< draft-ietf-masque-h3-datagram-01.txt		draft-ietf-masque-h3-datagram-02.txt >
	MASQUE D. Schinazi		MASQUE D. Schinazi
	Internet-Draft Google LLC		Internet-Draft Google LLC
	Intended status: Standards Track L. Pardue		Intended status: Standards Track L. Pardue
	Expires: 14 November 2021 Cloudflare		Expires: 28 November 2021 Cloudflare
	13 May 2021		27 May 2021
	Using QUIC Datagrams with HTTP/3		Using QUIC Datagrams with HTTP/3
	draft-ietf-masque-h3-datagram-01		draft-ietf-masque-h3-datagram-02
	Abstract		Abstract
	The QUIC DATAGRAM extension provides application protocols running		The QUIC DATAGRAM extension provides application protocols running
	over QUIC with a mechanism to send unreliable data while leveraging		over QUIC with a mechanism to send unreliable data while leveraging
	the security and congestion-control properties of QUIC. However,		the security and congestion-control properties of QUIC. However,
	QUIC DATAGRAM frames do not provide a means to demultiplex		QUIC DATAGRAM frames do not provide a means to demultiplex
	application contexts. This document describes how to use QUIC		application contexts. This document describes how to use QUIC
	DATAGRAM frames when the application protocol running over QUIC is		DATAGRAM frames when the application protocol running over QUIC is
	HTTP/3. It associates datagrams with client-initiated bidirectional		HTTP/3. It associates datagrams with client-initiated bidirectional
	skipping to change at page 1, line 43 ¶		skipping to change at page 1, line 43 ¶
	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
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	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 14 November 2021.		This Internet-Draft will expire on 28 November 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2021 IETF Trust and the persons identified as the		Copyright (c) 2021 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 (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 21 ¶		skipping to change at page 2, line 21 ¶
	as described in Section 4.e of the Trust Legal Provisions and are		as described in Section 4.e of the Trust Legal Provisions and are
	provided without warranty as described in the Simplified BSD License.		provided without warranty as described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3		1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
	2. Multiplexing . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Multiplexing . . . . . . . . . . . . . . . . . . . . . . . . 3
	2.1. Datagram Contexts . . . . . . . . . . . . . . . . . . . . 3		2.1. Datagram Contexts . . . . . . . . . . . . . . . . . . . . 3
	2.2. Context ID Allocation . . . . . . . . . . . . . . . . . . 4		2.2. Context ID Allocation . . . . . . . . . . . . . . . . . . 4
	3. HTTP/3 DATAGRAM Frame Format . . . . . . . . . . . . . . . . 4		3. HTTP/3 DATAGRAM Format . . . . . . . . . . . . . . . . . . . 4
	4. CAPSULE HTTP/3 Frame Definition . . . . . . . . . . . . . . . 5		4. CAPSULE HTTP/3 Frame Definition . . . . . . . . . . . . . . . 6
	4.1. The REGISTER_DATAGRAM_CONTEXT Capsule . . . . . . . . . . 6		4.1. The REGISTER_DATAGRAM_CONTEXT Capsule . . . . . . . . . . 7
	4.2. The CLOSE_DATAGRAM_CONTEXT Capsule . . . . . . . . . . . 7		4.2. The REGISTER_DATAGRAM_NO_CONTEXT Capsule . . . . . . . . 8
	4.3. The DATAGRAM Capsule . . . . . . . . . . . . . . . . . . 8		4.3. The CLOSE_DATAGRAM_CONTEXT Capsule . . . . . . . . . . . 10
	5. The H3_DATAGRAM HTTP/3 SETTINGS Parameter . . . . . . . . . . 9		4.4. The DATAGRAM Capsule . . . . . . . . . . . . . . . . . . 11
	6. HTTP/1.x and HTTP/2 Support . . . . . . . . . . . . . . . . . 9		5. Context Extensibility . . . . . . . . . . . . . . . . . . . . 12
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 10		5.1. The CLOSE_CODE Context Extension Type . . . . . . . . . . 12
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10		5.2. The DETAILS Context Extension Type . . . . . . . . . . . 13
	8.1. HTTP/3 CAPSULE Frame . . . . . . . . . . . . . . . . . . 10		6. The H3_DATAGRAM HTTP/3 SETTINGS Parameter . . . . . . . . . . 13
	8.2. HTTP SETTINGS Parameter . . . . . . . . . . . . . . . . . 10		7. Prioritization . . . . . . . . . . . . . . . . . . . . . . . 14
	8.3. Capsule Types . . . . . . . . . . . . . . . . . . . . . . 10		8. HTTP/1.x and HTTP/2 Support . . . . . . . . . . . . . . . . . 14
	8.4. Context Extension Keys . . . . . . . . . . . . . . . . . 11		9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
	9. Normative References . . . . . . . . . . . . . . . . . . . . 11		10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
	Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 12		10.1. HTTP/3 CAPSULE Frame . . . . . . . . . . . . . . . . . . 14
	A.1. CONNECT-UDP . . . . . . . . . . . . . . . . . . . . . . . 12		10.2. HTTP SETTINGS Parameter . . . . . . . . . . . . . . . . 14
	A.2. CONNECT-UDP with Timestamp Extension . . . . . . . . . . 13		10.3. Capsule Types . . . . . . . . . . . . . . . . . . . . . 15
	A.3. CONNECT-IP with IP compression . . . . . . . . . . . . . 14		10.4. Context Extension Types . . . . . . . . . . . . . . . . 16
	A.4. WebTransport . . . . . . . . . . . . . . . . . . . . . . 15		10.5. Context Close Codes . . . . . . . . . . . . . . . . . . 16
	Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16		11. Normative References . . . . . . . . . . . . . . . . . . . . 17
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16		Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 18
			A.1. CONNECT-UDP . . . . . . . . . . . . . . . . . . . . . . . 18
			A.2. CONNECT-UDP with Timestamp Extension . . . . . . . . . . 19
			A.3. CONNECT-IP with IP compression . . . . . . . . . . . . . 19
			A.4. WebTransport . . . . . . . . . . . . . . . . . . . . . . 20
			Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 21
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
	1. Introduction		1. Introduction
	The QUIC DATAGRAM extension [DGRAM] provides application protocols		The QUIC DATAGRAM extension [DGRAM] provides application protocols
	running over QUIC [QUIC] with a mechanism to send unreliable data		running over QUIC [QUIC] with a mechanism to send unreliable data
	while leveraging the security and congestion-control properties of		while leveraging the security and congestion-control properties of
	QUIC. However, QUIC DATAGRAM frames do not provide a means to		QUIC. However, QUIC DATAGRAM frames do not provide a means to
	demultiplex application contexts. This document describes how to use		demultiplex application contexts. This document describes how to use
	QUIC DATAGRAM frames when the application protocol running over QUIC		QUIC DATAGRAM frames when the application protocol running over QUIC
	is HTTP/3 [H3]. It associates datagrams with client-initiated		is HTTP/3 [H3]. It associates datagrams with client-initiated
	skipping to change at page 3, line 36 ¶		skipping to change at page 3, line 36 ¶
	"OPTIONAL" in this document are to be interpreted as described in BCP		"OPTIONAL" in this document are to be interpreted as described in BCP
	14 [RFC2119] [RFC8174] when, and only when, they appear in all		14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	2. Multiplexing		2. Multiplexing
	In order to allow multiple exchanges of datagrams to coexist on a		In order to allow multiple exchanges of datagrams to coexist on a
	given QUIC connection, HTTP datagrams contain two layers of		given QUIC connection, HTTP datagrams contain two layers of
	multiplexing. First, the QUIC DATAGRAM frame payload starts with an		multiplexing. First, the QUIC DATAGRAM frame payload starts with an
	encoded stream identifier that associates the datagram with a given		encoded stream identifier that associates the datagram with a given
	QUIC stream. Second, datagrams carry a context identifier (see		QUIC stream. Second, datagrams optionally carry a context identifier
	Section 2.1) that allows multiplexing multiple datagram contexts		(see Section 2.1) that allows multiplexing multiple datagram contexts
	related to a given HTTP request. Conceptually, the first layer of		related to a given HTTP request. Conceptually, the first layer of
	multiplexing is per-hop, while the second is end-to-end.		multiplexing is per-hop, while the second is end-to-end.
