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HTTP/3 and QPACK qlog event definitions
draft-ietf-quic-qlog-h3-events-03

Document Type Active Internet-Draft (quic WG)
Authors Robin Marx , Luca Niccolini , Marten Seemann , Lucas Pardue
Last updated 2022-10-24
Replaces draft-marx-quic-qlog-h3-events
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draft-ietf-quic-qlog-h3-events-03
QUIC                                                        R. Marx, Ed.
Internet-Draft                                                    Akamai
Intended status: Standards Track                       L. Niccolini, Ed.
Expires: 27 April 2023                                              Meta
                                                         M. Seemann, Ed.
                                                           Protocol Labs
                                                          L. Pardue, Ed.
                                                              Cloudflare
                                                         24 October 2022

                HTTP/3 and QPACK qlog event definitions
                   draft-ietf-quic-qlog-h3-events-03

Abstract

   This document describes concrete qlog event definitions and their
   metadata for HTTP/3 and QPACK-related events.  These events can then
   be embedded in the higher level schema defined in [QLOG-MAIN].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   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 27 April 2023.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Usage with QUIC . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Raw packet and frame information  . . . . . . . . . . . .   5
   3.  HTTP/3 and QPACK Event Overview . . . . . . . . . . . . . . .   5
   4.  HTTP/3 Events . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  parameters_set  . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  parameters_restored . . . . . . . . . . . . . . . . . . .   8
     4.3.  stream_type_set . . . . . . . . . . . . . . . . . . . . .   8
     4.4.  frame_created . . . . . . . . . . . . . . . . . . . . . .   9
     4.5.  frame_parsed  . . . . . . . . . . . . . . . . . . . . . .  10
     4.6.  push_resolved . . . . . . . . . . . . . . . . . . . . . .  10
   5.  HTTP/3 Data Field Definitions . . . . . . . . . . . . . . . .  11
     5.1.  Owner . . . . . . . . . . . . . . . . . . . . . . . . . .  11
     5.2.  HTTPFrame . . . . . . . . . . . . . . . . . . . . . . . .  11
       5.2.1.  HTTPDataFrame . . . . . . . . . . . . . . . . . . . .  12
       5.2.2.  HTTPHeadersFrame  . . . . . . . . . . . . . . . . . .  12
       5.2.3.  HTTPCancelPushFrame . . . . . . . . . . . . . . . . .  13
       5.2.4.  HTTPSettingsFrame . . . . . . . . . . . . . . . . . .  13
       5.2.5.  HTTPPushPromiseFrame  . . . . . . . . . . . . . . . .  13
       5.2.6.  HTTPGoAwayFrame . . . . . . . . . . . . . . . . . . .  14
       5.2.7.  HTTPMaxPushIDFrame  . . . . . . . . . . . . . . . . .  14
       5.2.8.  HTTPReservedFrame . . . . . . . . . . . . . . . . . .  14
       5.2.9.  HTTPUnknownFrame  . . . . . . . . . . . . . . . . . .  14
       5.2.10. HTTPApplicationError  . . . . . . . . . . . . . . . .  14
   6.  QPACK Events  . . . . . . . . . . . . . . . . . . . . . . . .  15
     6.1.  state_updated . . . . . . . . . . . . . . . . . . . . . .  16
     6.2.  stream_state_updated  . . . . . . . . . . . . . . . . . .  16
     6.3.  dynamic_table_updated . . . . . . . . . . . . . . . . . .  17
     6.4.  headers_encoded . . . . . . . . . . . . . . . . . . . . .  17
     6.5.  headers_decoded . . . . . . . . . . . . . . . . . . . . .  18
     6.6.  instruction_created . . . . . . . . . . . . . . . . . . .  19
     6.7.  instruction_parsed  . . . . . . . . . . . . . . . . . . .  19
   7.  QPACK Data Field Definitions  . . . . . . . . . . . . . . . .  20
     7.1.  QPACKInstruction  . . . . . . . . . . . . . . . . . . . .  20
       7.1.1.  SetDynamicTableCapacityInstruction  . . . . . . . . .  20

