Internet DRAFT - draft-ietf-quic-qlog-main-schema
draft-ietf-quic-qlog-main-schema
QUIC R. Marx, Ed.
Internet-Draft Akamai
Intended status: Standards Track L. Niccolini, Ed.
Expires: 5 September 2024 Meta
M. Seemann, Ed.
L. Pardue, Ed.
Cloudflare
4 March 2024
Main logging schema for qlog
draft-ietf-quic-qlog-main-schema-08
Abstract
This document defines qlog, an extensible high-level schema for a
standardized logging format. It allows easy sharing of data,
benefitting common debug and analysis methods and tooling. The high-
level schema is independent of protocol; separate documents extend
qlog for protocol-specific data. The schema is also independent of
serialization format, allowing logs to be represented in many ways
such as JSON, CSV, or protobuf.
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.
Concrete examples of integrations of this schema in various
programming languages can be found at https://github.com/quiclog/
qlog/ (https://github.com/quiclog/qlog/).
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/.
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on 5 September 2024.
Copyright Notice
Copyright (c) 2024 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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
1.1.1. Schema definition . . . . . . . . . . . . . . . . . . 5
1.1.2. Serialization examples . . . . . . . . . . . . . . . 6
2. Design goals . . . . . . . . . . . . . . . . . . . . . . . . 6
3. QlogFile schema . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Traces . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Trace . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3. TraceError . . . . . . . . . . . . . . . . . . . . . . . 9
4. QlogFileSeq schema . . . . . . . . . . . . . . . . . . . . . 10
4.1. TraceSeq . . . . . . . . . . . . . . . . . . . . . . . . 11
5. VantagePoint . . . . . . . . . . . . . . . . . . . . . . . . 12
6. Events . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Timestamps . . . . . . . . . . . . . . . . . . . . . . . 14
6.2. Names . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3. Data . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.4. Path . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.5. ProtocolType . . . . . . . . . . . . . . . . . . . . . . 19
6.6. Triggers . . . . . . . . . . . . . . . . . . . . . . . . 19
6.7. Grouping . . . . . . . . . . . . . . . . . . . . . . . . 20
6.8. SystemInformation . . . . . . . . . . . . . . . . . . . . 21
6.9. CommonFields . . . . . . . . . . . . . . . . . . . . . . 22
7. Raw packet and frame information . . . . . . . . . . . . . . 24
8. Common events and data classes . . . . . . . . . . . . . . . 24
8.1. Generic events . . . . . . . . . . . . . . . . . . . . . 25
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8.1.1. error . . . . . . . . . . . . . . . . . . . . . . . . 25
8.1.2. warning . . . . . . . . . . . . . . . . . . . . . . . 25
8.1.3. info . . . . . . . . . . . . . . . . . . . . . . . . 25
8.1.4. debug . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1.5. verbose . . . . . . . . . . . . . . . . . . . . . . . 26
8.2. Simulation events . . . . . . . . . . . . . . . . . . . . 26
8.2.1. scenario . . . . . . . . . . . . . . . . . . . . . . 26
8.2.2. marker . . . . . . . . . . . . . . . . . . . . . . . 27
9. Event definition guidelines . . . . . . . . . . . . . . . . . 27
9.1. Event design . . . . . . . . . . . . . . . . . . . . . . 27
9.2. Event importance levels . . . . . . . . . . . . . . . . . 28
9.3. Custom fields . . . . . . . . . . . . . . . . . . . . . . 29
10. Serializing qlog . . . . . . . . . . . . . . . . . . . . . . 29
10.1. qlog to JSON mapping . . . . . . . . . . . . . . . . . . 30
10.2. qlog to JSON Text Sequences mapping . . . . . . . . . . 31
10.2.1. Supporting JSON Text Sequences in tooling . . . . . 32
10.3. JSON Interoperability . . . . . . . . . . . . . . . . . 32
10.4. Truncated values . . . . . . . . . . . . . . . . . . . . 32
10.5. Optimization of serialized data . . . . . . . . . . . . 34
11. Methods of access and generation . . . . . . . . . . . . . . 34
11.1. Set file output destination via an environment
variable . . . . . . . . . . . . . . . . . . . . . . . . 34
12. Tooling requirements . . . . . . . . . . . . . . . . . . . . 36
13. Security and privacy considerations . . . . . . . . . . . . . 36
13.1. Data at risk . . . . . . . . . . . . . . . . . . . . . . 37
13.2. Operational implications and recommendations . . . . . . 37
13.3. Data minimization or anonymization . . . . . . . . . . . 38
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 39
15.1. Normative References . . . . . . . . . . . . . . . . . . 39
15.2. Informative References . . . . . . . . . . . . . . . . . 40
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 41
Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Since draft-ietf-quic-qlog-main-schema-07: . . . . . . . . . . 41
Since draft-ietf-quic-qlog-main-schema-06: . . . . . . . . . . 41
Since draft-ietf-quic-qlog-main-schema-05: . . . . . . . . . . 41
Since draft-ietf-quic-qlog-main-schema-04: . . . . . . . . . . 42
Since draft-ietf-quic-qlog-main-schema-03: . . . . . . . . . . 42
Since draft-ietf-quic-qlog-main-schema-02: . . . . . . . . . . 42
Since draft-ietf-quic-qlog-main-schema-01: . . . . . . . . . . 42
Since draft-ietf-quic-qlog-main-schema-00: . . . . . . . . . . 42
Since draft-marx-qlog-main-schema-draft-02: . . . . . . . . . . 42
Since draft-marx-qlog-main-schema-01: . . . . . . . . . . . . . 42
Since draft-marx-qlog-main-schema-00: . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43
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1. Introduction
Endpoint logging is a useful strategy for capturing and understanding
how applications using network protocols are behaving, particularly
where protocols have an encrypted wire image that restricts
observers' ability to see what is happening.
Many applications implement logging using a custom, non-standard
logging format. This has an effect on the tools and methods that are
used to analyze the logs, for example to perform root cause analysis
of an interoperability failure between distinct implementations. A
lack of a common format impedes the development of common tooling
that can be used by all parties that have access to logs.
This document defines qlog, an extensible high-level schema and
harness that provides a shareable, aggregatable and structured
logging format. This high-level schema is independent of protocol,
with logging entries for specific protocols and use cases being
defined in other documents (see for example [QLOG-QUIC] for QUIC and
[QLOG-H3] for HTTP/3-related event definitions).
The goal of this high-level schema is to provide amenities and
default characteristics that each logging file should contain (or
should be able to contain), such that generic and reusable toolsets
can be created that can deal with logs from a variety of different
protocols and use cases.
As such, qlog provides versioning, metadata inclusion, log
aggregation, event grouping and log file size reduction techniques.
The qlog schema can be serialized in many ways (e.g., JSON, CBOR,
protobuf, etc). This document describes only how to employ [JSON],
its subset [I-JSON], and its streamable derivative
[JSON-Text-Sequences].
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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1.1.1. Schema definition
To define events and data structures, all qlog documents use the
Concise Data Definition Language [CDDL]. This document uses the
basic syntax, the specific text, uint, float32, float64, bool, and
any types, as well as the .default, .size, and .regexp control
operators, the ~ unwrapping operator, and the $ extension point
syntax from [CDDL].
Additionally, this document defines the following custom types for
clarity:
; CDDL's uint is defined as being 64-bit in size
; but for many protocol fields it is better to be restrictive
; and explicit
uint8 = uint .size 1
uint16 = uint .size 2
uint32 = uint .size 4
uint64 = uint .size 8
; an even-length lowercase string of hexadecimally encoded bytes
; examples: 82dc, 027339, 4cdbfd9bf0
; this is needed because the default CDDL binary string (bytes/bstr)
; is only CBOR and not JSON compatible
hexstring = text .regexp "([0-9a-f]{2})*"
Figure 1: Additional CDDL type definitions
All timestamps and time-related values (e.g., offsets) in qlog are
logged as float64 in the millisecond resolution.