	2.1. Datagram Contexts		2.1. Datagram Contexts
	Within the scope of a given HTTP request, contexts provide an		Within the scope of a given HTTP request, contexts provide an
	additional demultiplexing layer. Contexts determine the encoding of		additional demultiplexing layer. Contexts determine the encoding of
	datagrams, and can be used to implicitly convey metadata. For		datagrams, and can be used to implicitly convey metadata. For
	example, contexts can be used for compression to elide some parts of		example, contexts can be used for compression to elide some parts of
	the datagram: the context identifier then maps to a compression		the datagram: the context identifier then maps to a compression
	context that the receiver can use to reconstruct the elided data.		context that the receiver can use to reconstruct the elided data.
	Contexts are identified within the scope of a given request by a		Contexts are optional, their use is negotiated on each request stream
	numeric value, referred to as the context ID. A context ID is a		using registration capsules, see Section 4.1 and Section 4.2. When
	62-bit integer (0 to 2^62-1).		contexts are used, they are identified within the scope of a given
			request by a numeric value, referred to as the context ID. A context
			ID is a 62-bit integer (0 to 2^62-1).
	While stream IDs are a per-hop concept, context IDs are an end-to-end		While stream IDs are a per-hop concept, context IDs are an end-to-end
	concept. In other words, if a datagram travels through one or more		concept. In other words, if a datagram travels through one or more
	intermediaries on its way from client to server, the stream ID will		intermediaries on its way from client to server, the stream ID will
	most likely change from hop to hop, but the context ID will remain		most likely change from hop to hop, but the context ID will remain
	the same. Context IDs are opaque to intermediaries.		the same. Context IDs are opaque to intermediaries.
	2.2. Context ID Allocation		2.2. Context ID Allocation
	Implementations of HTTP/3 that support the DATAGRAM extension MUST		Implementations of HTTP/3 that support the DATAGRAM extension MUST
	skipping to change at page 4, line 32 ¶		skipping to change at page 4, line 38 ¶
	context IDs are server-initiated. This means that an HTTP/3 client		context IDs are server-initiated. This means that an HTTP/3 client
	implementation of the context ID allocation service MUST only provide		implementation of the context ID allocation service MUST only provide
	even-numbered IDs, while a server implementation MUST only provide		even-numbered IDs, while a server implementation MUST only provide
	odd-numbered IDs. Note that, once allocated, any context ID can be		odd-numbered IDs. Note that, once allocated, any context ID can be
	used by both client and server - only allocation carries separate		used by both client and server - only allocation carries separate
	namespaces to avoid requiring synchronization. Additionally, note		namespaces to avoid requiring synchronization. Additionally, note
	that the context ID namespace is tied to a given HTTP request: it is		that the context ID namespace is tied to a given HTTP request: it is
	possible for the same numeral context ID to be used simultaneously in		possible for the same numeral context ID to be used simultaneously in
	distinct requests.		distinct requests.
	3. HTTP/3 DATAGRAM Frame Format		3. HTTP/3 DATAGRAM Format
	When used with HTTP/3, the Datagram Data field of QUIC DATAGRAM		When used with HTTP/3, the Datagram Data field of QUIC DATAGRAM
	frames uses the following format (using the notation from the		frames uses the following format (using the notation from the
	"Notational Conventions" section of [QUIC]):		"Notational Conventions" section of [QUIC]):
	HTTP/3 Datagram {		HTTP/3 Datagram {
	Quarter Stream ID (i),		Quarter Stream ID (i),
	Context ID (i),		[Context ID (i)],
	HTTP/3 Datagram Payload (..),		HTTP/3 Datagram Payload (..),
	}		}
	Figure 1: HTTP/3 DATAGRAM Frame Format		Figure 1: HTTP/3 DATAGRAM Format
	Quarter Stream ID: A variable-length integer that contains the value		Quarter Stream ID: A variable-length integer that contains the value
	of the client-initiated bidirectional stream that this datagram is		of the client-initiated bidirectional stream that this datagram is
	associated with, divided by four. (The division by four stems		associated with, divided by four. (The division by four stems
	from the fact that HTTP requests are sent on client-initiated		from the fact that HTTP requests are sent on client-initiated
	bidirectional streams, and those have stream IDs that are		bidirectional streams, and those have stream IDs that are
	divisible by four.)		divisible by four.)
	Context ID: A variable-length integer indicating the context ID of		Context ID: A variable-length integer indicating the context ID of
	the datagram (see Section 2.1).		the datagram (see Section 2.1). Whether or not this field is
			present depends on which registration capsules were exchanged on
			the associated stream: if a REGISTER_DATAGRAM_CONTEXT capsule (see
			Section 4.1) has been sent or received on this stream, then the
			field is present; if a REGISTER_DATAGRAM_NO_CONTEXT capsule (see
			Section 4.2) has been sent or received, then this field is absent;
			if neither has been sent or received, then it is not yet possible
			to parse this datagram and the receiver MUST either drop that
			datagram silently or buffer it temporarily while awaiting the
			registration capsule.
	HTTP/3 Datagram Payload: The payload of the datagram, whose		HTTP/3 Datagram Payload: The payload of the datagram, whose
	semantics are defined by individual applications. Note that this		semantics are defined by individual applications. Note that this
	field can be empty.		field can be empty.
	Intermediaries parse the Quarter Stream ID field in order to		Intermediaries parse the Quarter Stream ID field in order to
	associate the QUIC DATAGRAM frame with a stream. If an intermediary		associate the QUIC DATAGRAM frame with a stream. If an intermediary
	receives a QUIC DATAGRAM frame whose payload is too short to allow		receives a QUIC DATAGRAM frame whose payload is too short to allow
	parsing the Quarter Stream ID field, the intermediary MUST treat it		parsing the Quarter Stream ID field, the intermediary MUST treat it
	as an HTTP/3 connection error of type H3_GENERAL_PROTOCOL_ERROR.		as an HTTP/3 connection error of type H3_GENERAL_PROTOCOL_ERROR. The
	Intermediaries MUST ignore any HTTP/3 Datagram fields after the		Context ID field is optional and its use is negotiated end-to-end,
	Quarter Stream ID.		see Section 4.2. Therefore intermediaries cannot know whether the
			Context ID field is present or absent and they MUST ignore any HTTP/3
			Datagram fields after the Quarter Stream ID.
