draft-ietf-httpbis-retrofit-06.txt		draft-ietf-httpbis-retrofit-latest.txt
	HTTP Working Group M. Nottingham		HTTP Working Group M. Nottingham
	Internet-Draft March 31, 2023		Internet-Draft December 12, 2024
	Intended status: Standards Track		Intended status: Standards Track
	Expires: October 2, 2023		Expires: June 15, 2025
	Retrofit Structured Fields for HTTP		Retrofit Structured Fields for HTTP
	draft-ietf-httpbis-retrofit-06		draft-ietf-httpbis-retrofit-latest
	Abstract		Abstract
	This specification nominates a selection of existing HTTP fields as		This specification nominates a selection of existing HTTP fields
	having syntax that is compatible with Structured Fields, so that they		whose values are compatible with Structured Fields syntax, so that
	can be handled as such (subject to certain caveats).		they can be handled as such (subject to certain caveats).
	To accommodate some additional fields whose syntax is not compatible,		To accommodate some additional fields whose syntax is not compatible,
	it also defines mappings of their semantics into new Structured		it also defines mappings of their semantics into Structured Fields.
	Fields. It does not specify how to negotiate their use.		It does not specify how to convey them in HTTP messages.
	About This Document		About This Document
	This note is to be removed before publishing as an RFC.		This note is to be removed before publishing as an RFC.
	Status information for this document may be found at		Status information for this document may be found at
	<https://datatracker.ietf.org/doc/draft-ietf-httpbis-retrofit/>.		<https://datatracker.ietf.org/doc/draft-ietf-httpbis-retrofit/>.
	Discussion of this document takes place on the HTTP Working Group		Discussion of this document takes place on the HTTP Working Group
	mailing list (<mailto:ietf-http-wg@w3.org>), which is archived at		mailing list (<mailto:ietf-http-wg@w3.org>), which is archived at
	skipping to change at page 2, line 4 ¶		skipping to change at page 2, line 4 ¶
	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
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	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 October 2, 2023.		This Internet-Draft will expire on June 15, 2025.
	Copyright Notice		Copyright Notice
	Copyright (c) 2023 IETF Trust and the persons identified as the		Copyright (c) 2024 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
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3		1.1. Using Retrofit Structured Fields . . . . . . . . . . . . 3
	2. Compatible Fields . . . . . . . . . . . . . . . . . . . . . . 3		1.2. Notational Conventions . . . . . . . . . . . . . . . . . 4
	3. Mapped Fields . . . . . . . . . . . . . . . . . . . . . . . . 6		2. Compatible Fields . . . . . . . . . . . . . . . . . . . . . . 4
			2.1. Caveats . . . . . . . . . . . . . . . . . . . . . . . . . 6
			3. Mapped Fields . . . . . . . . . . . . . . . . . . . . . . . . 7
	3.1. URLs . . . . . . . . . . . . . . . . . . . . . . . . . . 7		3.1. URLs . . . . . . . . . . . . . . . . . . . . . . . . . . 7
	3.2. Dates . . . . . . . . . . . . . . . . . . . . . . . . . . 7		3.2. Dates . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	3.3. ETags . . . . . . . . . . . . . . . . . . . . . . . . . . 8		3.3. ETags . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	3.4. Cookies . . . . . . . . . . . . . . . . . . . . . . . . . 8		3.4. Cookies . . . . . . . . . . . . . . . . . . . . . . . . . 9
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 10		5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
	6. Normative References . . . . . . . . . . . . . . . . . . . . 11		6. Normative References . . . . . . . . . . . . . . . . . . . . 11
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	Structured Field Values for HTTP [STRUCTURED-FIELDS] introduced a		Structured Field Values for HTTP [STRUCTURED-FIELDS] introduced a
	data model with associated parsing and serialization algorithms for		data model with associated parsing and serialization algorithms for
	use by new HTTP field values. Fields that are defined as Structured		use by new HTTP field values. Fields that are defined as Structured
	Fields can realise a number of benefits, including:		Fields can bring advantages that include:
	o Improved interoperability and security: precisely defined parsing		o Improved interoperability and security: precisely defined parsing
	and serialisation algorithms are typically not available for		and serialisation algorithms are typically not available for
	fields defined with just ABNF and/or prose.		fields defined with just ABNF and/or prose.