Other qlog documents can define their own CDDL-compatible (struct)
types (e.g., separately for each Packet type that a protocol
supports).
Note to RFC editor: Please remove the following text in this
section before publication.
The main general CDDL syntax conventions in this document a reader
should be aware of for easy reading comprehension are:
* ? obj : this object is optional
* TypeName1 / TypeName2 : a union of these two types (object can be
either type 1 OR type 2)
* obj: TypeName : this object has this concrete type
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* obj: [* TypeName] : this object is an array of this type with
minimum size of 0 elements
* obj: [+ TypeName] : this object is an array of this type with
minimum size of 1 element
* TypeName = ... : defines a new type
* EnumName = "entry1" / "entry2" / entry3 / ...: defines an enum
* StructName = { ... } : defines a new struct type
* ; : single-line comment
* * text => any : special syntax to indicate 0 or more fields that
have a string key that maps to any value. Used to indicate a
generic JSON object.
All timestamps and time-related values (e.g., offsets) in qlog are
logged as float64 in the millisecond resolution.
Other qlog documents can define their own CDDL-compatible (struct)
types (e.g., separately for each Packet type that a protocol
supports).
1.1.2. Serialization examples
Serialization examples in this document use JSON ([JSON]) unless
otherwise indicated.
2. Design goals
The main tenets for the qlog schema design are:
* Streamable, event-based logging
* A flexible format that can reduce log producer overhead, at the
cost of increased complexity for consumers (e.g. tools)
* Extensible and pragmatic
* Aggregation and transformation friendly (e.g., the top-level
element for the non-streaming format is a container for individual
traces, group_ids can be used to tag events to a particular
context)
* Metadata is stored together with event data
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3. QlogFile schema
A qlog using the QlogFile schema can contain several individual
traces and logs from multiple vantage points that are in some way
related. The top-level element in this schema defines only a small
set of "header" fields and an array of component traces, defined in
Figure 2 as:
QlogFile = {
qlog_version: text
? qlog_format: text .default "JSON"
? title: text
? description: text
? traces: [+ Trace /
TraceError]
}
Figure 2: QlogFile definition
The required "qlog_version" field MUST have the value "0.4".
The optional "qlog_format" field indicates the serialization format.
Its value MUST either be one of the options defined in this document
(i.e., Section 10) or the field MUST be omitted entirely. When the
field is omitted the default value of "JSON" applies.
The optional "title" and "description" fields provide additional
free-text information about the file.
The optional "traces" field contains an array of qlog traces
(Section 3.2), each of which contain metadata and an array of qlog
events (Section 6).
In order to make it easier to parse and identify qlog files and their
serialization format, the "qlog_version" and "qlog_format" fields and
their values SHOULD be in the first 256 characters/bytes of the
resulting log file.
Where a qlog file is serialized to a JSON format, one of the
downsides is that it is inherently a non-streamable format. Put
differently, it is not possible to simply append new qlog events to a
log file without "closing" this file at the end by appending "]}]}".
Without these closing tags, most JSON parsers will be unable to parse
the file entirely. The alternative QlogFileSeq (Section 4) is better
suited to streaming.
JSON serialization example:
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{
"qlog_version": "0.4",
"qlog_format": "JSON",
"title": "Name of this particular qlog file (short)",
"description": "Description for this group of traces (long)",
"traces": [...]
}
Figure 3: QlogFile example
3.1. Traces
It can be advantageous to group several related qlog traces together
in a single file. For example, it is possible to simultaneously
perform logging on the client, on the server, and on a single point
on their common network path. For analysis, it is useful to
aggregate these three individual traces together into a single file,
so it can be uniquely stored, transferred, and annotated.
The QlogFile "traces" field is an array that contains a list of
individual qlog traces. When capturing a qlog at a vantage point, it
is expected that the traces field contains a single entry. Files can
be aggregated, for example as part of a post-processing operation, by
copying the traces in component to files into the combined "traces"
array of a new, aggregated qlog file.
3.2. Trace
The exact conceptual definition of a Trace can be fluid. For
example, a trace could contain all events for a single connection,
for a single endpoint, for a single measurement interval, for a
single protocol, etc. In the normal use case however, a trace is a
log of a single data flow collected at a single location or vantage
point. For example, for QUIC, a single trace only contains events
for a single logical QUIC connection for either the client or the
server.
A Trace contains some metadata in addition to qlog events, defined in
Figure 4 as:
Trace = {
? title: text
? description: text
? common_fields: CommonFields
? vantage_point: VantagePoint
events: [* Event]
}
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Figure 4: Trace definition
The optional "title" and "description" fields provide additional
free-text information about the trace.
The optional "common_fields" field is described in Section 6.9.
The optional "vantage_point" field is described in Section 5.
The semantics and context of the trace can mainly be deduced from the
entries in the "common_fields" list and "vantage_point" field.
JSON serialization example:
{
"title": "Name of this particular trace (short)",
"description": "Description for this trace (long)",
"common_fields": {
"ODCID": "abcde1234",
"time_format": "absolute"
},
"vantage_point": {
"name": "backend-67",
"type": "server"
},
"events": [...]
}
Figure 5: Trace example
3.3. TraceError
A TraceError indicates that an attempt to find/convert a file for
inclusion in the aggregated qlog was made, but there was an error
during the process. Rather than silently dropping the erroneous
file, it can be explicitly included in the qlog file as an entry in
the "traces" array, defined in Figure 6 as:
TraceError = {
error_description: text
; the original URI used for attempted find of the file
? uri: text
? vantage_point: VantagePoint
}
Figure 6: TraceError definition
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JSON serialization example:
{
"error_description": "File could not be found",
"uri": "/srv/traces/today/latest.qlog",
"vantage_point": { type: "server" }
}
Figure 7: TraceError example
Note that another way to combine events of different traces in a
single qlog file is through the use of the "group_id" field,
discussed in Section 6.7.
4. QlogFileSeq schema
A qlog file using the QlogFileSeq schema can be serialized to a
streamable JSON format called JSON Text Sequences (JSON-SEQ)
([RFC7464]). The top-level element in this schema defines only a
small set of "header" fields and an array of component traces,
defined in Figure 2 as:
QlogFileSeq = {
qlog_format: "JSON-SEQ"
qlog_version: text
? title: text
? description: text
trace: TraceSeq
}
Figure 8: QlogFileSeq definition
The required "qlog_format" field MUST have the value "JSON-SEQ".
The required "qlog_version" field MUST have the value "0.4".
The optional "title" and "description" fields provide additional
free-text information about the file.
The optional "trace" field contains a singular trace metadata. All
qlog events in the file are related to this trace.
JSON-SEQ serialization example:
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// list of qlog events, serialized in accordance with RFC 7464,
// starting with a Record Separator character and ending with a
// newline.
// For display purposes, Record Separators are rendered as <RS>
<RS>{
"qlog_version": "0.4",
"qlog_format": "JSON-SEQ",
"title": "Name of JSON Text Sequence qlog file (short)",
"description": "Description for this trace file (long)",
"trace": {
"common_fields": {
"protocol_type": ["QUIC","HTTP3"],
"group_id":"127ecc830d98f9d54a42c4f0842aa87e181a",
"time_format":"relative",
"reference_time": 1553986553572
},
"vantage_point": {
"name":"backend-67",
"type":"server"
}
}
}
<RS>{"time": 2, "name": "quic:parameters_set", "data": { ... } }
<RS>{"time": 7, "name": "quic:packet_sent", "data": { ... } }
...
