QUIC event definitions for qlog

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. Raw packet and frame information

QUIC packets always include an AEAD authentication tag at the end. In general, the length of the AEAD tag depends on the TLS cipher suite, although all cipher suites used in QUIC v1 use a 16 byte tag.¶

Note:

As QUIC appends an authentication tag after the packet payload, the packet header_lengths can be calculated as:¶

header_length = length - payload_length - 16¶

For UDP datagrams, the calculation is simpler:¶

header_length = length - payload_length¶

Note:

In some cases, the length fields are also explicitly reflected inside of packet headers. For example, the QUIC STREAM frame has a "length" field indicating its payload size. Similarly, the QUIC Long Header has a "length" field which is equal to the payload length plus the packet number length. 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 QUIC specifications to qlog, making it easier for users to interpret.¶

2.2. Events not belonging to a single connection

A single qlog event trace is typically associated with a single QUIC connection. However, for several types of events (for example, a Section 5.7 event with trigger value of "connection_unknown"), it can be impossible to tie them to a specific QUIC connection, especially on the server.¶

There are various ways to handle these events, each making certain tradeoffs between file size overhead, flexibility, ease of use, or ease of implementation. Some options include:¶

• Log them in a separate endpoint-wide trace (or use a special group_id value) not associated with a single connection.¶
• Log them in the most recently used trace.¶
• Use additional heuristics for connection identification (for example use the four-tuple in addition to the Connection ID).¶
• Buffer events until they can be assigned to a connection (for example for version negotiation and retry events).¶

4.1. server_listening

Importance: Extra¶

Emitted when the server starts accepting connections.¶

Definition:¶

ConnectivityServerListening = {
    ? ip_v4: IPAddress
    ? ip_v6: IPAddress
    ? port_v4: uint16
    ? port_v6: uint16

    ; the server will always answer client initials with a retry
    ; (no 1-RTT connection setups by choice)
    ? retry_required: bool
}

Some QUIC stacks do not handle sockets directly and are thus unable to log IP and/or port information.¶

4.2. connection_started

Importance: Base¶

Used for both attempting (client-perspective) and accepting (server-perspective) new connections. Note that this event has overlap with connection_state_updated and this is a separate event mainly because of all the additional data that should be logged.¶

Definition:¶

ConnectivityConnectionStarted = {
    ? ip_version: IPVersion
    src_ip: IPAddress
    dst_ip: IPAddress

    ; transport layer protocol
    ? protocol: text .default "QUIC"
    ? src_port: uint16
    ? dst_port: uint16
    ? src_cid: ConnectionID
    ? dst_cid: ConnectionID
}

Some QUIC stacks do not handle sockets directly and are thus unable to log IP and/or port information.¶

4.3. connection_closed

Importance: Base¶

Used for logging when a connection was closed, typically when an error or timeout occurred. Note that this event has overlap with connectivity:connection_state_updated, as well as the CONNECTION_CLOSE frame. However, in practice, when analyzing large deployments, it can be useful to have a single event representing a connection_closed event, which also includes an additional reason field to provide additional information. Additionally, it is useful to log closures due to timeouts, which are difficult to reflect using the other options.¶

In QUIC there are two main connection-closing error categories: connection and application errors. They have well-defined error codes and semantics. Next to these however, there can be internal errors that occur that may or may not get mapped to the official error codes in implementation-specific ways. As such, multiple error codes can be set on the same event to reflect this.¶

Definition:¶

ConnectivityConnectionClosed = {

    ; which side closed the connection
    ? owner: Owner
    ? connection_code: TransportError /
                       CryptoError /
                       uint32
    ? application_code: $ApplicationError /
                        uint32
    ? internal_code: uint32
    ? reason: text
    ? trigger:
        "clean" /
        "handshake_timeout" /
        "idle_timeout" /
        ; this is called the "immediate close" in the QUIC RFC
        "error" /
        "stateless_reset" /
        "version_mismatch" /
        ; for example HTTP/3's GOAWAY frame
        "application"
}

4.4. connection_id_updated

Importance: Base¶

This event is emitted when either party updates their current Connection ID. As this typically happens only sparingly over the course of a connection, this event allows loggers to be more efficient than logging the observed CID with each packet in the .header field of the "packet_sent" or "packet_received" events.¶

This is viewed from the perspective of the endpoint applying the new id. As such, when the endpoint receives a new connection id from the peer, it will see the dst_ fields are set. When the endpoint updates its own connection id (e.g., NEW_CONNECTION_ID frame), it logs the src_ fields.¶

Definition:¶

ConnectivityConnectionIDUpdated = {
    owner: Owner
    ? old: ConnectionID
    ? new: ConnectionID
}

4.5. spin_bit_updated

Importance: Base¶

To be emitted when the spin bit changes value. It SHOULD NOT be emitted if the spin bit is set without changing its value.¶

Definition:¶

ConnectivitySpinBitUpdated = {
    state: bool
}

4.6. connection_state_updated

Importance: Base¶

This event is used to track progress through QUIC's complex handshake and connection close procedures. It is intended to provide exhaustive options to log each state individually, but also provides a more basic, simpler set for implementations less interested in tracking each smaller state transition. As such, users should not expect to see -all- these states reflected in all qlogs and implementers should focus on support for the SimpleConnectionState set.¶

Definition:¶

ConnectivityConnectionStateUpdated = {
    ? old: ConnectionState /
           SimpleConnectionState
    new: ConnectionState /
         SimpleConnectionState
}

