wdiff draft-ietf-masque-h3-datagram-03.txt draft-ietf-masque-h3-datagram-04.txt

MASQUE D. Schinazi
Internet-Draft Google LLC
Intended status: Standards Track L. Pardue
Expires: 13 January 10 April 2022 Cloudflare
12 July
7 October 2021

Using Datagrams with HTTP
draft-ietf-masque-h3-datagram-03
draft-ietf-masque-h3-datagram-04

Abstract

The QUIC DATAGRAM extension provides application protocols running
over QUIC with a mechanism to send unreliable data while leveraging
the security and congestion-control properties of QUIC. However,
QUIC DATAGRAM frames do not provide a means to demultiplex
application contexts. This document describes how to use QUIC
DATAGRAM frames when the application protocol running over QUIC is
HTTP/3. It associates datagrams with client-initiated bidirectional
streams and defines an optional additional demultiplexing layer.
Additionally, this document defines how to convey datagrams over
prior versions of HTTP.

Discussion Venues

This note is to be removed before publishing as an RFC.

Discussion of this document takes place on the MASQUE WG mailing list
(masque@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/masque/.

Source for this draft and an issue tracker can be found at
https://github.com/ietf-wg-masque/draft-ietf-masque-h3-datagram.

Status of This Memo

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provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on 13 January 10 April 2022.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3 4
2. Multiplexing . . . . . . . . . . . . . . . . . . . . . . . . 3 4
2.1. Datagram Contexts . . . . . . . . . . . . . . . . . . . . 4
2.2. Datagram Formats . . . . . . . . . . . . . . . . . . . . 5
2.3. Context ID Allocation . . . . . . . . . . . . . . . . . . 4 5
3. HTTP/3 DATAGRAM Format . . . . . . . . . . . . . . . . . . . 4 6
4. CAPSULE HTTP/3 Frame Definition Capsules . . . . . . . . . . . . . . . 6 . . . . . . . . . . . 7
4.1. The REGISTER_DATAGRAM_CONTEXT Capsule Protocol . . . . . . . . . . 7 . . . . . . . . . . 8
4.2. The REGISTER_DATAGRAM_NO_CONTEXT Capsule Requirements . . . . . . . . . . . . . . . . . . . . . . 9
4.3. The CLOSE_DATAGRAM_CONTEXT Capsule Intermediary Processing . . . . . . . . . . . 10 . . . . . . 9
4.4. The DATAGRAM Capsule Types . . . . . . . . . . . . . . . . . . 11
5. Context Extensibility . . . . 10
4.4.1. The REGISTER_DATAGRAM_CONTEXT Capsule . . . . . . . . 10
4.4.2. The REGISTER_DATAGRAM_NO_CONTEXT Capsule . . . . . . 11
4.4.3. The CLOSE_DATAGRAM_CONTEXT Capsule . . 12
5.1. The CLOSE_CODE Context Extension Type . . . . . . . 12
4.4.4. The DATAGRAM Capsule . . . 13
5.2. The DETAILS Context Extension Type . . . . . . . . . . . 13
6. . . 14
5. The H3_DATAGRAM HTTP/3 SETTINGS Parameter . . . . . . . . . . 13
7. Prioritization . 16
5.1. Note About Draft Versions . . . . . . . . . . . . . . . . 16
6. Prioritization . . . . . . 14
8. HTTP/1.x and HTTP/2 Support . . . . . . . . . . . . . . . . . 14
9. 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10.1. 17
8.1. HTTP/3 CAPSULE Frame SETTINGS Parameter . . . . . . . . . . . . . . . . 17
8.2. Capsule Types . . . 14
10.2. HTTP/3 SETTINGS Parameter . . . . . . . . . . . . . . . 15
10.3. Capsule Types . . . . 17
8.3. Datagram Format Types . . . . . . . . . . . . . . . . . . 15
10.4. 18
8.4. Context Extension Types Close Codes . . . . . . . . . . . . . . . . 16
10.5. Context Close Codes . . . 19
9. References . . . . . . . . . . . . . . . 17
11. . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . 17 . . . . . . . . . . . . . . 20
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 18 21
A.1. CONNECT-UDP . . . . . . . . . . . . . . . . . . . . . . . 18 21
A.2. CONNECT-UDP with Timestamp Extension . . . . . . . . . . 19 21
A.3. CONNECT-IP with IP compression . . . . . . . . . . . . . 20 22
A.4. WebTransport . . . . . . . . . . . . . . . . . . . . . . 21 24
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 22 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 24

1. Introduction

The QUIC DATAGRAM extension [DGRAM] provides application protocols
running over QUIC [QUIC] with a mechanism to send unreliable data
while leveraging the security and congestion-control properties of
QUIC. However, QUIC DATAGRAM frames do not provide a means to
demultiplex application contexts. This document describes how to use
QUIC DATAGRAM frames when the application protocol running over QUIC
is HTTP/3 [H3]. It associates datagrams with client-initiated
bidirectional streams and defines an optional additional
demultiplexing layer. Additionally, this document defines how to
convey datagrams over prior versions of HTTP.