	Endpoints parse both the Quarter Stream ID field and the Context ID		Endpoints parse both the Quarter Stream ID field and the Context ID
	field in order to associate the QUIC DATAGRAM frame with a stream and		field in order to associate the QUIC DATAGRAM frame with a stream and
	context within that stream. If an endpoint receives a QUIC DATAGRAM		context within that stream. If an endpoint receives a QUIC DATAGRAM
	frame whose payload is too short to allow parsing the Quarter Stream		frame whose payload is too short to allow parsing the Quarter Stream
	ID field, the endpoint MUST treat it as an HTTP/3 connection error of		ID field, the endpoint MUST treat it as an HTTP/3 connection error of
	type H3_GENERAL_PROTOCOL_ERROR. If an endpoint receives a QUIC		type H3_GENERAL_PROTOCOL_ERROR. If an endpoint receives a QUIC
	DATAGRAM frame whose payload is long enough to allow parsing the		DATAGRAM frame whose payload is long enough to allow parsing the
	Quarter Stream ID field but too short to allow parsing the Context ID		Quarter Stream ID field but too short to allow parsing the Context ID
	field, the endpoint MUST abruptly terminate the corresponding stream		field, the endpoint MUST abruptly terminate the corresponding stream
	with a stream error of type H3_GENERAL_PROTOCOL_ERROR.		with a stream error of type H3_GENERAL_PROTOCOL_ERROR.
	If a DATAGRAM frame is received and its Quarter Stream ID maps to a		Endpoints MUST NOT send HTTP/3 datagrams unless the corresponding
	stream that has already been closed, the receiver MUST silently drop		stream's send side is open. On a given endpoint, once the receive
	that frame. If a DATAGRAM frame is received and its Quarter Stream		side of a stream is closed, incoming datagrams for this stream are no
	ID maps to a stream that has not yet been created, the receiver SHALL		longer expected so the endpoint can release related state. Endpoints
	either drop that frame silently or buffer it temporarily while		MAY keep state for a short time to account for reordering. Once the
	awaiting the creation of the corresponding stream.		state is released, the endpoint MUST silently drop received
			associated datagrams.
			If an HTTP/3 datagram is received and its Quarter Stream ID maps to a
			stream that has not yet been created, the receiver SHALL either drop
			that datagram silently or buffer it temporarily while awaiting the
			creation of the corresponding stream.
	4. CAPSULE HTTP/3 Frame Definition		4. CAPSULE HTTP/3 Frame Definition
	CAPSULE allows reliably sending request-related information end-to-		CAPSULE allows reliably sending request-related information end-to-
	end, even in the presence of HTTP intermediaries.		end, even in the presence of HTTP intermediaries.
	CAPSULE is an HTTP/3 Frame (as opposed to a QUIC frame) which SHALL		CAPSULE is an HTTP/3 Frame (as opposed to a QUIC frame) which SHALL
	only be sent in client-initiated bidirectional streams.		only be sent in client-initiated bidirectional streams.
	Intermediaries MUST forward all received CAPSULE frames in their		Intermediaries forward received CAPSULE frames on the same stream
	unmodified entirety on the same stream where it would forward DATA		where it would forward DATA frames. Each Capsule Type determines
	frames. Intermediaries MUST NOT send any CAPSULE frames other than		whether it is opaque or transparent to intermediaries: opaque
	the ones it is forwarding.		capsules are forwarded unmodified while transparent ones can be
			parsed, added, or removed by intermediaries.
	This specification of CAPSULE currently uses HTTP/3 frame type		This specification of CAPSULE currently uses HTTP/3 frame type
	0xffcab5. If this document is approved, a lower number will be		0xffcab5. If this document is approved, a lower number will be
	requested from IANA.		requested from IANA.
	CAPSULE HTTP/3 Frame {		CAPSULE HTTP/3 Frame {
	Type (i) = 0xffcab5,		Type (i) = 0xffcab5,
	Length (i),		Length (i),
	Capsule Type (i),		Capsule Type (i),
	Capsule Data (..),		Capsule Data (..),
	skipping to change at page 6, line 21 ¶		skipping to change at page 7, line 5 ¶
	Figure 2: CAPSULE HTTP/3 Frame Format		Figure 2: CAPSULE HTTP/3 Frame Format
	The Type and Length fields follows the definition of HTTP/3 frames		The Type and Length fields follows the definition of HTTP/3 frames
	from [H3]. The payload consists of:		from [H3]. The payload consists of:
	Capsule Type: The type of this capsule.		Capsule Type: The type of this capsule.
	Capsule Data: Data whose semantics depends on the Capsule Type.		Capsule Data: Data whose semantics depends on the Capsule Type.
			Unless otherwise specified, all Capsule Types are defined as opaque
			to intermediaries. Intermediaries MUST forward all received opaque
			CAPSULE frames in their unmodified entirety. Intermediaries MUST NOT
			send any opaque CAPSULE frames other than the ones it is forwarding.
			All Capsule Types defined in this document are opaque, with the
			exception of the DATAGRAM Capsule, see Section 4.4. Definitions of
			new Capsule Types MAY specify that the newly introduced type is
			transparent. Intermediaries MUST treat unknown Capsule Types as
			opaque.
			Intermediaries respect the order of opaque CAPSULE frames: if an
			intermediary receives two opaque CAPSULE frames in a given order, it
			MUST forward them in the same order.
	Endpoints which receive a Capsule with an unknown Capsule Type MUST		Endpoints which receive a Capsule with an unknown Capsule Type MUST
	silently drop that Capsule. Intermediaries MUST forward Capsules,		silently drop that Capsule.
	even if they do not know the Capsule Type or cannot parse the Capsule
	Data.		Receipt of a CAPSULE HTTP/3 Frame on a stream that is not a client-
			initiated bidirectional stream MUST be treated as a connection error
			of type H3_FRAME_UNEXPECTED.
	4.1. The REGISTER_DATAGRAM_CONTEXT Capsule		4.1. The REGISTER_DATAGRAM_CONTEXT Capsule
	The REGISTER_DATAGRAM_CONTEXT capsule (type=0x00) allows an endpoint		The REGISTER_DATAGRAM_CONTEXT capsule (type=0x00) allows an endpoint
	to inform its peer of the encoding and semantics of datagrams		to inform its peer of the encoding and semantics of datagrams
	associated with a given context ID. Its Capsule Data field consists		associated with a given context ID. Its Capsule Data field consists
	of:		of:
	REGISTER_DATAGRAM_CONTEXT Capsule {		REGISTER_DATAGRAM_CONTEXT Capsule {
	Context ID (i),		Context ID (i),
	Extension String (..),		Context Extensions (..),
	}		}
	Figure 3: REGISTER_DATAGRAM_CONTEXT Capsule Format		Figure 3: REGISTER_DATAGRAM_CONTEXT Capsule Format
	Context ID: The context ID to register.		Context ID: The context ID to register.
	Extension String: A string of comma-separated key-value pairs to		Context Extensions: See Section 5.
	enable extensibility. Keys are registered with IANA, see
	Section 8.4.
	The ABNF for the Extension String field is as follows (using syntax
	from Section 3.2.6 of [RFC7230]):
	extension-string = [ ext-member *( "," ext-member ) ]
	ext-member = ext-member-key "=" ext-member-value
	ext-member-key = token
	ext-member-value = token
	Note that these registrations are unilateral and bidirectional: the		Note that these registrations are unilateral and bidirectional: the
	sender of the frame unilaterally defines the semantics it will apply		sender of the frame unilaterally defines the semantics it will apply
	to the datagrams it sends and receives using this context ID. Once a		to the datagrams it sends and receives using this context ID. Once a
	context ID is registered, it can be used in both directions.		context ID is registered, it can be used in both directions.