ConnectionState =
    ; initial sent/received
    "attempted" /
    ; peer address validated by: client sent Handshake packet OR
    ; client used CONNID chosen by the server.
    ; transport-draft-32, section-8.1
    "peer_validated" /
    "handshake_started" /
    ; 1 RTT can be sent, but handshake isn't done yet
    "early_write" /
    ; TLS handshake complete: Finished received and sent
    ; tls-draft-32, section-4.1.1
    "handshake_complete" /
    ; HANDSHAKE_DONE sent/received (connection is now "active", 1RTT
    ; can be sent). tls-draft-32, section-4.1.2
    "handshake_confirmed" /
    "closing" /
    ; connection_close sent/received
    "draining" /
    ; draining period done, connection state discarded
    "closed"

SimpleConnectionState =
    "attempted" /
    "handshake_started" /
    "handshake_confirmed" /
    "closed"

These states correspond to the following transitions for both client and server:¶

Client:¶

• send initial¶

  • state = attempted¶

• get initial¶

  • state = validated (not really "needed" at the client, but somewhat useful to indicate progress nonetheless)¶

• get first Handshake packet¶

  • state = handshake_started¶

• get Handshake packet containing ServerFinished¶

  • state = handshake_complete¶

• send ClientFinished¶

  • state = early_write (1RTT can now be sent)¶

• get HANDSHAKE_DONE¶

  • state = handshake_confirmed¶

Server:¶

• get initial¶

  • state = attempted¶
• send initial (TODO don't think this needs a separate state, since some handshake will always be sent in the same flight as this?)¶

• send handshake EE, CERT, CV, ...¶

  • state = handshake_started¶

• send ServerFinished¶

  • state = early_write (1RTT can now be sent)¶

• get first handshake packet / something using a server-issued CID of min length¶

  • state = validated¶

• get handshake packet containing ClientFinished¶

  • state = handshake_complete¶

• send HANDSHAKE_DONE¶

  • state = handshake_confirmed¶

Note:

connection_state_changed with a new state of "attempted" is the same conceptual event as the connection_started event above from the client's perspective. Similarly, a state of "closing" or "draining" corresponds to the connection_closed event.¶

4.7. mtu_updated

Importance: Extra¶

ConnectivityMTUUpdated = {
  ? old: uint16
  new: uint16

  ; at some point, MTU discovery stops, as a "good enough"
  ; packet size has been found
  ? done: bool .default false
}

This event indicates that the estimated Path MTU was updated. This happens as part of the Path MTU discovery process.¶

5.1. version_information

Importance: Core¶

QUIC endpoints each have their own list of of QUIC versions they support. The client uses the most likely version in their first initial. If the server does support that version, it replies with a version_negotiation packet, containing supported versions. From this, the client selects a version. This event aggregates all this information in a single event type. It also allows logging of supported versions at an endpoint without actual version negotiation needing to happen.¶

Definition:¶

QUICVersionInformation = {
    ? server_versions: [+ QuicVersion]
    ? client_versions: [+ QuicVersion]
    ? chosen_version: QuicVersion
}

Intended use:¶

• When sending an initial, the client logs this event with client_versions and chosen_version set¶
• Upon receiving a client initial with a supported version, the server logs this event with server_versions and chosen_version set¶
• Upon receiving a client initial with an unsupported version, the server logs this event with server_versions set and client_versions to the single-element array containing the client's attempted version. The absence of chosen_version implies no overlap was found.¶
• Upon receiving a version negotiation packet from the server, the client logs this event with client_versions set and server_versions to the versions in the version negotiation packet and chosen_version to the version it will use for the next initial packet¶

5.2. alpn_information

Importance: Core¶

QUIC implementations each have their own list of application level protocols and versions thereof they support. The client includes a list of their supported options in its first initial as part of the TLS Application Layer Protocol Negotiation (alpn) extension. If there are common option(s), the server chooses the most optimal one and communicates this back to the client. If not, the connection is closed.¶

Definition:¶

QUICALPNInformation = {
    ? server_alpns: [* text]
    ? client_alpns: [* text]
    ? chosen_alpn: text
}

Intended use:¶

• When sending an initial, the client logs this event with client_alpns set¶
• When receiving an initial with a supported alpn, the server logs this event with server_alpns set, client_alpns equalling the client-provided list, and chosen_alpn to the value it will send back to the client.¶
• When receiving an initial with an alpn, the client logs this event with chosen_alpn to the received value.¶
• Alternatively, a client can choose to not log the first event, but wait for the receipt of the server initial to log this event with both client_alpns and chosen_alpn set.¶

5.3. parameters_set

Importance: Core¶

This event groups settings from several different sources (transport parameters, TLS ciphers, etc.) into a single event. This is done to minimize the amount of events and to decouple conceptual setting impacts from their underlying mechanism for easier high-level reasoning.¶

All these settings are typically set once and never change. However, they are typically set at different times during the connection, so there will typically 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.¶

In the case of connection resumption and 0-RTT, some of the server's parameters are stored up-front at the client and used for the initial connection startup. They are later updated with the server's reply. In these cases, utilize the separate parameters_restored event to indicate the initial values, and this event to indicate the updated values, as normal.¶

Definition:¶

QUICParametersSet = {
    ? owner: Owner

    ; true if valid session ticket was received
    ? resumption_allowed: bool

    ; true if early data extension was enabled on the TLS layer
    ? early_data_enabled: bool