1.1. Conventions and Definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this

This document are to be interpreted is structured as described in BCP
14 follows:

* Section 2 presents core concepts for multiplexing across HTTP
versions.

- Section 2.1 defines datagram contexts, an optional end-to-end
multiplexing concept scoped to each HTTP request.

- Section 2.2 defines datagram formats, which are scoped to
contexts. Formats communicate the format and encoding of
datagrams sent using the associated context.

- Contexts are identified using a variable-length integer.
Requirements for allocating identifier values are detailed in
Section 2.3.

* Section 3 defines how QUIC DATAGRAM frames are used with HTTP/3.
Section 5 defines an HTTP/3 setting that endpoints can use to
advertise support of the frame.

* Section 4 introduces the Capsule Protocol and the "data stream"
concept. Data streams are initiated using special-purpose HTTP
requests, after which Capsules, an end-to-end message, can be
sent.

- The following Capsule types are defined, together with guidance
for defining new types:

o REGISTER_DATAGRAM_CONTEXT Section 4.4.1
o REGISTER_DATAGRAM_NO_CONTEXT Section 4.4.2

o CLOSE_DATAGRAM_CONTEXT Section 4.4.3

o DATAGRAM Section 4.4.4

1.1. Conventions and Definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

2. Multiplexing

When running over HTTP/3, multiple exchanges of datagrams need the
ability to coexist on a given QUIC connection. To allow this, HTTP
datagrams contain two layers of multiplexing. First, the QUIC
DATAGRAM frame payload starts with an encoded stream identifier that
associates the datagram with a given QUIC stream. Second, datagrams
optionally carry a context identifier (see Section 2.1) that allows
multiplexing multiple datagram contexts related to a given HTTP
request. Conceptually, the first layer of multiplexing is per-hop,
while the second is end-to-end.

When running over HTTP/2, the first level of demultiplexing is
provided by the HTTP/2 framing layer. When running over HTTP/1,
requests are strictly serialized in the connection, therefore the
first layer of demultiplexing is not needed.

2.1. Datagram Contexts

Within the scope of a given HTTP request, contexts provide an
additional demultiplexing layer. Contexts determine the encoding of
datagrams, and can be used to implicitly convey metadata. For
example, contexts can be used for compression to elide some parts of
the datagram: the context identifier then maps to a compression
context that the receiver can use to reconstruct the elided data.

Contexts are optional, their whether to use them or not is negotiated decided by the
client on each request stream using registration capsules, see
Section 4.1 4.4.1 and Section 4.2. 4.4.2. When 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
concept. In other words, if a datagram travels through one or more
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
the same. Context IDs are opaque to intermediaries.

2.2. Context ID Allocation

Implementations of HTTP Datagrams MUST provide a context ID
allocation service. That service will allow applications co-located
with HTTP to request Datagram Formats

When an endpoint registers a unique datagram context ID that they can subsequently
use for their own purposes. The HTTP implementation will then parse (or the context ID lack of incoming HTTP Datagrams and use
contexts), it to deliver communicates the
frame to format (i.e., the appropriate application semantics and
encoding) of datagrams sent using this context.

Even-numbered context IDs are client-initiated, while odd-numbered
context IDs are server-initiated. This means that an HTTP client
implementation is
acccomplished by sending a Datagram Format Type as part of the context ID allocation
registration capsule, see Section 4.4.1 and Section 4.4.2. This type
identifier is registered with IANA (see Section 8.3) and allows
applications that use HTTP Datagrams to indicate what the content of
datagrams are. Registration capsules carry a Datagram Format
Additional Data field which allows sending some additional
information that would impact the format of datagrams.

For example, a protocol which proxies IP packets can define a
Datagram Format Type which represents an IP packet. The
corresponding Datagram Format Additional Data field would be empty.
An extension to such a protocol that wishes to compress IP addresses
could define a distinct Datagram Format Type and exchange two IP
addresses via the Datagram Format Additional Data field. Then any
datagrams with that type would contain the IP packet with addresses
elided.

2.3. Context ID Allocation

Implementations of HTTP Datagrams MUST provide a context ID
allocation service. That service will allow applications co-located
with HTTP to request a unique context ID that they can subsequently
use for their own purposes. The HTTP implementation will then parse
the context ID of incoming HTTP Datagrams and use it to deliver the
frame to the appropriate application context.