	Endpoints MUST NOT send DATAGRAM frames using a Context ID until they		Endpoints MUST NOT send DATAGRAM frames using a Context ID until they
	have either sent or received a REGISTER_DATAGRAM_CONTEXT Capsule with		have either sent or received a REGISTER_DATAGRAM_CONTEXT Capsule with
	the same Context ID. However, due to reordering, an endpoint that		the same Context ID. However, due to reordering, an endpoint that
	receives a DATAGRAM frame with an unknown Context ID MUST NOT treat		receives a DATAGRAM frame with an unknown Context ID MUST NOT treat
	skipping to change at page 7, line 27 ¶		skipping to change at page 8, line 17 ¶
	Endpoints MUST NOT register the same Context ID twice on the same		Endpoints MUST NOT register the same Context ID twice on the same
	stream. This also applies to Context IDs that have been closed using		stream. This also applies to Context IDs that have been closed using
	a CLOSE_DATAGRAM_CONTEXT capsule. Clients MUST NOT register server-		a CLOSE_DATAGRAM_CONTEXT capsule. Clients MUST NOT register server-
	initiated Context IDs and servers MUST NOT register client-initiated		initiated Context IDs and servers MUST NOT register client-initiated
	Context IDs. If an endpoint receives a REGISTER_DATAGRAM_CONTEXT		Context IDs. If an endpoint receives a REGISTER_DATAGRAM_CONTEXT
	capsule that violates one or more of these requirements, the endpoint		capsule that violates one or more of these requirements, the endpoint
	MUST abruptly terminate the corresponding stream with a stream error		MUST abruptly terminate the corresponding stream with a stream error
	of type H3_GENERAL_PROTOCOL_ERROR.		of type H3_GENERAL_PROTOCOL_ERROR.
	4.2. The CLOSE_DATAGRAM_CONTEXT Capsule		Endpoints MUST NOT send a REGISTER_DATAGRAM_CONTEXT capsule on a
			stream before they have sent at least one HEADERS frame on that
			stream. This removes the need to buffer REGISTER_DATAGRAM_CONTEXT
			capsules when the endpoint needs information from headers to
			determine how to react to the capsule. If an endpoint receives a
			REGISTER_DATAGRAM_CONTEXT capsule on a stream that hasn't yet
			received a HEADERS frame, the endpoint MUST abruptly terminate the
			corresponding stream with a stream error of type
			H3_GENERAL_PROTOCOL_ERROR.
			Servers MUST NOT send a REGISTER_DATAGRAM_CONTEXT capsule on a stream
			before they have received at least one REGISTER_DATAGRAM_CONTEXT
			capsule or one REGISTER_DATAGRAM_NO_CONTEXT capsule from the client
			on that stream. This ensures that clients control whether datagrams
			are allowed for a given request. If a client receives a
			REGISTER_DATAGRAM_CONTEXT capsule on a stream where the client has
			not yet sent a REGISTER_DATAGRAM_CONTEXT capsule, the client MUST
			abruptly terminate the corresponding stream with a stream error of
			type H3_GENERAL_PROTOCOL_ERROR.
			Servers MUST NOT send a REGISTER_DATAGRAM_CONTEXT capsule on a stream
			where it has received a REGISTER_DATAGRAM_NO_CONTEXT capsule. If a
			client receives a REGISTER_DATAGRAM_CONTEXT capsule on a stream where
			the client has sent a REGISTER_DATAGRAM_NO_CONTEXT capsule, the
			client MUST abruptly terminate the corresponding stream with a stream
			error of type H3_GENERAL_PROTOCOL_ERROR.
			4.2. The REGISTER_DATAGRAM_NO_CONTEXT Capsule
			The REGISTER_DATAGRAM_NO_CONTEXT capsule (type=0x03) allows a client
			to inform the server that datagram contexts will not be used with
			this stream. It also informs the server of the encoding and
			semantics of datagrams associated with this stream. Its Capsule Data
			field consists of:
			REGISTER_DATAGRAM_NO_CONTEXT Capsule {
			Context Extensions (..),
			}
			Figure 4: REGISTER_DATAGRAM_NO_CONTEXT Capsule Format
			Context Extensions: See Section 5.
			Note that this registration is unilateral and bidirectional: the
			client unilaterally defines the semantics it will apply to the
			datagrams it sends and receives with this stream.
			Endpoints MUST NOT send DATAGRAM frames without a Context ID until
			they have either sent or received a REGISTER_DATAGRAM_NO_CONTEXT
			Capsule. However, due to reordering, an endpoint that receives a
			DATAGRAM frame before receiving either a REGISTER_DATAGRAM_CONTEXT
			capsule or a REGISTER_DATAGRAM_NO_CONTEXT capsule MUST NOT treat it
			as an error, it SHALL instead drop the DATAGRAM frame silently, or
			buffer it temporarily while awaiting a REGISTER_DATAGRAM_NO_CONTEXT
			capsule or the corresponding REGISTER_DATAGRAM_CONTEXT capsule.
			Servers MUST NOT send the REGISTER_DATAGRAM_NO_CONTEXT capsule. If a
			client receives a REGISTER_DATAGRAM_NO_CONTEXT capsule, the client
			MUST abruptly terminate the corresponding stream with a stream error
			of type H3_GENERAL_PROTOCOL_ERROR.
			Clients MUST NOT send more than one REGISTER_DATAGRAM_NO_CONTEXT
			capsule on a stream. If a server receives a second
			REGISTER_DATAGRAM_NO_CONTEXT capsule on the same stream, the server
			MUST abruptly terminate the corresponding stream with a stream error
			of type H3_GENERAL_PROTOCOL_ERROR.
			Clients MUST NOT send a REGISTER_DATAGRAM_NO_CONTEXT capsule on a
			stream before they have sent at least one HEADERS frame on that
			stream. This removes the need to buffer REGISTER_DATAGRAM_CONTEXT
			capsules when the server needs information from headers to determine
			how to react to the capsule. If a server receives a
			REGISTER_DATAGRAM_NO_CONTEXT capsule on a stream that hasn't yet
			received a HEADERS frame, the server MUST abruptly terminate the
			corresponding stream with a stream error of type
			H3_GENERAL_PROTOCOL_ERROR.
			Clients MUST NOT send both REGISTER_DATAGRAM_CONTEXT capsules and
			REGISTER_DATAGRAM_NO_CONTEXT capsules on the same stream. If a
			server receives both a REGISTER_DATAGRAM_CONTEXT capsule and a
			REGISTER_DATAGRAM_NO_CONTEXT capsule on the same stream, the server
			MUST abruptly terminate the corresponding stream with a stream error
			of type H3_GENERAL_PROTOCOL_ERROR.
			Extensions MAY define a different mechanism to negotiate the presence
			of contexts, and they MAY do so in a way which is opaque to
			intermediaries.
