Internet DRAFT - draft-ietf-masque-h3-datagram
draft-ietf-masque-h3-datagram
MASQUE D. Schinazi
Internet-Draft Google LLC
Intended status: Standards Track L. Pardue
Expires: 19 December 2022 Cloudflare
17 June 2022
HTTP Datagrams and the Capsule Protocol
draft-ietf-masque-h3-datagram-11
Abstract
This document describes HTTP Datagrams, a convention for conveying
multiplexed, potentially unreliable datagrams inside an HTTP
connection.
In HTTP/3, HTTP Datagrams can be sent unreliably using the QUIC
DATAGRAM extension. When the QUIC DATAGRAM frame is unavailable or
undesirable, they can be sent using the Capsule Protocol, a more
general convention for conveying data in HTTP connections.
HTTP Datagrams and the Capsule Protocol are intended for use by HTTP
extensions, not applications.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at https://ietf-wg-
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/.
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
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Schinazi & Pardue Expires 19 December 2022 [Page 1]
Internet-Draft HTTP Datagrams June 2022
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 19 December 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
2. HTTP Datagrams . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. HTTP/3 Datagrams . . . . . . . . . . . . . . . . . . . . 4
2.1.1. The SETTINGS_H3_DATAGRAM HTTP/3 Setting . . . . . . . 5
2.2. HTTP Datagrams using Capsules . . . . . . . . . . . . . . 6
3. Capsules . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. HTTP Data Streams . . . . . . . . . . . . . . . . . . . . 7
3.2. The Capsule Protocol . . . . . . . . . . . . . . . . . . 8
3.3. Error Handling . . . . . . . . . . . . . . . . . . . . . 9
3.4. The Capsule-Protocol Header Field . . . . . . . . . . . . 10
3.5. The DATAGRAM Capsule . . . . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 12
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
5.1. HTTP/3 Setting . . . . . . . . . . . . . . . . . . . . . 12
5.2. HTTP/3 Error Code . . . . . . . . . . . . . . . . . . . . 13
5.3. HTTP Header Field Name . . . . . . . . . . . . . . . . . 13
5.4. Capsule Types . . . . . . . . . . . . . . . . . . . . . . 13
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1. Normative References . . . . . . . . . . . . . . . . . . 14
Schinazi & Pardue Expires 19 December 2022 [Page 2]
Internet-Draft HTTP Datagrams June 2022
6.2. Informative References . . . . . . . . . . . . . . . . . 15
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
HTTP extensions (as defined in Section 16 of [HTTP]) sometimes need
to access underlying transport protocol features such as unreliable
delivery (as offered by [DGRAM]) to enable desirable features. For
example, this could allow introducing an unreliable version of the
CONNECT method, or adding unreliable delivery to WebSockets
[WEBSOCKET].
In Section 2, this document describes HTTP Datagrams, a convention
that supports the bidirectional and optionally multiplexed exchange
of data inside an HTTP connection. While HTTP Datagrams are
associated with HTTP requests, they are not part of message content;
instead, they are intended for use by HTTP extensions (such as the
CONNECT method), and are compatible with all versions of HTTP.
When HTTP is running over a transport protocol that supports
unreliable delivery (such as when the QUIC DATAGRAM extension [DGRAM]
is available to HTTP/3 [HTTP/3]), HTTP Datagrams can use that
capability.
This document also describes the HTTP Capsule Protocol in Section 3,
to allow conveyance of HTTP Datagrams using reliable delivery. This
addresses HTTP/3 cases where use of the QUIC DATAGRAM frame is
unavailable or undesirable, or where the transport protocol only
provides reliable delivery, such as with HTTP/1.1 [HTTP/1.1] or
HTTP/2 [HTTP/2] over TCP [TCP].
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.
This document uses terminology from [QUIC].
Where this document defines protocol types, the definition format
uses the notation from Section 1.3 of [QUIC]. Where fields within
types are integers, they are encoded using the variable-length
integer encoding from Section 16 of [QUIC]. Integer values do not
need to be encoded on the minimum number of bytes necessary.
Schinazi & Pardue Expires 19 December 2022 [Page 3]
Internet-Draft HTTP Datagrams June 2022
In this document, the term "intermediary" refers to an HTTP
intermediary as defined in Section 3.7 of [HTTP].