	o Reuse of common implementations: many parsers for other fields are		o Reuse of common implementations: many parsers for other fields are
	specific to a single field or a small family of fields.		specific to a single field or a small family of fields.
	o Canonical form: because a deterministic serialisation algorithm is		o Canonical form: because a deterministic serialisation algorithm is
	defined for each type, Structure Fields have a canonical		defined for each type, Structure Fields have a canonical
	skipping to change at page 3, line 32 ¶		skipping to change at page 3, line 32 ¶
	can be handled as Structured Fields, so that these benefits can be		can be handled as Structured Fields, so that these benefits can be
	realised -- thereby making them Retrofit Structured Fields.		realised -- thereby making them Retrofit Structured Fields.
	It does so using two techniques. Section 2 lists compatible fields		It does so using two techniques. Section 2 lists compatible fields
	-- those that can be handled as if they were Structured Fields due to		-- those that can be handled as if they were Structured Fields due to
	the similarity of their defined syntax to that in Structured Fields.		the similarity of their defined syntax to that in Structured Fields.
	Section 3 lists mapped fields -- those whose syntax needs to be		Section 3 lists mapped fields -- those whose syntax needs to be
	transformed into an underlying data model which is then mapped into		transformed into an underlying data model which is then mapped into
	that defined by Structured Fields.		that defined by Structured Fields.
	Note that while implementations can parse and serialise compatible		1.1. Using Retrofit Structured Fields
	fields as Structured Fields subject to the caveats in Section 2, a
	sender cannot generate mapped fields from Section 3 and expect them
	to be understood and acted upon by the recipient without prior
	negotiation. This specification does not define such a mechanism.
	1.1. Notational Conventions		Retrofitting data structures onto existing and widely-deployed HTTP
			fields requires careful handling to assure interoperability and
			security. This section highlights considerations for applications
			that use Retrofit Structured Fields.
			While the majority of field values seen in HTTP traffic should be
			able to be parsed or mapped successfully, some will not. An
			application using Retrofit Structured Fields will need to define how
			unsuccessful values will be handled.
			For example, an API that exposes field values using Structured Fields
			data types might make the field value available as a string in cases
			where the field did not successfully parse or map.
			The mapped field values described in Section 3 are not compatible
			with the original syntax of their fields, and so cannot be used
			unless parties processing them have explicitly indicated their
			support for that form of the field value. An application using
			Retrofit Structured Fields will need to define how to negotiate
			support for them.
			For example, an alternative serialization of fields that takes
			advantage of Structured Fields would need to establish an explicit
			negotiation mechanism to assure that both peers would handle that
			serialization appropriately before using it.
			See also the security considerations in Section 5.
			1.2. Notational Conventions
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all		BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	2. Compatible Fields		2. Compatible Fields
	The HTTP fields listed in Table 1 can usually have their values		The HTTP fields listed in Table 1 have values that can be handled as
	handled as Structured Fields according to the listed parsing and		Structured Field Values according to the parsing and serialisation
	serialisation algorithms in [STRUCTURED-FIELDS], subject to the		algorithms in [STRUCTURED-FIELDS] corresponding to the listed top-
	listed caveats.		level type, subject to the caveats in Section 2.1.
	The listed types are chosen for compatibility with the defined syntax		The top-level types are chosen for compatibility with the defined
	of the field as well as with actual internet traffic. However, not		syntax of the field as well as with actual internet traffic.
	all instances of these fields will successfully parse. This might be		However, not all instances of these fields will successfully parse as
	because the field value is clearly invalid, or it might be because it		a Structured Field Value. This might be because the field value is
	is valid but not parseable as a Structured Field.		clearly invalid, or it might be because it is valid but not parseable
			as a Structured Field.