			4.3. The CLOSE_DATAGRAM_CONTEXT Capsule
	The CLOSE_DATAGRAM_CONTEXT capsule (type=0x01) allows an endpoint to		The CLOSE_DATAGRAM_CONTEXT capsule (type=0x01) allows an endpoint to
	inform its peer that it will no longer send or parse received		inform its peer that it will no longer send or parse received
	datagrams associated with a given context ID. Its Capsule Data field		datagrams associated with a given context ID. Its Capsule Data field
	consists of:		consists of:
	CLOSE_DATAGRAM_CONTEXT Capsule {		CLOSE_DATAGRAM_CONTEXT Capsule {
	Context ID (i),		Context ID (i),
	Extension String (..),		Context Extensions (..),
	}		}
	Figure 4: CLOSE_DATAGRAM_CONTEXT Capsule Format		Figure 5: CLOSE_DATAGRAM_CONTEXT Capsule Format
	Context ID: The context ID to close.		Context ID: The context ID to close.
	Extension String: A string of comma-separated key-value pairs to		Context Extensions: See Section 5.
	enable extensibility, see the definition of the same field in
	Section 4.1 for details.
	Note that this close is unilateral and bidirectional: the sender of		Note that this close is unilateral and bidirectional: the sender of
	the frame unilaterally informs its peer of the closure. Endpoints		the frame unilaterally informs its peer of the closure. Endpoints
	can use CLOSE_DATAGRAM_CONTEXT capsules to close a context that was		can use CLOSE_DATAGRAM_CONTEXT capsules to close a context that was
	initially registered by either themselves, or by their peer.		initially registered by either themselves, or by their peer.
	Endpoints MAY use the CLOSE_DATAGRAM_CONTEXT capsule to immediately		Endpoints MAY use the CLOSE_DATAGRAM_CONTEXT capsule to immediately
	reject a context that was just registered using a		reject a context that was just registered using a
	REGISTER_DATAGRAM_CONTEXT capsule if they find its Extension String		REGISTER_DATAGRAM_CONTEXT capsule if they find its Context Extensions
	to be unacceptable.		field to be unacceptable.
	After an endpoint has either sent or received a		After an endpoint has either sent or received a
	CLOSE_DATAGRAM_CONTEXT frame, it MUST NOT send any DATAGRAM frames		CLOSE_DATAGRAM_CONTEXT frame, it MUST NOT send any DATAGRAM frames
	with that Context ID. However, due to reordering, an endpoint that		with that Context ID. However, due to reordering, an endpoint that
	receives a DATAGRAM frame with a closed Context ID MUST NOT treat it		receives a DATAGRAM frame with a closed Context ID MUST NOT treat it
	as an error, it SHALL instead drop the DATAGRAM frame silently.		as an error, it SHALL instead drop the DATAGRAM frame silently.
	Endpoints MUST NOT close a Context ID that was not previously		Endpoints MUST NOT close a Context ID that was not previously
	registered. Endpoints MUST NOT close a Context ID that has already		registered. Endpoints MUST NOT close a Context ID that has already
	been closed. If an endpoint receives a CLOSE_DATAGRAM_CONTEXT		been closed. If an endpoint receives a CLOSE_DATAGRAM_CONTEXT
	capsule that violates one or more of these requirements, the endpoint		capsule that violates one or more of these requirements, the endpoint
	MUST abruptly terminate the corresponding stream with a stream error		MUST abruptly terminate the corresponding stream with a stream error
	of type H3_GENERAL_PROTOCOL_ERROR.		of type H3_GENERAL_PROTOCOL_ERROR.
	4.3. The DATAGRAM Capsule		All CLOSE_DATAGRAM_CONTEXT capsules MUST contain a CLOSE_CODE context
			extension, see Section 5.1. If an endpoint receives a
			CLOSE_DATAGRAM_CONTEXT capsule without a CLOSE_CODE context
			extension, the endpoint MUST abruptly terminate the corresponding
			stream with a stream error of type H3_GENERAL_PROTOCOL_ERROR.
			4.4. The DATAGRAM Capsule
	The DATAGRAM capsule (type=0x02) allows an endpoint to send a		The DATAGRAM capsule (type=0x02) allows an endpoint to send a
	datagram frame over an HTTP stream. This is particularly useful when		datagram frame over an HTTP stream. This is particularly useful when
	using a version of HTTP that does not support QUIC DATAGRAM frames.		using a version of HTTP that does not support QUIC DATAGRAM frames.
	Its Capsule Data field consists of:		Its Capsule Data field consists of:
	DATAGRAM Capsule {		DATAGRAM Capsule {
	Context ID (i),		[Context ID (i)],
	HTTP/3 Datagram Payload (..),		HTTP/3 Datagram Payload (..),
	}		}
	Figure 5: DATAGRAM Capsule Format		Figure 6: DATAGRAM Capsule Format
	Context ID: A variable-length integer indicating the context ID of		Context ID: A variable-length integer indicating the context ID of
	the datagram (see Section 2.1).		the datagram (see Section 2.1). Whether or not this field is
			present depends on which registration capsules were exchanged on
			the associated stream: if a REGISTER_DATAGRAM_CONTEXT capsule (see
			Section 4.1) has been sent or received on this stream, then the
			field is present; if a REGISTER_DATAGRAM_NO_CONTEXT capsule (see
			Section 4.2) has been sent or received, then this field is absent;
			if neither has been sent or received, then it is not yet possible
			to parse this datagram and the receiver MUST either drop that
			datagram silently or buffer it temporarily while awaiting the
			registration capsule.
	HTTP/3 Datagram Payload: The payload of the datagram, whose		HTTP/3 Datagram Payload: The payload of the datagram, whose
	semantics are defined by individual applications. Note that this		semantics are defined by individual applications. Note that this
	field can be empty.		field can be empty.
	Datagrams sent using the DATAGRAM Capsule have the exact same		Datagrams sent using the DATAGRAM Capsule have the exact same
	semantics as datagrams sent in QUIC DATAGRAM frames.		semantics as datagrams sent in QUIC DATAGRAM frames. In particular,
			the restrictions on when it is allowed to send an HTTP/3 datagram and
			how to process them from Section 3 also apply to HTTP/3 datagrams
			sent and received using the DATAGRAM capsule.
	5. The H3_DATAGRAM HTTP/3 SETTINGS Parameter		The DATAGRAM Capsule is transparent to intermediaries, meaning that
			intermediaries MAY parse it and send DATAGRAM Capsules that they did
			not receive. This allows an intermediary to reencode HTTP/3
			Datagrams as it forwards them: in other words, an intermediary MAY
			send a DATAGRAM Capsule to forward an HTTP/3 Datagram which was
			received in a QUIC DATAGRAM frame, and vice versa.
			Note that while DATAGRAM capsules are sent on a stream,
			intermediaries can reencode HTTP/3 datagrams into QUIC DATAGRAM
			frames over the next hop, and those could be dropped. Because of
			this, applications have to always consider HTTP/3 datagrams to be
			unreliable, even if they were initially sent in a capsule.
			5. Context Extensibility
			In order to facilitate extensibility of contexts, the
			REGISTER_DATAGRAM_CONTEXT, REGISTER_DATAGRAM_NO_CONTEXT, and the
			CLOSE_DATAGRAM_CONTEXT capsules carry a Context Extensions field.
			That field contains a sequence of context extensions:
			Context Extensions {
			Context Extension (..) ...,
			}
			Each context extension is encoded as a (type, length, value) tuple:
			Context Extension {
			Context Extension Type (i),
			Context Extension Length (i),
			Context Extension Value (..),
			}
			Context Extension Types are registered with IANA, see Section 10.4.