    ; e.g., "AES_128_GCM_SHA256"
    ? tls_cipher: text

    ; RFC9000
    ? original_destination_connection_id: ConnectionID
    ? initial_source_connection_id: ConnectionID
    ? retry_source_connection_id: ConnectionID
    ? stateless_reset_token: StatelessResetToken
    ? disable_active_migration: bool
    ? max_idle_timeout: uint64
    ? max_udp_payload_size: uint32
    ? ack_delay_exponent: uint16
    ? max_ack_delay: uint16
    ? active_connection_id_limit: uint32
    ? initial_max_data: uint64
    ? initial_max_stream_data_bidi_local: uint64
    ? initial_max_stream_data_bidi_remote: uint64
    ? initial_max_stream_data_uni: uint64
    ? initial_max_streams_bidi: uint64
    ? initial_max_streams_uni: uint64
    ? preferred_address: PreferredAddress

    ; RFC9221
    ? max_datagram_frame_size: uint64

    ; RFC9287
    ; true if present, absent or false if extension not negotiated
    ? grease_quic_bit: bool
}

PreferredAddress = {
    ip_v4: IPAddress
    ip_v6: IPAddress
    port_v4: uint16
    port_v6: uint16
    connection_id: ConnectionID
    stateless_reset_token: StatelessResetToken
}

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

5.4. parameters_restored

Importance: Base¶

When using QUIC 0-RTT, clients are expected to remember and restore the server's transport parameters from the previous connection. This event is used to indicate which parameters were restored and to which values when utilizing 0-RTT. Note that not all transport parameters should be restored (many are even prohibited from being re-utilized). The ones listed here are the ones expected to be useful for correct 0-RTT usage.¶

Definition:¶

QUICParametersRestored = {
    ? disable_active_migration: bool
    ? max_idle_timeout: uint64
    ? max_udp_payload_size: uint32
    ? active_connection_id_limit: uint32
    ? initial_max_data: uint64
    ? initial_max_stream_data_bidi_local: uint64
    ? initial_max_stream_data_bidi_remote: uint64,
    ? initial_max_stream_data_uni: uint64
    ? initial_max_streams_bidi: uint64
    ? initial_max_streams_uni: uint64
}

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

5.5. packet_sent

Importance: Core¶

Definition:¶

QUICPacketSent = {
    header: PacketHeader
    ? frames: [* $QuicFrame]
    ? is_coalesced: bool .default false

    ; only if header.packet_type === "retry"
    ? retry_token: Token

    ; only if header.packet_type === "stateless_reset"
    ; is always 128 bits in length.
    ? stateless_reset_token: StatelessResetToken

    ; only if header.packet_type === "version_negotiation"
    ? supported_versions: [+ QuicVersion]
    ? raw: RawInfo
    ? datagram_id: uint32
    ? is_mtu_probe_packet: bool .default false

    ? trigger:
      ; draft-23 5.1.1
      "retransmit_reordered" /
      ; draft-23 5.1.2
      "retransmit_timeout" /
      ; draft-23 5.3.1
      "pto_probe" /
      ; draft-19 6.2
      "retransmit_crypto" /
      ; needed for some CCs to figure out bandwidth allocations
      ; when there are no normal sends
      "cc_bandwidth_probe"
}

The encryption_level and packet_number_space are not logged explicitly: the header.packet_type specifies this by inference (assuming correct implementation)¶

For more details on "datagram_id", see Section 5.10. It is only needed when keeping track of packet coalescing.¶

5.6. packet_received

Importance: Core¶

Definition:¶

QUICPacketReceived = {
    header: PacketHeader
    ? frames: [* $QuicFrame]
    ? is_coalesced: bool .default false

    ; only if header.packet_type === "retry"
    ? retry_token: Token

    ; only if header.packet_type === "stateless_reset"
    ; Is always 128 bits in length.
    ? stateless_reset_token: StatelessResetToken

    ; only if header.packet_type === "version_negotiation"
    ? supported_versions: [+ QuicVersion]
    ? raw: RawInfo
    ? datagram_id: uint32

    ? trigger:
        ; if packet was buffered because it couldn't be
        ; decrypted before
        "keys_available"
}

The encryption_level and packet_number_space are not logged explicitly: the header.packet_type specifies this by inference (assuming correct implementation)¶

For more details on "datagram_id", see Section 5.10. It is only needed when keeping track of packet coalescing.¶

5.7. packet_dropped

Importance: Base¶

This event indicates a QUIC-level packet was dropped.¶

The trigger field indicates a general reason category for dropping the packet, while the details field can contain additional implementation-specific information.¶

Definition:¶

QUICPacketDropped = {

    ; Primarily packet_type should be filled here,
    ; as other fields might not be decrypteable or parseable
    ? header: PacketHeader
    ? raw: RawInfo
    ? datagram_id: uint32
    ? details: {* text => any}
    ? trigger:
        "internal_error" /
        "rejected" /
        "unsupported" /
        "invalid" /
        "connection_unknown" /
        "decryption_failure" /
        "general"
}

Some example situations for each of the trigger categories include:¶

• internal_error: not initialized, out of memory¶
• rejected: limits reached, DDoS protection, unwilling to track more paths, duplicate packet¶
• unsupported: unknown or unsupported version. See also Section 2.2.¶
• invalid: packet parsing or validation error¶
• connection_unknown: packet does not relate to a known connection or Connection ID¶
• decryption_failure: decryption key was unavailable, decryption failed¶
• general: situations not clearly covered in the other categories¶

