QUIC event definitions for qlog
draft-ietf-quic-qlog-quic-events-12
| Document | Type | Active Internet-Draft (quic WG) | |
|---|---|---|---|
| Authors | Robin Marx , Luca Niccolini , Marten Seemann , Lucas Pardue | ||
| Last updated | 2025-10-20 | ||
| Replaces | draft-marx-quic-qlog-quic-events | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Associated WG milestone |
|
||
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-quic-qlog-quic-events-12
QUIC R. Marx, Ed.
Internet-Draft Akamai
Intended status: Standards Track L. Niccolini, Ed.
Expires: 23 April 2026 Meta
M. Seemann, Ed.
L. Pardue, Ed.
Cloudflare
20 October 2025
QUIC event definitions for qlog
draft-ietf-quic-qlog-quic-events-12
Abstract
This document describes a qlog event schema containing concrete qlog
event definitions and their metadata for the core QUIC protocol and
selected extensions.
Note to Readers
Note to RFC editor: Please remove 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.
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 23 April 2026.
Marx, et al. Expires 23 April 2026 [Page 1]
Internet-Draft QUIC event definitions for qlog October 2025
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Use of group IDs . . . . . . . . . . . . . . . . . . . . 5
1.2. Raw packet and frame information . . . . . . . . . . . . 5
1.3. Events not belonging to a single connection . . . . . . . 5
1.4. Notational Conventions . . . . . . . . . . . . . . . . . 6
2. Event Schema Definition . . . . . . . . . . . . . . . . . . . 6
2.1. Draft Event Schema Identification . . . . . . . . . . . . 6
3. QUIC Event Overview . . . . . . . . . . . . . . . . . . . . . 7
4. Connectivity events . . . . . . . . . . . . . . . . . . . . . 10
4.1. server_listening . . . . . . . . . . . . . . . . . . . . 10
4.2. connection_started . . . . . . . . . . . . . . . . . . . 10
4.3. connection_closed . . . . . . . . . . . . . . . . . . . . 11
4.4. connection_id_updated . . . . . . . . . . . . . . . . . . 12
4.5. spin_bit_updated . . . . . . . . . . . . . . . . . . . . 13
4.6. connection_state_updated . . . . . . . . . . . . . . . . 13
4.7. tuple_assigned . . . . . . . . . . . . . . . . . . . . . 15
4.8. mtu_updated . . . . . . . . . . . . . . . . . . . . . . . 16
5. Transport events . . . . . . . . . . . . . . . . . . . . . . 16
5.1. version_information . . . . . . . . . . . . . . . . . . . 16
5.2. alpn_information . . . . . . . . . . . . . . . . . . . . 17
5.3. parameters_set . . . . . . . . . . . . . . . . . . . . . 18
5.4. parameters_restored . . . . . . . . . . . . . . . . . . . 21
5.5. packet_sent . . . . . . . . . . . . . . . . . . . . . . . 21
5.6. packet_received . . . . . . . . . . . . . . . . . . . . . 22
5.7. packet_dropped . . . . . . . . . . . . . . . . . . . . . 23
5.8. packet_buffered . . . . . . . . . . . . . . . . . . . . . 25
5.9. packets_acked . . . . . . . . . . . . . . . . . . . . . . 25
5.10. udp_datagrams_sent . . . . . . . . . . . . . . . . . . . 26
5.11. udp_datagrams_received . . . . . . . . . . . . . . . . . 27
5.12. udp_datagram_dropped . . . . . . . . . . . . . . . . . . 27
5.13. stream_state_updated . . . . . . . . . . . . . . . . . . 28
5.14. frames_processed . . . . . . . . . . . . . . . . . . . . 30
Marx, et al. Expires 23 April 2026 [Page 2]
Internet-Draft QUIC event definitions for qlog October 2025
5.15. stream_data_moved . . . . . . . . . . . . . . . . . . . . 31
5.16. datagram_data_moved . . . . . . . . . . . . . . . . . . . 33
5.17. connection_data_blocked_updated . . . . . . . . . . . . . 33
5.18. stream_data_blocked_updated . . . . . . . . . . . . . . . 34
5.19. datagram_data_blocked_updated . . . . . . . . . . . . . . 34
5.20. migration_state_updated . . . . . . . . . . . . . . . . . 35
5.21. timer_updated . . . . . . . . . . . . . . . . . . . . . . 36
6. Security Events . . . . . . . . . . . . . . . . . . . . . . . 38
6.1. key_updated . . . . . . . . . . . . . . . . . . . . . . . 38
6.2. key_discarded . . . . . . . . . . . . . . . . . . . . . . 38
7. Recovery events . . . . . . . . . . . . . . . . . . . . . . . 39
7.1. recovery_parameters_set . . . . . . . . . . . . . . . . . 39
7.2. recovery_metrics_updated . . . . . . . . . . . . . . . . 40
7.3. congestion_state_updated . . . . . . . . . . . . . . . . 42
7.4. packet_lost . . . . . . . . . . . . . . . . . . . . . . . 42
7.5. marked_for_retransmit . . . . . . . . . . . . . . . . . . 43
7.6. ecn_state_updated . . . . . . . . . . . . . . . . . . . . 44
8. QUIC data type definitions . . . . . . . . . . . . . . . . . 44
8.1. QuicVersion . . . . . . . . . . . . . . . . . . . . . . . 44
8.2. ConnectionID . . . . . . . . . . . . . . . . . . . . . . 44
8.3. Initiator . . . . . . . . . . . . . . . . . . . . . . . . 45
8.4. IPAddress . . . . . . . . . . . . . . . . . . . . . . . . 45
8.5. TupleEndpointInfo . . . . . . . . . . . . . . . . . . . . 45
8.6. PacketType . . . . . . . . . . . . . . . . . . . . . . . 46
8.7. PacketNumberSpace . . . . . . . . . . . . . . . . . . . . 46
8.8. PacketHeader . . . . . . . . . . . . . . . . . . . . . . 46
8.9. Token . . . . . . . . . . . . . . . . . . . . . . . . . . 47
8.10. Stateless Reset Token . . . . . . . . . . . . . . . . . . 48
8.11. KeyType . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.12. ECN . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.13. QUIC Frames . . . . . . . . . . . . . . . . . . . . . . . 49
8.13.1. PaddingFrame . . . . . . . . . . . . . . . . . . . . 50
8.13.2. PingFrame . . . . . . . . . . . . . . . . . . . . . 50
8.13.3. AckFrame . . . . . . . . . . . . . . . . . . . . . . 50
8.13.4. ResetStreamFrame . . . . . . . . . . . . . . . . . . 51
8.13.5. StopSendingFrame . . . . . . . . . . . . . . . . . . 52
8.13.6. CryptoFrame . . . . . . . . . . . . . . . . . . . . 52
8.13.7. NewTokenFrame . . . . . . . . . . . . . . . . . . . 53
8.13.8. StreamFrame . . . . . . . . . . . . . . . . . . . . 53
8.13.9. MaxDataFrame . . . . . . . . . . . . . . . . . . . . 53
8.13.10. MaxStreamDataFrame . . . . . . . . . . . . . . . . . 53
8.13.11. MaxStreamsFrame . . . . . . . . . . . . . . . . . . 54
8.13.12. DataBlockedFrame . . . . . . . . . . . . . . . . . . 54
8.13.13. StreamDataBlockedFrame . . . . . . . . . . . . . . . 54
8.13.14. StreamsBlockedFrame . . . . . . . . . . . . . . . . 54
8.13.15. NewConnectionIDFrame . . . . . . . . . . . . . . . . 54
8.13.16. RetireConnectionIDFrame . . . . . . . . . . . . . . 55
8.13.17. PathChallengeFrame . . . . . . . . . . . . . . . . . 55
Marx, et al. Expires 23 April 2026 [Page 3]
Internet-Draft QUIC event definitions for qlog October 2025
8.13.18. PathResponseFrame . . . . . . . . . . . . . . . . . 55
8.13.19. ConnectionCloseFrame . . . . . . . . . . . . . . . . 56
8.13.20. HandshakeDoneFrame . . . . . . . . . . . . . . . . . 56
8.13.21. UnknownFrame . . . . . . . . . . . . . . . . . . . . 57
8.13.22. DatagramFrame . . . . . . . . . . . . . . . . . . . 57
8.13.23. TransportError . . . . . . . . . . . . . . . . . . . 57
8.13.24. ApplicationError . . . . . . . . . . . . . . . . . . 58
8.13.25. CryptoError . . . . . . . . . . . . . . . . . . . . 59
9. Security and Privacy Considerations . . . . . . . . . . . . . 59
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 59
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 60
11.1. Normative References . . . . . . . . . . . . . . . . . . 60
11.2. Informative References . . . . . . . . . . . . . . . . . 61
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 61
Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Since draft-ietf-qlog-quic-events-11: . . . . . . . . . . . . . 61
Since draft-ietf-qlog-quic-events-09: . . . . . . . . . . . . . 62
Since draft-ietf-qlog-quic-events-08: . . . . . . . . . . . . . 62
Since draft-ietf-qlog-quic-events-07: . . . . . . . . . . . . . 62
Since draft-ietf-qlog-quic-events-06: . . . . . . . . . . . . . 62
Since draft-ietf-qlog-quic-events-05: . . . . . . . . . . . . . 63
Since draft-ietf-qlog-quic-events-04: . . . . . . . . . . . . . 63
Since draft-ietf-qlog-quic-events-03: . . . . . . . . . . . . . 63
Since draft-ietf-qlog-quic-events-02: . . . . . . . . . . . . . 63
Since draft-ietf-qlog-quic-events-01: . . . . . . . . . . . . . 64
Since draft-ietf-qlog-quic-events-00: . . . . . . . . . . . . . 64
Since draft-marx-qlog-event-definitions-quic-h3-02: . . . . . . 64
Since draft-marx-qlog-event-definitions-quic-h3-01: . . . . . . 64
Since draft-marx-qlog-event-definitions-quic-h3-00: . . . . . . 66
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 66
1. Introduction
This document defines a qlog event schema (Section 8 of [QLOG-MAIN])
containing concrete events for the core QUIC protocol (see
[QUIC-TRANSPORT], [QUIC-RECOVERY], and [QUIC-TLS]) and some of its
extensions (see [QUIC-DATAGRAM] and [GREASEBIT]).