Even-numbered context IDs are client-initiated, while odd-numbered
context IDs are server-initiated. This means that an HTTP client
implementation of the context ID allocation service 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
used by both client and server - only allocation carries separate
namespaces to avoid requiring synchronization. Additionally, note
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
distinct requests.

3. HTTP/3 DATAGRAM Format

When used with HTTP/3, the Datagram Data field of QUIC DATAGRAM
frames uses the following format (using the notation from the
"Notational Conventions" section of [QUIC]):

HTTP/3 Datagram {
Quarter Stream ID (i),
[Context ID (i)],
HTTP Datagram Payload (..),
}

Figure 1: HTTP/3 DATAGRAM Format

Quarter Stream ID: A variable-length integer that contains the value
of the client-initiated bidirectional stream that this datagram is
associated with, divided by four. (The four (the division by four stems from
the fact that HTTP requests are sent on client-initiated
bidirectional streams, and those have stream IDs that are
divisible by four.) four). The largest legal QUIC stream ID value is
2^62-1, so the largest legal value of Quarter Stream ID is 2^62-1
/ 4. Receipt of a frame that includes a larger value MUST be
treated as a connection error of type FRAME_ENCODING_ERROR.

Context ID: A variable-length integer indicating the context ID of
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) 4.4.1) has been sent or received on this stream, then the
field is present; if a REGISTER_DATAGRAM_NO_CONTEXT capsule (see
Section 4.2) 4.4.2) 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 Datagram Payload: The payload of the datagram, whose semantics
are defined by individual applications. Note that this field can
be empty.

Intermediaries parse the Quarter Stream ID field in order to
associate the QUIC DATAGRAM frame with a stream. If an intermediary
receives a QUIC DATAGRAM frame whose payload is too short to allow
parsing the Quarter Stream ID field, the intermediary MUST treat it
as an HTTP/3 connection error of type H3_GENERAL_PROTOCOL_ERROR. The
Context ID field is optional and its use whether it is present or not is negotiated end-to-end,
decided end-to-end by the client, see Section 4.2. 4.4.2. 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
field in order to associate the QUIC DATAGRAM frame with a stream and
context within that stream. If an endpoint receives a QUIC DATAGRAM
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
type H3_GENERAL_PROTOCOL_ERROR. If an endpoint receives a QUIC
DATAGRAM frame whose payload is long enough to allow parsing the
Quarter Stream ID field but too short to allow parsing the Context ID
field, the endpoint MUST abruptly terminate the corresponding stream
with a stream error of type H3_GENERAL_PROTOCOL_ERROR.

Endpoints MUST NOT send HTTP/3 datagrams unless the corresponding
stream's send side is open. On a given endpoint, once the receive
side of a stream is closed, incoming datagrams for this stream are no
longer expected so the endpoint can release related state. Endpoints
MAY keep state for a short time to account for reordering. Once the
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

CAPSULE Capsules

This specification introduces the Capsule Protocol. The Capsule
Protocol is a sequence of type-length-value tuples that allows
endpoints to reliably sending communicate request-related information end-to-
end, even in the presence of HTTP intermediaries.

CAPSULE is

4.1. Capsule Protocol

This specification defines the "data stream" of an HTTP/3 Frame (as opposed to HTTP request as
the bidirectional stream of bytes that follow the headers in both
directions. In HTTP/1.x, the data stream consists of all bytes on
the connection that follow the blank line that concludes either the
request header section, or the 2xx (Successful) response header
section. In HTTP/2 and HTTP/3, the data stream of a QUIC frame) which SHALL
only be given HTTP
request consists of all bytes sent in client-initiated bidirectional streams.
Intermediaries forward received CAPSULE DATA frames on with the same
corresponding stream ID. The concept of a data stream is
particularly relevant for methods such as CONNECT where it would forward DATA frames. Each Capsule Type determines
whether it there is opaque or transparent to intermediaries: opaque
capsules are forwarded unmodified while transparent ones can be
parsed, added, no
HTTP message content after the headers.

Definitions of new HTTP Methods or removed by intermediaries.

This specification of CAPSULE currently new HTTP Upgrade Tokens can
state that their data stream uses HTTP/3 frame type
0xffcab5. the Capsule Protocol. If this document is approved, a lower number will be
requested they do
so, that means that the contents of their data stream uses the
following format (using the notation from IANA.

CAPSULE HTTP/3 Frame the "Notational
Conventions" section of [QUIC]):

Capsule Protocol {
Capsule (..) ...,
}

Figure 2: Capsule Protocol Stream Format

Capsule {
Capsule Type (i) = 0xffcab5,
Length (i),
Capsule Type Length (i),
Capsule Data Value (..),
}

Figure 2: CAPSULE HTTP/3 Frame 3: Capsule Format

The Type and Length fields follows the definition of HTTP/3 frames
from [H3]. The payload consists of:

Capsule Type: The type A variable-length integer indicating the Type of this the
capsule. Endpoints that receive a capsule with an unknown Capsule Data: Data whose semantics depends on
Type MUST silently skip over that capsule.