For more details on "datagram_id", see Section 5.10.¶

5.8. packet_buffered

Importance: Base¶

This event is emitted when a packet is buffered because it cannot be processed yet. Typically, this is because the packet cannot be parsed yet, and thus only the full packet contents can be logged when it was parsed in a packet_received event.¶

Definition:¶

QUICPacketBuffered = {

    ; primarily packet_type and possible packet_number should be
    ; filled here as other elements might not be available yet
    ? header: PacketHeader
    ? raw: RawInfo
    ? datagram_id: uint32
    ? trigger:
        ; indicates the parser cannot keep up, temporarily buffers
        ; packet for later processing
        "backpressure" /
        ; if packet cannot be decrypted because the proper keys were
        ; not yet available
        "keys_unavailable"
}

For more details on "datagram_id", see Section 5.10. It is only needed when keeping track of packet coalescing.¶

5.9. packets_acked

Importance: Extra¶

This event is emitted when a (group of) sent packet(s) is acknowledged by the remote peer for the first time. This information could also be deduced from the contents of received ACK frames. However, ACK frames require additional processing logic to determine when a given packet is acknowledged for the first time, as QUIC uses ACK ranges which can include repeated ACKs. Additionally, this event can be used by implementations that do not log frame contents.¶

Definition:¶

QUICPacketsAcked = {
    ? packet_number_space: PacketNumberSpace
    ? packet_numbers: [+ uint64]
}

If packet_number_space is omitted, it assumes the default value of PacketNumberSpace.application_data, as this is by far the most prevalent packet number space a typical QUIC connection will use.¶

5.10. datagrams_sent

Importance: Extra¶

When one or more UDP-level datagrams are passed to the socket. This is useful for determining how QUIC packet buffers are drained to the OS.¶

Definition:¶

QUICDatagramsSent = {

    ; to support passing multiple at once
    ? count: uint16

    ; The RawInfo fields do not include the UDP headers,
    ; only the UDP payload
    ? raw: [+ RawInfo]

    ; ECN bits in the IP header
    ; if not set, defaults to the value used on the last
    ; QUICDatagramsSent event
    ? ecn: [+ ECN]

    ? datagram_ids: [+ uint32]
}

Since QUIC implementations rarely control UDP logic directly, the raw data excludes UDP-level headers in all fields.¶

The "datagram_id" is a qlog-specific concept to allow tracking of QUIC packet coalescing inside UDP datagrams. Since QUIC generates many UDP datagrams, unique identifiers are required to be able to track them individually in qlog traces. However, neither UDP nor QUIC exchanges datagram identifiers on the wire. Selecting identifier values is thus left to qlog implementations, which should consider how to generate unique values within the scope of their created traces.¶

5.11. datagrams_received

Importance: Extra¶

When one or more UDP-level datagrams are received from the socket. This is useful for determining how datagrams are passed to the user space stack from the OS.¶

Definition:¶

QUICDatagramsReceived = {

    ; to support passing multiple at once
    ? count: uint16

    ; The RawInfo fields do not include the UDP headers,
    ; only the UDP payload
    ? raw: [+ RawInfo]

    ; ECN bits in the IP header
    ; if not set, defaults to the value on the last
    ; QUICDatagramsReceived event
    ? ecn: [+ ECN]

    ? datagram_ids: [+ uint32]
}

For more details on "datagram_ids", see Section 5.10.¶

5.12. datagram_dropped

Importance: Extra¶

When a UDP-level datagram is dropped. This is typically done if it does not contain a valid QUIC packet. If it does, but the QUIC packet is dropped for other reasons, packet_dropped (Section 5.7) should be used instead.¶

Definition:¶

QUICDatagramDropped = {

    ; The RawInfo fields do not include the UDP headers,
    ; only the UDP payload
    ? raw: RawInfo
}

5.13. stream_state_updated

Importance: Base¶

This event is emitted whenever the internal state of a QUIC stream is updated, as described in QUIC transport draft-23 section 3. Most of this can be inferred from several types of frames going over the wire, but it's much easier to have explicit signals for these state changes.¶

Definition:¶

StreamType = "unidirectional" /
             "bidirectional"

QUICStreamStateUpdated = {
    stream_id: uint64

    ; mainly useful when opening the stream
    ? stream_type: StreamType
    ? old: StreamState
    new: StreamState
    ? stream_side: "sending" /
                   "receiving"
}

StreamState =
    ; bidirectional stream states, draft-23 3.4.
    "idle" /
    "open" /
    "half_closed_local" /
    "half_closed_remote" /
    "closed" /
    ; sending-side stream states, draft-23 3.1.
    "ready" /
    "send" /
    "data_sent" /
    "reset_sent" /
    "reset_received" /
    ; receive-side stream states, draft-23 3.2.
    "receive" /
    "size_known" /
    "data_read" /
    "reset_read" /
    ; both-side states
    "data_received" /
    ; qlog-defined:
    ; memory actually freed
    "destroyed"

QUIC implementations SHOULD mainly log the simplified bidirectional (HTTP/2-alike) stream states (e.g., idle, open, closed) instead of the more fine-grained stream states (e.g., data_sent, reset_received). These latter ones are mainly for more in-depth debugging. Tools SHOULD be able to deal with both types equally.¶

5.14. frames_processed

Importance: Extra¶

This event's main goal is to prevent a large proliferation of specific purpose events (e.g., packets_acknowledged, flow_control_updated, stream_data_received). Implementations have the opportunity to (selectively) log this type of signal without having to log packet-level details (e.g., in packet_received). Since for almost all cases, the effects of applying a frame to the internal state of an implementation can be inferred from that frame's contents, these events are aggregated into this single "frames_processed" event.¶