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       7.1.2.  InsertWithNameReferenceInstruction  . . . . . . . . .  20
       7.1.3.  InsertWithoutNameReferenceInstruction . . . . . . . .  20
       7.1.4.  DuplicateInstruction  . . . . . . . . . . . . . . . .  21
       7.1.5.  SectionAcknowledgementInstruction . . . . . . . . . .  21
       7.1.6.  StreamCancellationInstruction . . . . . . . . . . . .  21
       7.1.7.  InsertCountIncrementInstruction . . . . . . . . . . .  21
     7.2.  QPACKHeaderBlockRepresentation  . . . . . . . . . . . . .  22
       7.2.1.  IndexedHeaderField  . . . . . . . . . . . . . . . . .  22
       7.2.2.  LiteralHeaderFieldWithName  . . . . . . . . . . . . .  22
       7.2.3.  LiteralHeaderFieldWithoutName . . . . . . . . . . . .  23
     7.3.  QPACKHeaderBlockPrefix  . . . . . . . . . . . . . . . . .  23
     7.4.  QPACKTableType  . . . . . . . . . . . . . . . . . . . . .  23
   8.  Security and Privacy Considerations . . . . . . . . . . . . .  23
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  23
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  23
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  24
     A.1.  Since draft-ietf-quic-qlog-h3-events-02:  . . . . . . . .  24
     A.2.  Since draft-ietf-quic-qlog-h3-events-01:  . . . . . . . .  25
     A.3.  Since draft-ietf-quic-qlog-h3-events-00:  . . . . . . . .  25
     A.4.  Since draft-marx-qlog-event-definitions-quic-h3-02: . . .  25
     A.5.  Since draft-marx-qlog-event-definitions-quic-h3-01: . . .  25
     A.6.  Since draft-marx-qlog-event-definitions-quic-h3-00: . . .  27
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   This document describes the values of the qlog name ("category" +
   "event") and "data" fields and their semantics for HTTP/3 [HTTP/3]
   and QPACK [QPACK].

      Note to RFC editor: Please remove the follow paragraphs in this
      section before publication.

   Feedback and discussion are welcome at https://github.com/quicwg/qlog
   (https://github.com/quicwg/qlog).  Readers are advised to refer to
   the "editor's draft" at that URL for an up-to-date version of this
   document.

   Concrete examples of integrations of this schema in various
   programming languages can be found at https://github.com/quiclog/
   qlog/ (https://github.com/quiclog/qlog/).

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1.1.  Notational Conventions

   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.

   The event and data structure definitions in ths document are
   expressed in the Concise Data Definition Language [CDDL] and its
   extensions described in [QLOG-MAIN].

   The following fields from [QLOG-MAIN] are imported and used: name,
   category, type, data, group_id, protocol_type, importance, RawInfo,
   and time-related fields.

2.  Overview

   This document describes how the HTTP/3 and QPACK can be expressed in
   qlog using the schema defined in [QLOG-MAIN].  HTTP/3 and QPACK
   events are defined with a category, a name (the concatenation of
   "category" and "event"), an "importance", an optional "trigger", and
   "data" fields.

   Some data fields use complex datastructures.  These are represented
   as enums or re-usable definitions, which are grouped together on the
   bottom of this document for clarity.

   When any event from this document is included in a qlog trace, the
   "protocol_type" qlog array field MUST contain an entry with the value
   "HTTP3".

2.1.  Usage with QUIC

   The events described in this document can be used with or without
   logging the related QUIC events defined in [QLOG-QUIC].  If used with
   QUIC events, the QUIC document takes precedence in terms of
   recommended filenames and trace separation setups.

   If used without QUIC events, it is recommended that the
   implementation assign a globally unique identifier to each HTTP/3
   connection.  This ID can then be used as the value of the qlog
   "group_id" field, as well as the qlog filename or file identifier,
   potentially suffixed by the vantagepoint type (For example,
   abcd1234_server.qlog would contain the server-side trace of the
   connection with GUID abcd1234).

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2.2.  Raw packet and frame information

   This document re-uses the definition of the RawInfo data class from
   [QLOG-MAIN].

   Note:  As HTTP/3 does not use trailers in frames, each HTTP/3 frame
      header_length can be calculated as header_length = RawInfo:length
      - RawInfo:payload_length

   Note:  In some cases, the length fields are also explicitly reflected
      inside of frame headers.  For example, all HTTP/3 frames include
      their explicit payload lengths in the frame header.  In these
      cases, those fields are intentionally preserved in the event
      definitions.  Even though this can lead to duplicate data when the
      full RawInfo is logged, it allows a more direct mapping of the
      HTTP/3 specifications to qlog, making it easier for users to
      interpret.  In this case, both fields MUST have the same value.

3.  HTTP/3 and QPACK Event Overview

   This document defines events in two categories, written as lowercase
   to follow convention: http (Section 4) and qpack (Section 6).

   As described in Section 3.4.2 of [QLOG-MAIN], the qlog "name" field
   is the concatenation of category and type.

   Table 1 summarizes the name value of each event type that is defined
   in this specification.

