draft-ietf-masque-h3-datagram-08.txt   draft-ietf-masque-h3-datagram-09.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: 29 September 2022 Cloudflare Expires: 13 October 2022 Cloudflare
28 March 2022 11 April 2022
HTTP Datagrams and the Capsule Protocol HTTP Datagrams and the Capsule Protocol
draft-ietf-masque-h3-datagram-08 draft-ietf-masque-h3-datagram-09
Abstract Abstract
This document describes HTTP Datagrams, a convention for conveying This document describes HTTP Datagrams, a convention for conveying
multiplexed, potentially unreliable datagrams inside an HTTP multiplexed, potentially unreliable datagrams inside an HTTP
connection. connection.
In HTTP/3, HTTP Datagrams can be conveyed natively using the QUIC In HTTP/3, HTTP Datagrams can be conveyed natively using the QUIC
DATAGRAM extension. When the QUIC DATAGRAM frame is unavailable or DATAGRAM extension. When the QUIC DATAGRAM frame is unavailable or
undesirable, they can be sent using the Capsule Protocol, a more undesirable, they can be sent using the Capsule Protocol, a more
general convention for conveying data in HTTP connections. general convention for conveying data in HTTP connections.
Both are intended for use by HTTP extensions, not applications. HTTP Datagrams and the Capsule Protocol are intended for use by HTTP
extensions, not applications.
Discussion Venues About This Document
This note is to be removed before publishing as an RFC. This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the MASQUE WG mailing list The latest revision of this draft can be found at https://ietf-wg-
(masque@ietf.org), which is archived at masque.github.io/draft-ietf-masque-h3-datagram/draft-ietf-masque-
h3-datagram.html. Status information for this document may be found
at https://datatracker.ietf.org/doc/draft-ietf-masque-h3-datagram/.
Discussion of this document takes place on the MASQUE Working Group
mailing list (mailto:masque@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/masque/. https://mailarchive.ietf.org/arch/browse/masque/.
Source for this draft and an issue tracker can be found at Source for this draft and an issue tracker can be found at
https://github.com/ietf-wg-masque/draft-ietf-masque-h3-datagram. https://github.com/ietf-wg-masque/draft-ietf-masque-h3-datagram.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 29 September 2022.
This Internet-Draft will expire on 13 October 2022.
Copyright Notice Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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extracted from this document must include Revised BSD License text as extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License. provided without warranty as described in the Revised 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. HTTP Datagrams . . . . . . . . . . . . . . . . . . . . . . . 3 2. HTTP Datagrams . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. HTTP/3 Datagrams . . . . . . . . . . . . . . . . . . . . 4 2.1. HTTP/3 Datagrams . . . . . . . . . . . . . . . . . . . . 4
2.1.1. The H3_DATAGRAM HTTP/3 SETTINGS Parameter . . . . . . 5 2.1.1. The SETTINGS_H3_DATAGRAM HTTP/3 Setting . . . . . . . 5
2.2. HTTP Datagrams using Capsules . . . . . . . . . . . . . . 6 2.2. HTTP Datagrams using Capsules . . . . . . . . . . . . . . 6
3. Capsules . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Capsules . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. HTTP Data Streams . . . . . . . . . . . . . . . . . . . . 7 3.1. HTTP Data Streams . . . . . . . . . . . . . . . . . . . . 7
3.2. The Capsule Protocol . . . . . . . . . . . . . . . . . . 7 3.2. The Capsule Protocol . . . . . . . . . . . . . . . . . . 8
3.3. Error Handling . . . . . . . . . . . . . . . . . . . . . 8 3.3. Error Handling . . . . . . . . . . . . . . . . . . . . . 9
3.4. The Capsule-Protocol Header Field . . . . . . . . . . . . 9 3.4. The Capsule-Protocol Header Field . . . . . . . . . . . . 9
3.5. The DATAGRAM Capsule . . . . . . . . . . . . . . . . . . 9 3.5. The DATAGRAM Capsule . . . . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 11 4. Security Considerations . . . . . . . . . . . . . . . . . . . 12
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
5.1. HTTP/3 SETTINGS Parameter . . . . . . . . . . . . . . . . 11 5.1. HTTP/3 Setting . . . . . . . . . . . . . . . . . . . . . 12
5.2. HTTP/3 Error Code . . . . . . . . . . . . . . . . . . . . 12 5.2. HTTP/3 Error Code . . . . . . . . . . . . . . . . . . . . 12
5.3. HTTP Header Field Name . . . . . . . . . . . . . . . . . 12 5.3. HTTP Header Field Name . . . . . . . . . . . . . . . . . 12
5.4. Capsule Types . . . . . . . . . . . . . . . . . . . . . . 12 5.4. Capsule Types . . . . . . . . . . . . . . . . . . . . . . 13
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Normative References . . . . . . . . . . . . . . . . . . 13 6.1. Normative References . . . . . . . . . . . . . . . . . . 13
6.2. Informative References . . . . . . . . . . . . . . . . . 14 6.2. Informative References . . . . . . . . . . . . . . . . . 15
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 15 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
HTTP extensions sometimes need to access underlying transport HTTP extensions sometimes need to access underlying transport
protocol features such as unreliable delivery (as offered by [DGRAM]) protocol features such as unreliable delivery (as offered by [DGRAM])
to enable desirable features like an unreliable version of the to enable desirable features. For example, this could allow
CONNECT method, and unreliable delivery in WebSockets [RFC6455] (or introducing an unreliable version of the CONNECT method, or adding
its successors). unreliable delivery to WebSockets [RFC6455].