The event namespace with identifier quic is defined; see Section 2.
In this namespace multiple events derive from the qlog abstract Event
class (Section 7 of [QLOG-MAIN]), each extending the "data" field and
defining their "name" field values and semantics. Some event data
fields use complex data types. These are represented as enums or re-
usable definitions, which are grouped together on the bottom of this
document for clarity.
Marx, et al. Expires 23 April 2026 [Page 4]
Internet-Draft QUIC event definitions for qlog October 2025
1.1. Use of group IDs
When the qlog group_id field is used, it is recommended to use QUIC's
Original Destination Connection ID (ODCID, the CID chosen by the
client when first contacting the server), as this is the only value
that does not change over the course of the connection and can be
used to link more advanced QUIC packets (e.g., Retry, Version
Negotiation) to a given connection. Similarly, the ODCID should be
used 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 ODCID abcd1234).
1.2. 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.
For the purposes of calculating the lengths in fields of type RawInfo
(as defined in [QLOG-MAIN]) related to QUIC packets, the AEAD tag is
regarded as a trailer with a fixed size of 16 bytes.
1.3. 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).
Marx, et al. Expires 23 April 2026 [Page 5]
Internet-Draft QUIC event definitions for qlog October 2025
1.4. 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,
namespace, type, data, tuple, group_id, RawInfo, and time-related
fields.
Events are defined with an importance level as described in
Section 8.3 of [QLOG-MAIN].
As is the case for [QLOG-MAIN], the qlog schema definitions in this
document are intentionally agnostic to serialization formats. The
choice of format is an implementation decision.
2. Event Schema Definition
This document describes how the core QUIC protocol and selected
extensions can be expressed in qlog using a newly defined event
schema. Per the requirements in Section 8 of [QLOG-MAIN], this
document registers the quic namespace. The event schema URI is
urn:ietf:params:qlog:events:quic.
2.1. Draft Event Schema Identification
This section is to be removed before publishing as an RFC.
Only implementations of the final, published RFC can use the events
belonging to the event schema with the URI
urn:ietf:params:qlog:events:quic. Until such an RFC exists,
implementations MUST NOT identify themselves using this URI.
Implementations of draft versions of the event schema MUST append the
string "-" and the corresponding draft number to the URI. For
example, draft 07 of this document is identified using the URI
urn:ietf:params:qlog:events:quic-07.
The namespace identifier itself is not affected by this requirement.
Marx, et al. Expires 23 April 2026 [Page 6]
Internet-Draft QUIC event definitions for qlog October 2025
3. QUIC Event Overview
Table 1 summarizes the name value of each event type that is defined
in this specification.
+======================================+============+==============+
| Name value | Importance | Definition |
+======================================+============+==============+
| quic:server_listening | Extra | Section 4.1 |
+--------------------------------------+------------+--------------+
| quic:connection_started | Base | Section 4.2 |
+--------------------------------------+------------+--------------+
| quic:connection_closed | Base | Section 4.3 |
+--------------------------------------+------------+--------------+
| quic:connection_id_updated | Base | Section 4.4 |
+--------------------------------------+------------+--------------+
| quic:spin_bit_updated | Base | Section 4.5 |
+--------------------------------------+------------+--------------+
| quic:connection_state_updated | Base | Section 4.6 |
+--------------------------------------+------------+--------------+
| quic:tuple_assigned | Base | Section 4.7 |
+--------------------------------------+------------+--------------+
| quic:mtu_updated | Extra | Section 4.8 |
+--------------------------------------+------------+--------------+
| quic:version_information | Core | Section 5.1 |
+--------------------------------------+------------+--------------+
| quic:alpn_information | Core | Section 5.2 |
+--------------------------------------+------------+--------------+
| quic:parameters_set | Core | Section 5.3 |
+--------------------------------------+------------+--------------+
| quic:parameters_restored | Base | Section 5.4 |
+--------------------------------------+------------+--------------+
| quic:packet_sent | Core | Section 5.5 |
+--------------------------------------+------------+--------------+
| quic:packet_received | Core | Section 5.6 |
+--------------------------------------+------------+--------------+
| quic:packet_dropped | Base | Section 5.7 |
+--------------------------------------+------------+--------------+
| quic:packet_buffered | Base | Section 5.8 |
+--------------------------------------+------------+--------------+
| quic:packets_acked | Extra | Section 5.9 |
+--------------------------------------+------------+--------------+
| quic:udp_datagrams_sent | Extra | Section 5.10 |
+--------------------------------------+------------+--------------+
| quic:udp_datagrams_received | Extra | Section 5.11 |
+--------------------------------------+------------+--------------+
| quic:udp_datagram_dropped | Extra | Section 5.12 |
+--------------------------------------+------------+--------------+
Marx, et al. Expires 23 April 2026 [Page 7]
Internet-Draft QUIC event definitions for qlog October 2025
| quic:stream_state_updated | Base | Section 5.13 |
+--------------------------------------+------------+--------------+
| quic:frames_processed | Extra | Section 5.14 |
+--------------------------------------+------------+--------------+
| quic:stream_data_moved | Base | Section 5.15 |
+--------------------------------------+------------+--------------+
| quic:datagram_data_moved | Base | Section 5.16 |
+--------------------------------------+------------+--------------+
| quic:connection_data_blocked_updated | Extra | Section 5.17 |
+--------------------------------------+------------+--------------+
| quic:stream_data_blocked_updated | Extra | Section 5.18 |
+--------------------------------------+------------+--------------+
| quic:datagram_data_blocked_updated | Extra | Section 5.19 |
+--------------------------------------+------------+--------------+
| quic:migration_state_updated | Extra | Section 5.20 |
+--------------------------------------+------------+--------------+
| quic:timer_updated | Extra | Section 5.21 |
+--------------------------------------+------------+--------------+
| quic:key_updated | Base | Section 6.1 |
+--------------------------------------+------------+--------------+
| quic:key_discarded | Base | Section 6.2 |
+--------------------------------------+------------+--------------+
| quic:recovery_parameters_set | Base | Section 7.1 |
+--------------------------------------+------------+--------------+
| quic:recovery_metrics_updated | Core | Section 7.2 |
+--------------------------------------+------------+--------------+
| quic:congestion_state_updated | Base | Section 7.3 |
+--------------------------------------+------------+--------------+
| quic:packet_lost | Core | Section 7.4 |
+--------------------------------------+------------+--------------+
| quic:marked_for_retransmit | Extra | Section 7.5 |
+--------------------------------------+------------+--------------+
| quic:ecn_state_updated | Extra | Section 7.6 |
+--------------------------------------+------------+--------------+
Table 1: QUIC Events
QUIC events extend the $ProtocolEventData extension point defined in
[QLOG-MAIN]. Additionally, they allow for direct extensibility by
their use of per-event extension points via the $$ CDDL "group
socket" syntax, as also described in [QLOG-MAIN].
Marx, et al. Expires 23 April 2026 [Page 8]
Internet-Draft QUIC event definitions for qlog October 2025
QuicEventData = QUICServerListening /
QUICConnectionStarted /
QUICConnectionClosed /
QUICConnectionIDUpdated /
QUICSpinBitUpdated /
QUICConnectionStateUpdated /
QUICTupleAssigned /
QUICMTUUpdated /
QUICVersionInformation /
QUICALPNInformation /
QUICParametersSet /
QUICParametersRestored /
QUICPacketSent /
QUICPacketReceived /
QUICPacketDropped /
QUICPacketBuffered /
QUICPacketsAcked /
QUICUDPDatagramsSent /
QUICUDPDatagramsReceived /
QUICUDPDatagramDropped /
QUICStreamStateUpdated /
QUICFramesProcessed /
QUICStreamDataMoved /
QUICDatagramDataMoved /
QUICConnectionDataBlockedUpdated /
QUICStreamDataBlockedUpdated /
QUICDatagramDataBlockedUpdated /
QUICMigrationStateUpdated /
QUICTimerUpdated /
QUICKeyUpdated /
QUICKeyDiscarded /
QUICRecoveryParametersSet /
QUICRecoveryMetricsUpdated /
QUICCongestionStateUpdated /
QUICPacketLost /
QUICMarkedForRetransmit /
QUICECNStateUpdated
$ProtocolEventData /= QuicEventData
Figure 1: QuicEventData definition and ProtocolEventData extension
The concrete QUIC event types are further defined below, their type
identifier is the heading name. The subdivisions in sections on
Connectivity, Security, Transport and Recovery are purely for
readability.
Marx, et al. Expires 23 April 2026 [Page 9]
Internet-Draft QUIC event definitions for qlog October 2025
4. Connectivity events
4.1. server_listening
Emitted when the server starts accepting connections. It has Extra
importance level.
QUICServerListening = {
? ip_v4: IPAddress
? port_v4: uint16
? ip_v6: IPAddress
? port_v6: uint16
; the server will always answer client initials with a retry
; (no 1-RTT connection setups by choice)
? retry_required: bool
* $$quic-serverlistening-extension
}
Figure 2: QUICServerListening definition
Some QUIC stacks do not handle sockets directly and are thus unable
to log IP and/or port information.
4.2. connection_started
The connection_started event is used for both attempting (client-
perspective) and accepting (server-perspective) new connections.
Note that while there is overlap with the connection_state_updated
event, this event is separate event in order to capture additional
data that can be useful to log. It has Base importance level.
