HTTP/3 and QPACK qlog event definitions

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.¶

2.1. 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).¶

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.¶

The "owner" field reflects how Settings are exchanged on a connection. Sent settings have the value "local" and received settings have the value "received". A qlog can have multiple instances of this event.¶

As a reminder the CDDL unwrap operator (~), see [RFC8610]), copies the fields from the referenced type (H3Parameters) into the target type directly, extending the target with the unwrapped fields.¶

Definition:¶

H3ParametersSet = {
    ? owner: Owner
    ~H3Parameters

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

H3Parameters = {
    ; RFC9114
    ? max_field_section_size: uint64

    ; RFC9204
    ? max_table_capacity: uint64
    ? blocked_streams_count: uint64

    ; RFC9220 (SETTINGS_ENABLE_CONNECT_PROTOCOL)
    ? extended_connect: uint16

    ; RFC9297 (SETTINGS_H3_DATAGRAM)
    ? h3_datagram: uint16

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

This event can contain any number of unspecified fields. This allows for representation of reserved settings (aka GREASE) or ad-hoc support for extension settings that do not have a related qlog schema definition.¶

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:¶

H3ParametersRestored = {
    ~H3Parameters
}

Similar to H3ParametersSet this event can contain any number of unspecified fields to allow for reserved or extension 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.¶

The stream_type_value field is the numerical value without VLIE encoding.¶

Definition:¶

H3StreamTypeSet = {
    ? owner: Owner
    stream_id: uint64
    stream_type: H3StreamType

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

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

H3StreamType =  "request" /
                  "control" /
                  "push" /
                  "reserved" /
                  "unknown" /
                  "qpack_encode" /
                  "qpack_decode"

4.4. priority_updated

Importance: Base¶

Emitted when the priority of a request stream or push stream is initialized or updated through mechanisms defined in [RFC9218]. For example, the priority can be updated through signals received from client and/or server (e.g., in HTTP/3 HEADERS or PRIORITY_UPDATE frames) or it can be changed or overridden due to local policies.¶

Definition:¶

H3PriorityUpdated = {
    ; if the prioritized element is a request stream
    ? stream_id: uint64

    ; if the prioritized element is a push stream
    ? push_id: uint64

    ? old: H3Priority
    new: H3Priority
}

4.5. frame_created

Importance: Core¶

This event is emitted when the HTTP/3 framing actually happens. This does not necessarily coincide with HTTP/3 data getting passed to the QUIC layer. For that, see the "stream_data_moved" event in [QLOG-QUIC].¶

Definition:¶

H3FrameCreated = {
    stream_id: uint64
    ? length: uint64
    frame: $H3Frame
    ? raw: RawInfo
}

4.6. frame_parsed

Importance: Core¶

This event is emitted when the HTTP/3 frame is parsed. This is not necessarily the same as when the HTTP/3 data is actually received on the QUIC layer. For that, see the "stream_data_moved" event in [QLOG-QUIC].¶

Definition:¶

H3FrameParsed = {
    stream_id: uint64
    ? length: uint64
    frame: $H3Frame
    ? raw: RawInfo
}

HTTP/3 DATA frames can have arbitrarily large lengths to reduce frame header overhead. As such, DATA frames can span multiple QUIC packets. In this case, the frame_parsed event is emitted once for the frame header, and further streamed data is indicated using the stream_data_moved event.¶

4.7. datagram_created

Importance: Base¶

This event is emitted when an HTTP/3 Datagram is created (see [RFC9297]). This does not necessarily coincide with the HTTP/3 Datagram getting passed to the QUIC layer. For that, see the "datagram_data_moved" event in [QLOG-QUIC].¶

Definition:¶

H3DatagramCreated = {
    quarter_stream_id: uint64
    ? datagram: $H3Datagram
    ? raw: RawInfo
}

4.8. datagram_parsed

Importance: Base¶

This event is emitted when the HTTP/3 Datagram is parsed (see [RFC9297]). This is not necessarily the same as when the HTTP/3 Datagram is actually received on the QUIC layer. For that, see the "datagram_data_moved" event in [QLOG-QUIC].¶

Definition:¶

H3DatagramParsed = {
    quarter_stream_id: uint64
    ? datagram: $H3Datagram
    ? raw: RawInfo
}

4.9. 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:¶

H3PushResolved = {
    ? push_id: uint64

    ; in case this is logged from a place that does not have access
    ; to the push_id
    ? stream_id: uint64
    decision: H3PushDecision
}

H3PushDecision = "claimed" /
                   "abandoned"

5.1. Owner

Owner = "local" /
        "remote"

5.2. H3Frame

The generic $H3Frame is defined here as a CDDL extension point (a "socket" or "plug"). It can be extended to support additional HTTP/3 frame types.¶

; The H3Frame is any key-value map (e.g., JSON object)
$H3Frame /= {
    * text => any
}