Figure 9: Top-level element
For further information about serialization, see Section 10.2.
4.1. TraceSeq
TraceSeq is used with QlogFileSeq. It is conceptually similar to a
Trace, with the exception that qlog events are not contained within
it, but rather appended after it in a QlogFileSeq.
TraceSeq = {
? title: text
? description: text
? common_fields: CommonFields
? vantage_point: VantagePoint
}
Figure 10: TraceSeq definition
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5. VantagePoint
A VantagePoint describes the vantage point from which a trace
originates, defined in Figure 11 as:
VantagePoint = {
? name: text
type: VantagePointType
? flow: VantagePointType
}
; client = endpoint which initiates the connection
; server = endpoint which accepts the connection
; network = observer in between client and server
VantagePointType = "client" /
"server" /
"network" /
"unknown"
Figure 11: VantagePoint definition
JSON serialization examples:
{
"name": "aioquic client",
"type": "client"
}
{
"name": "wireshark trace",
"type": "network",
"flow": "client"
}
Figure 12: VantagePoint example
The flow field is only required if the type is "network" (for
example, the trace is generated from a packet capture). It is used
to disambiguate events like "packet sent" and "packet received".
This is indicated explicitly because for multiple reasons (e.g.,
privacy) data from which the flow direction can be otherwise inferred
(e.g., IP addresses) might not be present in the logs.
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Meaning of the different values for the flow field: * "client"
indicates that this vantage point follows client data flow semantics
(a "packet sent" event goes in the direction of the server). *
"server" indicates that this vantage point follow server data flow
semantics (a "packet sent" event goes in the direction of the
client). * "unknown" indicates that the flow's direction is unknown.
Depending on the context, tools confronted with "unknown" values in
the vantage_point can either try to heuristically infer the semantics
from protocol-level domain knowledge (e.g., in QUIC, the client
always sends the first packet) or give the user the option to switch
between client and server perspectives manually.
6. Events
A qlog event is specified as a generic object with a number of member
fields and their associated data. Depending on the protocol and use
case, the exact member field names and their formats can differ
across implementations. This section lists the main, pre-defined and
reserved field names with specific semantics and expected
corresponding value formats.
An Event is defined in Figure 13 as:
Event = {
time: float64
name: text
data: $ProtocolEventData
? path: PathID
? time_format: TimeFormat
? protocol_type: ProtocolType
? group_id: GroupID
? system_info: SystemInformation
; events can contain any amount of custom fields
* text => any
}
Figure 13: Event definition
Each qlog event MUST contain the mandatory fields: "time"
(Section 6.1), "name" (Section 6.2), and "data" (Section 6.3).
Each qlog event MAY contain the optional fields: "time_format"
(Section 6.1), "protocol_type" (Section 6.5), "trigger"
(Section 6.6), and "group_id" (Section 6.7).
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Multiple events can appear in a Trace or TraceSeq and they might
contain fields with identical values. It is possible to optimize out
this duplication using "common_fields" (Section 6.9).
The specific values for each of these fields and their semantics are
defined in separate documents, depending on protocol or use case.
For example: event definitions for QUIC and HTTP/3 can be found in
[QLOG-QUIC] and [QLOG-H3].
Events are intended to be extended with custom fields, therefore they
MAY contain other fields not defined in this document. Custom fields
may be known or unknown to tools. Tools SHOULD allow for the
presence of unknown event fields, but their semantics depend on the
context of the log usage.
JSON serialization:
{
"time": 1553986553572,
"name": "quic:packet_sent",
"data": { ... },
"protocol_type": ["QUIC","HTTP3"],
"group_id": "127ecc830d98f9d54a42c4f0842aa87e181a",
"time_format": "absolute",
"ODCID": "127ecc830d98f9d54a42c4f0842aa87e181a"
}
Figure 14: Event example
6.1. Timestamps
An event's "time" field indicates the timestamp at which the event
occurred. Its value is typically the Unix timestamp since the 1970
epoch (number of milliseconds since midnight UTC, January 1, 1970,
ignoring leap seconds). However, qlog supports two more succinct
timestamps formats to allow reducing file size. The employed format
is indicated in the "time_format" field, which allows one of three
values: "absolute", "delta" or "relative".
TimeFormat = "absolute" /
"delta" /
"relative"
Figure 15: TimeFormat definition
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* Absolute: Include the full absolute timestamp with each event.
This approach uses the largest amount of characters. This is also
the default value of the "time_format" field.
* Delta: Delta-encode each time value on the previously logged
value. The first event in a trace typically logs the full
absolute timestamp. This approach uses the least amount of
characters.
* Relative: Specify a full "reference_time" timestamp (typically
this is done up-front in "common_fields", see Section 6.9) and
include only relatively-encoded values based on this
reference_time with each event. The "reference_time" value is
typically the first absolute timestamp. This approach uses a
medium amount of characters.
The first option is good for stateless loggers, the second and third
for stateful loggers. The third option is generally preferred, since
it produces smaller files while being easier to reason about. An
example for each option can be seen in Figure 16.
The absolute approach will use:
1500, 1505, 1522, 1588
The delta approach will use:
1500, 5, 17, 66
The relative approach will:
- set the reference_time to 1500 in "common_fields"
- use: 0, 5, 22, 88
Figure 16: Three different approaches for logging timestamps
One of these options is typically chosen for the entire trace (put
differently: each event has the same value for the "time_format"
field). Each event MUST include a timestamp in the "time" field.
Events in each individual trace SHOULD be logged in strictly
ascending timestamp order (though not necessarily absolute value, for
the "delta" format). Tools MAY sort all events on the timestamp
before processing them, though are not required to (as this could
impose a significant processing overhead). This can be a problem
especially for multi-threaded and/or streaming loggers, who could
consider using a separate post-processor to order qlog events in time
if a tool do not provide this feature.
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Timestamps do not have to use the UNIX epoch timestamp as their
reference. For example for privacy considerations, any initial
reference timestamps (for example "endpoint uptime in ms" or "time
since connection start in ms") can be chosen. Tools SHOULD NOT
assume the ability to derive the absolute Unix timestamp from qlog
traces, nor allow on them to relatively order events across two or
more separate traces (in this case, clock drift should also be taken
into account).
6.2. Names
Events differ mainly in the type of metadata associated with them.
The "name" field is an identifier that parsers can use to decide how
to interpret the event metadata contained in the "data" field (see
Section 6.3).
Event names indicate a category and type. The "name" field MUST
contain a non-empty character sequence representing a category,
followed by a colon (':'), followed by a non-empty character sequence
representing a type.
Category allows a higher-level grouping of events per specific event
type. For example for QUIC and HTTP/3, the different categories
could be "quic", "h3", "qpack", and "recovery". Within these
categories, the event type provides additional granularity. For
example for QUIC and HTTP/3, within the "quic" category, there would
be "packet_sent" and "packet_received" events.
JSON serialization example:
{
"name": "quic:packet_sent"
}
Figure 17: An event with category "quic" and type "packet_sent".
6.3. Data
An event's "data" field is a generic object. It contains the per-
event metadata and its form and semantics are defined per specific
sort of event. For example, data field value definitions for QUIC
and HTTP/3 can be found in [QLOG-QUIC] and [QLOG-H3].
This field is defined here as a CDDL extension point (a "socket" or
"plug") named $ProtocolEventData. Other documents MUST properly
extend this extension point when defining new data field content
options to enable automated validation of aggregated qlog schemas.
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The only common field defined for the data field is the trigger
field, which is discussed in Section 6.6.