In Section 2, this document describes HTTP Datagrams, a convention In Section 2, this document describes HTTP Datagrams, a convention
that supports the bidirectional and possibly multiplexed exchange of that supports the bidirectional and optionally multiplexed exchange
data inside an HTTP connection. While HTTP datagrams are associated of data inside an HTTP connection. While HTTP datagrams are
with HTTP requests, they are not part of message content; instead, associated with HTTP requests, they are not part of message content;
they are intended for use by HTTP extensions (such as the CONNECT instead, they are intended for use by HTTP extensions (such as the
method), and are compatible with all versions of HTTP. When the CONNECT method), and are compatible with all versions of HTTP.
underlying transport protocol supports unreliable delivery (such as
when the QUIC DATAGRAM extension is available in HTTP/3), they can When HTTP is running over a transport protocol that supports
use that capability. unreliable delivery (such as when the QUIC DATAGRAM extension is
available to HTTP/3), HTTP Datagrams can use that capability.
This document also describes the HTTP Capsule Protocol in Section 3, This document also describes the HTTP Capsule Protocol in Section 3,
to allow conveyance of HTTP Datagrams when the QUIC DATAGRAM frame is to allow conveyance of HTTP Datagrams using reliable delivery. This
unavailable or undesirable, such as when earlier versions of HTTP are addresses HTTP/3 cases where use of the QUIC DATAGRAM frame is
in use. unavailable or undesirable, or where the transport protocol only
provides reliable delivery, such as with HTTP/1 or HTTP/2 over TCP.
1.1. Conventions and Definitions 1.1. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. HTTP Datagrams 2. HTTP Datagrams
HTTP Datagrams are a convention for conveying bidirectional and HTTP Datagrams are a convention for conveying bidirectional and
potentially unreliable datagrams inside an HTTP connection, with potentially unreliable datagrams inside an HTTP connection, with
multiplexing when possible. All HTTP Datagrams are associated with multiplexing when possible. All HTTP Datagrams are associated with
an HTTP request. an HTTP request.
When HTTP Datagrams are conveyed on an HTTP/3 connection, the QUIC When HTTP Datagrams are conveyed on an HTTP/3 connection, the QUIC
DATAGRAM frame can be used to achieve these goals, including DATAGRAM frame can be used to achieve these goals, including
unreliable delivery; see Section 2.1. Negotiation is achieved using unreliable delivery; see Section 2.1. Negotiating the use of QUIC
a setting; see Section 2.1.1. DATAGRAM frames for HTTP Datagrams is achieved via the exchange of
HTTP/3 settings; see Section 2.1.1.
When running over HTTP/2, demultiplexing is provided by the HTTP/2 When running over HTTP/2, demultiplexing is provided by the HTTP/2
framing layer, but unreliable delivery is unavailable. HTTP framing layer, but unreliable delivery is unavailable. HTTP
Datagrams are negotiated and conveyed using the Capsule Protocol; see Datagrams are negotiated and conveyed using the Capsule Protocol; see
Section 3.5. Section 3.5.
When running over HTTP/1, requests are strictly serialized in the When running over HTTP/1, requests are strictly serialized in the
connection, and therefore demultiplexing is not available. connection, and therefore demultiplexing is not available.
Unreliable delivery is likewise not available. HTTP Datagrams are Unreliable delivery is likewise not available. HTTP Datagrams are
negotiated and conveyed using the Capsule Protocol; see Section 3.5. negotiated and conveyed using the Capsule Protocol; see Section 3.5.
HTTP Datagrams MUST only be sent with an association to a stream HTTP Datagrams MUST only be sent with an association to an HTTP
whose HTTP semantics explicitly supports HTTP Datagrams. For request that explicitly supports them. For example, existing HTTP
example, existing HTTP methods GET and POST do not define semantics methods GET and POST do not define semantics for associated HTTP
for associated HTTP Datagrams; therefore, HTTP Datagrams cannot be Datagrams; therefore, HTTP Datagrams cannot be sent associated with
sent associated with GET or POST request streams. GET or POST request streams.
If an HTTP Datagram associated with a method that has no known If an HTTP Datagram is received and it is associated with a request
semantics for HTTP Datagrams is received, the receiver MUST abort the that has no known semantics for HTTP Datagrams, the receiver MUST
corresponding stream; if HTTP/3 is in use, the stream MUST be aborted terminate the request; if HTTP/3 is in use, the request stream MUST
with H3_DATAGRAM_ERROR. HTTP extensions can override these be aborted with H3_DATAGRAM_ERROR (0x33). HTTP extensions can
requirements by defining a negotiation mechanism and semantics for override these requirements by defining a negotiation mechanism and
HTTP Datagrams. semantics for HTTP Datagrams.