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

H3BaseFrames = H3DataFrame /
               H3HeadersFrame /
               H3CancelPushFrame /
               H3SettingsFrame /
               H3PushPromiseFrame /
               H3GoawayFrame /
               H3MaxPushIDFrame /
               H3ReservedFrame /
               H3UnknownFrame

$H3Frame /= H3BaseFrames

5.3. H3Datagram

The generic $H3Datagram is defined here as a CDDL extension point (a "socket" or "plug"). It can be extended to support additional HTTP/3 datagram types. This document intentionally does not define any specific HTTP/3 Datagram types.¶

; The H3Datagram is any key-value map (e.g., JSON object)
$H3Datagram /= {
    * text => any
}

H3DataFrame = {
    frame_type: "data"
    ? raw: RawInfo
}

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

H3HeadersFrame = {
    frame_type: "headers"
    headers: [* H3HTTPField]
}

H3HTTPField = {
    name: text
    ? value: text
}

H3CancelPushFrame = {
    frame_type: "cancel_push"
    push_id: uint64
}

H3SettingsFrame = {
    frame_type: "settings"
    settings: [* H3Setting]
}

H3Setting = {
    name: text
    value: uint64
}

H3PushPromiseFrame = {
    frame_type: "push_promise"
    push_id: uint64
    headers: [* H3HTTPField]
}

H3GoawayFrame = {
    frame_type: "goaway"

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

H3MaxPushIDFrame = {
    frame_type: "max_push_id"
    push_id: uint64
}

H3PriorityUpdateFrame = {
    frame_type: "priority_update"

    ; if the prioritized element is a request stream
    ? stream_id: uint64

    ; if the prioritized element is a push stream
    ? push_id: uint64

    priority_field_value: H3Priority
}

; The priority value in ASCII text, encoded using Structured Fields
; Example: u=5, i
H3Priority = text

H3ReservedFrame = {
    frame_type: "reserved"
    ? length: uint64
}

H3UnknownFrame = {
    frame_type: "unknown"
    frame_type_value: uint64
    ? raw: RawInfo
}

H3ApplicationError = "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"

; ensure HTTP errors are properly validate in QUIC events as well
; e.g., QUIC's ConnectionClose Frame
$ApplicationError /= H3ApplicationError

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
}

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.¶

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

Definition:¶

QPACKStreamStateUpdate = {
    stream_id: uint64

    ; streams are assumed to start "unblocked"
    ; until they become "blocked"
    state: QPACKStreamState
}

QPACKStreamState = "blocked" /
                   "unblocked"

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
}

6.4. headers_encoded

Importance: Base¶

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

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: [+ H3HTTPField]
    block_prefix: QPACKHeaderBlockPrefix
    header_block: [+ QPACKHeaderBlockRepresentation]
    ? raw: RawInfo
}

6.5. headers_decoded

Importance: Base¶

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

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: [+ H3HTTPField]
    block_prefix: QPACKHeaderBlockPrefix
    header_block: [+ QPACKHeaderBlockRepresentation]
    ? raw: RawInfo
}

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
    ? raw: RawInfo
}

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
    ? raw: RawInfo
}

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)¶

7.1. QPACKInstruction

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

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

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

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
}

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

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

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

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

7.2. QPACKHeaderBlockRepresentation

QPACKHeaderBlockRepresentation = IndexedHeaderField /
                                 LiteralHeaderFieldWithName /
                                 LiteralHeaderFieldWithoutName

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
}

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
}

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
}

7.3. QPACKHeaderBlockPrefix

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

7.4. QPACKTableType

QPACKTableType = "static" /
                 "dynamic"

A.1. Since draft-ietf-quic-qlog-h3-events-04:

• Renamed 'http' category to 'h3' (#300)¶
• H3HTTPField.value is now optional (#296)¶
• Added definitions for RFC9297 (HTTP/3 Datagram extension) (#310)¶
• Added definitions for RFC9218 (HTTP Extensible Prioritizations extension) (#312)¶
• Added definitions for RFC9220 (Extended Connect extension) (#325)¶
• Editorial and formatting changes (#298, #258, #299, #304, #327)¶

A.2. Since draft-ietf-quic-qlog-h3-events-03:

• Ensured consistent use of RawInfo to indicate raw wire bytes (#243)¶
• Changed HTTPStreamTypeSet:raw_stream_type to stream_type_value (#54)¶
• Changed HTTPUnknownFrame:raw_frame_type to frame_type_value (#54)¶
• Renamed max_header_list_size to max_field_section_size (#282)¶

A.3. Since draft-ietf-quic-qlog-h3-events-02:

• Renamed HTTPStreamType data to request (#222)¶
• Added HTTPStreamType value unknown (#227)¶
• Added HTTPUnknownFrame (#224)¶
• 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.4. Since draft-ietf-quic-qlog-h3-events-01:

• No changes - new draft to prevent expiration¶

A.5. Since draft-ietf-quic-qlog-h3-events-00:

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

A.6. 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.7. 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)¶
• 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)¶
• Extended connection_state_updated with more fine-grained states (#49)¶

A.8. 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)¶