single spaces and kept the wording exactly as shown.

{"answers":[
{"field":"Age","rfc":"9111","section":"5.1","quote":"The \"Age\" response header field conveys the sender's estimate of the time since the response was generated or successfully validated at the origin server.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Cache-Control","rfc":"9111","section":"5.2","quote":"The \"Cache-Control\" header field is used to list directives for caches along the request/response chain.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Expires","rfc":"9111","section":"5.3","quote":"The \"Expires\" response header field gives the date/time after which the response is considered stale.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Last-Modified","rfc":"9110","section":"8.8.2","quote":"The \"Last-Modified\" header field in a response provides a timestamp indicating the date and time at which the origin server believes the selected representation was last modified, as determined at the conclusion of handling the request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"ETag","rfc":"9110","section":"8.8.3","quote":"The \"ETag\" field in a response provides the current entity tag for the selected representation, as determined at the conclusion of handling the request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Location","rfc":"9110","section":"10.2.2","quote":"The \"Location\" header field is used in some responses to refer to a specific resource in relation to the response.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Retry-After","rfc":"9110","section":"10.2.3","quote":"Servers send the \"Retry-After\" header field to indicate how long the user agent ought to wait before making a follow-up request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Vary","rfc":"9110","section":"12.5.5","quote":"The \"Vary\" header field in a response describes what parts of a request message, aside from the method and target URI, might have influenced the origin server's process for selecting the content of this response.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Strict-Transport-Security","rfc":"6797","section":"6.1","quote":"The Strict-Transport-Security HTTP response header field (STS header field) indicates to a UA that it MUST enforce the HSTS Policy in regards to the host emitting the response message containing this header field.","url":"https://www.rfc-editor.org/rfc/rfc6797.html"},
{"field":"Link","rfc":"8288","section":"3","quote":"The Link header field provides a means for serialising one or more links into HTTP headers.","url":"https://www.rfc-editor.org/rfc/rfc8288.html"}
]}