2.1. HTTP/3 Datagrams 2.1. HTTP/3 Datagrams
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),
HTTP Datagram Payload (..), HTTP Datagram Payload (..),
skipping to change at page 4, line 44 skipping to change at page 5, line 6
Figure 1: HTTP/3 Datagram 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 from associated with, divided by four (the division by four stems from
the fact that HTTP requests are sent on client-initiated 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). The largest legal QUIC stream ID value is divisible by four). The largest legal QUIC stream ID value is
2^62-1, so the largest legal value of Quarter Stream ID is 2^60-1. 2^62-1, so the largest legal value of Quarter Stream ID is 2^60-1.
Receipt of an HTTP/3 Datagram that includes a larger value MUST be Receipt of an HTTP/3 Datagram that includes a larger value MUST be
treated as an HTTP/3 connection error of type H3_DATAGRAM_ERROR. treated as an HTTP/3 connection error of type H3_DATAGRAM_ERROR
(0x33).
HTTP Datagram Payload: The payload of the datagram, whose semantics HTTP Datagram Payload: The payload of the datagram, whose semantics
are defined by the extension that is using HTTP Datagrams. Note are defined by the extension that is using HTTP Datagrams. Note
that this field can be empty. that this field can be empty.
Receipt of a QUIC DATAGRAM frame whose payload is too short to allow Receipt of a QUIC DATAGRAM frame whose payload is too short to allow
parsing the Quarter Stream ID field MUST be treated as an HTTP/3 parsing the Quarter Stream ID field MUST be treated as an HTTP/3
connection error of type H3_DATAGRAM_ERROR. connection error of type H3_DATAGRAM_ERROR (0x33).
HTTP/3 Datagrams MUST NOT be sent unless the corresponding stream's HTTP/3 Datagrams MUST NOT be sent unless the corresponding stream's
send side is open. Once the receive side of a stream is closed, send side is open. If a datagram is received after the corresponding
incoming datagrams for this stream are no longer expected so related stream's receive side is closed, the received datagrams MUST be
state can be released. State MAY be kept for a short time to account silently dropped.
for reordering. Once the state is released, the received associated
datagrams MUST be silently dropped.
If an HTTP/3 datagram is received and its Quarter Stream ID maps to a 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 stream that has not yet been created, the receiver SHALL either drop
that datagram silently or buffer it temporarily (on the order of a that datagram silently or buffer it temporarily (on the order of a
round trip) while awaiting the creation of the corresponding stream. round trip) while awaiting the creation of the corresponding stream.
If an HTTP/3 datagram is received and its Quarter Stream ID maps to a If an HTTP/3 datagram is received and its Quarter Stream ID maps to a
stream that cannot be created due to client-initiated bidirectional stream that cannot be created due to client-initiated bidirectional
stream limits, it SHOULD be treated as an HTTP/3 connection error of stream limits, it SHOULD be treated as an HTTP/3 connection error of
type H3_ID_ERROR. Generating an error is not mandatory in this case type H3_ID_ERROR. Generating an error is not mandatory in this case
because HTTP/3 implementations might have practical barriers to because HTTP/3 implementations might have practical barriers to
determining the active stream concurrency limit that is applied by determining the active stream concurrency limit that is applied by
the QUIC layer. the QUIC layer.
Prioritization of HTTP/3 datagrams is not defined in this document. Prioritization of HTTP/3 datagrams is not defined in this document.
Future extensions MAY define how to prioritize datagrams, and MAY Future extensions MAY define how to prioritize datagrams, and MAY
define signaling to allow communicating prioritization preferences. define signaling to allow communicating prioritization preferences.
2.1.1. The H3_DATAGRAM HTTP/3 SETTINGS Parameter 2.1.1. The SETTINGS_H3_DATAGRAM HTTP/3 Setting
Implementations of HTTP/3 that support HTTP Datagrams can indicate Endpoints can indicate to their peer that they are willing to receive
that to their peer by sending the H3_DATAGRAM SETTINGS parameter with HTTP/3 Datagrams by sending the SETTINGS_H3_DATAGRAM (0x33) setting
a value of 1. with a value of 1.
The value of the H3_DATAGRAM SETTINGS parameter MUST be either 0 or The value of the SETTINGS_H3_DATAGRAM setting MUST be either 0 or 1.
1. A value of 0 indicates that HTTP Datagrams are not supported. If A value of 0 indicates that the implementation is not willing to
the H3_DATAGRAM SETTINGS parameter is received with a value that is receive HTTP Datagrams. If the SETTINGS_H3_DATAGRAM setting is
neither 0 or 1, the receiver MUST terminate the connection with error received with a value that is neither 0 or 1, the receiver MUST
H3_SETTINGS_ERROR. terminate the connection with error H3_SETTINGS_ERROR.
QUIC DATAGRAM frames MUST NOT be sent until the H3_DATAGRAM SETTINGS QUIC DATAGRAM frames MUST NOT be sent until the SETTINGS_H3_DATAGRAM
parameter has been both sent and received with a value of 1. setting has been both sent and received with a value of 1.