QUICConnectionStarted = {
local: TupleEndpointInfo
remote: TupleEndpointInfo
* $$quic-connectionstarted-extension
}
Figure 3: QUICConnectionStarted definition
Some QUIC stacks do not handle sockets directly and are thus unable
to log IP and/or port information.
Marx, et al. Expires 23 April 2026 [Page 10]
Internet-Draft QUIC event definitions for qlog October 2025
4.3. connection_closed
The connection_closed event is used for logging when a connection was
closed, typically when an error or timeout occurred. It has Base
importance level.
Note that this event has overlap with the connection_state_updated
event, 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 more information. Furthermore, it
is useful to log closures due to timeouts or explicit application
actions (such as racing multiple connections and aborting the
slowest), which are difficult to reflect using the other options.
The connection_closed event is intended to be logged either when the
local endpoint silently discards the connection due to an idle
timeout, when a CONNECTION_CLOSE frame is sent (the connection enters
the 'closing' state on the sender side), when a CONNECTION_CLOSE
frame is received (the connection enters the 'draining' state on the
receiver side) or when a Stateless Reset packet is received (the
connection is discarded at the receiver side). Connectivity-related
updates after this point (e.g., exiting a 'closing' or 'draining'
state), should be logged using the connection_state_updated event
instead.
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, and more fine-
grained internal error codes can be reflected in the internal_code
field.
If the error code does not map to a known error string, the
connection_error or application_error value of "unknown" type can be
used and the raw value captured in the error_code field; a numerical
value without variable-length integer encoding.
Marx, et al. Expires 23 April 2026 [Page 11]
Internet-Draft QUIC event definitions for qlog October 2025
QUICConnectionClosed = {
; which side closed the connection
? initiator: Initiator
? connection_error: $TransportError /
CryptoError
? application_error: $ApplicationError
; if connection_error or application_error === "unknown"
? error_code: uint64
? internal_code: uint64
? reason: text
? trigger:
"idle_timeout" /
"application" /
"error" /
"version_mismatch" /
; when received from peer
"stateless_reset" /
"aborted" /
; when it is unclear what triggered the CONNECTION_CLOSE
"unspecified"
* $$quic-connectionclosed-extension
}
Figure 4: QUICConnectionClosed definition
Loggers SHOULD use the most descriptive trigger for a
connection_closed event that they are able to deduce. This is often
clear at the peer closing the connection (and sending the
CONNECTION_CLOSE), but can sometimes be more opaque at the receiving
end.
4.4. connection_id_updated
The connection_id_updated event is emitted when either party updates
their current Connection ID. As this typically happens only
sparingly over the course of a connection, using this event is more
efficient than logging the observed CID with each and every
packet_sent or packet_received events. It has Base importance level.
The connection_id_updated event 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, the initiator field will be
"remote". When the endpoint updates its own connection ID, the
initiator field will be "local".
Marx, et al. Expires 23 April 2026 [Page 12]
Internet-Draft QUIC event definitions for qlog October 2025
QUICConnectionIDUpdated = {
initiator: Initiator
? old: ConnectionID
? new: ConnectionID
* $$quic-connectionidupdated-extension
}
Figure 5: QUICConnectionIDUpdated definition
4.5. spin_bit_updated
The spin_bit_updated event conveys information about the QUIC latency
spin bit; see Section 17.4 of [QUIC-TRANSPORT]. The event is emitted
when the spin bit changes value, it SHOULD NOT be emitted if the spin
bit is set without changing its value. It has Base importance level.
QUICSpinBitUpdated = {
state: bool
* $$quic-spinbitupdated-extension
}
Figure 6: QUICSpinBitUpdated definition
4.6. connection_state_updated
The connection_state_updated event is used to track progress through
QUIC's complex handshake and connection close procedures. It has
Base importance level.
[QUIC-TRANSPORT] does not contain an exhaustive flow diagram with
possible connection states nor their transitions (though some are
explicitly mentioned, like the 'closing' and 'draining' states). As
such, this document *non-exhaustively* defines those states that are
most likely to be useful for debugging QUIC connections.
QUIC implementations SHOULD mainly log the simplified
BaseConnectionStates, adding the more fine-grained
GranularConnectionStates when more in-depth debugging is required.
Tools SHOULD be able to deal with both types equally.
QUICConnectionStateUpdated = {
? old: $ConnectionState
new: $ConnectionState
* $$quic-connectionstateupdated-extension
}
Marx, et al. Expires 23 April 2026 [Page 13]
Internet-Draft QUIC event definitions for qlog October 2025
BaseConnectionStates =
; Initial packet sent/received
"attempted" /
; Handshake packet sent/received
"handshake_started" /
; Both sent a TLS Finished message
; and verified the peer's TLS Finished message
; 1-RTT packets can be sent
; RFC 9001 Section 4.1.1
"handshake_complete" /
; CONNECTION_CLOSE sent/received,
; stateless reset received or idle timeout
"closed"
GranularConnectionStates =
; RFC 9000 Section 8.1
; client sent Handshake packet OR
; client used connection ID chosen by the server OR
; client used valid address validation token
"peer_validated" /
; 1-RTT data can be sent by the server,
; but handshake is not done yet
; (server has sent TLS Finished; sometimes called 0.5 RTT data)
"early_write" /
; HANDSHAKE_DONE sent/received.
; RFC 9001 Section 4.1.2
"handshake_confirmed" /
; CONNECTION_CLOSE sent
"closing" /
; CONNECTION_CLOSE received
"draining" /
; draining or closing period done, connection state discarded
"closed"
$ConnectionState /= BaseConnectionStates / GranularConnectionStates
Figure 7: QUICConnectionStateUpdated definition
Marx, et al. Expires 23 April 2026 [Page 14]
Internet-Draft QUIC event definitions for qlog October 2025
The connection_state_changed event has some overlap with the
connection_closed and connection_started events, and the handling of
various frames (for example in a packet_received event). Still, it
can be useful to log these logical state transitions separately,
especially if they map to an internal implementation state machine,
to explicitly track progress. As such, implementations are allowed
to use other ConnectionState values that adhere more closely to their
internal logic. Tools SHOULD be able to deal with these custom
states in a similar way to the pre-defined states in this document.
4.7. tuple_assigned
Importance: Base
This event is used to associate a single TupleID's value with other
parameters that describe a unique network tuple.
As described in [QLOG-MAIN], each qlog event can be linked to a
single network tuple by means of the top-level "tuple" field, whose
value is a TupleID. However, since it can be cumbersome to encode
additional tuple metadata (such as IP addresses or Connection IDs)
directly into the TupleID, this event allows such an association to
happen separately. As such, TupleIDs can be short and unique, and
can even be updated to be associated with new metadata as the
connection's state evolves.
Definition:
QUICTupleAssigned = {
tuple_id: TupleID
; the information for traffic going towards the remote receiver
? tuple_remote: TupleEndpointInfo
; the information for traffic coming in at the local endpoint
? tuple_local: TupleEndpointInfo
* $$quic-tupleassigned-extension
}
Figure 8: QUICTupleAssigned definition
Choosing the different tuple_id values is left up to the
implementation. Some options include using a uniquely incrementing
integer, using the (first) Destination Connection ID associated with
a tuple (or its sequence number), or using (a hash of) the two
endpoint IP addresses.
Marx, et al. Expires 23 April 2026 [Page 15]
Internet-Draft QUIC event definitions for qlog October 2025
It is important to note that the empty string ("") is a valid TupleID
and that it is the default assigned to events that do not explicitly
set a "tuple" field. Put differently, the initial tuple of a QUIC
connection on which the handshake occurs (see also Section 4.2) is
implicitly associated with the TupleID with value "". Associating
metadata with this default tuple is possible by logging the
QUICTupleAssigned event with a value of "" for the tuple_id field.
As the usage of TupleIDs and their metadata can evolve over time,
multiple QUICTupleAssigned events can be emitted for each unique
TupleID. The latest event contains the most up-to-date information
for that TupleID. As such, the first time a TupleID is seen in a
QUICTupleAssigned event, it is an indication that the TupleID is
created. Subsequent occurrences indicate the TupleID is updated,
while a final occurrence with both tuple_local and tuple_remote
fields omitted implicitly indicates the TupleID has been abandoned.
4.8. mtu_updated
The mtu_updated event indicates that the estimated Path MTU was
updated. This happens as part of the Path MTU discovery process. It
has Extra importance level.
QUICMTUUpdated = {
? old: uint32
new: uint32
; at some point, MTU discovery stops, as a "good enough"
; packet size has been found
? done: bool .default false
* $$quic-mtuupdated-extension
}
Figure 9: QUICMTUUpdated definition
5. Transport events
5.1. version_information
The version_information event supports QUIC version negotiation; see
Section 6 of [QUIC-TRANSPORT]. It has Core importance level.
QUIC endpoints each have their own list of QUIC versions they
support. The client uses the most likely version in their first
initial. If the server does not support that version, it replies
with a Version Negotiation packet, which contains its supported
versions. From this, the client selects a version. The
Marx, et al. Expires 23 April 2026 [Page 16]
Internet-Draft QUIC event definitions for qlog October 2025
version_information event aggregates all this information in a single
event type. It also allows logging of supported versions at an
endpoint without actual version negotiation needing to happen.
QUICVersionInformation = {
? server_versions: [+ QuicVersion]
? client_versions: [+ QuicVersion]
? chosen_version: QuicVersion
* $$quic-versioninformation-extension
}
Figure 10: QUICVersionInformation definition
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. If the client receives a set of server_versions with no
viable overlap with its own supported versions, this event should
be logged without the chosen_version set
5.2. alpn_information
The alpn_information event supports Application-Layer Protocol
Negotiation (ALPN) over the QUIC transport; see [RFC7301] and
Section 7.4 of [QUIC-TRANSPORT]. It has Core importance level.
QUIC endpoints are configured with a list of supported ALPN
identifiers. Clients send the list in a TLS ClientHello, and servers
match against their list. On success, a single ALPN identifier is
chosen and sent back in a TLS ServerHello. If no match is found, the
connection is closed.