	An application using this specification will need to consider how to		An application using this specification will need to consider how to
	handle such field values. Depending on its requirements, it might be		handle such field values. Depending on its requirements, it might be
	advisable to reject such values, treat them as opaque strings, or		advisable to reject such values, treat them as opaque strings, or
	attempt to recover a structured value from them in an ad hoc fashion.		attempt to recover a Structured Field Value from them in an ad hoc
			fashion.
	+----------------------------------+-----------------+		+----------------------------------+-----------------+
	| Field Name | Structured Type |		| Field Name | Structured Type |
	+----------------------------------+-----------------+		+----------------------------------+-----------------+
	| Accept | List |		| Accept | List |
	| Accept-Encoding | List |		| Accept-Encoding | List |
	| Accept-Language | List |		| Accept-Language | List |
	| Accept-Patch | List |		| Accept-Patch | List |
	| Accept-Post | List |		| Accept-Post | List |
	| Accept-Ranges | List |		| Accept-Ranges | List |
	skipping to change at page 5, line 24 ¶		skipping to change at page 6, line 4 ¶
	| TE | List |		| TE | List |
	| Timing-Allow-Origin | List |		| Timing-Allow-Origin | List |
	| Trailer | List |		| Trailer | List |
	| Transfer-Encoding | List |		| Transfer-Encoding | List |
	| Upgrade-Insecure-Requests | Item |		| Upgrade-Insecure-Requests | Item |
	| Vary | List |		| Vary | List |
	| X-Content-Type-Options | Item |		| X-Content-Type-Options | Item |
	| X-Frame-Options | Item |		| X-Frame-Options | Item |
	| X-XSS-Protection | List |		| X-XSS-Protection | List |
	+----------------------------------+-----------------+		+----------------------------------+-----------------+
	Table 1: Compatible Fields		Table 1: Compatible Fields
			2.1. Caveats
	Note the following caveats regarding compatibility:		Note the following caveats regarding compatibility:
	Parsing differences: Some values may fail to parse as Structured		Parsing differences: Some values may fail to parse as Structured
	Fields, even though they are valid according to their originally		Fields, even though they are valid according to their originally
	specified syntax. For example, HTTP parameter names are case-		specified syntax. For example, HTTP parameter names are case-
	insensitive (per Section 5.6.6 of [HTTP]), but Structured Fields		insensitive (per Section 5.6.6 of [HTTP]), but Structured Fields
	require them to be all-lowercase. Likewise, many Dictionary-based		require them to be all-lowercase. Likewise, many Dictionary-based
	fields (e.g., Cache-Control, Expect-CT, Pragma, Prefer,		fields (e.g., Cache-Control, Expect-CT, Pragma, Prefer,
	Preference-Applied, Surrogate-Control) have case-insensitive keys.		Preference-Applied, Surrogate-Control) have case-insensitive keys.
	Similarly, the parameters rule in HTTP (see Section 5.6.6 of		Similarly, the parameters rule in HTTP (see Section 5.6.6 of
	skipping to change at page 6, line 42 ¶		skipping to change at page 7, line 24 ¶
	requirements.		requirements.
	Retry-After: Only the delta-seconds form of Retry-After can be		Retry-After: Only the delta-seconds form of Retry-After can be
	represented; a Retry-After value containing a http-date will need		represented; a Retry-After value containing a http-date will need
	to be converted into delta-seconds to be conveyed as a Structured		to be converted into delta-seconds to be conveyed as a Structured
	Field Value.		Field Value.
	3. Mapped Fields		3. Mapped Fields
	Some HTTP field values have syntax that cannot be successfully parsed		Some HTTP field values have syntax that cannot be successfully parsed
	as Structured Fields. Instead, it is necessary to map them into a		as Structured Field values. Instead, it is necessary to map them
	separate Structured Field with an alternative name.		into a Structured Field value.