When clients use 0-RTT, they MAY store the value of the server's When clients use 0-RTT, they MAY store the value of the server's
H3_DATAGRAM SETTINGS parameter. Doing so allows the client to send SETTINGS_H3_DATAGRAM setting. Doing so allows the client to send
QUIC DATAGRAM frames in 0-RTT packets. When servers decide to accept QUIC DATAGRAM frames in 0-RTT packets. When servers decide to accept
0-RTT data, they MUST send a H3_DATAGRAM SETTINGS parameter greater 0-RTT data, they MUST send a SETTINGS_H3_DATAGRAM setting 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 SETTINGS_H3_DATAGRAM setting with their 0-RTT
0-RTT state, they MUST validate that the new value of the H3_DATAGRAM state, they MUST validate that the new value of the
SETTINGS parameter sent by the server in the handshake is greater SETTINGS_H3_DATAGRAM setting sent by the server in the handshake is
than or equal to the stored value; if not, the client MUST terminate greater than or equal to the stored value; if not, the client MUST
the connection with error H3_SETTINGS_ERROR. In all cases, the terminate the connection with error H3_SETTINGS_ERROR. In all cases,
maximum permitted value of the H3_DATAGRAM SETTINGS parameter is 1. the maximum permitted value of the SETTINGS_H3_DATAGRAM setting
parameter is 1.
It is RECOMMENDED that implementations that support receiving HTTP It is RECOMMENDED that implementations that support receiving HTTP/3
Datagrams using QUIC always send the H3_DATAGRAM SETTINGS parameter Datagrams always send the SETTINGS_H3_DATAGRAM setting with a value
with a value of 1, even if the application does not intend to use of 1, even if the application does not intend to use HTTP/3
HTTP Datagrams. This helps to avoid "sticking out"; see Section 4. Datagrams. This helps to avoid "sticking out"; see Section 4.
2.1.1.1. Note About Draft Versions 2.1.1.1. Note About Draft Versions
[[RFC editor: please remove this section before publication.]] [[RFC editor: please remove this section before publication.]]
Some revisions of this draft specification use a different value (the Some revisions of this draft specification use a different value (the
Identifier field of a Setting in the HTTP/3 SETTINGS frame) for the Identifier field of a Setting in the HTTP/3 SETTINGS frame) for the
H3_DATAGRAM Settings Parameter. This allows new draft revisions to SETTINGS_H3_DATAGRAM setting. This allows new draft revisions to
make incompatible changes. Multiple draft versions MAY be supported make incompatible changes. Multiple draft versions MAY be supported
by sending multiple values for H3_DATAGRAM. Once SETTINGS have been by sending multiple values for SETTINGS_H3_DATAGRAM. Once SETTINGS
sent and received, an implementation that supports multiple drafts have been sent and received, an implementation that supports multiple
MUST compute the intersection of the values it has sent and received, drafts MUST compute the intersection of the values it has sent and
and then it MUST select and use the most recent draft version from received, and then it MUST select and use the most recent draft
the intersection set. This ensures that both peers negotiate the version from the intersection set. This ensures that both peers
same draft version. negotiate the same draft version.
2.2. HTTP Datagrams using Capsules 2.2. HTTP Datagrams using Capsules
When HTTP/3 Datagrams are unavailable or undesirable, HTTP Datagrams When HTTP/3 Datagrams are unavailable or undesirable, HTTP Datagrams
can be sent using the Capsule Protocol, see Section 3.5. can be sent using the Capsule Protocol, see Section 3.5.
3. Capsules 3. Capsules
One mechanism to extend HTTP is to introduce new HTTP Upgrade Tokens One mechanism to extend HTTP is to introduce new HTTP Upgrade Tokens
(see Section 16.7 of [HTTP]). In HTTP/1.x, these tokens are used via (see Section 16.7 of [HTTP]). In HTTP/1.x, these tokens are used via
skipping to change at page 6, line 48 skipping to change at page 7, line 20
HTTP/3, these tokens are used via the Extended CONNECT mechanism (see HTTP/3, these tokens are used via the Extended CONNECT mechanism (see
[EXT-CONNECT2] and [EXT-CONNECT3]). [EXT-CONNECT2] and [EXT-CONNECT3]).
This specification introduces the Capsule Protocol. The Capsule This specification introduces the Capsule Protocol. The Capsule
Protocol is a sequence of type-length-value tuples that definitions Protocol is a sequence of type-length-value tuples that definitions
of new HTTP Upgrade Tokens can choose to use. It allows endpoints to of new HTTP Upgrade Tokens can choose to use. It allows endpoints to
reliably communicate request-related information end-to-end on HTTP reliably communicate request-related information end-to-end on HTTP
request streams, even in the presence of HTTP intermediaries. The request streams, even in the presence of HTTP intermediaries. The
Capsule Protocol can be used to exchange HTTP Datagrams, which is Capsule Protocol can be used to exchange HTTP Datagrams, which is
necessary when HTTP is running over a transport that does not support necessary when HTTP is running over a transport that does not support
the QUIC DATAGRAM frame. the QUIC DATAGRAM frame. The Capsule Protocol can also be used to
communicate reliable and bidirectional control messages associated
with a datagram-based protocol even when HTTP/3 Datagrams are in use.