2. HTTP Datagrams
HTTP Datagrams are a convention for conveying bidirectional and
potentially unreliable datagrams inside an HTTP connection, with
multiplexing when possible. All HTTP Datagrams are associated with
an HTTP request.
When HTTP Datagrams are conveyed on an HTTP/3 connection, the QUIC
DATAGRAM frame can be used to achieve these goals, including
unreliable delivery; see Section 2.1. Negotiating the use of QUIC
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
framing layer, but unreliable delivery is unavailable. HTTP
Datagrams are negotiated and conveyed using the Capsule Protocol; see
Section 3.5.
When running over HTTP/1.x, requests are strictly serialized in the
connection, and therefore demultiplexing is not available.
Unreliable delivery is likewise not available. HTTP Datagrams are
negotiated and conveyed using the Capsule Protocol; see Section 3.5.
HTTP Datagrams MUST only be sent with an association to an HTTP
request that explicitly supports them. For example, existing HTTP
methods GET and POST do not define semantics for associated HTTP
Datagrams; therefore, HTTP Datagrams cannot be sent associated with
GET or POST request streams.
If an HTTP Datagram is received and it is associated with a request
that has no known semantics for HTTP Datagrams, the receiver MUST
terminate the request; if HTTP/3 is in use, the request stream MUST
be aborted with H3_DATAGRAM_ERROR (0x33). HTTP extensions MAY
override these requirements by defining a negotiation mechanism and
semantics for HTTP Datagrams.
2.1. HTTP/3 Datagrams
When used with HTTP/3, the Datagram Data field of QUIC DATAGRAM
frames uses the following format:
HTTP/3 Datagram {
Quarter Stream ID (i),
HTTP Datagram Payload (..),
}
Schinazi & Pardue Expires 19 December 2022 [Page 4]
Internet-Draft HTTP Datagrams June 2022
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 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). The largest legal QUIC stream ID value is
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
treated as an HTTP/3 connection error of type H3_DATAGRAM_ERROR
(0x33).
HTTP Datagram Payload: The payload of the datagram, whose semantics
are defined by the extension that is using HTTP Datagrams. Note
that this field can be empty.
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
connection error of type H3_DATAGRAM_ERROR (0x33).
HTTP/3 Datagrams MUST NOT be sent unless the corresponding stream's
send side is open. If a datagram is received after the corresponding
stream's receive side is closed, the received datagrams MUST be
silently dropped.
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 (on the order of a
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
stream that cannot be created due to client-initiated bidirectional
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
because HTTP/3 implementations might have practical barriers to
determining the active stream concurrency limit that is applied by
the QUIC layer.
Prioritization of HTTP/3 Datagrams is not defined in this document.
Future extensions MAY define how to prioritize datagrams, and MAY
define signaling to allow communicating prioritization preferences.
2.1.1. The SETTINGS_H3_DATAGRAM HTTP/3 Setting
Endpoints can indicate to their peer that they are willing to receive
HTTP/3 Datagrams by sending the SETTINGS_H3_DATAGRAM (0x33) setting
with a value of 1.
Schinazi & Pardue Expires 19 December 2022 [Page 5]
Internet-Draft HTTP Datagrams June 2022
The value of the SETTINGS_H3_DATAGRAM setting MUST be either 0 or 1.
A value of 0 indicates that the implementation is not willing to
receive HTTP Datagrams. If the SETTINGS_H3_DATAGRAM setting is
received with a value that is neither 0 nor 1, the receiver MUST
terminate the connection with error H3_SETTINGS_ERROR.
QUIC DATAGRAM frames MUST NOT be sent until the SETTINGS_H3_DATAGRAM
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
SETTINGS_H3_DATAGRAM setting. Doing so allows the client to send
QUIC DATAGRAM frames in 0-RTT packets. When servers decide to accept
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
where they sent them the NewSessionTicket message. If a client
stores the value of the SETTINGS_H3_DATAGRAM setting with their 0-RTT
state, they MUST validate that the new value of the
SETTINGS_H3_DATAGRAM setting 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 SETTINGS_H3_DATAGRAM setting
parameter is 1.
It is RECOMMENDED that implementations that support receiving HTTP/3
Datagrams always send the SETTINGS_H3_DATAGRAM setting with a value
of 1, even if the application does not intend to use HTTP/3
Datagrams. This helps to avoid "sticking out"; see Section 4.