Capsule Length: The length of the Capsule Type.

Unless otherwise specified, all Value field following this
field, encoded as a variable-length integer. Note that this field
can have a value of zero.

Capsule Value: The payload of this capsule. Its semantics are
determined by the value of the Capsule Type field.

4.2. Requirements

If the definition of an HTTP Method or HTTP Upgrade Token states that
it uses the capsule protocol, its implementations MUST follow the
following requirements:

* A server MUST NOT send any Transfer-Encoding or Content-Length
header fields in a 2xx (Successful) response. If a client
receives a Content-Length or Transfer-Encoding header fields in a
successful response, it MUST treat that response as malformed.

* A request message does not have content.

* A successful response message does not have content.

* Responses are not cacheable.

4.3. Intermediary Processing

Intermediaries MUST operate in one of the two following modes:

Pass-through mode: In this mode, the intermediary forwards the data
stream between two associated streams without any modification of
the data stream.

Participant mode: In this mode, the intermediary terminates the data
stream and parses all Capsule Type and Capsule Length fields it
receives.

Each Capsule Type determines whether it is opaque or transparent to
intermediaries in participant mode: opaque capsules are forwarded
unmodified while transparent ones can be parsed, added, or removed by
intermediaries. Intermediaries MAY modify the contents of the
Capsule Data field of transparent capsule types.

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. 4.4.4. 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
silently drop that Capsule.

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.

4.4. Capsule Types

4.4.1. The REGISTER_DATAGRAM_CONTEXT Capsule

The REGISTER_DATAGRAM_CONTEXT capsule (type=0x00) (see Section 8.2 for the value
of the capsule type) allows an endpoint to inform its peer of the
encoding and semantics of datagrams associated with a given context
ID. Its Capsule Data field consists
of:

REGISTER_DATAGRAM_CONTEXT Capsule {
Type (i) = REGISTER_DATAGRAM_CONTEXT,
Length (i),
Context ID (i),
Context Extensions
Datagram Format Type (i),
Datagram Format Additional Data (..),
}

Figure 3: 4: REGISTER_DATAGRAM_CONTEXT Capsule Format

Context ID: The context ID to register.

Context Extensions: See Section 5.

Note

Datagram Format Type: A variable-length integer that these registrations are unilateral and bidirectional: defines the
semantics and encoding of the HTTP Datagram Payload field of
datagrams with this context ID, see Section 2.2.

Datagram Format Additional Data: This field carries additional
information that impact the format of datagrams with this context
ID, see Section 2.2.

Note that these registrations are unilateral and bidirectional: the
sender of the frame unilaterally defines the semantics it will apply
to the datagrams it sends and receives using this context ID. Once a
context ID is registered, it can be used in both directions.

Endpoints MUST NOT send DATAGRAM frames using a Context ID until they
have either sent or received a REGISTER_DATAGRAM_CONTEXT Capsule with
the same Context ID. However, due to reordering, an endpoint that
receives a reordering can cause DATAGRAM frame frames
to be received with an unknown Context ID ID. Receipt of such frames
MUST NOT treat
it be treated as an error, it error. Endpoints SHALL instead drop the DATAGRAM
frame silently, or buffer it temporarily while awaiting the
corresponding REGISTER_DATAGRAM_CONTEXT Capsule. Intermediaries
SHALL drop the DATAGRAM frame silently, MAY buffer it, or forward it
on immediately.

Endpoints MUST NOT register the same Context ID twice on the same
stream. This also applies to Context IDs that have been closed using
a CLOSE_DATAGRAM_CONTEXT capsule. Clients MUST NOT register server-
initiated Context IDs and servers MUST NOT register client-initiated
Context IDs. If an endpoint receives a REGISTER_DATAGRAM_CONTEXT
capsule that violates one or more of these requirements, the endpoint
MUST abruptly terminate the corresponding stream with a stream error
of type H3_GENERAL_PROTOCOL_ERROR.

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.

4.4.2. The REGISTER_DATAGRAM_NO_CONTEXT Capsule

The REGISTER_DATAGRAM_NO_CONTEXT capsule (type=0x03) (see Section 8.2 for the
value of the capsule type) 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
Type (i) = REGISTER_DATAGRAM_NO_CONTEXT,
Length (i),
Datagram Format Type (i),
Datagram Format Additional Data (..),
}

Figure 4: 5: REGISTER_DATAGRAM_NO_CONTEXT Capsule Format

Context Extensions: See

Datagram Format Type: A variable-length integer that defines the
semantics and encoding of the HTTP Datagram Payload field of
datagrams, see Section 5. 2.2.