3.1. HTTP Data Streams 3.1. HTTP Data Streams
This specification defines the "data stream" of an HTTP request as This specification defines the "data stream" of an HTTP request as
the bidirectional stream of bytes that follows the header section of the bidirectional stream of bytes that follows the header section of
the request message and the final, successful (i.e., 2xx) response the request message and the final, successful (i.e., 2xx) response
message. message.
In HTTP/1.x, the data stream consists of all bytes on the connection 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 that follow the blank line that concludes either the request header
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forward capsules without modification, unless the definition of the forward capsules without modification, unless the definition of the
Capsule Type in use specifies additional intermediary processing. Capsule Type in use specifies additional intermediary processing.
One such Capsule Type is the DATAGRAM capsule; see Section 3.5. In One such Capsule Type is the DATAGRAM capsule; see Section 3.5. In
particular, intermediaries SHOULD forward Capsules with an unknown particular, intermediaries SHOULD forward Capsules with an unknown
Capsule Type without modification. Capsule Type without modification.
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 and skip over it to parse the next silently drop that Capsule and skip over it to parse the next
Capsule. Capsule.
By virtue of the definition of the data stream, the Capsule Protocol By virtue of the definition of the data stream:
is not in use on responses unless the response includes a 2xx
(Successful) status code. * The Capsule Protocol is not in use unless the response includes a
2xx (Successful) status code.
* When the Capsule Protocol is in use, the associated HTTP request
and response do not carry HTTP content. A future extension MAY
define a new capsule type to carry HTTP content.
The Capsule Protocol MUST NOT be used with messages that contain The Capsule Protocol MUST NOT be used with messages that contain
Content-Length, Content-Type, or Transfer-Encoding header fields. Content-Length, Content-Type, or Transfer-Encoding header fields.
Additionally, HTTP status codes 204 (No Content), 205 (Reset Additionally, HTTP status codes 204 (No Content), 205 (Reset
Content), and 206 (Partial Content) MUST NOT be sent on responses Content), and 206 (Partial Content) MUST NOT be sent on responses
that use the Capsule Protocol. A receiver that observes a violation that use the Capsule Protocol. A receiver that observes a violation
of these requirements MUST treat the HTTP message as malformed. of these requirements MUST treat the HTTP message as malformed.
3.3. Error Handling 3.3. Error Handling
When an error occurs in processing the Capsule Protocol, the receiver When an error occurs in processing the Capsule Protocol, the receiver
MUST treat the message as malformed or incomplete, according to the MUST treat the message as malformed or incomplete, according to the
underlying transport protocol. For HTTP/3, the handling of malformed underlying transport protocol. For HTTP/3, the handling of malformed
messages is described in Section 4.1.3 of [H3]. For HTTP/2, the messages is described in Section 4.1.3 of [HTTP/3]. For HTTP/2, the
handling of malformed messages is described in Section 8.1.1 of [H2]. handling of malformed messages is described in Section 8.1.1 of
For HTTP/1.1, the handling of incomplete messages is described in [HTTP/2]. For HTTP/1.1, the handling of incomplete messages is
Section 8 of [H1]. described in Section 8 of [HTTP/1.1].
Each capsule's payload MUST contain exactly the fields identified in Each capsule's payload MUST contain exactly the fields identified in
its description. A capsule payload that contains additional bytes its description. A capsule payload that contains additional bytes
after the identified fields or a capsule payload that terminates after the identified fields or a capsule payload that terminates
before the end of the identified fields MUST be treated as a before the end of the identified fields MUST be treated as a
malformed or incomplete message. In particular, redundant length malformed or incomplete message. In particular, redundant length
encodings MUST be verified to be self-consistent. encodings MUST be verified to be self-consistent.
When a stream carrying capsules terminates cleanly, if the last If the receive side of a stream carrying capsules is terminated
capsule on the stream was truncated, this MUST be treated as a cleanly (for example, in HTTP/3 this is defined as receiving a QUIC
malformed or incomplete message. STREAM frame with the FIN bit set) and the last capsule on the stream
was truncated, this MUST be treated as a malformed or incomplete
message.
3.4. The Capsule-Protocol Header Field 3.4. The Capsule-Protocol Header Field
The "Capsule-Protocol" header field is an Item Structured Field, see The "Capsule-Protocol" header field is an Item Structured Field, see
Section 3.3 of [STRUCT-FIELD]; its value MUST be a Boolean; any other Section 3.3 of [STRUCT-FIELD]; its value MUST be a Boolean; any other
value type MUST be handled as if the field were not present by value type MUST be handled as if the field were not present by
recipients (for example, if this field is included multiple times, recipients (for example, if this field is included multiple times,
its type will become a List and the field will therefore be ignored). its type will become a List and the field will therefore be ignored).
This document does not define any parameters for the Capsule-Protocol This document does not define any parameters for the Capsule-Protocol
header field value, but future documents might define parameters. header field value, but future documents might define parameters.
skipping to change at page 9, line 46 skipping to change at page 10, line 26
The Capsule-Protocol header field MUST NOT be used on HTTP responses The Capsule-Protocol header field MUST NOT be used on HTTP responses
with a status code outside the 2xx range. with a status code outside the 2xx range.