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        +=============================+============+=============+
        | Name value                  | Importance | Definition  |
        +=============================+============+=============+
        | http:parameters_set         | Base       | Section 4.1 |
        +-----------------------------+------------+-------------+
        | http:parameters_restored    | Base       | Section 4.2 |
        +-----------------------------+------------+-------------+
        | http:stream_type_set        | Base       | Section 4.3 |
        +-----------------------------+------------+-------------+
        | http:frame_created          | Core       | Section 4.4 |
        +-----------------------------+------------+-------------+
        | http:frame_parsed           | Core       | Section 4.5 |
        +-----------------------------+------------+-------------+
        | http:push_resolved          | Extra      | Section 4.6 |
        +-----------------------------+------------+-------------+
        | qpack:state_updated         | Base       | Section 6.1 |
        +-----------------------------+------------+-------------+
        | qpack:stream_state_updated  | Core       | Section 6.2 |
        +-----------------------------+------------+-------------+
        | qpack:dynamic_table_updated | Extra      | Section 6.3 |
        +-----------------------------+------------+-------------+
        | qpack:headers_encoded       | Base       | Section 6.4 |
        +-----------------------------+------------+-------------+
        | qpack:headers_decoded       | Base       | Section 6.5 |
        +-----------------------------+------------+-------------+
        | qpack:instruction_created   | Base       | Section 6.6 |
        +-----------------------------+------------+-------------+
        | qpack:instruction_parsed    | Base       | Section 6.7 |
        +-----------------------------+------------+-------------+

                     Table 1: HTTP/3 and QPACK Events

4.  HTTP/3 Events

   HTTP/3 events extend the $ProtocolEventBody extension point defined
   in [QLOG-MAIN].

   HTTPEvents = HTTPParametersSet / HTTPParametersRestored /
                HTTPStreamTypeSet / HTTPFrameCreated /
                HTTPFrameParsed / HTTPPushResolved

   $ProtocolEventBody /= HTTPEvents

      Figure 1: HTTPEvents definition and ProtocolEventBody extension

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4.1.  parameters_set

   Importance: Base

   This event contains HTTP/3 and QPACK-level settings, mostly those
   received from the HTTP/3 SETTINGS frame.  All these parameters are
   typically set once and never change.  However, they are typically set
   at different times during the connection, so there can be several
   instances of this event with different fields set.

   Note that some settings have two variations (one set locally, one
   requested by the remote peer).  This is reflected in the "owner"
   field.  As such, this field MUST be correct for all settings included
   a single event instance.  If you need to log settings from two sides,
   you MUST emit two separate event instances.

   Note: we use the CDDL unwrap operator (~) here to make HTTPParameters
   into a re-usable list of fields.  The unwrap operator copies the
   fields from the referenced type into the target type directly,
   extending the target with the unwrapped fields.  TODO: explain this
   better + provide reference and maybe an example.

   Definition:

   HTTPParametersSet = {
       ? owner: Owner

       ~HTTPParameters

       ; qlog-specific
       ; indicates whether this implementation waits for a SETTINGS
       ; frame before processing requests
       ? waits_for_settings: bool
   }

   HTTPParameters = {
       ? max_header_list_size: uint64
       ? max_table_capacity: uint64
       ? blocked_streams_count: uint64

       ; additional settings for grease and extensions
       * text => uint64
   }

                   Figure 2: HTTPParametersSet definition

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   Note: enabling server push is not explicitly done in HTTP/3 by use of
   a setting or parameter.  Instead, it is communicated by use of the
   MAX_PUSH_ID frame, which should be logged using the frame_created and
   frame_parsed events below.

   Additionally, this event can contain any number of unspecified
   fields.  This is to reflect setting of for example unknown (greased)
   settings or parameters of (proprietary) extensions.

4.2.  parameters_restored

   Importance: Base

   When using QUIC 0-RTT, HTTP/3 clients are expected to remember and
   reuse the server's SETTINGs from the previous connection.  This event
   is used to indicate which HTTP/3 settings were restored and to which
   values when utilizing 0-RTT.

   Definition:

   HTTPParametersRestored = {

       ~HTTPParameters

   }

                Figure 3: HTTPParametersRestored definition

   Note that, like for parameters_set above, this event can contain any
   number of unspecified fields to allow for additional and custom
   settings.

4.3.  stream_type_set

   Importance: Base

   Emitted when a stream's type becomes known.  This is typically when a
   stream is opened and the stream's type indicator is sent or received.

   Note: most of this information can also be inferred by looking at a
   stream's id, since id's are strictly partitioned at the QUIC level.
   Even so, this event has a "Base" importance because it helps a lot in
   debugging to have this information clearly spelled out.