Marx, et al. Expires 23 April 2026 [Page 17]
Internet-Draft QUIC event definitions for qlog October 2025
ALPN identifiers are byte sequences, that may be possible to present
as UTF-8. The ALPNIdentifier` type supports either format.
Implementations SHOULD log at least one format, but MAY log both or
none.
QUICALPNInformation = {
? server_alpns: [* ALPNIdentifier]
? client_alpns: [* ALPNIdentifier]
? chosen_alpn: ALPNIdentifier
* $$quic-alpninformation-extension
}
ALPNIdentifier = {
? byte_value: hexstring
? string_value: text
}
Figure 11: QUICALPNInformation definition
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
The parameters_set 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. The event has Core importance level.
Marx, et al. Expires 23 April 2026 [Page 18]
Internet-Draft QUIC event definitions for qlog October 2025
Most of these settings are typically set once and never change.
However, they are usually set at different times during the
connection, so there will regularly 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 initiator
field. As such, this field MUST be correct for all settings included
a single event instance. If the settings from two sides are
required, they MUST be logged as two separate event instances. If
the local peer decides to change its behavior based on remote peer's
settings, a new event type can be used to reflect the outcome.
By default, each setting is assumed to either be absent (has an
undefined value) or have its default value (if it exists) at the
start of the connection. Subsequently, each setting's value in a
parameters_set event supersedes the previous value of that parameter
if present. If a setting does not appear in a given parameters_set
event, its value is unchanged.
Implementations are not required to recognize, process or support
every setting/parameter received in all situations. For example,
QUIC implementations MUST discard transport parameters that they do
not understand Section 7.4.2 of [QUIC-TRANSPORT]. The
unknown_parameters field can be used to log the raw values of any
unknown parameters (e.g., GREASE, private extensions, peer-side
experimentation).
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.
QUICParametersSet = {
? initiator: Initiator
; 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
Marx, et al. Expires 23 April 2026 [Page 19]
Internet-Draft QUIC event definitions for qlog October 2025
? 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: uint64
? ack_delay_exponent: uint64
? max_ack_delay: uint64
? active_connection_id_limit: uint64
? 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
? unknown_parameters: [* UnknownParameter]
; RFC9221
? max_datagram_frame_size: uint64
; RFC9287
; true if present, absent or false if extension not negotiated
? grease_quic_bit: bool
* $$quic-parametersset-extension
}
PreferredAddress = {
? ip_v4: IPAddress
? port_v4: uint16
? ip_v6: IPAddress
? port_v6: uint16
connection_id: ConnectionID
stateless_reset_token: StatelessResetToken
}
UnknownParameter = {
id: uint64
? value: hexstring
}
Figure 12: QUICParametersSet definition
Marx, et al. Expires 23 April 2026 [Page 20]
Internet-Draft QUIC event definitions for qlog October 2025
5.4. parameters_restored
When using QUIC 0-RTT, clients are expected to remember and restore
the server's transport parameters from the previous connection. The
parameters_restored event is used to indicate which parameters were
restored and to which values when utilizing 0-RTT. It has Base
importance level.
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.
QUICParametersRestored = {
; RFC9000
? disable_active_migration: bool
? max_idle_timeout: uint64
? max_udp_payload_size: uint64
? active_connection_id_limit: uint64
? 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
; RFC9221
? max_datagram_frame_size: uint64
; RFC9287
; can only be restored at the client.
; servers MUST NOT restore this parameter!
? grease_quic_bit: bool
* $$quic-parametersrestored-extension
}
Figure 13: QUICParametersRestored definition
5.5. packet_sent
The packet_sent event indicates a QUIC-level packet was sent. It has
Core importance level.
Marx, et al. Expires 23 April 2026 [Page 21]
Internet-Draft QUIC event definitions for qlog October 2025
QUICPacketSent = {
header: PacketHeader
? frames: [* $QuicFrame]
; only if header.packet_type === "stateless_reset"
; is always 128 bits in length.
? stateless_reset_token: StatelessResetToken
; only if header.packet_type === "version_negotiation"
? supported_versions: [+ QuicVersion]
? raw: RawInfo
? datagram_id: uint32
? is_mtu_probe_packet: bool .default false
? trigger:
; RFC 9002 Section 6.1.1
"retransmit_reordered" /
; RFC 9002 Section 6.1.2
"retransmit_timeout" /
; RFC 9002 Section 6.2.4
"pto_probe" /
; RFC 9002 6.2.3
"retransmit_crypto" /
; needed for some CCs to figure out bandwidth allocations
; when there are no normal sends
"cc_bandwidth_probe"
* $$quic-packetsent-extension
}
Figure 14: QUICPacketSent definition
The encryption_level and packet_number_space are not logged
explicitly: the header.packet_type specifies this by inference
(assuming correct implementation)
The datagram_id field is used to track packet coalescing, see
Section 5.10.
5.6. packet_received
The packet_received event indicates a QUIC-level packet was received.
It has Core importance level.
Marx, et al. Expires 23 April 2026 [Page 22]
Internet-Draft QUIC event definitions for qlog October 2025
QUICPacketReceived = {
header: PacketHeader
? frames: [* $QuicFrame]
; 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"
* $$quic-packetreceived-extension
}
Figure 15: QUICPacketReceived definition
The encryption_level and packet_number_space are not logged
explicitly: the header.packet_type specifies this by inference
(assuming correct implementation).
The datagram_id field is used to track packet coalescing, see
Section 5.10.
5.7. packet_dropped
The packet_dropped event indicates a QUIC-level packet was dropped.
It has Base importance level.
The trigger field indicates a general reason category for dropping
the packet, while the details field can contain additional
implementation-specific information.
Marx, et al. Expires 23 April 2026 [Page 23]
Internet-Draft QUIC event definitions for qlog October 2025
QUICPacketDropped = {
; Primarily packet_type should be filled here,
; as other fields might not be decrypteable or parseable
? header: PacketHeader
? raw: RawInfo
? datagram_id: uint32
? details: {* text => any}
? trigger:
"internal_error" /
"rejected" /
"unsupported" /
"invalid" /
"duplicate" /
"connection_unknown" /
"decryption_failure" /
"key_unavailable" /
"general"
* $$quic-packetdropped-extension
}
Figure 16: QUICPacketDropped definition
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 1.3.
* invalid: packet parsing or validation error
* duplicate: duplicate packet
* connection_unknown: packet does not relate to a known connection
or Connection ID
* decryption_failure: decryption failed
* key_unavailable: decryption key was unavailable
* general: situations not clearly covered in the other categories
Marx, et al. Expires 23 April 2026 [Page 24]
Internet-Draft QUIC event definitions for qlog October 2025
The datagram_id field is used to track packet coalescing, see
Section 5.10.
5.8. packet_buffered
The packet_buffered 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. The
event has Base importance level.
QUICPacketBuffered = {
; primarily packet_type 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"
* $$quic-packetbuffered-extension
}
Figure 17: QUICPacketBuffered definition
The datagram_id field is used to track packet coalescing, see
Section 5.10.
5.9. packets_acked
The packets_acked event is emitted when a (group of) sent packet(s)
is acknowledged by the remote peer _for the first time_. It has Extra
importance level.
This information could also be deduced from the contents of received
ACK frames. However, ACK frames require additional processing logic
to determine when a given packet is acknowledged for the first time,
as QUIC uses ACK ranges which can include repeated ACKs.
Additionally, this event can be used by implementations that do not
log frame contents.
Marx, et al. Expires 23 April 2026 [Page 25]
Internet-Draft QUIC event definitions for qlog October 2025
QUICPacketsAcked = {
? packet_number_space: $PacketNumberSpace
? packet_numbers: [+ uint64]
* $$quic-packetsacked-extension
}
Figure 18: QUICPacketsAcked definition
If packet_number_space is omitted, it assumes the default value of
application_data, as this is by far the most prevalent packet number
space a typical QUIC connection will use.
5.10. udp_datagrams_sent
The datagrams_sent event indicates when one or more UDP-level
datagrams are passed to the underlying network socket. This is
useful for determining how QUIC packet buffers are drained to the OS.
The event has Extra importance level.
QUICUDPDatagramsSent = {
; 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]
* $$quic-udpdatagramssent-extension
}
Figure 19: QUICUDPDatagramsSent definition
Since QUIC implementations rarely control UDP logic directly, the raw
data excludes UDP-level headers in all RawInfo fields.
Multiple QUIC packets can be coalesced in a single UDP datagram,
especially during the handshake (see Section 12.2 of
[QUIC-TRANSPORT]). However, neither QUIC nor UDP themselves provide
an explicit mechanism to track this behaviour. To make it possible
Marx, et al. Expires 23 April 2026 [Page 26]
Internet-Draft QUIC event definitions for qlog October 2025
for implementations to track coalescing across packet-level and
datagram-level qlog events, this document defines a qlog-specific
mechanism for tracking coalescing across packet-level and datagram-
level qlog events: a "datagram identifier" carried in datagram_id
fields. qlog implementations that want to track coalescing can use
this mechanism, where multiple events sharing the same datagram_id
indicate they were coalesced in the same UDP datagram. The selection
of specific and locally-unique datagram_id values is an
implementation choice.
5.11. udp_datagrams_received
When one or more UDP-level datagrams are received from the socket.
This is useful for determining how datagrams are passed to the user
space stack from the OS. The event has Extra importance level.
QUICUDPDatagramsReceived = {
; to support passing multiple at once
? count: uint16
; The RawInfo fields do not include the UDP headers,
; only the UDP payload
? raw: [+ RawInfo]
; ECN bits in the IP header
; if not set, defaults to the value on the last
; QUICDatagramsReceived event
? ecn: [+ ECN]
? datagram_ids: [+ uint32]
* $$quic-udpdatagramsreceived-extension
}
Figure 20: QUICUDPDatagramsReceived definition
The datagram_ids field is used to track packet coalescing, see
Section 5.10.