Datagram Format Additional Data: This field carries additional
information that impact the format of datagrams, see Section 2.2.

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 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, communicate whether
contexts are in use, and they MAY do so in a way which is opaque to
intermediaries.

4.3.

4.4.3. The CLOSE_DATAGRAM_CONTEXT Capsule

The CLOSE_DATAGRAM_CONTEXT capsule (type=0x01) (see Section 8.2 for the value of
the capsule type) allows an endpoint to inform its peer that it will
no longer send or parse received datagrams associated with a given
context ID. Its Capsule Data field
consists of:

CLOSE_DATAGRAM_CONTEXT Capsule {
Type (i) = CLOSE_DATAGRAM_CONTEXT,
Length (i),
Context ID (i),
Context Extensions
Close Code (i),
Close Details (..),
}

Figure 5: 6: CLOSE_DATAGRAM_CONTEXT Capsule Format

Context ID: The context ID to close.

Context Extensions: See

Close Code: The close code allows an endpoint to provide additional
information as to why a datagram context was closed.
Section 5. 4.4.3.1 defines a set of codes, the circumstances under
which an implementation sends them, and how receivers react.

Close Details: This is meant for debugging purposes. It consists of
a human-readable string encoded in UTF-8.

Note that this close is unilateral and bidirectional: the sender of
the frame unilaterally informs its peer of the closure. Endpoints
can use CLOSE_DATAGRAM_CONTEXT capsules to close a context that was
initially registered by either themselves, or by their peer.
Endpoints MAY use the CLOSE_DATAGRAM_CONTEXT capsule to immediately
reject a context that was just registered using a
REGISTER_DATAGRAM_CONTEXT capsule if they find its Context Extensions Datagram Format
Type field to be unacceptable.

After an endpoint has either sent or received a
CLOSE_DATAGRAM_CONTEXT frame, it MUST NOT send any DATAGRAM frames
with that Context ID. However, due to reordering, an endpoint that
receives a DATAGRAM frame with a closed Context ID MUST NOT treat it
as an error, it SHALL instead drop the DATAGRAM frame silently.

Endpoints MUST NOT close a Context ID that was not previously
registered. Endpoints MUST NOT close a Context ID that has already
been closed. If an endpoint receives a CLOSE_DATAGRAM_CONTEXT
capsule that violates one or more of these requirements, the endpoint
MUST abruptly terminate the corresponding stream with a stream error
of type H3_GENERAL_PROTOCOL_ERROR.

All CLOSE_DATAGRAM_CONTEXT capsules MUST contain a CLOSE_CODE

4.4.3.1. Close Codes

Close codes are intended to allow implementations to react
differently when they receive them - for example, some close codes
require the receiver to not open another context
extension, see under certain
conditions.

This specification defines the close codes below. Their numeric
values are in Section 5.1. If an endpoint receives a
CLOSE_DATAGRAM_CONTEXT capsule without 8.4. Extensions to this mechanism MAY define
new close codes and they SHOULD state how receivers react to them.

NO_ERROR: This indicates that a CLOSE_CODE context
extension, the endpoint MUST abruptly terminate was closed without any
action specified for the corresponding
stream receiver.

UNKNOWN_FORMAT: This indicates that the sender does not know how to
interpret the datagram format type associated with a stream error of this context.
The endpoint that had originally registered this context MUST NOT
try to register another context with the same datagram format type H3_GENERAL_PROTOCOL_ERROR.

4.4.
on this stream.

DENIED: 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 datagram format type and datagram
format data on this stream.

RESOURCE_LIMIT: This indicates that the context was closed to save
resources. The recipient SHOULD limit its future registration of
resource-intensive 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 8.4.

4.4.4. The DATAGRAM Capsule

The DATAGRAM capsule (type=0x02) (see Section 8.2 for the value of the capsule
type) allows an endpoint to send a datagram frame over an HTTP
stream. This is particularly useful when using a version of HTTP
that does not support QUIC DATAGRAM frames.
Its Capsule Data field consists of:

DATAGRAM Capsule {
Type (i) = DATAGRAM,
Length (i),
[Context ID (i)],
HTTP Datagram Payload (..),
}

Figure 6: 7: DATAGRAM Capsule Format

HTTP Datagram Payload: The payload of the datagram, whose semantics
are defined by individual applications. Note that this field can
be empty.

Datagrams sent using the DATAGRAM Capsule have the exact same
semantics as datagrams sent in QUIC DATAGRAM frames. In particular,
the restrictions on when it is allowed to send an HTTP Datagram and
how to process them from Section 3 also apply to HTTP Datagrams sent
and received using the DATAGRAM capsule.