When using the Capsule Protocol, HTTP endpoints SHOULD send the When using the Capsule Protocol, HTTP endpoints SHOULD send the
Capsule-Protocol header field to simplify intermediary processing. Capsule-Protocol header field to simplify intermediary processing.
Definitions of new HTTP Upgrade Tokens that use the Capsule Protocol Definitions of new HTTP Upgrade Tokens that use the Capsule Protocol
MAY alter this recommendation. MAY alter this recommendation.
3.5. The DATAGRAM Capsule 3.5. The DATAGRAM Capsule
This document defines the DATAGRAM capsule type (see Section 5.4 for This document defines the DATAGRAM (0x00) capsule type. This capsule
the value of the capsule type). This capsule allows HTTP Datagrams allows HTTP Datagrams to be sent on a stream using the Capsule
to be sent on a stream using the Capsule Protocol. This is Protocol. This is particularly useful when HTTP is running over a
particularly useful when HTTP is running over a transport that does transport that does not support the QUIC DATAGRAM frame.
not support the QUIC DATAGRAM frame.
Datagram Capsule { Datagram Capsule {
Type (i) = DATAGRAM, Type (i) = 0x00,
Length (i), Length (i),
HTTP Datagram Payload (..), HTTP Datagram Payload (..),
} }
Figure 4: DATAGRAM Capsule Format Figure 4: DATAGRAM Capsule Format
HTTP Datagram Payload: The payload of the datagram, whose semantics HTTP Datagram Payload: The payload of the datagram, whose semantics
are defined by the extension that is using HTTP Datagrams. Note are defined by the extension that is using HTTP Datagrams. Note
that this field can be empty. that this field can be empty.
HTTP Datagrams sent using the DATAGRAM capsule have the same HTTP Datagrams sent using the DATAGRAM capsule have the same
semantics as those sent in QUIC DATAGRAM frames. In particular, the semantics as those sent in QUIC DATAGRAM frames. In particular, the
restrictions on when it is allowed to send an HTTP Datagram and how restrictions on when it is allowed to send an HTTP Datagram and how
to process them from Section 2.1 also apply to HTTP Datagrams sent to process them from Section 2.1 also apply to HTTP Datagrams sent
and received using the DATAGRAM capsule. and received using the DATAGRAM capsule.
An intermediary can reencode HTTP Datagrams as it forwards them. In An intermediary can reencode HTTP Datagrams as it forwards them. In
other words, an intermediary MAY send a DATAGRAM capsule to forward other words, an intermediary MAY send a DATAGRAM capsule to forward
an HTTP Datagram which was received in a QUIC DATAGRAM frame, and an HTTP Datagram that was received in a QUIC DATAGRAM frame, and vice
vice versa. versa. Intermediaries MUST NOT perform this reencoding unless they
have identified the use of the Capsule Protocol on the corresponding
request stream; see Section 3.2.
Note that while DATAGRAM capsules that are sent on a stream are Note that while DATAGRAM capsules that are sent on a stream are
reliably delivered in order, intermediaries can reencode DATAGRAM reliably delivered in order, intermediaries can reencode DATAGRAM
capsules into QUIC DATAGRAM frames when forwarding messages, which capsules into QUIC DATAGRAM frames when forwarding messages, which
could result in loss or reordering. could result in loss or reordering.
If an intermediary receives an HTTP Datagram in a QUIC DATAGRAM frame If an intermediary receives an HTTP Datagram in a QUIC DATAGRAM frame
and is forwarding it on a connection that supports QUIC DATAGRAM and is forwarding it on a connection that supports QUIC DATAGRAM
frames, the intermediary SHOULD NOT convert that HTTP Datagram to a frames, the intermediary SHOULD NOT convert that HTTP Datagram to a
DATAGRAM capsule. If the HTTP Datagram is too large to fit in a DATAGRAM capsule. If the HTTP Datagram is too large to fit in a
skipping to change at page 11, line 8 skipping to change at page 11, line 41
While DATAGRAM capsules can theoretically carry a payload of length While DATAGRAM capsules can theoretically carry a payload of length
2^62-1, most HTTP extensions that use HTTP Datagrams will have their 2^62-1, most HTTP extensions that use HTTP Datagrams will have their
own limits on what datagram payload sizes are practical. own limits on what datagram payload sizes are practical.
Implementations SHOULD take those limits into account when parsing Implementations SHOULD take those limits into account when parsing
DATAGRAM capsules: if an incoming DATAGRAM capsule has a length that DATAGRAM capsules: if an incoming DATAGRAM capsule has a length that
is known to be so large as to not be usable, the implementation is known to be so large as to not be usable, the implementation
SHOULD discard the capsule without buffering its contents into SHOULD discard the capsule without buffering its contents into
memory. memory.