   Definition:

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   HTTPStreamTypeSet = {
       ? owner: Owner
       stream_id: uint64

       stream_type: HTTPStreamType

       ; only when stream_type === "unknown"
       ? raw_stream_type: uint64

       ; only when stream_type === "push"
       ? associated_push_id: uint64
   }

   HTTPStreamType =  "request" /
                     "control" /
                     "push" /
                     "reserved" /
                     "unknown" /
                     "qpack_encode" /
                     "qpack_decode"

                   Figure 4: HTTPStreamTypeSet definition

4.4.  frame_created

   Importance: Core

   HTTP equivalent to the packet_sent event.  This event is emitted when
   the HTTP/3 framing actually happens.  Note: this is not necessarily
   the same as when the HTTP/3 data is passed on to the QUIC layer.  For
   that, see the "data_moved" event in [QLOG-QUIC].

   Definition:

   HTTPFrameCreated = {
       stream_id: uint64
       ? length: uint64
       frame: $HTTPFrame
       ? raw: RawInfo
   }

                   Figure 5: HTTPFrameCreated definition

   Note: in HTTP/3, DATA frames can have arbitrarily large lengths to
   reduce frame header overhead.  As such, DATA frames can span many
   QUIC packets and can be created in a streaming fashion.  In this
   case, the frame_created event is emitted once for the frame header,
   and further streamed data is indicated using the data_moved event.

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4.5.  frame_parsed

   Importance: Core

   HTTP equivalent to the packet_received event.  This event is emitted
   when we actually parse the HTTP/3 frame.  Note: this is not
   necessarily the same as when the HTTP/3 data is actually received on
   the QUIC layer.  For that, see the "data_moved" event in [QLOG-QUIC].

   Definition:

   HTTPFrameParsed = {
       stream_id: uint64
       ? length: uint64
       frame: $HTTPFrame
       ? raw: RawInfo
   }

                    Figure 6: HTTPFrameParsed definition

   Note: in HTTP/3, DATA frames can have arbitrarily large lengths to
   reduce frame header overhead.  As such, DATA frames can span many
   QUIC packets and can be processed in a streaming fashion.  In this
   case, the frame_parsed event is emitted once for the frame header,
   and further streamed data is indicated using the data_moved event.

4.6.  push_resolved

   Importance: Extra

   This event is emitted when a pushed resource is successfully claimed
   (used) or, conversely, abandoned (rejected) by the application on top
   of HTTP/3 (e.g., the web browser).  This event is added to help debug
   problems with unexpected PUSH behaviour, which is commonplace with
   HTTP/2.

   Definition:

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   HTTPPushResolved = {
       ? push_id: uint64

       ; in case this is logged from a place that does not have access
       ; to the push_id
       ? stream_id: uint64

       decision: HTTPPushDecision
   }

   HTTPPushDecision = "claimed" / "abandoned"

                   Figure 7: HTTPPushResolved definition

5.  HTTP/3 Data Field Definitions

   The following data field definitions can be used in HTTP/3 events.

5.1.  Owner

   Owner = "local" / "remote"

                         Figure 8: Owner definition

5.2.  HTTPFrame

   The generic $HTTPFrame is defined here as a CDDL extension point (a
   "socket" or "plug").  It can be extended to support additional HTTP/3
   frame types.

   ; The HTTPFrame is any key-value map (e.g., JSON object)
   $HTTPFrame /= {
       * text => any
   }

                    Figure 9: HTTPFrame plug definition

   The HTTP/3 frame types defined in this document are as follows:

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   HTTPBaseFrames =  HTTPDataFrame /
                HTTPHeadersFrame /
                HTTPCancelPushFrame /
                HTTPSettingsFrame /
                HTTPPushPromiseFrame /
                HTTPGoawayFrame /
                HTTPMaxPushIDFrame /
                HTTPReservedFrame /
                HTTPUnknownFrame

   $HTTPFrame /= HTTPBaseFrames

                    Figure 10: HTTPBaseFrames definition

5.2.1.  HTTPDataFrame

   HTTPDataFrame = {
       frame_type: "data"
       ? raw: hexstring
   }

                    Figure 11: HTTPDataFrame definition

5.2.2.  HTTPHeadersFrame

   This represents an _uncompressed_, plaintext HTTP Headers frame
   (e.g., no QPACK compression is applied).