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 Datagrams
as it forwards them: in other words, an intermediary MAY send a
DATAGRAM Capsule to forward an HTTP 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 Datagrams into QUIC DATAGRAM frames
over the next hop, and those could be dropped. Because of this,
applications have to always consider HTTP 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

If an intermediary receives an HTTP Datagram in a sequence of context extensions:

Context Extensions {
Context Extension (..) ...,
}

Each context extension QUIC DATAGRAM frame
and is encoded as forwarding it on 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 connection that supports QUIC DATAGRAM
frames, 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 intermediary SHOULD NOT convert that HTTP Datagram to why a datagram context was
closed. This type SHALL only be sent
DATAGRAM capsule. If the HTTP Datagram is too large to fit in CLOSE_DATAGRAM_CONTEXT
capsules. Its Context Extension Value field consists of a single
variable-length integer which contains
DATAGRAM frame (for example because the close code. The following
codes are defined:

NO_ERROR (code=0x00): This indicates path MTU of that QUIC
connection is too low or if the registration was
closed without any additional information.

DENIED (code=0x01): This indicates maximum UDP payload size advertised
on that connection is too low), the sender has rejected intermediary SHOULD drop the
context registration based on its local policy. The endpoint that
had originally registered this context MUST NOT try HTTP
Datagram instead of converting it to register
another context with the same context extensions on this stream.

RESOURCE_LIMIT (code=0x02): a DATAGRAM capsule. This indicates that
preserves 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 end-to-end unreliability characteristic that methods
such 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 Datagram Packetization Layer Path MTU Discovery (DPLPMTUD)
depend on [RFC8899]. An intermediary that converts QUIC DATAGRAM
frames to
provide additional details DATAGRAM capsules allows HTTP Datagrams to context capsules. It is meant for
debugging purposes. Its Context Extension Value field consists of be arbitrarily
large without suffering any loss; this can misrepresent the true path
properties, defeating methods such a
human-readable string encoded in UTF-8.

6. DPLPMTUD.

5. The H3_DATAGRAM HTTP/3 SETTINGS Parameter

Implementations of HTTP/3 that support this mechanism HTTP Datagrams can indicate
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
be either 0 or 1. A value of 0 indicates that this mechanism is HTTP Datagrams are not
supported. An endpoint that receives the H3_DATAGRAM SETTINGS
parameter with a value that is neither 0 or 1 MUST terminate the
connection with error H3_SETTINGS_ERROR.

An endpoint that sends the H3_DATAGRAM SETTINGS parameter with a
value of 1

Endpoints MUST NOT send the max_datagram_frame_size QUIC Transport
Parameter [DGRAM]. An endpoint that receives DATAGRAM frames until they have both
sent and received the H3_DATAGRAM SETTINGS parameter with a value of 1 on a QUIC connection that did
not also receive the max_datagram_frame_size QUIC Transport Parameter
MUST terminate the connection with error H3_SETTINGS_ERROR.
1.

When clients use 0-RTT, they MAY store the value of the server's
H3_DATAGRAM SETTINGS parameter. Doing so allows the client to use
HTTP/3 datagrams send
QUIC DATAGRAM frames in 0-RTT packets. When servers decide to accept
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
where they sent them the NewSessionTicket message. If a client
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
SETTINGS parameter sent by the server in the handshake is greater
than or equal to the stored value; if not, the client MUST terminate
the connection with error H3_SETTINGS_ERROR. In all cases, the
maximum permitted value of the H3_DATAGRAM SETTINGS parameter is 1.

7. Prioritization

Prioritization

5.1. Note About Draft Versions

[[RFC editor: please remove this section before publication.]]

Some revisions of HTTP/3 datagrams is not defined in this document.
Future extensions MAY define how draft specification use a different value (the
Identifier field of a Setting in the HTTP/3 SETTINGS frame) for the
H3_DATAGRAM Settings Parameter. This allows new draft revisions to prioritize datagrams, and
make incompatible changes. Multiple draft versions MAY
define signaling to allow be supported
by either endpoint in a connection. Such endpoints to communicate their
prioritization preferences.

8. HTTP/1.x MUST send
multiple values for H3_DATAGRAM. Once an endpoint has sent and HTTP/2 Support

We can provide DATAGRAM support in HTTP/2 by defining
received SETTINGS, it MUST compute the CAPSULE
frame in HTTP/2.

We intersection of the values it
has sent and received, and then it MUST select and use the most
recent draft version from the intersection set. This ensures that
both endpoints negotiate the same draft version.

