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Transport QUIC Internet-Draft This document describes concrete qlog event definitions and their metadata for HTTP/3 and QPACK-related events. These events can then be embedded in the higher level schema defined in .

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

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

Feedback and discussion are welcome at https://github.com/quicwg/qlog. Readers are advised to refer to the "editor's draft" at that URL for an up-to-date version of this document. Concrete examples of integrations of this schema in various programming languages can be found at https://github.com/quiclog/qlog/.

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 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 and its extensions described in . The following fields from are imported and used: name, category, type, data, group_id, protocol_type, importance, RawInfo, and time-related fields.

Overview This document describes how the HTTP/3 and QPACK can be expressed in qlog using the schema defined in . HTTP/3 and QPACK events are defined with a category, a name (the concatenation of "category" and "event"), an "importance", an optional "trigger", and "data" fields. Some data fields use complex datastructures. These are represented as enums or re-usable definitions, which are grouped together on the bottom of this document for clarity. When any event from this document is included in a qlog trace, the "protocol_type" qlog array field MUST contain an entry with the value "HTTP3".

Usage with QUIC The events described in this document can be used with or without logging the related QUIC events defined in . If used with QUIC events, the QUIC document takes precedence in terms of recommended filenames and trace separation setups. If used without QUIC events, it is recommended that the implementation assign a globally unique identifier to each HTTP/3 connection. This ID can then be used as the value of the qlog "group_id" field, as well as the qlog filename or file identifier, potentially suffixed by the vantagepoint type (For example, abcd1234_server.qlog would contain the server-side trace of the connection with GUID abcd1234).

Raw packet and frame information This document re-uses the definition of the RawInfo data class from .

Note:

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

Note:

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

HTTP/3 and QPACK Event Overview This document defines events in two categories, written as lowercase to follow convention: http () and qpack (). As described in , the qlog "name" field is the concatenation of category and type. summarizes the name value of each event type that is defined in this specification. HTTP/3 and QPACK Events

Name value	Importance	Definition
http:parameters_set	Base
http:parameters_restored	Base
http:stream_type_set	Base
http:frame_created	Core
http:frame_parsed	Core
http:push_resolved	Extra
qpack:state_updated	Base
qpack:stream_state_updated	Core
qpack:dynamic_table_updated	Extra
qpack:headers_encoded	Base
qpack:headers_decoded	Base
qpack:instruction_created	Base
qpack:instruction_parsed	Base

HTTP/3 Events HTTP/3 events extend the $ProtocolEventBody extension point defined in .

HTTPEvents definition and ProtocolEventBody extension

parameters_set Importance: Base This event contains HTTP/3 and QPACK-level settings, mostly those received from the HTTP/3 SETTINGS frame. All these parameters are typically set once and never change. However, they are typically set at different times during the connection, so there can be several instances of this event with different fields set. Note that some settings have two variations (one set locally, one requested by the remote peer). This is reflected in the "owner" field. As such, this field MUST be correct for all settings included a single event instance. If you need to log settings from two sides, you MUST emit two separate event instances. Note: we use the CDDL unwrap operator (~) here to make HTTPParameters into a re-usable list of fields. The unwrap operator copies the fields from the referenced type into the target type directly, extending the target with the unwrapped fields. TODO: explain this better + provide reference and maybe an example. Definition:

HTTPParametersSet definition uint64 } ]]>

Note: enabling server push is not explicitly done in HTTP/3 by use of a setting or parameter. Instead, it is communicated by use of the MAX_PUSH_ID frame, which should be logged using the frame_created and frame_parsed events below. Additionally, this event can contain any number of unspecified fields. This is to reflect setting of for example unknown (greased) settings or parameters of (proprietary) extensions.