5.12. udp_datagram_dropped
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, the packet_dropped event
(Section 5.7) should be used instead. The event has Extra importance
level.
Marx, et al. Expires 23 April 2026 [Page 27]
Internet-Draft QUIC event definitions for qlog October 2025
QUICUDPDatagramDropped = {
; The RawInfo fields do not include the UDP headers,
; only the UDP payload
? raw: RawInfo
* $$quic-udpdatagramdropped-extension
}
Figure 21: QUICUDPDatagramDropped definition
5.13. stream_state_updated
The stream_state_updated event is emitted whenever the internal state
of a QUIC stream is updated; see Section 3 of [QUIC-TRANSPORT]. Most
of this can be inferred from several types of frames going over the
wire, but it's often easier to have explicit signals for these state
changes. The event has Base importance level.
While QUIC stream IDs encode the type of stream, (see Section 2.1 of
[QUIC-TRANSPORT]), the optional stream_type field can be used to
provide a more-accessible form of the information.
Section 3 of [QUIC-TRANSPORT] describes streams in terms of their
send and receive components, with a state machine for each. The
stream_side field is used to indicate which side's state is updated
in the logged event. In case both sides of the stream change state
at the same time (for example both become closed), two separate
events with different stream_side fields SHOULD be logged.
In cases where it is useful to know which side of the connection
initiated a state change (for example, closed due to either
RESET_STREAM or STOP_SENDING), this can be reflected using the
trigger field.
Marx, et al. Expires 23 April 2026 [Page 28]
Internet-Draft QUIC event definitions for qlog October 2025
StreamType = "unidirectional" /
"bidirectional"
QUICStreamStateUpdated = {
stream_id: uint64
? stream_type: StreamType
? old: $StreamState
new: $StreamState
stream_side: "sending" /
"receiving"
? trigger:
; stream state change was initiated by a local action
"local" /
; stream state change was initiated by a remote action
"remote"
* $$quic-streamstateupdated-extension
}
BaseStreamStates = "idle" /
"open" /
"closed"
GranularStreamStates =
; bidirectional stream states, RFC 9000 Section 3.4.
"half_closed_local" /
"half_closed_remote" /
; sending-side stream states, RFC 9000 Section 3.1.
"ready" /
"send" /
"data_sent" /
"reset_sent" /
"reset_received" /
; receive-side stream states, RFC 9000 Section 3.2.
"receive" /
"size_known" /
"data_read" /
"reset_read" /
; both-side states
"data_received" /
; qlog-defined: memory actually freed
"destroyed"
$StreamState /= BaseStreamStates / GranularStreamStates
Figure 22: QUICStreamStateUpdated definition
Marx, et al. Expires 23 April 2026 [Page 29]
Internet-Draft QUIC event definitions for qlog October 2025
QUIC implementations SHOULD mainly log the simplified
BaseStreamStates instead of the more fine-grained
GranularStreamStates. These latter ones are mainly for more in-depth
debugging. Tools SHOULD be able to deal with both types equally.
5.14. frames_processed
The frame_processed event is intended to prevent a large
proliferation of specific purpose events (e.g., packets_acknowledged,
flow_control_updated, stream_data_received). It has Extra importance
level.
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.
The frame_processed 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).
The packet_received event can convey all constituent frames. It is
not expected that the frames_processed event will also be used for a
redundant purpose. Rather, implementations can use this event to
avoid having to log full packets or to convey extra information about
when frames are processed (for example, if frame processing is
deferred for any reason).
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, the frames_processed 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.
Marx, et al. Expires 23 April 2026 [Page 30]
Internet-Draft QUIC event definitions for qlog October 2025
QUICFramesProcessed = {
frames: [* $QuicFrame]
? packet_numbers: [* uint64]
* $$quic-framesprocessed-extension
}
Figure 23: QUICFramesProcessed definition
For example, an instance of the frames_processed 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,"raw":{"length":500}},
{"frame_type":"stream","stream_id":0,"offset":500,"raw":{"length":200}},
{"frame_type":"stream","stream_id":1,"offset":0,"raw":{"length":300}},
{"frame_type":"stream","stream_id":1,"offset":300,"raw":{"length":50}}
],
"packet_numbers":[
1,
1,
2,
2
]
5.15. stream_data_moved
The stream_data_moved event is used to indicate when QUIC stream data
moves between the different layers. This helps make clear the flow
of data, how long data remains in various buffers, and the overheads
introduced by individual layers. The event has Base importance
level.
The raw.length field is used to reflect how many bytes were moved.
As this event relates to stream data only, there are no packet or
frame headers and the raw.length field MUST reflect that.
For example, it can be useful to understand when data moves from an
application protocol (e.g., HTTP) to QUIC stream buffers and vice
versa.
Marx, et al. Expires 23 April 2026 [Page 31]
Internet-Draft QUIC event definitions for qlog October 2025
The stream_data_moved event can provide insight into 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 can help identify bottlenecks, flow control issues, or
scheduling problems.
The additional_info field supports optional logging of information
related to the stream state. For example, an application layer that
moves data into transport and simultaneously ends the stream, can log
fin_set. As another example, a transport layer that has received an
instruction to reset a stream can indicate this to the application
layer using reset_stream. In both cases, the raw.length field can be
omitted or have a zero value.
This event is only for data in QUIC streams. For data in QUIC
Datagram Frames, see the datagram_data_moved event defined in
Section 5.16.
QUICStreamDataMoved = {
? stream_id: uint64
? offset: uint64
? from: $DataLocation
? to: $DataLocation
? additional_info: $DataMovedAdditionalInfo
? raw: RawInfo
* $$quic-streamdatamoved-extension
}
$DataLocation /= "application" /
"transport" /
"network"
$DataMovedAdditionalInfo /= "fin_set" /
"stream_reset"
Figure 24: QUICStreamDataMoved definition
Marx, et al. Expires 23 April 2026 [Page 32]
Internet-Draft QUIC event definitions for qlog October 2025
5.16. datagram_data_moved
The datagram_data_moved event is used to indicate when QUIC Datagram
Frame data (see [RFC9221]) moves between the different layers. This
helps make clear the flow of data, how long data remains in various
buffers, and the overheads introduced by individual layers. The
event has Base importance level.
The raw.length field is used to reflect how many bytes were moved.
As this event relates to datagram data only, there are no packet or
frame headers and the raw.length field MUST reflect that.
For example, passing from the application protocol (e.g.,
WebTransport) to QUIC Datagram Frame buffers and vice versa.
The datagram_data_moved event can provide insight into 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
can help identify bottlenecks, flow control issues, or scheduling
problems.
This event is only for data in QUIC Datagram Frames. For data in
QUIC streams, see the stream_data_moved event defined in
Section 5.15.
QUICDatagramDataMoved = {
? from: $DataLocation
? to: $DataLocation
? raw: RawInfo
* $$quic-datagramdatamoved-extension
}
Figure 25: QUICDatagramDataMoved definition
5.17. connection_data_blocked_updated
The connection_blocked_updated event is used to indicate when the
QUIC connection becomes blocked or unblocked for sending data. When
a connection is "blocked", data can't be sent in streams and/or
datagrams until the blocking reason has been resolved. The event has
Extra importance level.
Use the stream_blocked_updated or datagram_blocked_updated event to
provide more fine-grained information for individual data types.
Marx, et al. Expires 23 April 2026 [Page 33]
Internet-Draft QUIC event definitions for qlog October 2025
QUICConnectionDataBlockedUpdated = {
? old: $BlockedState
new: $BlockedState
? reason: $BlockedReason
}
$BlockedState /= "blocked" /
"unblocked"
$BlockedReason /= "scheduling" /
"pacing" /
"amplification_protection" /
"congestion_control" /
"connection_flow_control" /
"stream_flow_control" /
"stream_id" /
"application"
Figure 26: QUICConnectionDataBlockedUpdated definition
5.18. stream_data_blocked_updated
The stream_data_blocked_updated event is used to indicate when a QUIC
stream becomes blocked or unblocked for sending. The event has Extra
importance level.
QUICStreamDataBlockedUpdated = {
? old: $BlockedState
new: $BlockedState
stream_id: uint64
? reason: $BlockedReason
}
Figure 27: QUICStreamDataBlockedUpdated definition
5.19. datagram_data_blocked_updated
The datagram_data_blocked_updated event is used to indicate when QUIC
datagrames becomes blocked or unblocked for sending. The event has
Extra importance level.
Marx, et al. Expires 23 April 2026 [Page 34]
Internet-Draft QUIC event definitions for qlog October 2025
QUICDatagramDataBlockedUpdated = {
? old: $BlockedState
new: $BlockedState
? reason: $BlockedReason
}
Figure 28: QUICDatagramDataBlockedUpdated definition
5.20. migration_state_updated
Use to provide additional information when attempting (client-side)
connection migration. While most details of the QUIC connection
migration process can be inferred by observing the PATH_CHALLENGE and
PATH_RESPONSE frames, in combination with the QUICTupleAssigned
event, it can be useful to explicitly log the progression of the
migration and potentially made decisions in a single location/event.
The event has Extra importance level.
Generally speaking, connection migration goes through two phases: a
probing phase (which is not always needed/present), and a migration
phase (which can be abandoned upon error).
Implementations that log per-path information in a
QUICMigrationStateUpdated, SHOULD also emit QUICTupleAssigned events,
to serve as a ground-truth source of information.
Definition:
Marx, et al. Expires 23 April 2026 [Page 35]
Internet-Draft QUIC event definitions for qlog October 2025
QUICMigrationStateUpdated = {
? old: MigrationState
new: MigrationState
? tuple_id: TupleID
; the information for traffic going towards the remote receiver
? tuple_remote: TupleEndpointInfo
; the information for traffic coming in at the local endpoint
? tuple_local: TupleEndpointInfo
* $$quic-migrationstateupdated-extension
}
; Note that MigrationState does not describe a full state machine
; These entries are not necessarily chronological,
; nor will they always all appear during
; a connection migration attempt.