; The ProtocolEventData is any key-value map (e.g., JSON object)
; only the optional trigger field is defined in this document
$ProtocolEventData /= {
? trigger: text
* text => any
}
; event documents are intended to extend this socket by using:
; NewProtocolEventData = EventType1 /
; EventType2 /
; ... /
; EventTypeN
; $ProtocolEventData /= NewProtocolEventData
Figure 18: ProtocolEventData definition
One purely illustrative example for a QUIC "packet_sent" event is
shown in Figure 19:
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TransportPacketSent = {
? packet_size: uint16
header: PacketHeader
? frames:[* QuicFrame]
? trigger: "pto_probe" /
"retransmit_timeout" /
"bandwidth_probe"
}
could be serialized as
{
"packet_size": 1280,
"header": {
"packet_type": "1RTT",
"packet_number": 123
},
"frames": [
{
"frame_type": "stream",
"length": 1000,
"offset": 456
},
{
"frame_type": "padding"
}
]
}
Figure 19: Example of the 'data' field for a QUIC packet_sent event
6.4. Path
A qlog event can be associated with a single "network path" (usually,
but not always, identified by a 4-tuple of IP addresses and ports).
In many cases, the path will be the same for all events in a given
trace, and does not need to be logged explicitly with each event. In
this case, the "path" field can be omitted (in which case the default
value of "" is assumed) or reflected in "common_fields" instead (see
Section 6.9).
However, in some situations, such as during QUIC's Connection
Migration or when using Multipath features, it is useful to be able
to split events across multiple (concurrent) paths.
Definition:
PathID = text .default ""
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Figure 20: PathID definition
The "path" field is an identifier that is associated with a single
network path. This document intentionally does not define further
how to choose this identifier's value per-path or how to potentially
log other parameters that can be associated with such a path. This
is left for other documents. Implementers are free to encode path
information directly into the PathID or to log associated info in a
separate event. For example, QUIC has the "path_assigned" event to
couple the PathID value to a specific path configuration, see
[QLOG-QUIC].
6.5. ProtocolType
An event's "protocol_type" array field indicates to which protocols
(or protocol "stacks") this event belongs. This allows a single qlog
file to aggregate traces of different protocols (e.g., a web server
offering both TCP+HTTP/2 and QUIC+HTTP/3 connections).
ProtocolType = [+ text]
Figure 21: ProtocolType definition
For example, QUIC and HTTP/3 events have the "QUIC" and "HTTP3"
protocol_type entry values, see [QLOG-QUIC] and [QLOG-H3].
Typically however, all events in a single trace are of the same few
protocols, and this array field is logged once in "common_fields",
see Section 6.9.
6.6. Triggers
Sometimes, additional information is needed in the case where a
single event can be caused by a variety of other events. In the
normal case, the context of the surrounding log messages gives a hint
as to which of these other events was the cause. However, in highly-
parallel and optimized implementations, corresponding log messages
might separated in time. Another option is to explicitly indicate
these "triggers" in a high-level way per-event to get more fine-
grained information without much additional overhead.
In qlog, the optional "trigger" field contains a string value
describing the reason (if any) for this event instance occurring, see
Section 6.3. While this "trigger" field could be a property of the
qlog Event itself, it is instead a property of the "data" field
instead. This choice was made because many event types do not
include a trigger value, and having the field at the Event-level
would cause overhead in some serializations. Additional information
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on the trigger can be added in the form of additional member fields
of the "data" field value, yet this is highly implementation-
specific, as are the trigger field's string values.
One purely illustrative example of some potential triggers for QUIC's
"packet_dropped" event is shown in Figure 22:
TransportPacketDropped = {
? packet_type: PacketType
? raw_length: uint16
? trigger: "key_unavailable" /
"unknown_connection_id" /
"decrypt_error" /
"unsupported_version"
}
Figure 22: Trigger example
6.7. Grouping
As discussed in Section 3.2, a single qlog file can contain several
traces taken from different vantage points. However, a single trace
from one endpoint can also contain events from a variety of sources.
For example, a server implementation might choose to log events for
all incoming connections in a single large (streamed) qlog file. As
such, a method for splitting up events belonging to separate logical
entities is required.
The simplest way to perform this splitting is by associating a "group
id" to each event that indicates to which conceptual "group" each
event belongs. A post-processing step can then extract events per
group. However, this group identifier can be highly protocol and
context-specific. In the example above, the QUIC "Original
Destination Connection ID" could be used to uniquely identify a
connection. As such, they might add a "ODCID" field to each event.
However, a middlebox logging IP or TCP traffic might rather use four-
tuples to identify connections, and add a "four_tuple" field.
As such, to provide consistency and ease of tooling in cross-protocol
and cross-context setups, qlog instead defines the common "group_id"
field, which contains a string value. Implementations are free to
use their preferred string serialization for this field, so long as
it contains a unique value per logical group. Some examples can be
seen in Figure 24.
GroupID = text
Figure 23: GroupID definition
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JSON serialization example for events grouped by four tuples and QUIC
connection IDs:
"events": [
{
"time": 1553986553579,
"protocol_type": ["TCP", "TLS", "HTTP2"],
"group_id": "ip1=2001:67c:1232:144:9498:6df6:f450:110b,
ip2=2001:67c:2b0:1c1::198,port1=59105,port2=80",
"name": "quic:packet_received",
"data": { ... }
},
{
"time": 1553986553581,
"protocol_type": ["QUIC","HTTP3"],
"group_id": "127ecc830d98f9d54a42c4f0842aa87e181a",
"name": "quic:packet_sent",
"data": { ... }
}
]
Figure 24: GroupID example
Note that in some contexts (for example a Multipath transport
protocol) it might make sense to add additional contextual per-event
fields (for example "path_id"), rather than use the group_id field
for that purpose.
Note also that, typically, a single trace only contains events
belonging to a single logical group (for example, an individual QUIC
connection). As such, instead of logging the "group_id" field with
an identical value for each event instance, this field is typically
logged once in "common_fields", see Section 6.9.
6.8. SystemInformation
The "system_info" field can be used to record system-specific details
related to an event. This is useful, for instance, where an
application splits work across CPUs, processes, or threads and events
for a single trace occur on potentially different combinations
thereof. Each field is optional to support deployment diversity.
SystemInformation = {
? processor_id: uint32
? process_id: uint32
? thread_id: uint32
}
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6.9. CommonFields
As discussed in the previous sections, information for a typical qlog
event varies in three main fields: "time", "name" and associated
data. Additionally, there are also several more advanced fields that
allow mixing events from different protocols and contexts inside of
the same trace (for example "protocol_type" and "group_id"). In most
"normal" use cases however, the values of these advanced fields are
consistent for each event instance (for example, a single trace
contains events for a single QUIC connection).
To reduce file size and making logging easier, qlog uses the
"common_fields" list to indicate those fields and their values that
are shared by all events in this component trace. This prevents
these fields from being logged for each individual event. An example
of this is shown in Figure 25.
JSON serialization with repeated field values
per-event instance:
{
"events": [{
"group_id": "127ecc830d98f9d54a42c4f0842aa87e181a",
"protocol_type": ["QUIC","HTTP3"],
"time_format": "relative",
"reference_time": 1553986553572,
"time": 2,
"name": "quic:packet_received",
"data": { ... }
},{
"group_id": "127ecc830d98f9d54a42c4f0842aa87e181a",
"protocol_type": ["QUIC","HTTP3"],
"time_format": "relative",
"reference_time": 1553986553572,
"time": 7,
"name": "http:frame_parsed",
"data": { ... }
}
]
}
JSON serialization with repeated field values instead
extracted to common_fields:
{
"common_fields": {
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"group_id": "127ecc830d98f9d54a42c4f0842aa87e181a",
"protocol_type": ["QUIC","HTTP3"],
"time_format": "relative",
"reference_time": 1553986553572
},
"events": [
{
"time": 2,
"name": "quic:packet_received",
"data": { ... }
},{
"time": 7,
"name": "http:frame_parsed",
"data": { ... }
}
]
}
Figure 25: CommonFields example
An event's "common_fields" field is a generic dictionary of key-value
pairs, where the key is always a string and the value can be of any
type, but is typically also a string or number. As such, unknown
entries in this dictionary MUST be disregarded by the user and tools
(i.e., the presence of an unknown field is explicitly NOT an error).