			The Context Extension Length field contains the length of the Context
			Extension Value field in bytes. The semantics of the Context
			Extension Value field are defined by the corresponding Context
			Extension Type.
			5.1. The CLOSE_CODE Context Extension Type
			The CLOSE_CODE context extension type (type=0x00) allows an endpoint
			to provide additional information as to why a datagram context was
			closed. This type SHALL only be sent in CLOSE_DATAGRAM_CONTEXT
			capsules. Its Context Extension Value field consists of a single
			variable-length integer which contains the close code. The following
			codes are defined:
			NO_ERROR (code=0x00): This indicates that the registration was
			closed without any additional information.
			DENIED (code=0x01): This indicates that the sender has rejected the
			context registration based on its local policy. The endpoint that
			had originally registered this context MUST NOT try to register
			another context with the same context extensions on this stream.
			RESOURCE_LIMIT (code=0x02): This indicates that the context was
			closed to save resources. The recipient SHOULD limit its future
			registration of resource-incentive contexts.
			Receipt of an unknown close code MUST be treated as if the NO_ERROR
			code was present. Close codes are registered with IANA, see
			Section 10.5.
			5.2. The DETAILS Context Extension Type
			The DETAILS context extension type (type=0x01) allows an endpoint to
			provide additional details to context capsules. It is meant for
			debugging purposes. Its Context Extension Value field consists of a
			human-readable string encoded in UTF-8.
			6. The H3_DATAGRAM HTTP/3 SETTINGS Parameter
	Implementations of HTTP/3 that support this mechanism can indicate		Implementations of HTTP/3 that support this mechanism can indicate
	that to their peer by sending the H3_DATAGRAM SETTINGS parameter with		that to their peer by sending the H3_DATAGRAM SETTINGS parameter with
	a value of 1. The value of the H3_DATAGRAM SETTINGS parameter MUST		a value of 1. The value of the H3_DATAGRAM SETTINGS parameter MUST
	be either 0 or 1. A value of 0 indicates that this mechanism is not		be either 0 or 1. A value of 0 indicates that this mechanism is not
	supported. An endpoint that receives the H3_DATAGRAM SETTINGS		supported. An endpoint that receives the H3_DATAGRAM SETTINGS
	parameter with a value that is neither 0 or 1 MUST terminate the		parameter with a value that is neither 0 or 1 MUST terminate the
	connection with error H3_SETTINGS_ERROR.		connection with error H3_SETTINGS_ERROR.
	An endpoint that sends the H3_DATAGRAM SETTINGS parameter with a		An endpoint that sends the H3_DATAGRAM SETTINGS parameter with a
	skipping to change at page 9, line 35 ¶		skipping to change at page 14, line 5 ¶
	0-RTT data, they MUST send a H3_DATAGRAM SETTINGS parameter greater		0-RTT data, they MUST send a H3_DATAGRAM SETTINGS parameter greater
	than or equal to the value they sent to the client in the connection		than or equal to the value they sent to the client in the connection
	where they sent them the NewSessionTicket message. If a client		where they sent them the NewSessionTicket message. If a client
	stores the value of the H3_DATAGRAM SETTINGS parameter with their		stores the value of the H3_DATAGRAM SETTINGS parameter with their
	0-RTT state, they MUST validate that the new value of the H3_DATAGRAM		0-RTT state, they MUST validate that the new value of the H3_DATAGRAM
	SETTINGS parameter sent by the server in the handshake is greater		SETTINGS parameter sent by the server in the handshake is greater
	than or equal to the stored value; if not, the client MUST terminate		than or equal to the stored value; if not, the client MUST terminate
	the connection with error H3_SETTINGS_ERROR. In all cases, the		the connection with error H3_SETTINGS_ERROR. In all cases, the
	maximum permitted value of the H3_DATAGRAM SETTINGS parameter is 1.		maximum permitted value of the H3_DATAGRAM SETTINGS parameter is 1.
	6. HTTP/1.x and HTTP/2 Support		7. Prioritization
			Prioritization of HTTP/3 datagrams is not defined in this document.
			Future extensions MAY define how to prioritize datagrams, and MAY
			define signaling to allow endpoints to communicate their
			prioritization preferences.
			8. HTTP/1.x and HTTP/2 Support
	We can provide DATAGRAM support in HTTP/2 by defining the CAPSULE		We can provide DATAGRAM support in HTTP/2 by defining the CAPSULE
	frame in HTTP/2.		frame in HTTP/2.
	We can provide DATAGRAM support in HTTP/1.x by defining its data		We can provide DATAGRAM support in HTTP/1.x by defining its data
	stream format to a sequence of length-value capsules.		stream format to a sequence of length-value capsules.
	TODO: Refactor this document into "HTTP Datagrams" with definitions		TODO: Refactor this document into "HTTP Datagrams" with definitions
	for HTTP/1.x, HTTP/2, and HTTP/3.		for HTTP/1.x, HTTP/2, and HTTP/3.
	7. Security Considerations		9. Security Considerations
	Since this feature requires sending an HTTP/3 Settings parameter, it		Since this feature requires sending an HTTP/3 Settings parameter, it
	"sticks out". In other words, probing clients can learn whether a		"sticks out". In other words, probing clients can learn whether a
	server supports this feature. Implementations that support this		server supports this feature. Implementations that support this
	feature SHOULD always send this Settings parameter to avoid leaking		feature SHOULD always send this Settings parameter to avoid leaking
	the fact that there are applications using HTTP/3 datagrams enabled		the fact that there are applications using HTTP/3 datagrams enabled
	on this endpoint.		on this endpoint.
	8. IANA Considerations		10. IANA Considerations
	8.1. HTTP/3 CAPSULE Frame		10.1. HTTP/3 CAPSULE Frame
	This document will request IANA to register the following entry in		This document will request IANA to register the following entry in
	the "HTTP/3 Frames" registry:		the "HTTP/3 Frames" registry:
	+------------+----------+---------------+		+------------+----------+---------------+
	| Frame Type | Value | Specification |		| Frame Type | Value | Specification |
	+============+==========+===============+		+============+==========+===============+
	| CAPSULE | 0xffcab5 | This Document |		| CAPSULE | 0xffcab5 | This Document |
	+------------+----------+---------------+		+------------+----------+---------------+
	8.2. HTTP SETTINGS Parameter		10.2. HTTP SETTINGS Parameter
	This document will request IANA to register the following entry in		This document will request IANA to register the following entry in
	the "HTTP/3 Settings" registry:		the "HTTP/3 Settings" registry:
	+--------------+----------+---------------+---------+		+--------------+----------+---------------+---------+
	| Setting Name | Value | Specification | Default |		| Setting Name | Value | Specification | Default |
	+==============+==========+===============+=========+		+==============+==========+===============+=========+
	| H3_DATAGRAM | 0xffd276 | This Document | 0 |		| H3_DATAGRAM | 0xffd276 | This Document | 0 |
	+--------------+----------+---------------+---------+		+--------------+----------+---------------+---------+
	8.3. Capsule Types		10.3. Capsule Types
	This document establishes a registry for HTTP/3 frame type codes.		This document establishes a registry for HTTP/3 capsule type codes.
	The "HTTP Capsule Types" registry governs a 62-bit space.		The "HTTP Capsule Types" registry governs a 62-bit space.
	Registrations in this registry MUST include the following fields:		Registrations in this registry MUST include the following fields:
	Type:		Type:
	A name or label for the capsule type.		A name or label for the capsule type.