	For example, the Date HTTP header field carries a date:		For example, the Date HTTP header field carries a date:
	Date: Sun, 06 Nov 1994 08:49:37 GMT		Date: Sun, 06 Nov 1994 08:49:37 GMT
	Its value would be mapped to:		Its value would be mapped to:
	SF-Date: @784111777		@784111777
	As in Section 2, these fields are unable to carry values that are not
	valid Structured Fields, and so an application using this
	specification will need to how to support such values. Typically,
	handling them using the original field name is sufficient.
	Each field name listed below indicates a replacement field name and a		Unlike those listed in Section 2, these representations are not
	means of mapping its original value into a Structured Field.		compatible with the original fields' syntax, and MUST NOT be used
			unless they are explicitly and unambiguously supported. For example,
			this means that sending them to a next-hop recipient in HTTP requires
			prior negotiation. This specification does not define how to do so.
	3.1. URLs		3.1. URLs
	The field names in Table 2 (paired with their mapped field names)		The field names in Table 2 have values that can be mapped into
	have values that can be mapped into Structured Fields by treating the		Structured Field values by treating the original field's value as a
	original field's value as a String.		String.
	+------------------+---------------------+		+------------------+
	| Field Name | Mapped Field Name |		| Field Name |
	+------------------+---------------------+		+------------------+
	| Content-Location | SF-Content-Location |		| Content-Location |
	| Location | SF-Location |		| Location |
	| Referer | SF-Referer |		| Referer |
	+------------------+---------------------+		+------------------+
	Table 2: URL Fields		Table 2: URL Fields
	For example, this Location field		For example, this Location field:
	Location: https://example.com/foo		Location: https://example.com/foo
	could be mapped as:		would have a mapped value of:
	SF-Location: "https://example.com/foo"		"https://example.com/foo"
	3.2. Dates		3.2. Dates
	The field names in Table 3 (paired with their mapped field names)		The field names in Table 3 have values that can be mapped into
	have values that can be mapped into Structured Fields by parsing		Structured Field values by parsing their payload according to
	their payload according to Section 5.6.7 of [HTTP] and representing		Section 5.6.7 of [HTTP] and representing the result as a Date.
	the result as a Date.
	+---------------------+------------------------+		+---------------------+
	| Field Name | Mapped Field Name |		| Field Name |
	+---------------------+------------------------+		+---------------------+
	| Date | SF-Date |		| Date |
	| Expires | SF-Expires |		| Expires |
	| If-Modified-Since | SF-If-Modified-Since |		| If-Modified-Since |
	| If-Unmodified-Since | SF-If-Unmodified-Since |		| If-Unmodified-Since |
	| Last-Modified | SF-Last-Modified |		| Last-Modified |
	+---------------------+------------------------+		+---------------------+
	Table 3: Date Fields		Table 3: Date Fields
	For example, an Expires field could be mapped as:		For example, an Expires field's value could be mapped as:
	SF-Expires: @1659578233		@1659578233
	3.3. ETags		3.3. ETags
	The field value of the ETag header field can be mapped into the SF-		The field value of the ETag header field can be mapped into a
	ETag Structured Field by representing the entity-tag as a String, and		Structured Field value by representing the entity-tag as a String,
	the weakness flag as a Boolean "w" parameter on it, where true		and the weakness flag as a Boolean "w" parameter on it, where true
	indicates that the entity-tag is weak; if 0 or unset, the entity-tag		indicates that the entity-tag is weak; if 0 or unset, the entity-tag
	is strong.		is strong.
	For example, this:		For example, this ETag header field:
	ETag: W/"abcdef"		ETag: W/"abcdef"
	SF-ETag: "abcdef"; w		would have a mapped value of:
	If-None-Match's field value can be mapped into the SF-If-None-Match		"abcdef"; w
	Structured Field, which is a List of the structure described above.
	When a field value contains "*", it is represented as a Token.
	Likewise, If-Match's field value can be mapped into the SF-If-Match		If-None-Match's field value can be mapped into a Structured Field
	Structured Field in the same manner.		value which is a List of the structure described above. When a field
			value contains "*", it is represented as a Token.
	For example:		Likewise, If-Match's field value can be mapped into a Structured
			Field value in the same manner.