This event can be used to signal internal state change not resulting directly from the actual "parsing" of a frame (e.g., the frame could have been parsed, data put into a buffer, then later processed, then logged with this event).¶

Implementations logging "packet_received" and which include all of the packet's constituent frames therein, are not expected to emit this "frames_processed" event. Rather, implementations not wishing to log full packets or that wish to explicitly convey extra information about when frames are processed (if not directly tied to their reception) can use this event.¶

Note that for some events, this approach will lose some information (e.g., for which encryption level are packets being acknowledged?). If this information is important, the packet_received event can be used instead.¶

In some implementations, it can be difficult to log frames directly, even when using packet_sent and packet_received events. For these cases, this event also contains the packet_numbers field, which can be used to more explicitly link this event to the packet_sent/received events. The field is an array, which supports using a single "frames_processed" event for multiple frames received over multiple packets. To map between frames and packets, the position and order of entries in the "frames" and "packet_numbers" is used. If the optional "packet_numbers" field is used, each frame MUST have a corresponding packet number at the same index.¶

Definition:¶

QUICFramesProcessed = {
    frames: [* $QuicFrame]
    ? packet_numbers: [* uint64]
}

For example, an instance of this event that represents four STREAM frames received over two packets would have the fields serialized as:¶

"frames":[
  {"frame_type":"stream","stream_id":0,"offset":0,"length":500},
  {"frame_type":"stream","stream_id":0,"offset":500,"length":200},
  {"frame_type":"stream","stream_id":1,"offset":0,"length":300},
  {"frame_type":"stream","stream_id":1,"offset":300,"length":50}
  ],
"packet_numbers":[
  1,
  1,
  2,
  2
]

5.15. stream_data_moved

Importance: Base¶

Used to indicate when QUIC stream data moves between the different layers (for example passing from the application protocol (e.g., HTTP) to QUIC stream buffers and vice versa) or between the application protocol (e.g., HTTP) and the actual user application on top (for example a browser engine). This helps make clear the flow of data, how long data remains in various buffers and the overheads introduced by individual layers.¶

For example, this helps make clear whether received data on a QUIC stream is moved to the application protocol immediately (for example per received packet) or in larger batches (for example, all QUIC packets are processed first and afterwards the application layer reads from the streams with newly available data). This in turn can help identify bottlenecks, flow control issues or scheduling problems.¶

This event is only for data in QUIC streams. For data in QUIC Datagram Frames, see Section 5.16.¶

Definition:¶

QUICStreamDataMoved = {
    ? stream_id: uint64
    ? offset: uint64

    ; byte length of the moved data
    ? length: uint64
    ? from: "user" /
            "application" /
            "transport" /
            "network" /
            text
    ? to: "user" /
          "application" /
          "transport" /
          "network" /
          text
    ? raw: RawInfo
}

5.16. datagram_data_moved

Importance: Base¶

Used to indicate when QUIC Datagram Frame data (see [RFC9221]) moves between the different layers (for example passing from the application protocol (e.g., WebTransport) to QUIC Datagram Frame buffers and vice versa) or between the application protocol and the actual user application on top (for example a gaming engine or media playback software). This helps make clear the flow of data, how long data remains in various buffers and the overheads introduced by individual layers.¶

For example, this helps make clear whether received data in a QUIC Datagram Frame is moved to the application protocol immediately (for example per received packet) or in larger batches (for example, all QUIC packets are processed first and afterwards the application layer reads all Datagrams at once). This in turn can help identify bottlenecks or scheduling problems.¶

This event is only for data in QUIC Datagram Frames. For data in QUIC streams, see Section 5.15.¶

Definition:¶

QUICDatagramDataMoved = {
    ; byte length of the moved data
    ? length: uint64
    ? from: "user" /
            "application" /
            "transport" /
            "network" /
            text
    ? to: "user" /
          "application" /
          "transport" /
          "network" /
          text
    ? raw: RawInfo
}

6.1. key_updated

Importance: Base¶

Definition:¶

SecurityKeyUpdated = {
    key_type: KeyType
    ? old: hexstring
    ? new: hexstring

    ; needed for 1RTT key updates
    ? generation: uint32
    ? trigger:
        ; (e.g., initial, handshake and 0-RTT keys
        ; are generated by TLS)
        "tls" /
        "remote_update" /
        "local_update"
}

6.2. key_discarded

Importance: Base¶

Definition:¶

SecurityKeyDiscarded = {
    key_type: KeyType
    ? key: hexstring

    ; needed for 1RTT key updates
    ? generation: uint32
    ? trigger:
        ; (e.g., initial, handshake and 0-RTT keys
        ; are generated by TLS)
        "tls" /
        "remote_update" /
        "local_update"
}

7.1. parameters_set

Importance: Base¶

This event groups initial parameters from both loss detection and congestion control into a single event. All these settings are typically set once and never change. Implementation that do, for some reason, change these parameters during execution, MAY emit the parameters_set event twice.¶

Definition:¶

RecoveryParametersSet = {

    ; Loss detection, see recovery draft-23, Appendix A.2
    ; in amount of packets
    ? reordering_threshold: uint16