2.1.1.1. Note About Draft Versions
[[RFC editor: please remove this section before publication.]]
Some revisions of this draft specification use a different value (the
Identifier field of a Setting in the HTTP/3 SETTINGS frame) for the
SETTINGS_H3_DATAGRAM setting. This allows new draft revisions to
make incompatible changes. Multiple draft versions MAY be supported
by sending multiple values for SETTINGS_H3_DATAGRAM. Once SETTINGS
have been sent and received, an implementation that supports multiple
drafts MUST compute the 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 peers
negotiate the same draft version.
2.2. HTTP Datagrams using Capsules
When HTTP/3 Datagrams are unavailable or undesirable, HTTP Datagrams
can be sent using the Capsule Protocol, see Section 3.5.
Schinazi & Pardue Expires 19 December 2022 [Page 6]
Internet-Draft HTTP Datagrams June 2022
3. Capsules
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
the Upgrade mechanism (see Section 7.8 of [HTTP]). In HTTP/2 and
HTTP/3, these tokens are used via the Extended CONNECT mechanism (see
[EXT-CONNECT2] and [EXT-CONNECT3]).
This specification introduces the Capsule Protocol. The Capsule
Protocol is a sequence of type-length-value tuples that definitions
of new HTTP Upgrade Tokens can choose to use. It allows endpoints to
reliably communicate request-related information end-to-end on HTTP
request streams, even in the presence of HTTP intermediaries. The
Capsule Protocol can be used to exchange HTTP Datagrams, which is
necessary when HTTP is running over a transport that does not support
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
This specification defines the "data stream" of an HTTP request as
the bidirectional stream of bytes that follows the header section of
the request message and the final response message that is either
successful (i.e., 2xx) or upgraded (i.e., 101).
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 final response header section. As a result, only the
last HTTP request on an HTTP/1.x connection can start the capsule
protocol.
In HTTP/2 and HTTP/3, the data stream of a given HTTP request
consists of all bytes sent in DATA frames with the corresponding
stream ID.
The concept of a data stream is particularly relevant for methods
such as CONNECT where there is no HTTP message content after the
headers.
Data streams can be prioritized using any means suited to stream or
request prioritization. For example, see Section 11 of [PRIORITY].
Data streams are subject to the flow control mechanisms of the
underlying layers (for example, HTTP/2 stream flow control, HTTP/2
connection flow control, and TCP flow control).
Schinazi & Pardue Expires 19 December 2022 [Page 7]
Internet-Draft HTTP Datagrams June 2022
3.2. The Capsule Protocol
Definitions of new HTTP Upgrade Tokens can state that their
associated request's data stream uses the Capsule Protocol. If they
do so, that means that the contents of the associated request's data
stream uses the following format:
Capsule Protocol {
Capsule (..) ...,
}
Figure 2: Capsule Protocol Stream Format
Capsule {
Capsule Type (i),
Capsule Length (i),
Capsule Value (..),
}
Figure 3: Capsule Format
Capsule Type: A variable-length integer indicating the Type of the
capsule. An IANA registry is used to manage the assignment of
Capsule Types; see Section 5.4.
Capsule Length: The length in bytes of the Capsule 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.
An intermediary can identify the use of the capsule protocol either
through the presence of the Capsule-Protocol header field
(Section 3.4) or by understanding the chosen HTTP Upgrade token.
Because new protocols or extensions might define new capsule types,
intermediaries that wish to allow for future extensibility SHOULD
forward capsules without modification, unless the definition of the
Capsule Type in use specifies additional intermediary processing.
One such Capsule Type is the DATAGRAM capsule; see Section 3.5. In
particular, intermediaries SHOULD forward Capsules with an unknown
Capsule Type without modification.
Endpoints which receive a Capsule with an unknown Capsule Type MUST
silently drop that Capsule and skip over it to parse the next
Capsule.
Schinazi & Pardue Expires 19 December 2022 [Page 8]
Internet-Draft HTTP Datagrams June 2022
By virtue of the definition of the data stream:
* The Capsule Protocol is not in use unless the response includes a
2xx (Successful) or 101 (Switching Protocols) 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.