MigrationState =
; probing packets are sent, migration not initiated yet
"probing_started" /
; did not get reply to probing packets,
; discarding path as an option
"probing_abandoned" /
; received reply to probing packets, path is migration candidate
"probing_successful" /
; non-probing packets are sent, attempting migration
"migration_started" /
; something went wrong during the migration, abandoning attempt
"migration_abandoned" /
; new path is now fully used, old path is discarded
"migration_complete"
Figure 29: QUICMigrationStateUpdated definition
5.21. timer_updated
The timer_updated event is emitted when a timer changes state. It
has Extra importance level.
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
Marx, et al. Expires 23 April 2026 [Page 36]
Internet-Draft QUIC event definitions for qlog October 2025
* cancelled: when a timer is cancelled
In order to indicate an active timer's timeout update, a new set
event is used.
QUICTimerUpdated events with the timer_type set to ackor pto indicate
changes to the individual timeouts defined by RFC 9002: the threshold
loss detection timeout (see Section 6.1.2 of [QUIC-RECOVERY]) and the
probe timeout (see Section 6.2 of [QUIC-RECOVERY]). Those set to
loss_timeout represent changes to the multi-modal loss detection
timer (see Section 3 of [QUIC-RECOVERY]).
The QUIC protocol conceptually employs a variety of timers, but their
usage can be implementation-dependent. Implementers can add
additional fields to this event if needed via $$quic-timerupdated-
extension or specify other/additional timer types via $TimerType.
; a non-exhaustive list of typically employed timers
$TimerType /= "ack" /
"pto" /
"loss_timeout" /
"path_validation" /
"handshake_timeout" /
"idle_timeout"
QUICTimerUpdated = {
? timer_type: $TimerType
; to disambiguate in case there are multiple timers
; of the same type
? timer_id: uint64
; if used for recovery timers, this can be useful information
? packet_number_space: $PacketNumberSpace
event_type: "set" /
"expired" /
"cancelled"
; if event_type === "set": delta time is in ms from
; this event's timestamp until when the timer should trigger
? delta: float32
* $$quic-timerupdated-extension
}
Figure 30: QUICTimerUpdated definition
Marx, et al. Expires 23 April 2026 [Page 37]
Internet-Draft QUIC event definitions for qlog October 2025
6. Security Events
6.1. key_updated
The key_updated event has Base importance level.
QUICKeyUpdated = {
key_type: $KeyType
? old: hexstring
? new: hexstring
; needed for 1RTT key updates
? key_phase: uint64
? trigger:
; (e.g., initial, handshake and 0-RTT keys
; are generated by TLS)
"tls" /
"remote_update" /
"local_update"
* $$quic-keyupdated-extension
}
Figure 31: QUICKeyUpdated definition
Note that the key_phase is the full value of the key phase (as
indicated by @M and @N in Figure 9 of [QUIC-TLS]). The key phase bit
used on the packet header is the least significant bit of the key
phase.
6.2. key_discarded
The key_discarded event has Base importance level.
Marx, et al. Expires 23 April 2026 [Page 38]
Internet-Draft QUIC event definitions for qlog October 2025
QUICKeyDiscarded = {
key_type: $KeyType
? key: hexstring
; needed for 1RTT key updates
? key_phase: uint64
? trigger:
; (e.g., initial, handshake and 0-RTT keys
; are generated by TLS)
"tls" /
"remote_update" /
"local_update"
* $$quic-keydiscarded-extension
}
Figure 32: QUICKeyDiscarded definition
7. Recovery events
Most of the events in this category are kept generic to support
different recovery approaches and various congestion control
algorithms. Tool creators SHOULD make an effort to support and
visualize even unknown data in these events (e.g., plot unknown
congestion states by name on a timeline visualization).
7.1. recovery_parameters_set
The recovery_parameters_set event groups initial parameters from both
loss detection and congestion control into a single event. It has
Base importance level.
All these settings are typically set once and never change.
Implementation that do, for some reason, change these parameters
during execution, MAY emit the recovery_parameters_set event more
than once.
Marx, et al. Expires 23 April 2026 [Page 39]
Internet-Draft QUIC event definitions for qlog October 2025
QUICRecoveryParametersSet = {
; Loss detection, see RFC 9002 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, see RFC 9002 Appendix B.2
; 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
* $$quic-recoveryparametersset-extension
}
Figure 33: QUICRecoveryParametersSet definition
Additionally, this event can contain any number of unspecified fields
to support different recovery approaches.
7.2. recovery_metrics_updated
The recovery_metrics_updated event is emitted when one or more of the
observable recovery metrics changes value. It has Core importance
level.
Marx, et al. Expires 23 April 2026 [Page 40]
Internet-Draft QUIC event definitions for qlog October 2025
This event SHOULD group all possible metric updates that happen at or
around the same time in a single event (e.g., if min_rtt and
smoothed_rtt change at the same time, they should be bundled in a
single recovery_metrics_updated entry, rather than split out into
two). Consequently, a recovery_metrics_updated event is only
guaranteed to contain at least one of the listed metrics.
QUICRecoveryMetricsUpdated = {
; Loss detection, see RFC 9002 Appendix A.3
; all following rtt fields are expressed in ms
? min_rtt: float32
? smoothed_rtt: float32
? latest_rtt: float32
? rtt_variance: float32
? pto_count: uint16
; Congestion control, see RFC 9002 Appendix B.2.
; in bytes
? congestion_window: uint64
? bytes_in_flight: uint64
; in bytes
? ssthresh: uint64
; qlog defined
; sum of all packet number spaces
? packets_in_flight: uint64
; in bits per second
? pacing_rate: uint64
* $$quic-recoverymetricsupdated-extension
}
Figure 34: QUICRecoveryMetricsUpdated definition
In order to make logging easier, implementations MAY log values even
if they are the same as previously reported values (e.g., two
subsequent QUICRecoveryMetricsUpdated entries can both report the
exact same value for min_rtt). However, applications SHOULD try to
log only actual updates to values.
Additionally, the recovery_metrics_updated event can contain any
number of unspecified fields to support different recovery
approaches.
Marx, et al. Expires 23 April 2026 [Page 41]
Internet-Draft QUIC event definitions for qlog October 2025
7.3. congestion_state_updated
The congestion_state_updated event indicates when the congestion
controller enters a significant new state and changes its behaviour.
It has Base importance level.
The values of the event's fields are intentionally unspecified here
in order to support different Congestion Control algorithms, as these
typically have different states and even different implementations of
these states across stacks. For example, for the algorithm defined
in the QUIC Recovery RFC ("enhanced" New Reno), the following states
are used: Slow Start, Congestion Avoidance, Application Limited and
Recovery. Similarly, states can be triggered by a variety of events,
including detection of Persistent Congestion or receipt of ECN
markings.
QUICCongestionStateUpdated = {
? old: text
new: text
? trigger: text
* $$quic-congestionstateupdated-extension
}
Figure 35: QUICCongestionStateUpdated definition
The trigger field SHOULD be logged if there are multiple ways in
which a state change can occur but MAY be omitted if a given state
can only be due to a single event occurring (for example Slow Start
is often exited only when ssthresh is exceeded).
7.4. packet_lost
The packet_lost event is emitted when a packet is deemed lost by loss
detection. It has Core importance level.
It is RECOMMENDED to populate the optional trigger field in order to
help disambiguate among the various possible causes of a loss
declaration.
Marx, et al. Expires 23 April 2026 [Page 42]
Internet-Draft QUIC event definitions for qlog October 2025
QUICPacketLost = {
; should include at least the packet_type and packet_number
? header: PacketHeader
; not all implementations will keep track of full
; packets, so these are optional
? frames: [* $QuicFrame]
? is_mtu_probe_packet: bool .default false
? trigger:
"reordering_threshold" /
"time_threshold" /
; RFC 9002 Section 6.2.4 paragraph 6, MAY
"pto_expired"
* $$quic-packetlost-extension
}
Figure 36: QUICPacketLost definition
7.5. marked_for_retransmit
The marked_for_retransmit event indicates which data was marked for
retransmission upon detection of packet loss (see packet_lost). It
has Extra importance level.
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).
Marx, et al. Expires 23 April 2026 [Page 43]
Internet-Draft QUIC event definitions for qlog October 2025
QUICMarkedForRetransmit = {
frames: [+ $QuicFrame]
* $$quic-markedforretransmit-extension
}
Figure 37: QUICMarkedForRetransmit definition
7.6. ecn_state_updated
The ecn_state_updated event indicates a progression in the ECN state
machine as described in section A.4 of [QUIC-TRANSPORT]. It has
Extra importance level.
QUICECNStateUpdated = {
? old: ECNState
new: ECNState
* $$quic-ecnstateupdated-extension
}
ECNState =
; ECN testing in progress
"testing" /
; ECN state unknown, waiting for acknowledgements
; for testing packets
"unknown" /
; ECN testing failed
"failed" /
; testing was successful
"capable"
Figure 38: QUICECNStateUpdated definition
8. QUIC data type definitions
8.1. QuicVersion
QuicVersion = hexstring
Figure 39: QuicVersion definition
8.2. ConnectionID
ConnectionID = hexstring
Figure 40: ConnectionID definition
Marx, et al. Expires 23 April 2026 [Page 44]
Internet-Draft QUIC event definitions for qlog October 2025
8.3. Initiator
Initiator = "local" /
"remote"
Figure 41: Initiator definition
8.4. IPAddress
; 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).
; Additionally, a hash-based or redacted representation
; can be used if needed for privacy or security reasons.
IPAddress = text /
hexstring
Figure 42: IPAddress definition
8.5. TupleEndpointInfo
TupleEndpointInfo indicates a single half/direction of a four-tuple.