The list of default qlog fields that are typically logged in
common_fields (as opposed to as individual fields per event instance)
are shown in the listing below:
CommonFields = {
? path: PathID
? time_format: TimeFormat
? reference_time: float64
? protocol_type: ProtocolType
? group_id: GroupID
* text => any
}
Figure 26: CommonFields definition
Tools MUST be able to deal with these fields being defined either on
each event individually or combined in common_fields. Note that if
at least one event in a trace has a different value for a given
field, this field MUST NOT be added to common_fields but instead
defined on each event individually. Good example of such fields are
"time" and "data", who are divergent by nature.
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7. Raw packet and frame information
While qlog is a high-level logging format, it also allows the
inclusion of most raw wire image information, such as byte lengths
and byte values. This is useful when for example investigating or
tuning packetization behavior or determining encoding/framing
overheads. However, these fields are not always necessary, can take
up considerable space, and can have a considerable privacy and
security impact (see Section 13). Where applicable, these fields are
grouped in a separate, optional, field named "raw" of type RawInfo.
The exact definition of entities, headers, trailers and payloads
depend on the protocol used.
RawInfo = {
; the full byte length of the entity (e.g., packet or frame),
; including possible headers and trailers
? length: uint64
; the byte length of the entity's payload,
; excluding possible headers or trailers
? payload_length: uint64
; the (potentially truncated) contents of the full entity,
; including headers and possibly trailers
? data: hexstring
}
Figure 27: RawInfo definition
The RawInfo:data field can be truncated for privacy or security
purposes, see Section 10.4. In this case, the length and
payload_length fields should still indicate the non-truncated lengths
when used for debugging purposes.
This document does not specify explicit header_length or
trailer_length fields. In protocols without trailers, header_length
can be calculated by subtracting the payload_length from the length.
In protocols with trailers (e.g., QUIC's AEAD tag), event definition
documents SHOULD define how to support header_length calculation.
8. Common events and data classes
There are some event types and data classes that are common across
protocols, applications, and use cases. This section specifies such
common definitions.
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8.1. Generic events
In typical logging setups, users utilize a discrete number of well-
defined logging categories, levels or severities to log freeform
(string) data. This generic events category replicates this approach
to allow implementations to fully replace their existing text-based
logging by qlog. This is done by providing events to log generic
strings for the typical well-known logging levels (error, warning,
info, debug, verbose).
For the events defined below, the "category" is "generic" and their
"type" is the name of the heading in lowercase (e.g., the "name" of
the error event is "generic:error").
8.1.1. error
Used to log details of an internal error that might not get reflected
on the wire. It has Core importance level; see Section 9.2.
GenericError = {
? code: uint64
? message: text
}
Figure 28: GenericError definition
8.1.2. warning
Used to log details of an internal warning that might not get
reflected on the wire. It has Base importance level; see
Section 9.2.
GenericWarning = {
? code: uint64
? message: text
}
Figure 29: GenericWarning definition
8.1.3. info
Used mainly for implementations that want to use qlog as their one
and only logging format but still want to support unstructured string
messages. The event has Extra importance level; see Section 9.2.
GenericInfo = {
message: text
}
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Figure 30: GenericInfo definition
8.1.4. debug
Used mainly for implementations that want to use qlog as their one
and only logging format but still want to support unstructured string
messages. The event has Extra importance level; see Section 9.2.
GenericDebug = {
message: text
}
Figure 31: GenericDebug definition
8.1.5. verbose
Used mainly for implementations that want to use qlog as their one
and only logging format but still want to support unstructured string
messages. The event has Extra importance level; see Section 9.2.
GenericVerbose = {
message: text
}
Figure 32: GenericVerbose definition
8.2. Simulation events
When evaluating a protocol implementation, one typically sets up a
series of interoperability or benchmarking tests, in which the test
situations can change over time. For example, the network bandwidth
or latency can vary during the test, or the network can be fully
disable for a short time. In these setups, it is useful to know when
exactly these conditions are triggered, to allow for proper
correlation with other events.
For the events defined below, the "category" is "simulation" and
their "type" is the name of the heading in lowercase (e.g., the
"name" of the scenario event is "simulation:scenario").
8.2.1. scenario
Used to specify which specific scenario is being tested at this
particular instance. This supports, for example, aggregation of
several simulations into one trace (e.g., split by group_id). It has
Extra importance level; see Section 9.2.
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SimulationScenario = {
? name: text
? details: {* text => any }
}
Figure 33: SimulationScenario definition
8.2.2. marker
Used to indicate when specific emulation conditions are triggered at
set times (e.g., at 3 seconds in 2% packet loss is introduced, at 10s
a NAT rebind is triggered). It has Extra importance level; see
Section 9.2.
SimulationMarker = {
? type: text
? message: text
}
Figure 34: SimulationMarker definition
9. Event definition guidelines
This document defines the main schema for the qlog format together
with some common events, which on their own do not provide much
logging utility. It is expected that logging is extended with
specific, per-protocol event definitions that specify the name
(category + type) and data needed for each individual event.
Examples include the QUIC event definitions [QLOG-QUIC] and HTTP/3
event definitions [QLOG-H3].
This section defines some basic annotations and concepts that SHOULD
be used by event definition documents. Doing so ensures a measure of
consistency that makes it easier for qlog implementers to support a
wide variety of protocols.
9.1. Event design
There are several ways of defining qlog events. In practice, two
main types of approach have been observed: a) those that map directly
to concepts seen in the protocols (e.g., packet_sent) and b) those
that act as aggregating events that combine data from several
possible protocol behaviors or code paths into one (e.g.,
parameters_set). The latter are typically used as a means to reduce
the amount of unique event definitions, as reflecting each possible
protocol event as a separate qlog entity would cause an explosion of
event types.
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Additionally, logging duplicate data is typically prevented as much
as possible. For example, packet header values that remain
consistent across many packets are split into separate events (for
example spin_bit_updated or connection_id_updated for QUIC).
Finally, when logging additional state change events, those state
changes can often be directly inferred from data on the wire (for
example flow control limit changes). As such, if the implementation
is bug-free and spec-compliant, logging additional events is
typically avoided. Exceptions have been made for common events that
benefit from being easily identifiable or individually logged (for
example packets_acked).
9.2. Event importance levels
Depending on how events are designed, it may be that several events
allow the logging of similar or overlapping data. For example the
separate QUIC connection_started event overlaps with the more generic
connection_state_updated. In these cases, it is not always clear
which event should be logged or used, and which event should take
precedence if e.g., both are present and provide conflicting
information.
To aid in this decision making, qlog defines three event importance
levels, in decreasing order of importance and expected usage:
* Core
* Base
* Extra
Events definitions SHOULD assign an importance level.
Core-level events SHOULD be present in all qlog files for a given
protocol. These are typically tied to basic packet and frame parsing
and creation, as well as listing basic internal metrics. Tool
implementers SHOULD expect and add support for these events, though
SHOULD NOT expect all Core events to be present in each qlog trace.
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Base-level events add additional debugging options and MAY be present
in qlog files. Most of these can be implicitly inferred from data in
Core events (if those contain all their properties), but for many it
is better to log the events explicitly as well, making it clearer how
the implementation behaves. These events are for example tied to
passing data around in buffers, to how internal state machines
change, and used to help show when decisions are actually made based
on received data. Tool implementers SHOULD at least add support for
showing the contents of these events, if they do not handle them
explicitly.