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

HTTPParametersRestored definition

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

stream_type_set Importance: Base Emitted when a stream's type becomes known. This is typically when a stream is opened and the stream's type indicator is sent or received. Note: most of this information can also be inferred by looking at a stream's id, since id's are strictly partitioned at the QUIC level. Even so, this event has a "Base" importance because it helps a lot in debugging to have this information clearly spelled out. Definition:

HTTPStreamTypeSet definition

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

HTTPFrameCreated definition

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

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

HTTPFrameParsed definition

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

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

HTTPPushResolved definition

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

Owner

Owner definition

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

HTTPFrame plug definition any } ]]>

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

HTTPBaseFrames definition

HTTPDataFrame

HTTPDataFrame definition

HTTPHeadersFrame This represents an uncompressed, plaintext HTTP Headers frame (e.g., no QPACK compression is applied). For example:

HTTPHeadersFrame example

HTTPHeadersFrame definition

HTTPField definition

HTTPCancelPushFrame

HTTPCancelPushFrame definition

HTTPSettingsFrame

HTTPSettingsFrame definition

HTTPPushPromiseFrame

HTTPPushPromiseFrame definition

HTTPGoAwayFrame

HTTPGoawayFrame definition

HTTPMaxPushIDFrame

HTTPMaxPushIDFrame definition

HTTPReservedFrame

HTTPReservedFrame definition

HTTPUnknownFrame

UnknownFrame definition

HTTPApplicationError

HTTPApplicationError definition

The HTTPApplicationError defines the general $ApplicationError definition in the qlog QUIC definition, see .

QPACK Events QPACK events extend the $ProtocolEventBody extension point defined in .

QPACKEvents definition and ProtocolEventBody extension

QPACK events mainly serve as an aid to debug low-level QPACK issues.The higher-level, plaintext header values SHOULD (also) be logged in the http.frame_created and http.frame_parsed event data (instead). Note: qpack does not have its own parameters_set event. This was merged with http.parameters_set for brevity, since qpack is a required extension for HTTP/3 anyway. Other HTTP/3 extensions MAY also log their SETTINGS fields in http.parameters_set or MAY define their own events.

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

QPACKStateUpdate definition

stream_state_updated Importance: Core This event is emitted when a stream becomes blocked or unblocked by header decoding requests or QPACK instructions. Note: This event is of "Core" importance, as it might have a large impact on HTTP/3's observed performance. Definition:

QPACKStreamStateUpdate definition

dynamic_table_updated Importance: Extra This event is emitted when one or more entries are inserted or evicted from QPACK's dynamic table. Definition:

QPACKDynamicTableUpdate definition

headers_encoded Importance: Base This event is emitted when an uncompressed header block is encoded successfully. Note: this event has overlap with http.frame_created for the HeadersFrame type. When outputting both events, implementers MAY omit the "headers" field in this event. Definition:

QPACKHeadersEncoded definition

headers_decoded Importance: Base This event is emitted when a compressed header block is decoded successfully. Note: this event has overlap with http.frame_parsed for the HeadersFrame type. When outputting both events, implementers MAY omit the "headers" field in this event. Definition:

QPACKHeadersDecoded definition

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

QPACKInstructionCreated definition

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

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

QPACKInstructionParsed definition

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

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

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

QPACKInstruction definition

SetDynamicTableCapacityInstruction

SetDynamicTableCapacityInstruction definition

InsertWithNameReferenceInstruction

InsertWithNameReferenceInstruction definition

InsertWithoutNameReferenceInstruction

InsertWithoutNameReferenceInstruction definition

DuplicateInstruction

DuplicateInstruction definition

SectionAcknowledgementInstruction

SectionAcknowledgementInstruction definition

StreamCancellationInstruction

StreamCancellationInstruction definition

InsertCountIncrementInstruction

InsertCountIncrementInstruction definition

QPACKHeaderBlockRepresentation

QPACKHeaderBlockRepresentation definition

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

IndexedHeaderField definition

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

LiteralHeaderFieldWithName definition

LiteralHeaderFieldWithoutName

LiteralHeaderFieldWithoutName definition

QPACKHeaderBlockPrefix

QPACKHeaderBlockPrefix definition

QPACKTableType

QPACKTableType definition

Security and Privacy Considerations The security and privacy considerations discussed in apply to this document as well.