   For example:

   headers: [
     {
       "name": ":path",
       "value": "/"
     },
     {
       "name": ":method",
       "value": "GET"
     },
     {
       "name": ":authority",
       "value": "127.0.0.1:4433"
     },
     {
       "name": ":scheme",
       "value": "https"
     }
   ]

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                    Figure 12: HTTPHeadersFrame example

   HTTPHeadersFrame = {
       frame_type: "headers"
       headers: [* HTTPField]
   }

                   Figure 13: HTTPHeadersFrame definition

   HTTPField = {
       name: text
       value: text
   }

                      Figure 14: HTTPField definition

5.2.3.  HTTPCancelPushFrame

   HTTPCancelPushFrame = {
       frame_type: "cancel_push"
       push_id: uint64
   }

                 Figure 15: HTTPCancelPushFrame definition

5.2.4.  HTTPSettingsFrame

   HTTPSettingsFrame = {
       frame_type: "settings"
       settings: [* HTTPSetting]
   }

   HTTPSetting = {
       name: text
       value: uint64
   }

                  Figure 16: HTTPSettingsFrame definition

5.2.5.  HTTPPushPromiseFrame

   HTTPPushPromiseFrame = {
       frame_type: "push_promise"
       push_id: uint64
       headers: [* HTTPField]
   }

                 Figure 17: HTTPPushPromiseFrame definition

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5.2.6.  HTTPGoAwayFrame

   HTTPGoawayFrame = {
       frame_type: "goaway"

       ; Either stream_id or push_id.
       ; This is implicit from the sender of the frame
       id: uint64
   }

                   Figure 18: HTTPGoawayFrame definition

5.2.7.  HTTPMaxPushIDFrame

   HTTPMaxPushIDFrame = {
       frame_type: "max_push_id"
       push_id: uint64
   }

                  Figure 19: HTTPMaxPushIDFrame definition

5.2.8.  HTTPReservedFrame

   HTTPReservedFrame = {
       frame_type: "reserved"

       ? length: uint64
   }

                  Figure 20: HTTPReservedFrame definition

5.2.9.  HTTPUnknownFrame

   HTTPUnknownFrame = {
       frame_type: "unknown"
       raw_frame_type: uint64

       ? raw_length: uint32
       ? raw: hexstring
   }

                     Figure 21: UnknownFrame definition

5.2.10.  HTTPApplicationError

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   HTTPApplicationError =  "http_no_error" /
                           "http_general_protocol_error" /
                           "http_internal_error" /
                           "http_stream_creation_error" /
                           "http_closed_critical_stream" /
                           "http_frame_unexpected" /
                           "http_frame_error" /
                           "http_excessive_load" /
                           "http_id_error" /
                           "http_settings_error" /
                           "http_missing_settings" /
                           "http_request_rejected" /
                           "http_request_cancelled" /
                           "http_request_incomplete" /
                           "http_early_response" /
                           "http_connect_error" /
                           "http_version_fallback"

                 Figure 22: HTTPApplicationError definition

   The HTTPApplicationError defines the general $ApplicationError
   definition in the qlog QUIC definition, see [QLOG-QUIC].

   ; ensure HTTP errors are properly validate in QUIC events as well
   ; e.g., QUIC's ConnectionClose Frame
   $ApplicationError /= HTTPApplicationError

6.  QPACK Events

   QPACK events extend the $ProtocolEventBody extension point defined in
   [QLOG-MAIN].

   QPACKEvents = QPACKStateUpdate / QPACKStreamStateUpdate /
                 QPACKDynamicTableUpdate / QPACKHeadersEncoded /
                 QPACKHeadersDecoded / QPACKInstructionCreated /
                 QPACKInstructionParsed

   $ProtocolEventBody /= QPACKEvents

     Figure 23: QPACKEvents definition and ProtocolEventBody extension

   QPACK events mainly serve as an aid to debug low-level QPACK
   issues.The higher-level, plaintext header values SHOULD (also) be
   logged in the http.frame_created and http.frame_parsed event data
   (instead).

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   Note: qpack does not have its own parameters_set event.  This was
   merged with http.parameters_set for brevity, since qpack is a
   required extension for HTTP/3 anyway.  Other HTTP/3 extensions MAY
   also log their SETTINGS fields in http.parameters_set or MAY define
   their own events.

6.1.  state_updated

   Importance: Base

   This event is emitted when one or more of the internal QPACK
   variables changes value.  Note that some variables have two
   variations (one set locally, one requested by the remote peer).  This
   is reflected in the "owner" field.  As such, this field MUST be
   correct for all variables included a single event instance.  If you
   need to log settings from two sides, you MUST emit two separate event
   instances.

   Definition:

   QPACKStateUpdate = {
       owner: Owner
       ? dynamic_table_capacity: uint64

       ; effective current size, sum of all the entries
       ? dynamic_table_size: uint64
       ? known_received_count: uint64
       ? current_insert_count: uint64
   }

                   Figure 24: QPACKStateUpdate definition

6.2.  stream_state_updated

   Importance: Core

   This event is emitted when a stream becomes blocked or unblocked by
   header decoding requests or QPACK instructions.

   Note: This event is of "Core" importance, as it might have a large
   impact on HTTP/3's observed performance.