Extra-level events are considered mostly useful for low-level
debugging of the implementation, rather than the protocol. They
allow more fine-grained tracking of internal behavior. As such, they
MAY be present in qlog files and tool implementers MAY add support
for these, but they are not required to.
Note that in some cases, implementers might not want to log for
example data content details in Core-level events due to performance
or privacy considerations. In this case, they SHOULD use (a subset
of) relevant Base-level events instead to ensure usability of the
qlog output. As an example, implementations that do not log QUIC
packet_received events and thus also not which (if any) ACK frames
the packet contains, SHOULD log packets_acked events instead.
Finally, for event types whose data (partially) overlap with other
event types' definitions, where necessary the event definition
document should include explicit guidance on which to use in specific
situations.
9.3. Custom fields
Event definition documents are free to define new category and event
types, top-level fields (e.g., a per-event field indicating its
privacy properties or path_id in multipath protocols), as well as
values for the "trigger" property within the "data" field, or other
member fields of the "data" field, as they see fit.
They however SHOULD NOT expect non-specialized tools to recognize or
visualize this custom data. However, tools SHOULD make an effort to
visualize even unknown data if possible in the specific tool's
context. If they do not, they MUST ignore these unknown fields.
10. Serializing qlog
qlog schema definitions in this document are intentionally agnostic
to serialization formats. The choice of format is an implementation
decision.
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Other documents related to qlog (for example event definitions for
specific protocols), SHOULD be similarly agnostic to the employed
serialization format and SHOULD clearly indicate this. If not, they
MUST include an explanation on which serialization formats are
supported and on how to employ them correctly.
Serialization formats make certain tradeoffs between usability,
flexibility, interoperability, and efficiency. Implementations
should take these into consideration when choosing a format. Some
examples of possible formats are JSON, CBOR, CSV, protocol buffers,
flatbuffers, etc. which each have their own characteristics. For
instance, a textual format like JSON can be more flexible than a
binary format but more verbose, typically making it less efficient
than a binary format. A plaintext readable (yet relatively large)
format like JSON is potentially more usable for users operating on
the logs directly, while a more optimized yet restricted format can
better suit the constraints of a large scale operation. A custom or
restricted format could be more efficient for analysis with custom
tooling but might not be interoperable with general-purpose qlog
tools.
Considering these tradeoffs, JSON-based serialization formats provide
features that make them a good starting point for qlog flexibility
and interoperability. For these reasons, JSON is a recommended
default and expanded considerations are given to how to map qlog to
JSON (Section 10.1, and its streaming counterpart JSON Text Sequences
(Section 10.2. Section 10.3 presents interoperability considerations
for both formats, and Section 10.5 presents potential optimizations.
Serialization formats require appropriate deserializers/parsers. The
"qlog_format" field (Section 3) is used to indicate the chosen
serialization format.
10.1. qlog to JSON mapping
As described in Section 3, JSON is the default qlog serialization.
When mapping qlog to normal JSON, QlogFile (Figure 2) is used and the
"qlog_format" field MUST have the value "JSON". The file extension/
suffix SHOULD be ".qlog". The Media Type, if any, SHOULD be
"application/qlog+json" per [RFC6839].
In accordance with Section 8.1 of [RFC8259], JSON files are required
to use UTF-8 both for the file itself and the string values it
contains. In addition, all qlog field names MUST be lowercase when
serialized to JSON.
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In order to serialize CDDL-based qlog event and data structure
definitions to JSON, the official CDDL-to-JSON mapping defined in
Appendix E of [CDDL] SHOULD be employed.
10.2. qlog to JSON Text Sequences mapping
One of the downsides of using normal JSON is that it is inherently a
non-streamable format. A qlog serializer could work around this by
opening a file, writing the required opening data, streaming qlog
events by appending them, and then finalizing the log by appending
appropriate closing tags e.g., "]}]}". However, failure to append
closing tags, could lead to problems because most JSON parsers will
fail if a document is malformed. Some streaming JSON parsers are
able to handle missing closing tags, however they are not widely
deployed in popular environments (e.g., Web browsers)
To overcome the issues related to JSON streaming, a qlog mapping to a
streamable JSON format called JSON Text Sequences (JSON-SEQ)
([RFC7464]) is provided.
JSON Text Sequences are very similar to JSON, except that objects are
serialized as individual records, each prefixed by an ASCII Record
Separator (<RS>, 0x1E), and each ending with an ASCII Line Feed
character (\n, 0x0A). Note that each record can also contain any
amount of newlines in its body, as long as it ends with a newline
character before the next <RS> character.
In order to leverage the streaming capability, each qlog event is
serialized and interpreted as an individual JSON Text Sequence
record, that is appended as a new object to the back of an event
stream or log file. Put differently, unlike default JSON, it does
not require a document to be wrapped as a full object with "{ ... }"
or "[... ]".
This alternative record streaming approach cannot be accommodated by
QlogFile (Figure 2). Instead, QlogFileSeq is defined in Figure 8,
which notably includes only a single trace (TraceSeq) and omits an
explicit "events" array. An example is provided in Figure 9. The
"group_id" field can still be used on a per-event basis to include
events from conceptually different sources in a single JSON-SEQ qlog
file.
When mapping qlog to JSON-SEQ, the "qlog_format" field MUST have the
value "JSON-SEQ". The file extension/suffix SHOULD be ".sqlog" (for
"streaming" qlog). The Media Type, if any, SHOULD be "application/
qlog+json-seq" per [RFC8091].
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While not specifically required by the JSON-SEQ specification, all
qlog field names MUST be lowercase when serialized to JSON-SEQ.
In order to serialize all other CDDL-based qlog event and data
structure definitions to JSON-SEQ, the official CDDL-to-JSON mapping
defined in Appendix E of [CDDL] SHOULD be employed.
10.2.1. Supporting JSON Text Sequences in tooling
Note that JSON Text Sequences are not supported in most default
programming environments (unlike normal JSON). However, several
custom JSON-SEQ parsing libraries exist in most programming languages
that can be used and the format is easy enough to parse with existing
implementations (i.e., by splitting the file into its component
records and feeding them to a normal JSON parser individually, as
each record by itself is a valid JSON object).
10.3. JSON Interoperability
Some JSON implementations have issues with the full JSON format,
especially those integrated within a JavaScript environment (e.g.,
Web browsers, NodeJS). I-JSON (Internet-JSON) is a subset of JSON
for such environments; see [I-JSON]. One of the key limitations of
JavaScript, and thus I-JSON, is that it cannot represent full 64-bit
integers in standard operating mode (i.e., without using BigInt
extensions), instead being limited to the range -(2^53)+1 to (2^53)-
1.
To accommodate such constraints in CDDL, Appendix E of [CDDL]
recommends defining new CDDL types for int64 and uint64 that limit
their values to the restricted 64-bit integer range. However, some
of the protocols that qlog is intended to support (e.g., QUIC,
HTTP/3), can use the full range of uint64 values.
As such, to support situations where I-JSON is in use, seralizers MAY
encode uint64 values using JSON strings. qlog parsers, therefore,
SHOULD support parsing of uint64 values from JSON strings or JSON
numbers unless there is out-of-band information indicating that
neither the serializer nor parser are constrained by I-JSON.
10.4. Truncated values
For some use cases (e.g., limiting file size, privacy), it can be
necessary not to log a full raw blob (using the hexstring type) but
instead a truncated value. For example, one might only store the
first 100 bytes of an HTTP response body to be able to discern which
file it actually contained. In these cases, the original byte-size
length cannot be obtained from the serialized value directly.