A full tuple is comprised of two halves. Firstly: the server sends
to the remote client IP + port using a specific destination
Connection ID. Secondly: the client sends to the remote server IP +
port using a different destination Connection ID.
As such, structures logging tuple information SHOULD include two
different TupleEndpointInfo instances, one for each half of the
tuple.
TupleEndpointInfo = {
? ip_v4: IPAddress
? port_v4: uint16
? ip_v6: IPAddress
? port_v6: uint16
; Even though usually only a single ConnectionID
; is associated with a given tuple/path at a time,
; there are situations where there can be an overlap
; or a need to keep track of previous ConnectionIDs
? connection_ids: [+ ConnectionID]
* $$quic-tupleendpointinfo-extension
}
Figure 43: TupleEndpointInfo definition
Marx, et al. Expires 23 April 2026 [Page 45]
Internet-Draft QUIC event definitions for qlog October 2025
8.6. PacketType
$PacketType /= "initial" /
"handshake" /
"0RTT" /
"1RTT" /
"retry" /
"version_negotiation" /
"stateless_reset" /
"unknown"
Figure 44: PacketType definition
8.7. PacketNumberSpace
$PacketNumberSpace /= "initial" /
"handshake" /
"application_data"
Figure 45: PacketNumberSpace definition
8.8. PacketHeader
If the packet_type numerical value does not map to a known
$PacketType string, the packet_type value of "unknown" can be used
and the raw value captured in the packet_type_bytes field; a
numerical value without variable-length integer encoding.
The fixed and reserved bits are omitted here because they must be 0;
see [QUIC-TRANSPORT]. If these bits have an invalid value, the raw
values can be captured in the raw.data field of the event logging the
PacketHeader.
QUIC extensions that do utilize these bits are expected to create new
events (analogous to spin_bit_updated) or use qlog extension
mechanisms to reflect that usage.
For long header packets of type initial, handshake, and 0RTT, the
length field of the packet header is logged in the qlog raw.length
field, and the value signifies the length of the packet number plus
the payload.
Marx, et al. Expires 23 April 2026 [Page 46]
Internet-Draft QUIC event definitions for qlog October 2025
PacketHeader = {
packet_type: $PacketType
; only if packet_type === "unknown"
? packet_type_bytes: uint64
; only if packet_type === "1RTT"
? spin_bit: bool
; only if packet_type === "1RTT", and if the key phase was
; determined from the key_phase_bit
? key_phase: uint64
; only if packet_type === "1RTT", and if key_phase is not set
? key_phase_bit: bool
; only if packet_type === "initial" || "handshake" || "0RTT" ||
; "1RTT"
? packet_number_length: uint8
; only if packet_type === "initial" || "handshake" || "0RTT" ||
; "1RTT"
? packet_number: uint64
; only if packet_type === "initial" || "retry"
? 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
* $$quic-packetheader-extension
}
Figure 46: PacketHeader definition
8.9. Token
Marx, et al. Expires 23 April 2026 [Page 47]
Internet-Draft QUIC event definitions for qlog October 2025
Token = {
? type: $TokenType
; decoded fields included in the token
; (typically: peer's IP address, creation time)
? details: {
* text => any
}
? raw: RawInfo
* $$quic-token-extension
}
$TokenType /= "retry" /
"resumption"
Figure 47: Token definition
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,
Token includes a general-purpose details field.
8.10. Stateless Reset Token
StatelessResetToken = hexstring .size 16
Figure 48: Stateless Reset Token definition
The stateless reset token is carried in stateless reset packets, in
transport parameters and in NEW_CONNECTION_ID frames.
8.11. 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"
Figure 49: KeyType definition
Marx, et al. Expires 23 April 2026 [Page 48]
Internet-Draft QUIC event definitions for qlog October 2025
8.12. ECN
ECN = "Not-ECT" / "ECT(1)" / "ECT(0)" / "CE"
Figure 50: ECN definition
The ECN bits carried in the IP header.
8.13. QUIC Frames
The generic $QuicFrame is defined here as a CDDL "type socket"
extension point. It can be extended to support additional QUIC frame
types.
; The QuicFrame is any key-value map (e.g., JSON object)
$QuicFrame /= {
* text => any
}
Figure 51: QuicFrame type socket definition
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
Marx, et al. Expires 23 April 2026 [Page 49]
Internet-Draft QUIC event definitions for qlog October 2025
Figure 52: QuicBaseFrames definition
8.13.1. PaddingFrame
In QUIC, PADDING frames are simply identified as a single byte of
value 0. As such, each padding byte could be theoretically
interpreted and logged as an individual PaddingFrame.
However, as this leads to heavy logging overhead, implementations
SHOULD instead emit just a single PaddingFrame and set the
raw.payload_length property to the amount of PADDING bytes/frames
included in the packet.
PaddingFrame = {
frame_type: "padding"
? raw: RawInfo
}
Figure 53: PaddingFrame definition
8.13.2. PingFrame
PingFrame = {
frame_type: "ping"
? raw: RawInfo
}
Figure 54: PingFrame definition
8.13.3. AckFrame
Marx, et al. Expires 23 April 2026 [Page 50]
Internet-Draft QUIC event definitions for qlog October 2025
; 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
? raw: RawInfo
}
Figure 55: AckFrame definition
Note that the packet ranges in AckFrame.acked_ranges do not
necessarily have to be ordered (e.g., [[5,9],[1,4]] is a valid
value).
Note that the two numbers in the packet range can be the same (e.g.,
[120,120] means that packet with number 120 was ACKed). However, in
that case, implementers SHOULD log [120] instead and tools MUST be
able to deal with both notations.
8.13.4. ResetStreamFrame
If the error numerical value does not map to a known ApplicationError
string, the error value of "unknown" can be used and the raw value
captured in the error_code field; a numerical value without variable-
length integer encoding.
Marx, et al. Expires 23 April 2026 [Page 51]
Internet-Draft QUIC event definitions for qlog October 2025
ResetStreamFrame = {
frame_type: "reset_stream"
stream_id: uint64
error: $ApplicationError
; if error_code === "unknown"
? error_code: uint64
; in bytes
final_size: uint64
? raw: RawInfo
}
Figure 56: ResetStreamFrame definition
8.13.5. StopSendingFrame
If the error numerical value does not map to a known ApplicationError
string, the error value of "unknown" can be used and the raw value
captured in the error_code field; a numerical value without variable-
length integer encoding.
StopSendingFrame = {
frame_type: "stop_sending"
stream_id: uint64
error: $ApplicationError
; if error_code === "unknown"
? error_code: uint64
? raw: RawInfo
}
Figure 57: StopSendingFrame definition
8.13.6. CryptoFrame
The length field of the Crypto frame MUST be logged in the qlog
raw.length field. The other sub-fields of the raw field are
optional.
CryptoFrame = {
frame_type: "crypto"
offset: uint64
raw: RawInfo
}
Figure 58: CryptoFrame definition
Marx, et al. Expires 23 April 2026 [Page 52]
Internet-Draft QUIC event definitions for qlog October 2025
8.13.7. NewTokenFrame
NewTokenFrame = {
frame_type: "new_token"
token: Token
? raw: RawInfo
}
Figure 59: NewTokenFrame definition
8.13.8. StreamFrame
If the stream frame contains a length field, it MUST be logged in the
qlog raw.length field. If it does not, the implementation MAY
calculate the actual frame byte length itself and log that in
raw.length if necessary.
StreamFrame = {
frame_type: "stream"
stream_id: uint64
? offset: uint64 .default 0
? fin: bool .default false
? raw: RawInfo
}
Figure 60: StreamFrame definition
8.13.9. MaxDataFrame
MaxDataFrame = {
frame_type: "max_data"
maximum: uint64
? raw: RawInfo
}
Figure 61: MaxDataFrame definition
8.13.10. MaxStreamDataFrame
MaxStreamDataFrame = {
frame_type: "max_stream_data"
stream_id: uint64
maximum: uint64
? raw: RawInfo
}
Figure 62: MaxStreamDataFrame definition
Marx, et al. Expires 23 April 2026 [Page 53]
Internet-Draft QUIC event definitions for qlog October 2025
8.13.11. MaxStreamsFrame
MaxStreamsFrame = {
frame_type: "max_streams"
stream_type: StreamType
maximum: uint64
? raw: RawInfo
}
Figure 63: MaxStreamsFrame definition
8.13.12. DataBlockedFrame
DataBlockedFrame = {
frame_type: "data_blocked"
limit: uint64
? raw: RawInfo
}
Figure 64: DataBlockedFrame definition
8.13.13. StreamDataBlockedFrame
StreamDataBlockedFrame = {
frame_type: "stream_data_blocked"
stream_id: uint64
limit: uint64
? raw: RawInfo
}
Figure 65: StreamDataBlockedFrame definition
8.13.14. StreamsBlockedFrame
StreamsBlockedFrame = {
frame_type: "streams_blocked"
stream_type: StreamType
limit: uint64
? raw: RawInfo
}
Figure 66: StreamsBlockedFrame definition
8.13.15. NewConnectionIDFrame
Marx, et al. Expires 23 April 2026 [Page 54]
Internet-Draft QUIC event definitions for qlog October 2025
NewConnectionIDFrame = {
frame_type: "new_connection_id"
sequence_number: uint64
retire_prior_to: uint64
; 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
? raw: RawInfo
}
Figure 67: NewConnectionIDFrame definition
8.13.16. RetireConnectionIDFrame
RetireConnectionIDFrame = {
frame_type: "retire_connection_id"
sequence_number: uint64
? raw: RawInfo
}
Figure 68: RetireConnectionIDFrame definition
8.13.17. PathChallengeFrame
PathChallengeFrame = {
frame_type: "path_challenge"
; always 64 bits
? data: hexstring
? raw: RawInfo
}
Figure 69: PathChallengeFrame definition
8.13.18. PathResponseFrame
PathResponseFrame = {
frame_type: "path_response"
; always 64 bits
? data: hexstring
? raw: RawInfo
}
Figure 70: PathResponseFrame definition
Marx, et al. Expires 23 April 2026 [Page 55]
Internet-Draft QUIC event definitions for qlog October 2025
8.13.19. ConnectionCloseFrame
An endpoint that receives unknown error codes can record it in the
error_code field using the numerical value without variable-length
integer encoding.