   Definition:

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   QPACKStreamStateUpdate = {
       stream_id: uint64
       ; streams are assumed to start "unblocked"
       ; until they become "blocked"
       state: QPACKStreamState
   }

   QPACKStreamState = "blocked" / "unblocked"

                Figure 25: QPACKStreamStateUpdate definition

6.3.  dynamic_table_updated

   Importance: Extra

   This event is emitted when one or more entries are inserted or
   evicted from QPACK's dynamic table.

   Definition:

   QPACKDynamicTableUpdate = {
       ; local = the encoder's dynamic table
       ; remote = the decoder's dynamic table
       owner: Owner

       update_type: QPACKDynamicTableUpdateType
       entries: [+ QPACKDynamicTableEntry]
   }

   QPACKDynamicTableUpdateType = "inserted" / "evicted"

   QPACKDynamicTableEntry = {
       index: uint64
       ? name: text / hexstring
       ? value: text / hexstring
   }

               Figure 26: QPACKDynamicTableUpdate definition

6.4.  headers_encoded

   Importance: Base

   This event is emitted when an uncompressed header block is encoded
   successfully.

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   Note: this event has overlap with http.frame_created for the
   HeadersFrame type.  When outputting both events, implementers MAY
   omit the "headers" field in this event.

   Definition:

   QPACKHeadersEncoded = {
       ? stream_id: uint64
       ? headers: [+ HTTPField]

       block_prefix: QPACKHeaderBlockPrefix
       header_block: [+ QPACKHeaderBlockRepresentation]

       ? length: uint
       ? raw: hexstring
   }

                 Figure 27: QPACKHeadersEncoded definition

6.5.  headers_decoded

   Importance: Base

   This event is emitted when a compressed header block is decoded
   successfully.

   Note: this event has overlap with http.frame_parsed for the
   HeadersFrame type.  When outputting both events, implementers MAY
   omit the "headers" field in this event.

   Definition:

   QPACKHeadersDecoded = {
       ? stream_id: uint64
       ? headers: [+ HTTPField]

       block_prefix: QPACKHeaderBlockPrefix
       header_block: [+ QPACKHeaderBlockRepresentation]

       ? length: uint32
       ? raw: hexstring
   }

                 Figure 28: QPACKHeadersDecoded definition

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6.6.  instruction_created

   Importance: Base

   This event is emitted when a QPACK instruction (both decoder and
   encoder) is created and added to the encoder/decoder stream.

   Definition:

   QPACKInstructionCreated = {
       ; see definition in appendix
       instruction: QPACKInstruction
       ? length: uint32
       ? raw: hexstring
   }

               Figure 29: QPACKInstructionCreated definition

   Note: encoder/decoder semantics and stream_id's are implicit in
   either the instruction types or can be logged via other events (e.g.,
   http.stream_type_set)

6.7.  instruction_parsed

   Importance: Base

   This event is emitted when a QPACK instruction (both decoder and
   encoder) is read from the encoder/decoder stream.

   Definition:

   QPACKInstructionParsed = {
       ; see QPACKInstruction definition in appendix
       instruction: QPACKInstruction

       ? length: uint32
       ? raw: hexstring
   }

                Figure 30: QPACKInstructionParsed definition

   Note: encoder/decoder semantics and stream_id's are implicit in
   either the instruction types or can be logged via other events (e.g.,
   http.stream_type_set)

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7.  QPACK Data Field Definitions

   The following data field definitions can be used in QPACK events.

7.1.  QPACKInstruction

   Note: the instructions do not have explicit encoder/decoder types,
   since there is no overlap between the instructions of both types in
   neither name nor function.

   QPACKInstruction =  SetDynamicTableCapacityInstruction /
                       InsertWithNameReferenceInstruction /
                       InsertWithoutNameReferenceInstruction /
                       DuplicateInstruction /
                       SectionAcknowledgementInstruction /
                       StreamCancellationInstruction /
                       InsertCountIncrementInstruction

                   Figure 31: QPACKInstruction definition

7.1.1.  SetDynamicTableCapacityInstruction

   SetDynamicTableCapacityInstruction = {
       instruction_type: "set_dynamic_table_capacity"
       capacity: uint32
   }

          Figure 32: SetDynamicTableCapacityInstruction definition

7.1.2.  InsertWithNameReferenceInstruction

   InsertWithNameReferenceInstruction = {
       instruction_type: "insert_with_name_reference"
       table_type: QPACKTableType
       name_index: uint32
       huffman_encoded_value: bool
       ? value_length: uint32
       ? value: text
   }