6. Prioritization

Data streams (see Section 4.1) can provide DATAGRAM support in HTTP/1.x by defining its data
stream format be prioritized using any means
suited to a sequence stream or request prioritization. For example, see
Section 11 of [PRIORITY].

Prioritization of length-value capsules.

TODO: Refactor HTTP/3 datagrams is not defined in this document and add definitions for HTTP/1.x document.
Future extensions MAY define how to prioritize datagrams, and
HTTP/2.

9. MAY
define signaling to allow endpoints to communicate their
prioritization preferences.

7. Security Considerations

Since this feature requires sending an HTTP/3 Settings parameter, it
"sticks out". In other words, probing clients can learn whether a
server supports this feature. Implementations that support this
feature SHOULD always send this Settings parameter to avoid leaking
the fact that there are applications using HTTP/3 datagrams enabled
on this endpoint.

10.

8. IANA Considerations

10.1. HTTP/3 CAPSULE Frame

This document will request IANA to register the following entry in
the "HTTP/3 Frames" registry:

10.2.

8.1. HTTP/3 SETTINGS Parameter

This document will request IANA to register the following entry in
the "HTTP/3 Settings" registry:

+--------------+----------+---------------+---------+

10.3.

Table 1: New HTTP/3 Settings

8.2. Capsule Types

This document establishes a registry for HTTP capsule type codes.
The "HTTP Capsule Types" registry governs a 62-bit space.
Registrations in this registry MUST include the following fields:

Type: A name or label for the capsule type.

Value: The value of the Capsule Type field (see Section 4) 4.1) is a
62bit
62-bit integer.

Reference: An optional reference to a specification for the type.
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.

This registry initially contains the following entries:

+------------------------------+-------+---------------+

+==============================+==========+===============+
| Capsule Type | Value | Specification |
+------------------------------+-------+---------------+
+==============================+==========+===============+
| REGISTER_DATAGRAM_CONTEXT DATAGRAM | 0x00 0xff37a0 | This Document |
+------------------------------+-------+---------------+
+------------------------------+----------+---------------+
| CLOSE_DATAGRAM_CONTEXT REGISTER_DATAGRAM_CONTEXT | 0x01 0xff37a1 | This Document |
+------------------------------+-------+---------------+
+------------------------------+----------+---------------+
| DATAGRAM REGISTER_DATAGRAM_NO_CONTEXT | 0x02 0xff37a2 | This Document |
+------------------------------+-------+---------------+
+------------------------------+----------+---------------+
| REGISTER_DATAGRAM_NO_CONTEXT CLOSE_DATAGRAM_CONTEXT | 0x03 0xff37a3 | This Document |
+------------------------------+-------+---------------+
+------------------------------+----------+---------------+

Table 2: Initial Capsule Types Registry Entries

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.

10.4. Context Extension

8.3. Datagram Format Types

This document establishes a registry for HTTP datagram context
extension format type
codes. The "HTTP Context Extension Datagram Format Types" registry governs a 62-bit
space. Registrations in this registry MUST include the following
fields:

Type: A name or label for the context extension datagram format type.

Value: The value of the Context Extension Datagram Format Type field (see Section 5) 2.2)
is a 62bit 62-bit 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 is initially contains the following entries:

Datagram format 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 datagram format types be ignored. These extensions format types 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.

8.4. Context Close Codes

This document establishes a registry for HTTP context extension type close 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 Close Code field (see Section 5.1) 4.4.3) is a 62bit
62-bit 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:

+------------------------------+-------+---------------+

Table 3: Initial Context Close Code Registry
Entries

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.

9. References

9.1. Normative References

[DGRAM] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", Work in Progress, Internet-
Draft, draft-ietf-quic-datagram-03, 12 July draft-ietf-quic-datagram-06, 5 October 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-quic-
datagram-03>.
datagram-06>.

[H3] Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-34, 2 February 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-quic-
http-34>.

[IANA-POLICY]
Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>.

[QUIC] Iyengar, J. J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", Work in Progress, Internet-Draft,
draft-ietf-quic-transport-34, 14 January RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-quic-
transport-34>.
<https://www.rfc-editor.org/rfc/rfc9000>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

9.2. Informative References

[PRIORITY] Oku, K. and L. Pardue, "Extensible Prioritization Scheme
for HTTP", Work in Progress, Internet-Draft, draft-ietf-
httpbis-priority-06, 30 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
priority-06>.

[RFC8899] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T.
Völker, "Packetization Layer Path MTU Discovery for
Datagram Transports", RFC 8899, DOI 10.17487/RFC8899,
September 2020, <https://www.rfc-editor.org/rfc/rfc8899>.