    ; as RTT multiplier
    ? time_threshold: float32

    ; in ms
    timer_granularity: uint16

    ; in ms
    ? initial_rtt:float32

    ; congestion control, Appendix B.1.
    ; in bytes. Note that this could be updated after pmtud
    ? max_datagram_size: uint32

    ; in bytes
    ? initial_congestion_window: uint64

    ; Note that this could change when max_datagram_size changes
    ; in bytes
    ? minimum_congestion_window: uint64
    ? loss_reduction_factor: float32

    ; as PTO multiplier
    ? persistent_congestion_threshold: uint16
}

Additionally, this event can contain any number of unspecified fields to support different recovery approaches.¶

7.2. metrics_updated

Importance: Core¶

This event is emitted when one or more of the observable recovery metrics changes value. This event SHOULD group all possible metric updates that happen at or around the same time in a single event (e.g., if min_rtt and smoothed_rtt change at the same time, they should be bundled in a single metrics_updated entry, rather than split out into two). Consequently, a metrics_updated event is only guaranteed to contain at least one of the listed metrics.¶

Definition:¶

RecoveryMetricsUpdated = {

    ; Loss detection, see recovery draft-23, Appendix A.3
    ; all following rtt fields are expressed in ms
    ? min_rtt: float32
    ? smoothed_rtt: float32
    ? latest_rtt: float32
    ? rtt_variance: float32
    ? pto_count: uint16

    ; Congestion control, Appendix B.2.
    ; in bytes
    ? congestion_window: uint64
    ? bytes_in_flight: uint64

    ; in bytes
    ? ssthresh: uint64

    ; qlog defined
    ; sum of all packet number spaces
    ? packets_in_flight: uint64

    ; in bits per second
    ? pacing_rate: uint64
}

In order to make logging easier, implementations MAY log values even if they are the same as previously reported values (e.g., two subsequent RecoveryMetricsUpdated entries can both report the exact same value for min_rtt). However, applications SHOULD try to log only actual updates to values.¶

Additionally, this event can contain any number of unspecified fields to support different recovery approaches.¶

7.3. congestion_state_updated

Importance: Base¶

This event signifies when the congestion controller enters a significant new state and changes its behaviour. This event's definition is kept generic to support different Congestion Control algorithms. For example, for the algorithm defined in the Recovery draft ("enhanced" New Reno), the following states are defined:¶

• slow_start¶
• congestion_avoidance¶
• application_limited¶
• recovery¶

Definition:¶

RecoveryCongestionStateUpdated = {
    ? old: text
    new: text
    ? trigger:
        "persistent_congestion" /
        "ECN"
}

The "trigger" field SHOULD be logged if there are multiple ways in which a state change can occur but MAY be omitted if a given state can only be due to a single event occurring (e.g., slow start is exited only when ssthresh is exceeded).¶

7.4. loss_timer_updated

Importance: Extra¶

This event is emitted when a recovery loss timer changes state. The three main event types are:¶

• set: the timer is set with a delta timeout for when it will trigger next¶
• expired: when the timer effectively expires after the delta timeout¶
• cancelled: when a timer is cancelled (e.g., all outstanding packets are acknowledged, start idle period)¶

In order to indicate an active timer's timeout update, a new "set" event is used.¶

Definition:¶

RecoveryLossTimerUpdated = {

    ; called "mode" in draft-23 A.9.
    ? timer_type: "ack" /
                  "pto"
    ? packet_number_space: PacketNumberSpace
    event_type: "set" /
                "expired" /
                "cancelled"

    ; if event_type === "set": delta time is in ms from
    ; this event's timestamp until when the timer will trigger
    ? delta: float32
}

7.5. packet_lost

Importance: Core¶

This event is emitted when a packet is deemed lost by loss detection. It is RECOMMENDED to populate the optional "trigger" field in order to help disambiguate among the various possible causes of a loss declaration.¶

Definition:¶

RecoveryPacketLost = {

    ; should include at least the packet_type and packet_number
    ? header: PacketHeader

    ; not all implementations will keep track of full
    ; packets, so these are optional
    ? frames: [* $QuicFrame]
    ? is_mtu_probe_packet: bool .default false
    ? trigger:
        "reordering_threshold" /
        "time_threshold" /
        ; RFC 9002 Section 6.2.4 paragraph 6, MAY
        "pto_expired"
}

7.6. marked_for_retransmit

Importance: Extra¶

This event indicates which data was marked for retransmit upon detecting a packet loss (see packet_lost). Similar to the reasoning for the "frames_processed" event, in order to keep the amount of different events low, this signal is grouped into in a single event based on existing QUIC frame definitions for all types of retransmittable data.¶

Implementations retransmitting full packets or frames directly can just log the constituent frames of the lost packet here (or do away with this event and use the contents of the packet_lost event instead). Conversely, implementations that have more complex logic (e.g., marking ranges in a stream's data buffer as in-flight), or that do not track sent frames in full (e.g., only stream offset + length), can translate their internal behaviour into the appropriate frame instance here even if that frame was never or will never be put on the wire.¶

Much of this data can be inferred if implementations log packet_sent events (e.g., looking at overlapping stream data offsets and length, one can determine when data was retransmitted).¶

Definition:¶

RecoveryMarkedForRetransmit = {
    frames: [+ $QuicFrame]
}

7.7. ecn_state_updated

Importance: Extra¶

This event indicates a progression in the ECN state machine as described in section A.4 of [QUIC-TRANSPORT].¶