Since the Capsule Protocol only applies to definitions of new HTTP
Upgrade Tokens, in HTTP/2 and HTTP/3 it can only be used with the
CONNECT method. Therefore, once both endpoints agree to use the
Capsule Protocol, the frame usage requirements of the stream change
as specified in Section 8.5 of [HTTP/2] and Section 4.2 of [HTTP/3].
The Capsule Protocol MUST NOT be used with messages that contain
Content-Length, Content-Type, or Transfer-Encoding header fields.
Additionally, HTTP status codes 204 (No Content), 205 (Reset
Content), and 206 (Partial Content) MUST NOT be sent on responses
that use the Capsule Protocol. A receiver that observes a violation
of these requirements MUST treat the HTTP message as malformed.
When processing capsules, a receiver might be tempted to accumulate
the full length of the capsule value in the data stream before
handling it. This approach SHOULD be avoided, because it can consume
flow control in underlying layers, and that might lead to deadlocks
if the capsule data exhausts the flow control window.
3.3. Error Handling
When a receiver encounters an error processing the Capsule Protocol,
the receiver MUST treat it as if it had received a malformed or
incomplete HTTP message. For HTTP/3, the handling of malformed
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
[HTTP/2]. For HTTP/1.x, the handling of incomplete messages is
described in Section 8 of [HTTP/1.1].
Each capsule's payload MUST contain exactly the fields identified in
its description. A capsule payload that contains additional bytes
after the identified fields or a capsule payload that terminates
before the end of the identified fields MUST be treated as it if were
a malformed or incomplete message. In particular, redundant length
encodings MUST be verified to be self-consistent.
Schinazi & Pardue Expires 19 December 2022 [Page 9]
Internet-Draft HTTP Datagrams June 2022
If the receive side of a stream carrying capsules is terminated
cleanly (for example, in HTTP/3 this is defined as receiving a QUIC
STREAM frame with the FIN bit set) and the last capsule on the stream
was truncated, this MUST be treated as if it were a malformed or
incomplete message.
3.4. The Capsule-Protocol Header Field
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
value type MUST be handled as if the field were not present by
recipients (for example, if this field is included multiple times,
its type will become a List and the field will therefore be ignored).
This document does not define any parameters for the Capsule-Protocol
header field value, but future documents might define parameters.
Receivers MUST ignore unknown parameters.
Endpoints indicate that the Capsule Protocol is in use on a data
stream by sending a Capsule-Protocol header field with a true value.
A Capsule-Protocol header field with a false value has the same
semantics as when the header is not present.
Intermediaries MAY use this header field to allow processing of HTTP
Datagrams for unknown HTTP Upgrade Tokens; note that this is only
possible for HTTP Upgrade or Extended CONNECT.
The Capsule-Protocol header field MUST NOT be used on HTTP responses
with a status code that is both different from 101 and outside the
2xx range.
When using the Capsule Protocol, HTTP endpoints SHOULD send the
Capsule-Protocol header field to simplify intermediary processing.
Definitions of new HTTP Upgrade Tokens that use the Capsule Protocol
MAY alter this recommendation.
3.5. The DATAGRAM Capsule
This document defines the DATAGRAM (0x00) capsule type. This capsule
allows HTTP Datagrams to be sent on a stream using the Capsule
Protocol. This is particularly useful when HTTP is running over a
transport that does not support the QUIC DATAGRAM frame.
Datagram Capsule {
Type (i) = 0x00,
Length (i),
HTTP Datagram Payload (..),
}
Schinazi & Pardue Expires 19 December 2022 [Page 10]
Internet-Draft HTTP Datagrams June 2022
Figure 4: DATAGRAM Capsule Format
HTTP Datagram Payload: The payload of the datagram, whose semantics
are defined by the extension that is using HTTP Datagrams. Note
that this field can be empty.
HTTP Datagrams sent using the DATAGRAM capsule have the same
semantics as those 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 2.1 also apply to HTTP Datagrams sent
and received using the DATAGRAM capsule.
An intermediary can reencode HTTP Datagrams as it forwards them. In
other words, an intermediary MAY send a DATAGRAM capsule to forward
an HTTP Datagram that was received in a QUIC DATAGRAM frame, and vice
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
reliably delivered in order, intermediaries can reencode DATAGRAM
capsules into QUIC DATAGRAM frames when forwarding messages, which
could result in loss or reordering.