Note that use of the Capsule Protocol is not required to use HTTP Note that it is possible for an HTTP extension to use HTTP Datagrams
Datagrams. If an HTTP extension that uses HTTP Datagrams is only without using the Capsule Protocol. For example, if an HTTP
defined over transports that support QUIC DATAGRAM frames, it might extension that uses HTTP Datagrams is only defined over transports
not need a stream encoding. Additionally, HTTP extensions can use that support QUIC DATAGRAM frames, it might not need a stream
HTTP Datagrams with their own data stream protocol. However, new encoding. Additionally, HTTP extensions can use HTTP Datagrams with
HTTP extensions that wish to use HTTP Datagrams SHOULD use the their own data stream protocol. However, new HTTP extensions that
Capsule Protocol unless they have a good reason not to. wish to use HTTP Datagrams SHOULD use the Capsule Protocol as failing
to do so will make it harder for the HTTP extension to support
versions of HTTP other than HTTP/3 and will prevent interoperability
with intermediaries that only support the Capsule Protocol.
4. Security Considerations 4. Security Considerations
Since transmitting HTTP Datagrams using QUIC DATAGRAM frames requires Since transmitting HTTP Datagrams using QUIC DATAGRAM frames requires
sending an HTTP/3 Settings parameter, it "sticks out". In other sending the HTTP/3 SETTINGS_H3_DATAGRAM setting, it "sticks out". In
words, probing clients can learn whether a server supports HTTP other words, probing clients can learn whether a server supports HTTP
Datagrams over QUIC DATAGRAM frames. As some servers might wish to Datagrams over QUIC DATAGRAM frames. As some servers might wish to
obfuscate the fact that they offer application services that use HTTP obfuscate the fact that they offer application services that use HTTP
datagrams, it's best for all implementations that support this datagrams, it's best for all implementations that support this
feature to always send this Settings parameter, see Section 2.1.1. feature to always send this setting, see Section 2.1.1.
Since use of the Capsule Protocol is restricted to new HTTP Upgrade Since use of the Capsule Protocol is restricted to new HTTP Upgrade
Tokens, it is not accessible from Web Platform APIs (such as those Tokens, it is not accessible from Web Platform APIs (such as those
commonly accessed via JavaScript in web browsers). commonly accessed via JavaScript in web browsers).
5. IANA Considerations 5. IANA Considerations
5.1. HTTP/3 SETTINGS Parameter 5.1. HTTP/3 Setting
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:
Value: 0xffd277 (note that this will switch to a lower value before Value: 0x33
publication) Setting Name: SETTINGS_H3_DATAGRAM
Setting Name: H3_DATAGRAM
Default: 0 Default: 0
Status: provisional (permanent if this document is approved) Status: provisional (permanent if this document is approved)
Specification: This Document Specification: This Document
Change Controller: IETF Change Controller: IETF
Contact: HTTP_WG; HTTP working group; ietf-http-wg@w3.org Contact: HTTP_WG; HTTP working group; ietf-http-wg@w3.org
5.2. HTTP/3 Error Code 5.2. HTTP/3 Error Code
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 Error Codes" registry: the "HTTP/3 Error Codes" registry:
Value: 0x4A1268 (note that this will switch to a lower value before Value: 0x33
publication)
Name: H3_DATAGRAM_ERROR Name: H3_DATAGRAM_ERROR
Description: Datagram or capsule protocol parse error Description: Datagram or capsule protocol parse error
Status: provisional (permanent if this document is approved) Status: provisional (permanent if this document is approved)
Specification: This Document Specification: This Document
Change Controller: IETF Change Controller: IETF
Contact: HTTP_WG; HTTP working group; ietf-http-wg@w3.org Contact: HTTP_WG; HTTP working group; ietf-http-wg@w3.org
5.3. HTTP Header Field Name 5.3. HTTP Header Field Name
This document will request IANA to register the following entry in This document will request IANA to register the following entry in
the "HTTP Field Name" registry: the "HTTP Field Name" registry:
Field Name: Capsule-Protocol Field Name: Capsule-Protocol
Template: None Template: None
Status: provisional (permanent if this document is approved) Status: provisional (permanent if this document is approved)
Reference: This document Reference: This document
Comments: None Comments: None
5.4. Capsule Types 5.4. Capsule Types
This document establishes a registry for HTTP capsule type codes. This document establishes a registry for HTTP capsule type codes.
The "HTTP Capsule Types" registry governs a 62-bit space. The "HTTP Capsule Types" registry governs a 62-bit space, and
Registrations in this registry MUST include the following fields: operates under the QUIC registration policy documented in
Section 22.1 of [QUIC]. This new registry includes the common set of
Type: A name or label for the capsule type. fields listed in Section 22.1.1 of [QUIC]. In addition to those
common fields, all registrations in this registry MUST include a
Value: The value of the Capsule Type field (see Section 3.2) is a "Capsule Type" field which contains a short name or label for the
62-bit integer. capsule type.
Reference: An optional reference to a specification for the type. Permanent registrations in this registry are assigned using the
This field MAY be empty. Specification Required policy (Section 4.6 of [IANA-POLICY]), except
for values between 0x00 and 0x3f (in hexadecimal; inclusive), which
are assigned using Standards Action or IESG Approval as defined in
Sections 4.9 and 4.10 of [IANA-POLICY].