ECNStateUpdated = {
   ? old: ECNState
    new: ECNState
}

ECNState =
  ; ECN testing in progress
  "testing" /
  ; ECN state unknown, waiting for acknowledgements
  ; for testing packets
  "unknown" /
  ; ECN testing failed
  "failed" /
  ; testing was successful, the endpoint now
  ; sends packets with ECT(0) marking
  "capable"

8.1. QuicVersion

QuicVersion = hexstring

8.2. ConnectionID

ConnectionID = hexstring

8.3. Owner

Owner = "local" /
        "remote"

8.4. IPAddress and IPVersion

; an IPAddress can either be a "human readable" form
; (e.g., "127.0.0.1" for v4 or
; "2001:0db8:85a3:0000:0000:8a2e:0370:7334" for v6) or
; use a raw byte-form (as the string forms can be ambiguous)
IPAddress = text /
            hexstring

IPVersion = "v4" /
            "v6"

8.5. PacketType

PacketType = "initial" /
             "handshake" /
             "0RTT" /
             "1RTT" /
             "retry" /
             "version_negotiation" /
             "stateless_reset" /
             "unknown"

8.6. PacketNumberSpace

PacketNumberSpace = "initial" /
                    "handshake" /
                    "application_data"

8.7. PacketHeader

PacketHeader = {
    ? quic_bit: bool .default true
    packet_type: PacketType

    ; only if packet_type === "initial" || "handshake" || "0RTT" ||
    ;                         "1RTT"
    ? packet_number: uint64

    ; the bit flags of the packet headers (spin bit, key update bit,
    ; etc. up to and including the packet number length bits
    ; if present
    ? flags: uint8

    ; only if packet_type === "initial"
    ? token: Token

    ; only if packet_type === "initial" || "handshake" || "0RTT"
    ; Signifies length of the packet_number plus the payload
    ? length: uint16

    ; only if present in the header
    ; if correctly using transport:connection_id_updated events,
    ; dcid can be skipped for 1RTT packets
    ? version: QuicVersion
    ? scil: uint8
    ? dcil: uint8
    ? scid: ConnectionID
    ? dcid: ConnectionID
}

8.8. Token

Token = {
    ? type: "retry" /
            "resumption"

    ; decoded fields included in the token
    ; (typically: peer's IP address, creation time)
    ? details: {
      * text => any
    }
    ? raw: RawInfo
}

The token carried in an Initial packet can either be a retry token from a Retry packet, or one originally provided by the server in a NEW_TOKEN frame used when resuming a connection (e.g., for address validation purposes). Retry and resumption tokens typically contain encoded metadata to check the token's validity when it is used, but this metadata and its format is implementation specific. For that, this event includes a general-purpose "details" field.¶

8.9. Stateless Reset Token

StatelessResetToken = hexstring .size 16

The stateless reset token is carried in stateless reset packets, in transport parameters and in NEW_CONNECTION_ID frames.¶

8.10. KeyType

KeyType = "server_initial_secret" /
          "client_initial_secret" /
          "server_handshake_secret" /
          "client_handshake_secret" /
          "server_0rtt_secret" /
          "client_0rtt_secret" /
          "server_1rtt_secret" /
          "client_1rtt_secret"

8.11. ECN

ECN = "Not-ECT" / "ECT(1)" / "ECT(0)" / "CE"

The ECN bits carried in the IP header.¶

8.12. QUIC Frames

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

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

The QUIC frame types defined in this document are as follows:¶

QuicBaseFrames /= PaddingFrame /
                  PingFrame /
                  AckFrame /
                  ResetStreamFrame /
                  StopSendingFrame /
                  CryptoFrame /
                  NewTokenFrame /
                  StreamFrame /
                  MaxDataFrame /
                  MaxStreamDataFrame /
                  MaxStreamsFrame /
                  DataBlockedFrame /
                  StreamDataBlockedFrame /
                  StreamsBlockedFrame /
                  NewConnectionIDFrame /
                  RetireConnectionIDFrame /
                  PathChallengeFrame /
                  PathResponseFrame /
                  ConnectionCloseFrame /
                  HandshakeDoneFrame /
                  UnknownFrame /
                  DatagramFrame

$QuicFrame /= QuicBaseFrames

PaddingFrame = {
    frame_type: "padding"

    ; total frame length, including frame header
    ? length: uint32
    payload_length: uint32
}

PingFrame = {
    frame_type: "ping"

    ; total frame length, including frame header
    ? length: uint32
    ? payload_length: uint32
}

; either a single number (e.g., [1]) or two numbers (e.g., [1,2]).
; For two numbers:
; the first number is "from": lowest packet number in interval
; the second number is "to": up to and including the highest
; packet number in the interval
AckRange = [1*2 uint64]

AckFrame = {
    frame_type: "ack"

    ; in ms
    ? ack_delay: float32

    ; e.g., looks like [[1,2],[4,5], [7], [10,22]] serialized
    ? acked_ranges: [+ AckRange]

    ; ECN (explicit congestion notification) related fields
    ; (not always present)
    ? ect1: uint64
    ? ect0: uint64
    ? ce: uint64

    ; total frame length, including frame header
    ? length: uint32
    ? payload_length: uint32
}

ResetStreamFrame = {
    frame_type: "reset_stream"
    stream_id: uint64
    error_code: $ApplicationError /
                uint32

    ; in bytes
    final_size: uint64

    ; total frame length, including frame header
    ? length: uint32
    ? payload_length: uint32
}

StopSendingFrame = {
    frame_type: "stop_sending"
    stream_id: uint64
    error_code: $ApplicationError /
                uint32