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As such, all qlog schema definitions SHOULD include a separate,
length-indicating field for all fields of type hexstring they
specify, see for example Section 7. This not only ensures the
original length can always be retrieved, but also allows the omission
of any raw value bytes of the field completely (e.g., out of privacy
or security considerations).
To reduce overhead however and in the case the full raw value is
logged, the extra length-indicating field can be left out. As such,
tools MUST be able to deal with this situation and derive the length
of the field from the raw value if no separate length-indicating
field is present. The main possible permutations are shown by
example in Figure 35.
// both the content's value and its length are present
// (length is redundant)
{
"content_length": 5,
"content": "051428abff"
}
// only the content value is present, indicating it
// represents the content's full value. The byte
// length is obtained by calculating content.length / 2
{
"content": "051428abff"
}
// only the length is present, meaning the value
// was omitted
{
"content_length": 5,
}
// both value and length are present, but the lengths
// do not match: the value was truncated to
// the first three bytes.
{
"content_length": 5,
"content": "051428"
}
Figure 35: Example for serializing truncated hexstrings
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10.5. Optimization of serialized data
Both the JSON and JSON-SEQ formatting options described above are
serviceable in general small to medium scale (debugging) setups.
However, these approaches tend to be relatively verbose, leading to
larger file sizes. Additionally, generalized JSON(-SEQ)
(de)serialization performance is typically (slightly) lower than that
of more optimized and predictable formats. Both aspects present
challenges to large scale setups, though they may still be practical
to deploy; see [ANRW-2020]. JSON and JSON-SEQ compress very well
using commonly-available algorithms such as GZIP or Brotli.
During the development of qlog, a multitude of alternative formatting
and optimization options were assessed and the results are summarized
on the qlog github repository (https://github.com/quiclog/internet-
drafts/issues/30#issuecomment-617675097).
Formal definition of additional qlog formats or encodings that use
the optimization techniques described here, or any other optimization
technique is left to future activity that can apply the following
guidelines.
In order to help tools correctly parse and process serialized qlog,
it is RECOMMENDED that new formats also define suitable file
extensions and media types. This provides a clear signal and avoids
the need to provide out-of-band information or to rely on heuristic
fallbacks; see Section 12.
11. Methods of access and generation
Different implementations will have different ways of generating and
storing qlogs. However, there is still value in defining a few
default ways in which to steer this generation and access of the
results.
11.1. Set file output destination via an environment variable
To provide users control over where and how qlog files are created,
two environment variables are defined. The first, QLOGFILE,
indicates a full path to where an individual qlog file should be
stored. This path MUST include the full file extension. The second,
QLOGDIR, sets a general directory path in which qlog files should be
placed. This path MUST include the directory separator character at
the end.
In general, QLOGDIR should be preferred over QLOGFILE if an endpoint
is prone to generate multiple qlog files. This can for example be
the case for a QUIC server implementation that logs each QUIC
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connection in a separate qlog file. An alternative that uses
QLOGFILE would be a QUIC server that logs all connections in a single
file and uses the "group_id" field (Section 6.7) to allow post-hoc
separation of events.
Implementations SHOULD provide support for QLOGDIR and MAY provide
support for QLOGFILE.
When using QLOGDIR, it is up to the implementation to choose an
appropriate naming scheme for the qlog files themselves. The chosen
scheme will typically depend on the context or protocols used. For
example, for QUIC, it is recommended to use the Original Destination
Connection ID (ODCID), followed by the vantage point type of the
logging endpoint. Examples of all options for QUIC are shown in
Figure 36.
Command: QLOGFILE=/srv/qlogs/client.qlog quicclientbinary
Should result in the the quicclientbinary executable logging a
single qlog file named client.qlog in the /srv/qlogs directory.
This is for example useful in tests when the client sets up
just a single connection and then exits.
Command: QLOGDIR=/srv/qlogs/ quicserverbinary
Should result in the quicserverbinary executable generating
several logs files, one for each QUIC connection.
Given two QUIC connections, with ODCID values "abcde" and
"12345" respectively, this would result in two files:
/srv/qlogs/abcde_server.qlog
/srv/qlogs/12345_server.qlog
Command: QLOGFILE=/srv/qlogs/server.qlog quicserverbinary
Should result in the the quicserverbinary executable logging
a single qlog file named server.qlog in the /srv/qlogs directory.
Given that the server handled two QUIC connections before it was
shut down, with ODCID values "abcde" and "12345" respectively,
this would result in event instances in the qlog file being
tagged with the "group_id" field with values "abcde" and "12345".
Figure 36: Environment variable examples for a QUIC implementation
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12. Tooling requirements
Tools ingestion qlog MUST indicate which qlog version(s), qlog
format(s), compression methods and potentially other input file
formats (for example .pcap) they support. Tools SHOULD at least
support .qlog files in the default JSON format (Section 10.1).
Additionally, they SHOULD indicate exactly which values for and
properties of the name (category and type) and data fields they look
for to execute their logic. Tools SHOULD perform a (high-level)
check if an input qlog file adheres to the expected qlog schema. If
a tool determines a qlog file does not contain enough supported
information to correctly execute the tool's logic, it SHOULD generate
a clear error message to this effect.
Tools MUST NOT produce breaking errors for any field names and/or
values in the qlog format that they do not recognize. Tools SHOULD
indicate even unknown event occurrences within their context (e.g.,
marking unknown events on a timeline for manual interpretation by the
user).
Tool authors should be aware that, depending on the logging
implementation, some events will not always be present in all traces.
For example, using a circular logging buffer of a fixed size, it
could be that the earliest events (e.g., connection setup events) are
later overwritten by "newer" events. Alternatively, some events can
be intentionally omitted out of privacy or file size considerations.
Tool authors are encouraged to make their tools robust enough to
still provide adequate output for incomplete logs.
13. Security and privacy considerations
Protocols such as TLS [RFC8446] and QUIC [RFC9000] offer secure
protection for the wire image [RFC8546]. Logging can reveal aspects
of the wire image that would ordinarily be protected, creating
tension between observability, security and privacy, especially if
data can be correlated across data sources.
Depending on the observability use case any data could be logged or
captured. As per [RFC6973], operators must be aware that such data
could be compromised, risking the privacy of all participants.
Entities that expect protocol features to ensure data privacy might
unknowingly be subject to broader privacy risks, undermining their
ability to assess or respond effectively.
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13.1. Data at risk
qlog operators and implementers need to consider security and privacy
risks when handling qlog data, including logging, storage, usage, and
more. The considerations presented in this section may pose varying
risks depending on the the data itself or its handling.
The following is a non-exhaustive list of example data types that
could contain sensitive information that might allow identification
or correlation of individual connections, endpoints, users or
sessions across qlog or other data sources (e.g., captures of
encrypted packets):
* IP addresses and transport protocol port numbers.
* Session, Connection, or User identifiers e.g., QUIC Connection IDs
Section 9.5 of [RFC9000]).
* System-level information e.g., CPU, process, or thread
identifiers.
* Stored State e.g., QUIC address validation and retry tokens, TLS
session tickets, and HTTP cookies.
* TLS decryption keys, passwords, and HTTP-level API access or
authorization tokens.
* High-resolution event timestamps or inter-event timings, event
counts, packet sizes, and frame sizes.
* Full or partial raw packet and frame payloads that are encrypted.
* Full or partial raw packet and frame payloads that are plaintext
e.g., HTTP Field values, HTTP response data, or TLS SNI field
values.
13.2. Operational implications and recommendations
Operational considerations should focus on authorizing capture and
access to logs. Logging of Internet protocols using qlog can be
equivalent to the ability to store or read plaintext communications.
Without a more detailed analysis, all of the security considerations
of plaintext access apply.