When the connection is closed due a connection-level error, the
trigger_frame_type field can be used to log the frame that triggered
the error. For known frame types, the appropriate string value is
used in the error field. For unknown frame types, the error field
has the value "unknown" and the numerical value without variable-
length integer encoding can be logged in error_code.
The CONNECTION_CLOSE reason phrase is a byte sequences. It is likely
that this sequence is presentable as UTF-8, in which case it can be
logged in the reason field. The reason_bytes field supports logging
the raw bytes, which can be useful when the value is not UTF-8 or
when an endpoint does not want to decode it. Implementations SHOULD
log at least one format, but MAY log both or none.
ErrorSpace = "transport" /
"application"
ConnectionCloseFrame = {
frame_type: "connection_close"
? error_space: ErrorSpace
? error: $TransportError / CryptoError /
$ApplicationError
; only if error_code === "unknown"
? error_code: uint64
? reason: text
? reason_bytes: hexstring
; when error_space === "transport"
? trigger_frame_type: uint64 /
text
? raw: RawInfo
}
Figure 71: ConnectionCloseFrame definition
8.13.20. HandshakeDoneFrame
Marx, et al. Expires 23 April 2026 [Page 56]
Internet-Draft QUIC event definitions for qlog October 2025
HandshakeDoneFrame = {
frame_type: "handshake_done"
? raw: RawInfo
}
Figure 72: HandshakeDoneFrame definition
8.13.21. UnknownFrame
The frame_type_bytes field is the numerical value without variable-
length integer encoding.
UnknownFrame = {
frame_type: "unknown"
frame_type_bytes: uint64
? raw: RawInfo
}
Figure 73: UnknownFrame definition
8.13.22. DatagramFrame
The QUIC DATAGRAM frame is defined in Section 4 of [RFC9221].
If the datagram frame contains a length field, it MUST be logged in
the qlog raw.length field. If it does not, the implementation MAY
calculate the actual datagram byte length itself and log that in
raw.length if necessary.
DatagramFrame = {
frame_type: "datagram"
? raw: RawInfo
}
Figure 74: DatagramFrame definition
8.13.23. TransportError
The generic $TransportError is defined here as a CDDL "type socket"
extension point. It can be extended to support additional Transport
errors.
Marx, et al. Expires 23 April 2026 [Page 57]
Internet-Draft QUIC event definitions for qlog October 2025
$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" /
"unknown"
; there is no value to reflect CRYPTO_ERROR
; use the CryptoError type instead
Figure 75: TransportError definition
8.13.24. ApplicationError
By definition, an application error is defined by the application-
level protocol running on top of QUIC (e.g., HTTP/3).
As such, it cannot be defined here completely. It is instead defined
as a CDDL "type socket" extension point, with a single "unknown"
value.
$ApplicationError /= "unknown"
Figure 76: ApplicationError definition
Application-level qlog definitions that wish to define new
ApplicationError strings MUST do so by extending the
$ApplicationError socket as such:
$ApplicationError /= "new_error_name" /
"another_new_error_name"
Marx, et al. Expires 23 April 2026 [Page 58]
Internet-Draft QUIC event definitions for qlog October 2025
8.13.25. CryptoError
These errors are defined in the TLS document as "A TLS alert is
turned into a QUIC connection error by converting the one-byte alert
description into a QUIC error code. The alert description is added
to 0x100 to produce a QUIC error code from the range reserved for
CRYPTO_ERROR."
This approach maps badly to a pre-defined enum. As such, the
crypto_error string is defined as having a dynamic component here,
which should include the hex-encoded and zero-padded value of the TLS
alert description.
; all strings from "crypto_error_0x100" to "crypto_error_0x1ff"
CryptoError = text .regexp "crypto_error_0x1[0-9a-f][0-9a-f]"
Figure 77: CryptoError definition
9. Security and Privacy Considerations
The security and privacy considerations discussed in [QLOG-MAIN]
apply to this document as well.
10. IANA Considerations
This document registers a new entry in the "qlog event schema URIs"
registry (created in Section 15 of [QLOG-MAIN]):
Event schema URI: urn:ietf:params:qlog:events:quic
Namespace quic
Event Types server_listening, connection_started, connection_closed,
connection_id_updated, spin_bit_updated, connection_state_updated,
tuple_assigned, mtu_updated, version_information,
alpn_information, parameters_set, parameters_restored,
packet_sent, packet_received, packet_dropped, packet_buffered,
packets_acked, udp_datagrams_sent, udp_datagrams_received,
udp_datagram_dropped, stream_state_updated, frames_processed,
stream_data_moved, datagram_data_moved, migration_state_updated,
key_updated, key_discarded, recovery_parameters_set,
recovery_metrics_updated, congestion_state_updated, timer_updated,
packet_lost, marked_for_retransmit, ecn_state_updated
Description: Event definitions related to the QUIC transport
protocol.
Reference: This Document
Marx, et al. Expires 23 April 2026 [Page 59]
Internet-Draft QUIC event definitions for qlog October 2025
11. References
11.1. Normative References
[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>.
[GREASEBIT]
Thomson, M., "Greasing the QUIC Bit", RFC 9287,
DOI 10.17487/RFC9287, August 2022,
<https://www.rfc-editor.org/rfc/rfc9287>.
[QLOG-MAIN]
Marx, R., Niccolini, L., Seemann, M., and L. Pardue,
"qlog: Structured Logging for Network Protocols", Work in
Progress, Internet-Draft, draft-ietf-quic-qlog-main-
schema-12, 7 July 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-quic-
qlog-main-schema-12>.
[QUIC-DATAGRAM]
Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", RFC 9221,
DOI 10.17487/RFC9221, March 2022,
<https://www.rfc-editor.org/rfc/rfc9221>.
[QUIC-RECOVERY]
Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
and Congestion Control", RFC 9002, DOI 10.17487/RFC9002,
May 2021, <https://www.rfc-editor.org/rfc/rfc9002>.
[QUIC-TLS] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
<https://www.rfc-editor.org/rfc/rfc9001>.
[QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
Marx, et al. Expires 23 April 2026 [Page 60]
Internet-Draft QUIC event definitions for qlog October 2025
[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>.
[RFC9221] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", RFC 9221,
DOI 10.17487/RFC9221, March 2022,
<https://www.rfc-editor.org/rfc/rfc9221>.
11.2. Informative References
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/rfc/rfc7301>.
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, Christian Huitema, Hugo
Landau, Will Hawkins, Mathis Engelbart, Kazuho Oku, and Jonathan
Lennox for their feedback and suggestions.
Change Log
This section is to be removed before publishing as an RFC.
Since draft-ietf-qlog-quic-events-11:
* Updated several fields to be uint64 per QUIC spec
* Renamed error and error_code fields and logic (#473)
* Clarified parameters_set usage (#493)
* Replaced all length fields with raw.length (#495)
* Change loss_timer_updated to timer_updated (#496)
* Renamed path_assigned to tuple_assigned (#491)
* Reworked stream_state_updated (#497)
* Renamed owner to initiator (#498)
Marx, et al. Expires 23 April 2026 [Page 61]
Internet-Draft QUIC event definitions for qlog October 2025
* Split up flags in PacketHeader (#478)
Since draft-ietf-qlog-quic-events-09:
* Several editorial changes
* Reworked QUICConnectionStarted to use PathEndpointInfo (#453)
* Consistent use of RawInfo and _bytes fields to log raw data (#450)
Since draft-ietf-qlog-quic-events-08:
* Removed individual categories and put every event in the single
quic event schema namespace. Major change (#439)
* Renamed recovery:metrics_updated to quic:recovery_metrics_updated
and recovery:parameters_set to quic:recovery_parameters_set (#439)
* Added unknown_parameters field to parameters_set (#438)
* Added extra parameters to parameters_restored (#441)
Since draft-ietf-qlog-quic-events-07:
* TODO (we forgot...)
Since draft-ietf-qlog-quic-events-06:
* Added PathAssigned and MigrationStateUpdated events (#336)
* Added extension points to parameters_set and parameters_restored
(#400)
* Removed error_code_value from connection_closed (#386, #392)
* Renamed generation to key_phase for key_updated and key_discarded
(#390)
* Removed retry_token from packet_sent and packet_received (#389)
* Updated ALPN handling (#385)
* Added key_unavailable trigger to packet_dropped (#381)
* Updated several uint32 to uint64
* ProtocolEventBody is now called ProtocolEventData (#352)
Marx, et al. Expires 23 April 2026 [Page 62]
Internet-Draft QUIC event definitions for qlog October 2025
* Editorial changes (#402, #404, #394, #393)
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)
Marx, et al. Expires 23 April 2026 [Page 63]
Internet-Draft QUIC event definitions for qlog October 2025
* 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)
Marx, et al. Expires 23 April 2026 [Page 64]
Internet-Draft QUIC event definitions for qlog October 2025
* 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
Marx, et al. Expires 23 April 2026 [Page 65]
Internet-Draft QUIC event definitions for qlog October 2025
* 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)
Authors' Addresses
Robin Marx (editor)
Akamai
Email: rmarx@akamai.com
Luca Niccolini (editor)
Meta
Email: lniccolini@meta.com
Marten Seemann (editor)
Email: martenseemann@gmail.com
Lucas Pardue (editor)
Cloudflare
Email: lucas@lucaspardue.com
Marx, et al. Expires 23 April 2026 [Page 66]