Orchestrator-workers on Where ten HTTP header fields are defined

All ten fields map to four RFCs: RFC 9111 for the caching fields, RFC 9110 for the semantics fields, RFC 6797 for Strict-Transport-Security and RFC 8288 for Link. One check is incomplete: none of the four could be confirmed as still current from an independent status page.

Caching fields: RFC 9111 (HTTP Caching, STD 98)

• Sections: Age is §5.1, Cache-Control is §5.2 and Expires is §5.3.
• Why this RFC: its header reads "Obsoletes: 7234", so RFC 7234 is out. The header has no "Obsoleted by" line. Source: https://www.rfc-editor.org/rfc/rfc9111.html
• Cache-Control subsections: §5.2.1–5.2.4 cover directives and the registry. The field itself and its syntax are defined in §5.2.

Semantics fields: RFC 9110 (HTTP Semantics, STD 97)

• Sections: Last-Modified is §8.8.2, ETag is §8.8.3, Location is §10.2.2, Retry-After is §10.2.3 and Vary is §12.5.5.
• Why this RFC: RFC 9110 replaces RFC 7232 (which had Last-Modified and ETag) and RFC 7231 (which had Location, Retry-After and Vary). Its header has no "Obsoleted by" line. Source: https://www.rfc-editor.org/rfc/rfc9110.html

Strict-Transport-Security: RFC 6797, §6.1

• §6.1 is titled "Strict-Transport-Security HTTP Response Header Field". It opens with the field's definition and grammar.
• The header has no "Obsoleted by" line, and no newer HSTS RFC was found. Source: https://www.rfc-editor.org/rfc/rfc6797.html

Link: RFC 8288, §3

• The header reads "Obsoletes: 5988", so RFC 5988 is out. §3 contains the grammar Link = #link-value.
• The introduction says "Section 3 defines an HTTP header field for conveying such links". Source: https://www.rfc-editor.org/rfc/rfc8288.html

What wasn't fully checked

• Current status: this rests only on each RFC's own header having no "Obsoleted by" line. The rfc-editor.org /info/ status pages and the IANA HTTP Field Name Registry returned 404. The datatracker pages only showed the same RFC text. No source disagreed.
• Quote line breaks: the RFC pages break sentences across lines. The quotes below join each sentence into one line with single spaces. If the checker compares text without normalising whitespace, a quote could fail to match.

{"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"}
]}