    ; total frame length, including frame header
    ? length: uint32
    ? payload_length: uint32
}

CryptoFrame = {
    frame_type: "crypto"
    offset: uint64
    length: uint64
    ? payload_length: uint32
}

NewTokenFrame = {
  frame_type: "new_token"
  token: Token
}

StreamFrame = {
    frame_type: "stream"
    stream_id: uint64

    ; These two MUST always be set
    ; If not present in the Frame type, log their default values
    offset: uint64
    length: uint64

    ; this MAY be set any time,
    ; but MUST only be set if the value is true
    ; if absent, the value MUST be assumed to be false
    ? fin: bool .default false
    ? raw: RawInfo
}

MaxDataFrame = {
  frame_type: "max_data"
  maximum: uint64
}

MaxStreamDataFrame = {
  frame_type: "max_stream_data"
  stream_id: uint64
  maximum: uint64
}

MaxStreamsFrame = {
  frame_type: "max_streams"
  stream_type: StreamType
  maximum: uint64
}

DataBlockedFrame = {
  frame_type: "data_blocked"
  limit: uint64
}

StreamDataBlockedFrame = {
  frame_type: "stream_data_blocked"
  stream_id: uint64
  limit: uint64
}

StreamsBlockedFrame = {
  frame_type: "streams_blocked"
  stream_type: StreamType
  limit: uint64
}

NewConnectionIDFrame = {
  frame_type: "new_connection_id"
  sequence_number: uint32
  retire_prior_to: uint32

  ; mainly used if e.g., for privacy reasons the full
  ; connection_id cannot be logged
  ? connection_id_length: uint8
  connection_id: ConnectionID
  ? stateless_reset_token: StatelessResetToken
}

RetireConnectionIDFrame = {
  frame_type: "retire_connection_id"
  sequence_number: uint32
}

PathChallengeFrame = {
  frame_type: "path_challenge"

  ; always 64-bit
  ? data: hexstring
}

PathResponseFrame = {
  frame_type: "path_response"

  ; always 64-bit
  ? data: hexstring
}

ErrorSpace = "transport" /
             "application"

ConnectionCloseFrame = {
    frame_type: "connection_close"
    ? error_space: ErrorSpace
    ? error_code: TransportError /
                  $ApplicationError /
                  uint32
    ? error_code_value: uint64
    ? reason: text

    ; For known frame types, the appropriate "frame_type" string
    ; For unknown frame types, the hex encoded frame identifier value
    ? trigger_frame_type: uint64 /
                          text
}

HandshakeDoneFrame = {
  frame_type: "handshake_done";
}

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

DatagramFrame = {
    frame_type: "datagram"
    ? length: uint64
    ? raw: RawInfo
}

TransportError = "no_error" /
                 "internal_error" /
                 "connection_refused" /
                 "flow_control_error" /
                 "stream_limit_error" /
                 "stream_state_error" /
                 "final_size_error" /
                 "frame_encoding_error" /
                 "transport_parameter_error" /
                 "connection_id_limit_error" /
                 "protocol_violation" /
                 "invalid_token" /
                 "application_error" /
                 "crypto_buffer_exceeded" /
                 "key_update_error" /
                 "aead_limit_reached" /
                 "no_viable_path"
                 ; there is no value to reflect CRYPTO_ERROR
                 ; use the CryptoError type instead

$ApplicationError /= "new_error_name" /
                     "another_new_error_name"

; all strings from "crypto_error_0x100" to "crypto_error_0x1ff"
CryptoError = text .regexp "crypto_error_0x1[0-9a-f][0-9a-f]"

Since draft-ietf-qlog-quic-events-05:

• SecurityKeyUpdated: the new key is no longer mandatory to log (#294)¶
• Added ECN related events and metadata (#263)¶

Since draft-ietf-qlog-quic-events-04:

• Updated guidance on logging events across connections (#279)¶
• Renamed 'transport' category to 'quic' (#302)¶
• Added support for multiple packet numbers in 'quic:frames_processed' (#307)¶
• Added definitions for RFC9287 (QUIC GREASE Bit extension) (#311)¶
• Added definitions for RFC9221 (QUIC Datagram Frame extension) (#310)¶
• (Temporarily) removed definitions for connection migration events (#317)¶
• Editorial and formatting changes (#298, #299, #304, #306, #327)¶

Since draft-ietf-qlog-quic-events-03:

• Ensured consistent use of RawInfo to indicate raw wire bytes (#243)¶
• Renamed UnknownFrame:raw_frame_type to :frame_type_value (#54)¶
• Renamed ConnectionCloseFrame:raw_error_code to :error_code_value (#54)¶
• Changed triggers for packet_dropped (#278)¶
• Added entries to TransportError enum (#285)¶
• Changed minimum_congestion_window to uint64 (#288)¶

Since draft-ietf-qlog-quic-events-02:

• Renamed key_retired to key_discarded (#185)¶
• Added fields and events for DPLPMTUD (#135)¶
• Made packet_number optional in PacketHeader (#244)¶
• Removed connection_retried event placeholder (#255)¶
• Changed QuicFrame to a CDDL plug type (#257)¶
• Moved data definitions out of the appendix into separate sections¶
• Added overview Table of Contents¶

Since draft-ietf-qlog-quic-events-01:

• Added Stateless Reset Token type (#122)¶

Since draft-ietf-qlog-quic-events-00:

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

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.¶
• Changed to/from value options of the data_moved event¶

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)¶

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)¶