	Value: The value of the Capsule Type field (see Section 4) is a		Value: The value of the Capsule Type field (see Section 4) is a
	62bit integer.		62bit integer.
	Reference: An optional reference to a specification for the type.		Reference: An optional reference to a specification for the type.
	This field MAY be empty.		This field MAY be empty.
	Registrations follow the "First Come First Served" policy (see		Registrations follow the "First Come First Served" policy (see
	Section 4.4 of [IANA-POLICY]) where two registrations MUST NOT have		Section 4.4 of [IANA-POLICY]) where two registrations MUST NOT have
	the same Type.		the same Type.
	This registry initially contains the following entries:		This registry initially contains the following entries:
	+---------------------------+-------+---------------+		+------------------------------+-------+---------------+
	| Capsule Type | Value | Specification |		| Capsule Type | Value | Specification |
	+---------------------------+-------+---------------+		+------------------------------+-------+---------------+
	| REGISTER_DATAGRAM_CONTEXT | 0x00 | This Document |		| REGISTER_DATAGRAM_CONTEXT | 0x00 | This Document |
	+---------------------------+-------+---------------+		+------------------------------+-------+---------------+
	| CLOSE_DATAGRAM_CONTEXT | 0x01 | This Document |		| CLOSE_DATAGRAM_CONTEXT | 0x01 | This Document |
	+---------------------------+-------+---------------+		+------------------------------+-------+---------------+
	| DATAGRAM | 0x02 | This Document |		| DATAGRAM | 0x02 | This Document |
	+---------------------------+-------+---------------+		+------------------------------+-------+---------------+
			| REGISTER_DATAGRAM_NO_CONTEXT | 0x03 | This Document |
			+------------------------------+-------+---------------+
	8.4. Context Extension Keys		Capsule types with a value of the form 41 * N + 23 for integer values
			of N are reserved to exercise the requirement that unknown capsule
			types be ignored. These capsules have no semantics and can carry
			arbitrary values. These values MUST NOT be assigned by IANA and MUST
			NOT appear in the listing of assigned values.
	REGISTER_DATAGRAM_CONTEXT capsules carry key-value pairs, see		10.4. Context Extension Types
	Section 4.1. This document will request IANA to create an "HTTP
	Datagram Context Extension Keys" registry. Registrations in this
	registry MUST include the following fields:
	Key: The key (see Section 4.1). Keys MUST be valid tokens as		This document establishes a registry for HTTP/3 datagram context
	defined in Section 3.2.6 of [RFC7230].		extension type codes. The "HTTP Context Extension Types" registry
			governs a 62-bit space. Registrations in this registry MUST include
			the following fields:
	Description: A brief description of the key semantics, which MAY be		Type:
	a summary if a specification reference is provided.
			A name or label for the context extension type.
			Value: The value of the Context Extension Type field (see Section 5)
			is a 62bit integer.
	Reference: An optional reference to a specification for the		Reference: An optional reference to a specification for the
	parameter. This field MAY be empty.		parameter. This field MAY be empty.
	Registrations follow the "First Come First Served" policy (see		Registrations follow the "First Come First Served" policy (see
	Section 4.4 of [IANA-POLICY]) where two registrations MUST NOT have		Section 4.4 of [IANA-POLICY]) where two registrations MUST NOT have
	the same Key. This registry is initially empty.		the same Type nor Value.
	9. Normative References		This registry initially contains the following entries:
			+------------------------------+-------+---------------+
			| Context Extension Type | Value | Specification |
			+------------------------------+-------+---------------+
			| CLOSE_CODE | 0x00 | This Document |
			+------------------------------+-------+---------------+
			| DETAILS | 0x01 | This Document |
			+------------------------------+-------+---------------+
			Context extension types with a value of the form 41 * N + 17 for
			integer values of N are reserved to exercise the requirement that
			unknown context extension types be ignored. These extensions have no
			semantics and can carry arbitrary values. These values MUST NOT be
			assigned by IANA and MUST NOT appear in the listing of assigned
			values.
			10.5. Context Close Codes
			This document establishes a registry for HTTP/3 context extension
			type codes. The "HTTP Context Close Codes" registry governs a 62-bit
			space. Registrations in this registry MUST include the following
			fields:
			Type:
			A name or label for the close code.
			Value: The value of the CLOSE_CODE Context Extension Value field
			(see Section 5.1) is a 62bit integer.
			Reference: An optional reference to a specification for the
			parameter. This field MAY be empty.
			Registrations follow the "First Come First Served" policy (see
			Section 4.4 of [IANA-POLICY]) where two registrations MUST NOT have
			the same Type nor Value.
			This registry initially contains the following entries:
			+------------------------------+-------+---------------+
			| Context Close Code | Value | Specification |
			+------------------------------+-------+---------------+
			| NO_ERROR | 0x00 | This Document |
			+------------------------------+-------+---------------+
			| DENIED | 0x01 | This Document |
			+------------------------------+-------+---------------+
			| RESOURCE_LIMIT | 0x02 | This Document |
			+------------------------------+-------+---------------+
			Context close codes with a value of the form 41 * N + 19 for integer
			values of N are reserved to exercise the requirement that unknown
			context close codes be treated as NO_ERROR. These values MUST NOT be
			assigned by IANA and MUST NOT appear in the listing of assigned
			values.
			11. Normative References
	[DGRAM] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable		[DGRAM] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
	Datagram Extension to QUIC", Work in Progress, Internet-		Datagram Extension to QUIC", Work in Progress, Internet-
	Draft, draft-ietf-quic-datagram-02, 16 February 2021,		Draft, draft-ietf-quic-datagram-02, 16 February 2021,
	<https://tools.ietf.org/html/draft-ietf-quic-datagram-02>.		<https://tools.ietf.org/html/draft-ietf-quic-datagram-02>.
	[H3] Bishop, M., "Hypertext Transfer Protocol Version 3		[H3] Bishop, M., "Hypertext Transfer Protocol Version 3
	(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-		(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
	quic-http-34, 2 February 2021,		quic-http-34, 2 February 2021,
	<https://tools.ietf.org/html/draft-ietf-quic-http-34>.		<https://tools.ietf.org/html/draft-ietf-quic-http-34>.
	skipping to change at page 12, line 22 ¶		skipping to change at page 18, line 16 ¶
	and Secure Transport", Work in Progress, Internet-Draft,		and Secure Transport", Work in Progress, Internet-Draft,
	draft-ietf-quic-transport-34, 14 January 2021,		draft-ietf-quic-transport-34, 14 January 2021,
	<https://tools.ietf.org/html/draft-ietf-quic-transport-		<https://tools.ietf.org/html/draft-ietf-quic-transport-
	34>.		34>.
	[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/rfc/rfc2119>.		<https://www.rfc-editor.org/rfc/rfc2119>.
	[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Message Syntax and Routing",
	RFC 7230, DOI 10.17487/RFC7230, June 2014,
	<https://www.rfc-editor.org/rfc/rfc7230>.