          Figure 33: InsertWithNameReferenceInstruction definition

7.1.3.  InsertWithoutNameReferenceInstruction

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   InsertWithoutNameReferenceInstruction = {
       instruction_type: "insert_without_name_reference"
       huffman_encoded_name: bool
       ? name_length: uint32
       ? name: text
       huffman_encoded_value: bool
       ? value_length: uint32
       ? value: text
   }

        Figure 34: InsertWithoutNameReferenceInstruction definition

7.1.4.  DuplicateInstruction

   DuplicateInstruction = {
       instruction_type: "duplicate"
       index: uint32
   }

                 Figure 35: DuplicateInstruction definition

7.1.5.  SectionAcknowledgementInstruction

   SectionAcknowledgementInstruction = {
       instruction_type: "section_acknowledgement"
       stream_id: uint64
   }

          Figure 36: SectionAcknowledgementInstruction definition

7.1.6.  StreamCancellationInstruction

   StreamCancellationInstruction = {
       instruction_type: "stream_cancellation"
       stream_id: uint64
   }

            Figure 37: StreamCancellationInstruction definition

7.1.7.  InsertCountIncrementInstruction

   InsertCountIncrementInstruction = {
       instruction_type: "insert_count_increment"
       increment: uint32
   }

           Figure 38: InsertCountIncrementInstruction definition

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7.2.  QPACKHeaderBlockRepresentation

   QPACKHeaderBlockRepresentation =  IndexedHeaderField /
                                     LiteralHeaderFieldWithName /
                                     LiteralHeaderFieldWithoutName

            Figure 39: QPACKHeaderBlockRepresentation definition

7.2.1.  IndexedHeaderField

   Note: also used for "indexed header field with post-base index"

   IndexedHeaderField = {
       header_field_type: "indexed_header"

       ; MUST be "dynamic" if is_post_base is true
       table_type: QPACKTableType
       index: uint32

       ; to represent the "indexed header field with post-base index"
       ; header field type
       is_post_base: bool .default false
   }

                  Figure 40: IndexedHeaderField definition

7.2.2.  LiteralHeaderFieldWithName

   Note: also used for "Literal header field with post-base name
   reference"

   LiteralHeaderFieldWithName = {
       header_field_type: "literal_with_name"

       ; the 3rd "N" bit
       preserve_literal: bool

       ; MUST be "dynamic" if is_post_base is true
       table_type: QPACKTableType
       name_index: uint32
       huffman_encoded_value: bool
       ? value_length: uint32
       ? value: text

       ; to represent the "indexed header field with post-base index"
       ; header field type
       is_post_base: bool .default false
   }

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              Figure 41: LiteralHeaderFieldWithName definition

7.2.3.  LiteralHeaderFieldWithoutName

   LiteralHeaderFieldWithoutName = {
       header_field_type: "literal_without_name"

       ; the 3rd "N" bit
       preserve_literal: bool
       huffman_encoded_name: bool
       ? name_length: uint32
       ? name: text

       huffman_encoded_value: bool
       ? value_length: uint32
       ? value: text
   }

            Figure 42: LiteralHeaderFieldWithoutName definition

7.3.  QPACKHeaderBlockPrefix

   QPACKHeaderBlockPrefix = {
       required_insert_count: uint32
       sign_bit: bool
       delta_base: uint32
   }

                Figure 43: QPACKHeaderBlockPrefix definition

7.4.  QPACKTableType

   QPACKTableType = "static" / "dynamic"

                    Figure 44: QPACKTableType definition

8.  Security and Privacy Considerations

   The security and privacy considerations discussed in [QLOG-MAIN]
   apply to this document as well.

9.  IANA Considerations

   TBD

10.  Normative References

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   [CDDL]     Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
              Definition Language (CDDL): A Notational Convention to
              Express Concise Binary Object Representation (CBOR) and
              JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
              June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.

   [HTTP/3]   Bishop, M., Ed., "HTTP/3", RFC 9114, DOI 10.17487/RFC9114,
              June 2022, <https://www.rfc-editor.org/rfc/rfc9114>.

   [QLOG-MAIN]
              Marx, R., Niccolini, L., and M. Seemann, "Main logging
              schema for qlog", Work in Progress, Internet-Draft, draft-
              ietf-quic-qlog-main-schema-03, 31 August 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
              qlog-main-schema-03>.

   [QLOG-QUIC]
              Marx, R., Niccolini, L., and M. Seemann, "QUIC event
              definitions for qlog", Work in Progress, Internet-Draft,
              draft-ietf-quic-qlog-quic-events-02, 31 August 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
              qlog-quic-events-02>.

   [QPACK]    Krasic, C., Bishop, M., and A. Frindell, Ed., "QPACK:
              Field Compression for HTTP/3", RFC 9204,
              DOI 10.17487/RFC9204, June 2022,
              <https://www.rfc-editor.org/rfc/rfc9204>.