If an intermediary receives an HTTP Datagram in a QUIC DATAGRAM frame
and is forwarding it on a connection that supports QUIC DATAGRAM
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 frame (for example because the path MTU of that QUIC
connection is too low or if the maximum UDP payload size advertised
on that connection is too low), the intermediary SHOULD drop the HTTP
Datagram instead of converting it to a DATAGRAM capsule. This
preserves the end-to-end unreliability characteristic that methods
such as Datagram Packetization Layer Path MTU Discovery (DPLPMTUD)
depend on [DPLPMTUD]. An intermediary that converts QUIC DATAGRAM
frames to DATAGRAM capsules allows HTTP Datagrams to be arbitrarily
large without suffering any loss; this can misrepresent the true path
properties, defeating methods such as DPLPMTUD.
While DATAGRAM capsules can theoretically carry a payload of length
2^62-1, most HTTP extensions that use HTTP Datagrams will have their
own limits on what datagram payload sizes are practical.
Implementations SHOULD take those limits into account when parsing
DATAGRAM capsules: if an incoming DATAGRAM capsule has a length that
is known to be so large as to not be usable, the implementation
SHOULD discard the capsule without buffering its contents into
memory.
Schinazi & Pardue Expires 19 December 2022 [Page 11]
Internet-Draft HTTP Datagrams June 2022
Since QUIC DATAGRAM frames are required to fit within a QUIC packet,
implementations that reencode DATAGRAM capsules into QUIC DATAGRAM
frames might be tempted to accumulate the entire capsule in the
stream before reencoding it. This SHOULD be avoided, because it can
cause flow control problems; see Section 3.2.
Note that it is possible for an HTTP extension to use HTTP Datagrams
without using the Capsule Protocol. For example, if an HTTP
extension that uses HTTP Datagrams is only defined over transports
that support QUIC DATAGRAM frames, it might not need a stream
encoding. Additionally, HTTP extensions can use HTTP Datagrams with
their own data stream protocol. However, new HTTP extensions that
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
Since transmitting HTTP Datagrams using QUIC DATAGRAM frames requires
sending the HTTP/3 SETTINGS_H3_DATAGRAM setting, it "sticks out". In
other words, probing clients can learn whether a server supports HTTP
Datagrams over QUIC DATAGRAM frames. As some servers might wish to
obfuscate the fact that they offer application services that use HTTP
Datagrams, it's best for all implementations that support this
feature to always send this setting, see Section 2.1.1.
Since use of the Capsule Protocol is restricted to new HTTP Upgrade
Tokens, it is not accessible from Web Platform APIs (such as those
commonly accessed via JavaScript in web browsers).
Definitions of new HTTP Upgrade Tokens that use the Capsule Protocol
need to perform a security analysis that considers the impact of HTTP
Datagrams and Capsules in the context of their protocol.
5. IANA Considerations
5.1. HTTP/3 Setting
This document will request IANA to register the following entry in
the "HTTP/3 Settings" registry maintained at
<https://www.iana.org/assignments/http3-parameters>:
Value: 0x33
Setting Name: SETTINGS_H3_DATAGRAM
Default: 0
Status: provisional (permanent if this document is approved)
Specification: This Document
Schinazi & Pardue Expires 19 December 2022 [Page 12]
Internet-Draft HTTP Datagrams June 2022
Change Controller: IETF
Contact: HTTP_WG; HTTP working group; ietf-http-wg@w3.org
5.2. HTTP/3 Error Code
This document will request IANA to register the following entry in
the "HTTP/3 Error Codes" registry maintained at
<https://www.iana.org/assignments/http3-parameters>:
Value: 0x33
Name: H3_DATAGRAM_ERROR
Description: Datagram or capsule protocol parse error
Status: provisional (permanent if this document is approved)
Specification: This Document
Change Controller: IETF
Contact: HTTP_WG; HTTP working group; ietf-http-wg@w3.org
5.3. HTTP Header Field Name
This document will request IANA to register the following entry in
the "HTTP Field Name" registry maintained at
<https://www.iana.org/assignments/http-fields>:
Field Name: Capsule-Protocol
Template: None
Status: provisional (permanent if this document is approved)
Reference: This document
Comments: None
5.4. Capsule Types
This document establishes a registry for HTTP capsule type codes.