	SF-If-None-Match: "abcdef"; w, "ghijkl", *		For example, this If-None-Match field:
			If-None-Match: W/"abcdef", "ghijkl", *
			would have a mapped value of:
			"abcdef"; w, "ghijkl", *
	3.4. Cookies		3.4. Cookies
	The field values of the Cookie and Set-Cookie fields [COOKIES] can be		The field values of the Cookie and Set-Cookie fields [COOKIES] can be
	mapped into the SF-Cookie Structured Field (a List) and SF-Set-Cookie		mapped into Structured Fields Lists.
	Structured Field (a List), respectively.
	In each case, a cookie is represented as an Inner List containing two		In each case, a cookie is represented as an Inner List containing two
	Items; the cookie name and value. The cookie name is always a		Items; the cookie name and value. The cookie name is always a
	String; the cookie value is a String, unless it can be successfully		String; the cookie value is a String, unless it can be successfully
	parsed as the textual representation of another, bare Item structured		parsed as the textual representation of another, bare Item structured
	type (e.g., Byte Sequence, Decimal, Integer, Token, or Boolean).		type (e.g., Byte Sequence, Decimal, Integer, Token, or Boolean).
	Cookie attributes map to Parameters on the Inner List, with the		Cookie attributes map to Parameters on the Inner List, with the
	parameter name being forced to lowercase. Cookie attribute values		parameter name being forced to lowercase. Cookie attribute values
	are Strings unless a specific type is defined for them. This		are Strings unless a specific type is defined for them. This
	skipping to change at page 9, line 34 ¶		skipping to change at page 10, line 22 ¶
	| Path | String |		| Path | String |
	| Secure | Boolean |		| Secure | Boolean |
	| SameSite | Token |		| SameSite | Token |
	+----------------+-----------------+		+----------------+-----------------+
	Table 4: Set-Cookie Parameter Types		Table 4: Set-Cookie Parameter Types
	The Expires attribute is mapped to a Date representation of parsed-		The Expires attribute is mapped to a Date representation of parsed-
	cookie-date (see Section 5.1.1 of [COOKIES]).		cookie-date (see Section 5.1.1 of [COOKIES]).
	For example, these unstructured fields:		For example, this Set-Cookie field:
	Set-Cookie: lang=en-US; Expires=Wed, 09 Jun 2021 10:18:14 GMT;		Set-Cookie: Lang=en-US; Expires=Wed, 09 Jun 2021 10:18:14 GMT;
	samesite=Strict; secure		samesite=Strict; secure
	Cookie: SID=31d4d96e407aad42; lang=en-US
	can be mapped into:		would have a mapped value of:
	SF-Set-Cookie: ("lang" "en-US"); expires=@1623233894;		("Lang" "en-US"); expires=@1623233894;
	samesite=Strict; secure		samesite=Strict; secure
	SF-Cookie: ("SID" "31d4d96e407aad42"), ("lang" "en-US")
			And this Cookie field:
			Cookie: SID=31d4d96e407aad42; lang=en-US
			would have a mapped value of:
			("SID" "31d4d96e407aad42"), ("lang" "en-US")
	4. IANA Considerations		4. IANA Considerations
	Please add the following note to the "Hypertext Transfer Protocol		Please add the following note to the "Hypertext Transfer Protocol
	(HTTP) Field Name Registry":		(HTTP) Field Name Registry":
	A prefix of "*" in the Structured Type column indicates that it is		A prefix of "*" in the Structured Type column indicates that it is
	a retrofit type (i.e., not natively Structured); see RFC nnnn.		a retrofit type (i.e., not natively Structured); see RFC nnnn.
	Then, add a new column, "Structured Type", with the values from		Then, add a new column, "Structured Type", with the values from
	Section 2 assigned to the nominated registrations, prefixing each		Section 2 assigned to the nominated registrations, prefixing each
	with "*" to indicate that it is a retrofit type.		with "*" to indicate that it is a retrofit type.