IANA Considerations TBD

Normative References The QUIC transport protocol has several features that are desirable in a transport for HTTP, such as stream multiplexing, per-stream flow control, and low-latency connection establishment. This document describes a mapping of HTTP semantics over QUIC. This document also identifies HTTP/2 features that are subsumed by QUIC and describes how HTTP/2 extensions can be ported to HTTP/3. KU Leuven Facebook Protocol Labs This document describes a high-level schema for a standardized logging format called qlog. This format allows easy sharing of data and the creation of reusable visualization and debugging tools. The high-level schema in this document is intended to be protocol- agnostic. Separate documents specify how the format should be used for specific protocol data. The schema is also format-agnostic, and can be represented in for example JSON, csv or protobuf. KU Leuven Facebook Protocol Labs This document describes concrete qlog event definitions and their metadata for QUIC events. These events can then be embedded in the higher level schema defined in [QLOG-MAIN]. This specification defines QPACK: a compression format for efficiently representing HTTP fields that is to be used in HTTP/3. This is a variation of HPACK compression that seeks to reduce head-of-line blocking. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This document proposes a notational convention to express Concise Binary Object Representation (CBOR) data structures (RFC 7049). Its main goal is to provide an easy and unambiguous way to express structures for protocol messages and data formats that use CBOR or JSON.

Change Log

Since draft-ietf-quic-qlog-h3-events-02:

• Renamed HTTPStreamType data to request (#222)
• Added HTTPStreamType value unknown (#227)
• Added HTTPUnknownFrame (#224)
• Replaced old and new fields with stream_type in HTTPStreamTypeSet (#240)
• Changed HTTPFrame to a CDDL plug type (#257)
• Moved data definitions out of the appendix into separate sections
• Added overview Table of Contents

Since draft-ietf-quic-qlog-h3-events-01:

• No changes - new draft to prevent expiration

Since draft-ietf-quic-qlog-h3-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.

Since draft-marx-qlog-event-definitions-quic-h3-01: Major changes:

• Moved data_moved from http to transport. Also made the "from" and "to" fields flexible strings instead of an enum (#111,#65)
• Moved packet_type fields to PacketHeader. Moved packet_size field out of PacketHeader to RawInfo:length (#40)
• Made events that need to log packet_type and packet_number use a header field instead of logging these fields individually
• Added support for logging retry, stateless reset and initial tokens (#94,#86,#117)
• Moved separate general event categories into a single category "generic" (#47)
• Added "transport:connection_closed" event (#43,#85,#78,#49)
• Added version_information and alpn_information events (#85,#75,#28)
• Added parameters_restored events to help clarify 0-RTT behaviour (#88)

Smaller changes:

• Merged loss_timer events into one loss_timer_updated event
• Field data types are now strongly defined (#10,#39,#36,#115)
• Renamed qpack instruction_received and instruction_sent to instruction_created and instruction_parsed (#114)
• Updated qpack:dynamic_table_updated.update_type. It now has the value "inserted" instead of "added" (#113)
• Updated qpack:dynamic_table_updated. It now has an "owner" field to differentiate encoder vs decoder state (#112)
• Removed push_allowed from http:parameters_set (#110)
• Removed explicit trigger field indications from events, since this was moved to be a generic property of the "data" field (#80)
• Updated transport:connection_id_updated to be more in line with other similar events. Also dropped importance from Core to Base (#45)
• Added length property to PaddingFrame (#34)
• Added packet_number field to transport:frames_processed (#74)
• Added a way to generically log packet header flags (first 8 bits) to PacketHeader
• Added additional guidance on which events to log in which situations (#53)
• Added "simulation:scenario" event to help indicate simulation details
• Added "packets_acked" event (#107)
• Added "datagram_ids" to the datagram_X and packet_X events to allow tracking of coalesced QUIC packets (#91)
• Extended connection_state_updated with more fine-grained states (#49)

Since draft-marx-qlog-event-definitions-quic-h3-00:

• Event and category names are now all lowercase
• Added many new events and their definitions
• "type" fields have been made more specific (especially important for PacketType fields, which are now called packet_type instead of type)
• Events are given an importance indicator (issue #22)
• Event names are more consistent and use past tense (issue #21)
• Triggers have been redefined as properties of the "data" field and updated for most events (issue #23)

Acknowledgements Much of the initial work by Robin Marx was done at the Hasselt and KU Leuven Universities. Thanks to Jana Iyengar, Brian Trammell, Dmitri Tikhonov, Stephen Petrides, Jari Arkko, Marcus Ihlar, Victor Vasiliev, Mirja Kuehlewind, Jeremy Laine, Kazu Yamamoto, and Christian Huitema for their feedback and suggestions.