Registrations follow the "First Come First Served" policy (see Capsule types with a value of the form 0x29 * N + 0x17 for integer
Section 4.4 of [IANA-POLICY]) where two registrations MUST NOT have values of N are reserved to exercise the requirement that unknown
the same Type. 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.
This registry initially contains the following entry: This registry initially contains the following entry:
Value: 0x00
Capsule Type: DATAGRAM Capsule Type: DATAGRAM
Status: permanent
Value: 0xff37a5 (note that this will switch to a lower value before Specification: This document
publication) Change Controller: IETF
Contact: MASQUE Working Group masque@ietf.org
Reference: This document (mailto:masque@ietf.org)
Notes: None
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.
6. References 6. References
6.1. Normative References 6.1. 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", RFC 9221,
Draft, draft-ietf-quic-datagram-10, 4 February 2022, DOI 10.17487/RFC9221, March 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-quic- <https://www.rfc-editor.org/rfc/rfc9221>.
datagram-10>.
[H1] Fielding, R. T., Nottingham, M., and J. Reschke, [HTTP] Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
Semantics", Work in Progress, Internet-Draft, draft-ietf-
httpbis-semantics-19, 12 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
semantics-19>.
[HTTP/1.1] Fielding, R. T., Nottingham, M., and J. Reschke,
"HTTP/1.1", Work in Progress, Internet-Draft, draft-ietf- "HTTP/1.1", Work in Progress, Internet-Draft, draft-ietf-
httpbis-messaging-19, 12 September 2021, httpbis-messaging-19, 12 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis- <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
messaging-19>. messaging-19>.
[H2] Thomson, M. and C. Benfield, "HTTP/2", Work in Progress, [HTTP/2] Thomson, M. and C. Benfield, "HTTP/2", Work in Progress,
Internet-Draft, draft-ietf-httpbis-http2bis-07, 24 January Internet-Draft, draft-ietf-httpbis-http2bis-07, 24 January
2022, <https://datatracker.ietf.org/doc/html/draft-ietf- 2022, <https://datatracker.ietf.org/doc/html/draft-ietf-
httpbis-http2bis-07>. httpbis-http2bis-07>.
[H3] Bishop, M., "Hypertext Transfer Protocol Version 3 [HTTP/3] 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://datatracker.ietf.org/doc/html/draft-ietf-quic- <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
http-34>. http-34>.
[HTTP] Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
Semantics", Work in Progress, Internet-Draft, draft-ietf-
httpbis-semantics-19, 12 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
semantics-19>.
[IANA-POLICY] [IANA-POLICY]
Cotton, M., Leiba, B., and T. Narten, "Guidelines for Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>. <https://www.rfc-editor.org/rfc/rfc8126>.
[QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based [QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000, Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021, DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>. <https://www.rfc-editor.org/rfc/rfc9000>.
skipping to change at page 15, line 28 skipping to change at page 15, line 40
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
RFC 6455, DOI 10.17487/RFC6455, December 2011, RFC 6455, DOI 10.17487/RFC6455, December 2011,
<https://www.rfc-editor.org/rfc/rfc6455>. <https://www.rfc-editor.org/rfc/rfc6455>.
Acknowledgments Acknowledgments
Portions of this document were previously part of the QUIC DATAGRAM Portions of this document were previously part of the QUIC DATAGRAM
frame definition itself, the authors would like to acknowledge the frame definition itself, the authors would like to acknowledge the
authors of that document and the members of the IETF MASQUE working authors of that document and the members of the IETF MASQUE working
group for their suggestions. Additionally, the authors would like to group for their suggestions. Additionally, the authors would like to
thank Martin Thomson for suggesting the use of an HTTP/3 SETTINGS thank Martin Thomson for suggesting the use of an HTTP/3 setting.
parameter. Furthermore, the authors would like to thank Ben Schwartz Furthermore, the authors would like to thank Ben Schwartz for writing
for writing the first proposal that used two layers of indirection. the first proposal that used two layers of indirection. The final
The final design in this document came out of the HTTP Datagrams design in this document came out of the HTTP Datagrams Design Team,
Design Team, whose members were Alan Frindell, Alex Chernyakhovsky, whose members were Alan Frindell, Alex Chernyakhovsky, Ben Schwartz,
Ben Schwartz, Eric Rescorla, Marcus Ihlar, Martin Thomson, Mike Eric Rescorla, Marcus Ihlar, Martin Thomson, Mike Bishop, Tommy
Bishop, Tommy Pauly, Victor Vasiliev, and the authors of this Pauly, Victor Vasiliev, and the authors of this document. The
document. The authors thank Mark Nottingham and Philipp Tiesel for authors thank Mark Nottingham and Philipp Tiesel for their helpful
their helpful comments. comments.
Authors' Addresses Authors' Addresses
David Schinazi David Schinazi
Google LLC Google LLC
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
Mountain View, California 94043, Mountain View, CA 94043
United States of America United States of America
Email: dschinazi.ietf@gmail.com Email: dschinazi.ietf@gmail.com
Lucas Pardue Lucas Pardue
Cloudflare Cloudflare
Email: lucaspardue.24.7@gmail.com Email: lucaspardue.24.7@gmail.com
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