	[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/rfc/rfc8174>.		May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
	Appendix A. Examples		Appendix A. Examples
	A.1. CONNECT-UDP		A.1. CONNECT-UDP
	Client Server		Client Server
	STREAM(44): HEADERS -------->		STREAM(44): HEADERS -------->
	:method = CONNECT-UDP		:method = CONNECT-UDP
	:scheme = https		:scheme = https
	:path = /		:path = /
	:authority = target.example.org:443		:authority = target.example.org:443
	STREAM(44): CAPSULE -------->		STREAM(44): CAPSULE -------->
	Capsule Type = REGISTER_DATAGRAM_CONTEXT		Capsule Type = REGISTER_DATAGRAM_CONTEXT
	Context ID = 0		Context ID = 0
	Extension String = ""		Context Extension = {}
	DATAGRAM -------->		DATAGRAM -------->
	Quarter Stream ID = 11		Quarter Stream ID = 11
	Context ID = 0		Context ID = 0
	Payload = Encapsulated UDP Payload		Payload = Encapsulated UDP Payload
	<-------- STREAM(44): HEADERS		<-------- STREAM(44): HEADERS
	:status = 200		:status = 200
	/* Wait for target server to respond to UDP packet. */		/* Wait for target server to respond to UDP packet. */
	skipping to change at page 14, line 4 ¶		skipping to change at page 19, line 6 ¶
	:status = 200		:status = 200
	/* Wait for target server to respond to UDP packet. */		/* Wait for target server to respond to UDP packet. */
	<-------- DATAGRAM		<-------- DATAGRAM
	Quarter Stream ID = 11		Quarter Stream ID = 11
	Context ID = 0		Context ID = 0
	Payload = Encapsulated UDP Payload		Payload = Encapsulated UDP Payload
	A.2. CONNECT-UDP with Timestamp Extension		A.2. CONNECT-UDP with Timestamp Extension
	Client Server		Client Server
	STREAM(44): HEADERS -------->		STREAM(44): HEADERS -------->
	:method = CONNECT-UDP		:method = CONNECT-UDP
	:scheme = https		:scheme = https
	:path = /		:path = /
	:authority = target.example.org:443		:authority = target.example.org:443
	STREAM(44): CAPSULE -------->		STREAM(44): CAPSULE -------->
	Capsule Type = REGISTER_DATAGRAM_CONTEXT		Capsule Type = REGISTER_DATAGRAM_CONTEXT
	Context ID = 0		Context ID = 0
	Extension String = ""		Context Extension = {}
	DATAGRAM -------->		DATAGRAM -------->
	Quarter Stream ID = 11		Quarter Stream ID = 11
	Context ID = 0		Context ID = 0
	Payload = Encapsulated UDP Payload		Payload = Encapsulated UDP Payload
	<-------- STREAM(44): HEADERS		<-------- STREAM(44): HEADERS
	:status = 200		:status = 200
	/* Wait for target server to respond to UDP packet. */		/* Wait for target server to respond to UDP packet. */
	<-------- DATAGRAM		<-------- DATAGRAM
	Quarter Stream ID = 11		Quarter Stream ID = 11
	Context ID = 0		Context ID = 0
	Payload = Encapsulated UDP Payload		Payload = Encapsulated UDP Payload
	STREAM(44): CAPSULE -------->		STREAM(44): CAPSULE -------->
	Capsule Type = REGISTER_DATAGRAM_CONTEXT		Capsule Type = REGISTER_DATAGRAM_CONTEXT
	Context ID = 2		Context ID = 2
	Extension String = "timestamp"		Context Extension = {TIMESTAMP=""}
	DATAGRAM -------->		DATAGRAM -------->
	Quarter Stream ID = 11		Quarter Stream ID = 11
	Context ID = 2		Context ID = 2
	Payload = Encapsulated UDP Payload With Timestamp		Payload = Encapsulated UDP Payload With Timestamp
	A.3. CONNECT-IP with IP compression		A.3. CONNECT-IP with IP compression
	Client Server		Client Server
	STREAM(44): HEADERS -------->		STREAM(44): HEADERS -------->
	:method = CONNECT-IP		:method = CONNECT-IP
	:scheme = https		:scheme = https
	:path = /		:path = /
	:authority = proxy.example.org:443		:authority = proxy.example.org:443
	<-------- STREAM(44): HEADERS		<-------- STREAM(44): HEADERS
	:status = 200		:status = 200
	/* Exchange CONNECT-IP configuration information. */		/* Exchange CONNECT-IP configuration information. */
	STREAM(44): CAPSULE -------->		STREAM(44): CAPSULE -------->
	Capsule Type = REGISTER_DATAGRAM_CONTEXT		Capsule Type = REGISTER_DATAGRAM_CONTEXT
	Context ID = 0		Context ID = 0
	Extension String = ""		Context Extension = {}
	DATAGRAM -------->		DATAGRAM -------->
	Quarter Stream ID = 11		Quarter Stream ID = 11
	Context ID = 0		Context ID = 0
	Payload = Encapsulated IP Packet		Payload = Encapsulated IP Packet
	/* Endpoint happily exchange encapsulated IP packets */		/* Endpoint happily exchange encapsulated IP packets */
	/* using Quarter Stream ID 11 and Context ID 0. */		/* using Quarter Stream ID 11 and Context ID 0. */
	DATAGRAM -------->		DATAGRAM -------->
	Quarter Stream ID = 11		Quarter Stream ID = 11
	Context ID = 0		Context ID = 0
	Payload = Encapsulated IP Packet		Payload = Encapsulated IP Packet
	/* After performing some analysis on traffic patterns, */		/* After performing some analysis on traffic patterns, */
	/* the client decides it wants to compress a 5-tuple. */		/* the client decides it wants to compress a 5-tuple. */
	STREAM(44): CAPSULE -------->		STREAM(44): CAPSULE -------->
	Capsule Type = REGISTER_DATAGRAM_CONTEXT		Capsule Type = REGISTER_DATAGRAM_CONTEXT
	Context ID = 2		Context ID = 2
	Extension String = "ip=192.0.2.42,port=443"		Context Extension = {IP_COMPRESSION=tcp,192.0.2.6:9876,192.0.2.7:443}
	DATAGRAM -------->		DATAGRAM -------->
	Quarter Stream ID = 11		Quarter Stream ID = 11
	Context ID = 2		Context ID = 2
	Payload = Compressed IP Packet		Payload = Compressed IP Packet
	A.4. WebTransport		A.4. WebTransport
	Client Server		Client Server
	STREAM(44): HEADERS -------->		STREAM(44): HEADERS -------->
	:method = CONNECT		:method = CONNECT
	:scheme = https		:scheme = https
	:method = webtransport		:method = webtransport
	:path = /hello		:path = /hello
	:authority = webtransport.example.org:443		:authority = webtransport.example.org:443
	Origin = https://www.example.org:443		Origin = https://www.example.org:443
	STREAM(44): CAPSULE -------->		STREAM(44): CAPSULE -------->
	Capsule Type = REGISTER_DATAGRAM_CONTEXT		Capsule Type = REGISTER_DATAGRAM_NO_CONTEXT
	Context ID = 0		Context Extension = {}
	Extension String = ""
	<-------- STREAM(44): HEADERS		<-------- STREAM(44): HEADERS
	:status = 200		:status = 200
	/* Both endpoints can now send WebTransport datagrams. */		/* Both endpoints can now send WebTransport datagrams. */
	Acknowledgments		Acknowledgments
	The DATAGRAM context identifier was previously part of the DATAGRAM		The DATAGRAM context identifier was previously part of the DATAGRAM
	frame definition itself, the authors would like to acknowledge the		frame definition itself, the authors would like to acknowledge the
End of changes. 60 change blocks.
	147 lines changed or deleted		421 lines changed or added
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