	Then, add the field names in Table 5, with the corresponding
	Structured Type as indicated, a status of "permanent" and referring
	to this document.
	+------------------------+-----------------+
	| Field Name | Structured Type |
	+------------------------+-----------------+
	| SF-Content-Location | Item |
	| SF-Cookie | List |
	| SF-Date | Item |
	| SF-ETag | Item |
	| SF-Expires | Item |
	| SF-If-Match | List |
	| SF-If-Modified-Since | Item |
	| SF-If-None-Match | List |
	| SF-If-Unmodified-Since | Item |
	| SF-Last-Modified | Item |
	| SF-Location | Item |
	| SF-Referer | Item |
	| SF-Set-Cookie | List |
	+------------------------+-----------------+
	Table 5: New Fields
	Finally, add a new column to the "Cookie Attribute Registry"		Finally, add a new column to the "Cookie Attribute Registry"
	established by [COOKIES] with the title "Structured Type", using		established by [COOKIES] with the title "Structured Type", using
	information from Table 4.		information from Table 4.
	5. Security Considerations		5. Security Considerations
	Section 2 identifies existing HTTP fields that can be parsed and		Section 2 identifies existing HTTP fields that can be parsed and
	serialised with the algorithms defined in [STRUCTURED-FIELDS].		serialised with the algorithms defined in [STRUCTURED-FIELDS].
	Variances from existing parser behavior might be exploitable,		Variances from existing parser behavior might be exploitable,
	particularly if they allow an attacker to target one implementation		particularly if they allow an attacker to target one implementation
	in a chain (e.g., an intermediary). However, given the considerable		in a chain (e.g., an intermediary). However, given the considerable
	variance in parsers already deployed, convergence towards a single		variance in parsers already deployed, convergence towards a single
	parsing algorithm is likely to have a net security benefit in the		parsing algorithm is likely to have a net security benefit in the
	longer term.		longer term.
	Section 3 defines alternative representations of existing fields.		Section 3 defines alternative representations of existing fields.
	Because downstream consumers might interpret the message differently		Because downstream consumers might interpret the message differently
	based upon whether they recognise the alternative representation,		based upon whether they recognise the alternative representation,
	implementations are prohibited from generating such fields unless		implementations are prohibited from generating such values unless
	they have negotiated support for them with their peer. This		they have negotiated support for them with their peer. This
	specification does not define such a mechanism, but any such		specification does not define such a mechanism, but any such
	definition needs to consider the implications of doing so carefully.		definition needs to consider the implications of doing so carefully.
	6. Normative References		6. Normative References
	[COOKIES] Bingler, S., West, M., and J. Wilander, "Cookies: HTTP		[COOKIES] Bingler, S., West, M., and J. Wilander, "Cookies: HTTP
	State Management Mechanism", draft-ietf-httpbis-		State Management Mechanism", draft-ietf-httpbis-
	rfc6265bis-11 (work in progress), November 2022.		rfc6265bis-16 (work in progress), December 2024.
	[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,		[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
	Ed., "HTTP Semantics", STD 97, RFC 9110,		Ed., "HTTP Semantics", STD 97, RFC 9110,
	DOI 10.17487/RFC9110, June 2022,		DOI 10.17487/RFC9110, June 2022,
	<https://www.rfc-editor.org/info/rfc9110>.		<https://www.rfc-editor.org/info/rfc9110>.
	[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]
	Nottingham, M. and P. Kamp, "Structured Field Values for		Nottingham, M. and P. Kamp, "Structured Field Values for
	HTTP", draft-ietf-httpbis-sfbis-01 (work in progress),		HTTP", draft-ietf-httpbis-sfbis-06 (work in progress),
	December 2022.		April 2024.
	Author's Address		Author's Address
	Mark Nottingham		Mark Nottingham
	Prahran		Prahran
	Australia		Australia
	Email: mnot@mnot.net		Email: mnot@mnot.net
	URI: https://www.mnot.net/		URI: https://www.mnot.net/
End of changes. 49 change blocks.
	121 lines changed or deleted		135 lines changed or added
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