The "HTTP Capsule Types" registry governs a 62-bit space, and
operates under the QUIC registration policy documented in
Section 22.1 of [QUIC]. This new registry includes the common set of
fields listed in Section 22.1.1 of [QUIC]. In addition to those
common fields, all registrations in this registry MUST include a
"Capsule Type" field which contains a short name or label for the
capsule type.
Permanent registrations in this registry are assigned using the
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].
Schinazi & Pardue Expires 19 December 2022 [Page 13]
Internet-Draft HTTP Datagrams June 2022
Capsule types with a value of the form 0x29 * N + 0x17 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.
This registry initially contains the following entry:
Value: 0x00
Capsule Type: DATAGRAM
Status: permanent
Specification: This document
Change Controller: IETF
Contact: MASQUE Working Group masque@ietf.org
(mailto:masque@ietf.org)
Notes: None
6. References
6.1. Normative References
[DGRAM] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", RFC 9221,
DOI 10.17487/RFC9221, March 2022,
<https://www.rfc-editor.org/rfc/rfc9221>.
[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/rfc/rfc9110>.
[HTTP/1.1] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP/1.1", STD 99, RFC 9112, DOI 10.17487/RFC9112,
June 2022, <https://www.rfc-editor.org/rfc/rfc9112>.
[HTTP/2] Thomson, M., Ed. and C. Benfield, Ed., "HTTP/2", RFC 9113,
DOI 10.17487/RFC9113, June 2022,
<https://www.rfc-editor.org/rfc/rfc9113>.
[HTTP/3] Bishop, M., Ed., "HTTP/3", RFC 9114, DOI 10.17487/RFC9114,
June 2022, <https://www.rfc-editor.org/rfc/rfc9114>.
[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>.
Schinazi & Pardue Expires 19 December 2022 [Page 14]
Internet-Draft HTTP Datagrams June 2022
[QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<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>.
[STRUCT-FIELD]
Nottingham, M. and P-H. Kamp, "Structured Field Values for
HTTP", RFC 8941, DOI 10.17487/RFC8941, February 2021,
<https://www.rfc-editor.org/rfc/rfc8941>.
[TCP] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/rfc/rfc793>.
6.2. Informative References
[DPLPMTUD] 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>.
[EXT-CONNECT2]
McManus, P., "Bootstrapping WebSockets with HTTP/2",
RFC 8441, DOI 10.17487/RFC8441, September 2018,
<https://www.rfc-editor.org/rfc/rfc8441>.
[EXT-CONNECT3]
Hamilton, R., "Bootstrapping WebSockets with HTTP/3",
RFC 9220, DOI 10.17487/RFC9220, June 2022,
<https://www.rfc-editor.org/rfc/rfc9220>.
[PRIORITY] Oku, K. and L. Pardue, "Extensible Prioritization Scheme
for HTTP", RFC 9218, DOI 10.17487/RFC9218, June 2022,
<https://www.rfc-editor.org/rfc/rfc9218>.
[WEBSOCKET]
Fette, I. and A. Melnikov, "The WebSocket Protocol",
RFC 6455, DOI 10.17487/RFC6455, December 2011,
<https://www.rfc-editor.org/rfc/rfc6455>.
Schinazi & Pardue Expires 19 December 2022 [Page 15]
Internet-Draft HTTP Datagrams June 2022
Acknowledgments
Portions of this document were previously part of the QUIC 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 setting.
Furthermore, the authors would like to thank Ben Schwartz for writing
the first proposal that used two layers of indirection. The final
design in this document came out of the HTTP Datagrams Design Team,
whose members were Alan Frindell, Alex Chernyakhovsky, Ben Schwartz,
Eric Rescorla, Marcus Ihlar, Martin Thomson, Mike Bishop, Tommy
Pauly, Victor Vasiliev, and the authors of this document. The
authors thank Mark Nottingham and Philipp Tiesel for their helpful
comments.
Authors' Addresses
David Schinazi
Google LLC
1600 Amphitheatre Parkway
Mountain View, CA 94043
United States of America
Email: dschinazi.ietf@gmail.com
Lucas Pardue
Cloudflare
Email: lucaspardue.24.7@gmail.com
Schinazi & Pardue Expires 19 December 2022 [Page 16]
