Internet Engineering Task Force (IETF)                       D. Schinazi
Request for Comments: 9297                                    Google LLC
Category: Standards Track                                      L. Pardue
ISSN: 2070-1721                                               Cloudflare
                                                            August 2022


               HTTP Datagrams and the Capsule Protocol

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, HTTP Datagrams can be sent using the Capsule Protocol,
  which is 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.

Status of This Memo

  This is an Internet Standards Track document.

  This document is a product of the Internet Engineering Task Force
  (IETF).  It represents the consensus of the IETF community.  It has
  received public review and has been approved for publication by the
  Internet Engineering Steering Group (IESG).  Further information on
  Internet Standards is available in Section 2 of RFC 7841.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  https://www.rfc-editor.org/info/rfc9297.

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
    1.1.  Conventions and Definitions
  2.  HTTP Datagrams
    2.1.  HTTP/3 Datagrams
      2.1.1.  The SETTINGS_H3_DATAGRAM HTTP/3 Setting
    2.2.  HTTP Datagrams Using Capsules
  3.  Capsules
    3.1.  HTTP Data Streams
    3.2.  The Capsule Protocol
    3.3.  Error Handling
    3.4.  The Capsule-Protocol Header Field
    3.5.  The DATAGRAM Capsule
  4.  Security Considerations
  5.  IANA Considerations
    5.1.  HTTP/3 Setting
    5.2.  HTTP/3 Error Code
    5.3.  HTTP Header Field Name
    5.4.  Capsule Types
  6.  References
    6.1.  Normative References
    6.2.  Informative References
  Acknowledgments
  Authors' Addresses

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 [QUIC-DGRAM]) to enable desirable features.
  For example, this could allow for the introduction of an unreliable
  version of the CONNECT method and the addition of unreliable delivery
  to WebSockets [WEBSOCKET].

  In Section 2, this document describes HTTP Datagrams, a convention
  for conveying bidirectional and potentially unreliable datagrams
  inside an HTTP connection, with multiplexing when possible.  While
  HTTP Datagrams are associated with HTTP requests, they are not a 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
  [QUIC-DGRAM] is available to HTTP/3 [HTTP/3]), HTTP Datagrams can use
  that capability.

  In Section 3, this document describes the HTTP Capsule Protocol,
  which allows the 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.

  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 provide demultiplexing and 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; 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 associated with GET or POST
  request streams cannot be sent.

  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 (..),
  }

                     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, which 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 the Quarter Stream ID field 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 field
  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 field
  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 because the QUIC stream limit might be unknown to the
  HTTP/3 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

  An endpoint can indicate to its peer that it is willing to receive
  HTTP/3 Datagrams by sending the SETTINGS_H3_DATAGRAM (0x33) setting
  with a value of 1.

  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.

2.2.  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.

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; examples include HTTP/2 stream flow control,
  HTTP/2 connection flow control, and TCP flow control.

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, 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,
     which follows 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 that receive a Capsule with an unknown Capsule Type MUST
  silently drop that Capsule and skip over it to parse the next
  Capsule.

  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.

  The Capsule Protocol only applies to definitions of new HTTP upgrade
  tokens; thus, 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 4.4 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 field 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 4.1.2 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.

  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 [STRUCTURED-FIELDS].  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 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 (Switching
  Protocols) and outside the 2xx (Successful) 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 (..),
  }

                    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 re-encode 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 re-encoding unless they
  have identified the use of the Capsule Protocol on the corresponding
  request stream; see Section 3.2.

  Note that while DATAGRAM Capsules, which are sent on a stream, are
  reliably delivered in order, intermediaries can re-encode 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 (PMTU) 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 PMTU 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.

  Since QUIC DATAGRAM frames are required to fit within a QUIC packet,
  implementations that re-encode DATAGRAM Capsules into QUIC DATAGRAM
  frames might be tempted to accumulate the entire Capsule in the
  stream before re-encoding 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 directly 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 include 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

  IANA has registered 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:  permanent
  Reference:  RFC 9297
  Change Controller:  IETF
  Contact:  HTTP_WG; HTTP working group; [email protected]
  Notes:  None

5.2.  HTTP/3 Error Code

  IANA has registered 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:  permanent
  Reference:  RFC 9297
  Change Controller:  IETF
  Contact:  HTTP_WG; HTTP working group; [email protected]
  Notes:  None

5.3.  HTTP Header Field Name

  IANA has registered the following entry in the "Hypertext Transfer
  Protocol (HTTP) Field Name Registry" maintained at
  <https://www.iana.org/assignments/http-fields>:

  Field Name:  Capsule-Protocol
  Template:  None
  Status:  permanent
  Reference:  RFC 9297
  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
  that 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].

  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
  Reference:  RFC 9297
  Change Controller:  IETF
  Contact:  MASQUE Working Group [email protected]
     (mailto:[email protected])
  Notes:  None

6.  References

6.1.  Normative References

  [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/info/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/info/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/info/rfc9113>.

  [HTTP/3]   Bishop, M., Ed., "HTTP/3", RFC 9114, DOI 10.17487/RFC9114,
             June 2022, <https://www.rfc-editor.org/info/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/info/rfc8126>.

  [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/info/rfc9000>.

  [QUIC-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/info/rfc9221>.

  [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/info/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/info/rfc8174>.

  [STRUCTURED-FIELDS]
             Nottingham, M. and P-H. Kamp, "Structured Field Values for
             HTTP", RFC 8941, DOI 10.17487/RFC8941, February 2021,
             <https://www.rfc-editor.org/info/rfc8941>.

  [TCP]      Eddy, W., Ed., "Transmission Control Protocol (TCP)",
             STD 7, RFC 9293, DOI 10.17487/RFC9293, August 2022,
             <https://www.rfc-editor.org/info/rfc9293>.

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/info/rfc8899>.

  [EXT-CONNECT2]
             McManus, P., "Bootstrapping WebSockets with HTTP/2",
             RFC 8441, DOI 10.17487/RFC8441, September 2018,
             <https://www.rfc-editor.org/info/rfc8441>.

  [EXT-CONNECT3]
             Hamilton, R., "Bootstrapping WebSockets with HTTP/3",
             RFC 9220, DOI 10.17487/RFC9220, June 2022,
             <https://www.rfc-editor.org/info/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/info/rfc9218>.

  [WEBSOCKET]
             Fette, I. and A. Melnikov, "The WebSocket Protocol",
             RFC 6455, DOI 10.17487/RFC6455, December 2011,
             <https://www.rfc-editor.org/info/rfc6455>.

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
  substantive input.  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: [email protected]


  Lucas Pardue
  Cloudflare
  Email: [email protected]

You are viewing proxied material from gopher.fnord.one. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.