   [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>.

Appendix A.  Change Log

A.1.  Since draft-ietf-quic-qlog-h3-events-02:

   *  Renamed HTTPStreamType data to request (#222)

   *  Added HTTPStreamType value unknown (#227)

   *  Added HTTPUnknownFrame (#224)

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   *  Replaced old and new fields with stream_type in HTTPStreamTypeSet
      (#240)

   *  Changed HTTPFrame to a CDDL plug type (#257)

   *  Moved data definitions out of the appendix into separate sections

   *  Added overview Table of Contents

A.2.  Since draft-ietf-quic-qlog-h3-events-01:

   *  No changes - new draft to prevent expiration

A.3.  Since draft-ietf-quic-qlog-h3-events-00:

   *  Change the data definition language from TypeScript to CDDL (#143)

A.4.  Since draft-marx-qlog-event-definitions-quic-h3-02:

   *  These changes were done in preparation of the adoption of the
      drafts by the QUIC working group (#137)

   *  Split QUIC and HTTP/3 events into two separate documents

   *  Moved RawInfo, Importance, Generic events and Simulation events to
      the main schema document.

A.5.  Since draft-marx-qlog-event-definitions-quic-h3-01:

   Major changes:

   *  Moved data_moved from http to transport.  Also made the "from" and
      "to" fields flexible strings instead of an enum (#111,#65)

   *  Moved packet_type fields to PacketHeader.  Moved packet_size field
      out of PacketHeader to RawInfo:length (#40)

   *  Made events that need to log packet_type and packet_number use a
      header field instead of logging these fields individually

   *  Added support for logging retry, stateless reset and initial
      tokens (#94,#86,#117)

   *  Moved separate general event categories into a single category
      "generic" (#47)

   *  Added "transport:connection_closed" event (#43,#85,#78,#49)

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   *  Added version_information and alpn_information events
      (#85,#75,#28)

   *  Added parameters_restored events to help clarify 0-RTT behaviour
      (#88)

   Smaller changes:

   *  Merged loss_timer events into one loss_timer_updated event

   *  Field data types are now strongly defined (#10,#39,#36,#115)

   *  Renamed qpack instruction_received and instruction_sent to
      instruction_created and instruction_parsed (#114)

   *  Updated qpack:dynamic_table_updated.update_type.  It now has the
      value "inserted" instead of "added" (#113)

   *  Updated qpack:dynamic_table_updated.  It now has an "owner" field
      to differentiate encoder vs decoder state (#112)

   *  Removed push_allowed from http:parameters_set (#110)

   *  Removed explicit trigger field indications from events, since this
      was moved to be a generic property of the "data" field (#80)

   *  Updated transport:connection_id_updated to be more in line with
      other similar events.  Also dropped importance from Core to Base
      (#45)

   *  Added length property to PaddingFrame (#34)

   *  Added packet_number field to transport:frames_processed (#74)

   *  Added a way to generically log packet header flags (first 8 bits)
      to PacketHeader

   *  Added additional guidance on which events to log in which
      situations (#53)

   *  Added "simulation:scenario" event to help indicate simulation
      details

   *  Added "packets_acked" event (#107)

   *  Added "datagram_ids" to the datagram_X and packet_X events to
      allow tracking of coalesced QUIC packets (#91)

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   *  Extended connection_state_updated with more fine-grained states
      (#49)

A.6.  Since draft-marx-qlog-event-definitions-quic-h3-00:

   *  Event and category names are now all lowercase

   *  Added many new events and their definitions

   *  "type" fields have been made more specific (especially important
      for PacketType fields, which are now called packet_type instead of
      type)

   *  Events are given an importance indicator (issue #22)

   *  Event names are more consistent and use past tense (issue #21)

   *  Triggers have been redefined as properties of the "data" field and
      updated for most events (issue #23)

Acknowledgements

   Much of the initial work by Robin Marx was done at the Hasselt and KU
   Leuven Universities.

   Thanks to Jana Iyengar, Brian Trammell, Dmitri Tikhonov, Stephen
   Petrides, Jari Arkko, Marcus Ihlar, Victor Vasiliev, Mirja
   Kuehlewind, Jeremy Laine, Kazu Yamamoto, and Christian Huitema for
   their feedback and suggestions.

Authors' Addresses

   Robin Marx (editor)
   Akamai
   Email: rmarx@akamai.com

   Luca Niccolini (editor)
   Meta
   Email: lniccolini@meta.com

   Marten Seemann (editor)
   Protocol Labs
   Email: marten@protocol.ai

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   Lucas Pardue (editor)
   Cloudflare
   Email: lucaspardue.24.7@gmail.com

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