Appendix A. Examples

A.1. CONNECT-UDP

Client Server

STREAM(44): HEADERS -------->
:method = CONNECT-UDP
:scheme = https
:path = /
:authority = target.example.org:443

STREAM(44): CAPSULE DATA -------->
Capsule Type = REGISTER_DATAGRAM_CONTEXT
Context ID = 0
Context Extension
Datagram Format Type = UDP_PAYLOAD
Datagram Format Additional Data = {} ""

DATAGRAM -------->
Quarter Stream ID = 11
Context ID = 0
Payload = Encapsulated UDP Payload

<-------- STREAM(44): HEADERS
:status = 200

/* Wait for target server to respond to UDP packet. */

<-------- DATAGRAM
Quarter Stream ID = 11
Context ID = 0
Payload = Encapsulated UDP Payload

A.2. CONNECT-UDP with Timestamp Extension
Client Server

STREAM(44): HEADERS -------->
:method = CONNECT-UDP
:scheme = https
:path = /
:authority = target.example.org:443

STREAM(44): CAPSULE DATA -------->
Capsule Type = REGISTER_DATAGRAM_CONTEXT
Context ID = 0
Context Extension
Datagram Format Type = {} UDP_PAYLOAD
Datagram Format Additional Data = ""

DATAGRAM -------->
Quarter Stream ID = 11
Context ID = 0
Payload = Encapsulated UDP Payload

<-------- STREAM(44): HEADERS
:status = 200

/* Wait for target server to respond to UDP packet. */

<-------- DATAGRAM
Quarter Stream ID = 11
Context ID = 0
Payload = Encapsulated UDP Payload

STREAM(44): CAPSULE DATA -------->
Capsule Type = REGISTER_DATAGRAM_CONTEXT
Context ID = 2
Context Extension
Datagram Format Type = UDP_PAYLOAD_WITH_TIMESTAMP
Datagram Format Additional Data = {TIMESTAMP=""} ""

DATAGRAM -------->
Quarter Stream ID = 11
Context ID = 2
Payload = Encapsulated UDP Payload With Timestamp

A.3. CONNECT-IP with IP compression
Client Server

STREAM(44): HEADERS -------->
:method = CONNECT-IP
:scheme = https
:path = /
:authority = proxy.example.org:443

<-------- STREAM(44): HEADERS
:status = 200

/* Exchange CONNECT-IP configuration information. */

STREAM(44): CAPSULE DATA -------->
Capsule Type = REGISTER_DATAGRAM_CONTEXT
Context ID = 0
Context Extension
Datagram Format Type = IP_PACKET
Datagram Format Additional Data = {} ""

DATAGRAM -------->
Quarter Stream ID = 11
Context ID = 0
Payload = Encapsulated IP Packet

/* Endpoint happily exchange encapsulated IP packets */
/* using Quarter Stream ID 11 and Context ID 0. */

DATAGRAM -------->
Quarter Stream ID = 11
Context ID = 0
Payload = Encapsulated IP Packet

/* After performing some analysis on traffic patterns, */
/* the client decides it wants to compress a 5-tuple. 2-tuple. */

STREAM(44): CAPSULE DATA -------->
Capsule Type = REGISTER_DATAGRAM_CONTEXT
Context ID = 2
Context Extension
Datagram Format Type = COMPRESSED_IP_PACKET
Datagram Format Additional Data = {IP_COMPRESSION=tcp,192.0.2.6:9876,192.0.2.7:443} "192.0.2.6,192.0.2.7"

DATAGRAM -------->
Quarter Stream ID = 11
Context ID = 2
Payload = Compressed IP Packet

A.4. WebTransport

Client Server

STREAM(44): HEADERS -------->
:method = CONNECT
:scheme = https
:method = webtransport
:path = /hello
:authority = webtransport.example.org:443
Origin = https://www.example.org:443

STREAM(44): CAPSULE DATA -------->
Capsule Type = REGISTER_DATAGRAM_NO_CONTEXT
Context Extension
Datagram Format Type = WEBTRANSPORT_DATAGRAM
Datagram Format Additional Data = {} ""

<-------- STREAM(44): HEADERS
:status = 200

/* Both endpoints can now send WebTransport datagrams. */

Acknowledgments

The DATAGRAM context identifier was previously part of the DATAGRAM
frame definition itself, the authors would like to acknowledge the
authors of that document and the members of the IETF MASQUE working
group for their suggestions. Additionally, the authors would like to
thank Martin Thomson for suggesting the use of an HTTP/3 SETTINGS
parameter. Furthermore, the authors would like to thank Ben Schwartz
for writing the first proposal that used two layers of indirection.

Authors' Addresses

David Schinazi
Google LLC
1600 Amphitheatre Parkway
Mountain View, California 94043,
United States of America

Email: dschinazi.ietf@gmail.com

Lucas Pardue
Cloudflare

Email: lucaspardue.24.7@gmail.com