It is recommended that qlog capture is subject to access control and
auditing. These controls should support granular levels of
information capture based on role and permissions (e.g., capture of
more-sensitive data requires higher privileges).
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It is recommended that access to stored qlogs is subject to access
control and auditing.
End users might not understand the implications of qlog to security
or privacy, and their environments might limit access control
techniques. Implementations should make enabling qlog conspicuous
(e.g., requiring clear and explicit actions to start a capture) and
resistant to social engineering, automation, or drive-by attacks; for
example, isolation or sandboxing of capture from other activities in
the same process or component.
It is recommended that data retention policies are defined for the
storage of qlog files.
It is recommended that qlog files are encrypted in transit and at
rest.
13.3. Data minimization or anonymization
Applying data minimization or anonymization techniques to qlog might
help address some security and privacy risks. However, removing or
anonymizing data without sufficient care might not enhance privacy or
security and could diminish the utility of qlog data.
Operators and implementers should balance the value of logged data
with the potential risks of (involuntary) disclosure, which can
depend on use cases (e.g., research datasets might have different
requirements to live operational troubleshooting).
The most extreme form of minimization or anonymization is deleting a
field, equivalent to not logging it. qlog implementations should
offer fine-grained control for this on a per-use-case or per-
connection basis.
Data can undergo anonymization, pseudonymization, permutation,
truncation, re-encryption, or aggregation; see Appendix B of
[DNS-PRIVACY] for techniques, especially regarding IP addresses.
However, operators should be cautious because many anonymization
methods have been shown to be insufficient to safeguard user privacy
or identity, particularly with large or easily correlated data sets.
Operators should consider end user rights and preferences. Active
user participation (as indicated by [RFC6973]) on a per-qlog basis is
challenging but aligning qlog capture, storage, and removal with
existing user preference and privacy controls is crucial. Operators
should consider agressive approaches to deletion or aggregation.
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The most sensitive data in qlog is typically contained in RawInfo
type fields (see Section 7). Therefore, qlog users should exercise
caution and limit the inclusion of such fields for all but the most
stringent use cases.
14. IANA Considerations
There are no IANA considerations.
15. References
15.1. 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>.
[DNS-PRIVACY]
Dickinson, S., Overeinder, B., van Rijswijk-Deij, R., and
A. Mankin, "Recommendations for DNS Privacy Service
Operators", BCP 232, RFC 8932, DOI 10.17487/RFC8932,
October 2020, <https://www.rfc-editor.org/rfc/rfc8932>.
[I-JSON] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015,
<https://www.rfc-editor.org/rfc/rfc7493>.
[JSON] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/rfc/rfc8259>.
[JSON-Text-Sequences]
Williams, N., "JavaScript Object Notation (JSON) Text
Sequences", RFC 7464, DOI 10.17487/RFC7464, February 2015,
<https://www.rfc-editor.org/rfc/rfc7464>.
[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>.
[RFC6839] Hansen, T. and A. Melnikov, "Additional Media Type
Structured Syntax Suffixes", RFC 6839,
DOI 10.17487/RFC6839, January 2013,
<https://www.rfc-editor.org/rfc/rfc6839>.
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[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<https://www.rfc-editor.org/rfc/rfc6973>.
[RFC7464] Williams, N., "JavaScript Object Notation (JSON) Text
Sequences", RFC 7464, DOI 10.17487/RFC7464, February 2015,
<https://www.rfc-editor.org/rfc/rfc7464>.
[RFC8091] Wilde, E., "A Media Type Structured Syntax Suffix for JSON
Text Sequences", RFC 8091, DOI 10.17487/RFC8091, February
2017, <https://www.rfc-editor.org/rfc/rfc8091>.
[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>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/rfc/rfc8259>.
[RFC9000] 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>.
15.2. Informative References
[ANRW-2020]
Marx, R., Piraux, M., Quax, P., and W. Lamotte, "Debugging
QUIC and HTTP/3 with qlog and qvis", September 2020,
<https://qlog.edm.uhasselt.be/anrw/>.
[QLOG-H3] Marx, R., Niccolini, L., Seemann, M., and L. Pardue,
"HTTP/3 qlog event definitions", Work in Progress,
Internet-Draft, draft-ietf-quic-qlog-h3-events-06, 5
January 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-quic-qlog-h3-events-06>.
[QLOG-QUIC]
Marx, R., Niccolini, L., Seemann, M., and L. Pardue, "QUIC
event definitions for qlog", Work in Progress, Internet-
Draft, draft-ietf-quic-qlog-quic-events-06, 23 October
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
quic-qlog-quic-events-06>.
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[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/rfc/rfc8446>.
[RFC8546] Trammell, B. and M. Kuehlewind, "The Wire Image of a
Network Protocol", RFC 8546, DOI 10.17487/RFC8546, April
2019, <https://www.rfc-editor.org/rfc/rfc8546>.
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, and Jeremy Laine for their feedback and suggestions.
Change Log
This section is to be removed before publishing as an RFC.
Since draft-ietf-quic-qlog-main-schema-07:
* Added path and PathID (#336)
* Removed custom definition of uint64 type (#360, #388)
* ProtocolEventBody is now called ProtocolEventData (#352)
* Editorial changes (#364, #289, #353, #361, #362)
Since draft-ietf-quic-qlog-main-schema-06:
* Editorial reworking of the document (#331, #332)
* Updated IANA considerations section (#333)
Since draft-ietf-quic-qlog-main-schema-05:
* Updated qlog_version to 0.4 (due to breaking changes) (#314)
* Renamed 'transport' category to 'quic' (#302)
* Added 'system_info' field (#305)
* Removed 'summary' and 'configuration' fields (#308)
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* Editorial and formatting changes (#298, #303, #304, #316, #320,
#321, #322, #326, #328)
Since draft-ietf-quic-qlog-main-schema-04:
* Updated RawInfo definition and guidance (#243)
Since draft-ietf-quic-qlog-main-schema-03:
* Added security and privacy considerations discussion (#252)
Since draft-ietf-quic-qlog-main-schema-02:
* No changes - new draft to prevent expiration
Since draft-ietf-quic-qlog-main-schema-01:
* Change the data definition language from TypeScript to CDDL (#143)
Since draft-ietf-quic-qlog-main-schema-00:
* Changed the streaming serialization format from NDJSON to JSON
Text Sequences (#172)
* Added Media Type definitions for various qlog formats (#158)
* Changed to semantic versioning
Since draft-marx-qlog-main-schema-draft-02:
* These changes were done in preparation of the adoption of the
drafts by the QUIC working group (#137)
* Moved RawInfo, Importance, Generic events and Simulation events to
this document.
* Added basic event definition guidelines
* Made protocol_type an array instead of a string (#146)
Since draft-marx-qlog-main-schema-01:
* Decoupled qlog from the JSON format and described a mapping
instead (#89)
- Data types are now specified in this document and proper
definitions for fields were added in this format
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- 64-bit numbers can now be either strings or numbers, with a
preference for numbers (#10)
- binary blobs are now logged as lowercase hex strings (#39, #36)
- added guidance to add length-specifiers for binary blobs (#102)
* Removed "time_units" from Configuration. All times are now in ms
instead (#95)
* Removed the "event_fields" setup for a more straightforward JSON
format (#101,#89)
* Added a streaming option using the NDJSON format (#109,#2,#106)
* Described optional optimization options for implementers (#30)
* Added QLOGDIR and QLOGFILE environment variables, clarified the
.well-known URL usage (#26,#33,#51)
* Overall tightened up the text and added more examples
Since draft-marx-qlog-main-schema-00:
* All field names are now lowercase (e.g., category instead of
CATEGORY)
* Triggers are now properties on the "data" field value, instead of
separate field types (#23)
* group_ids in common_fields is now just also group_id
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
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Lucas Pardue (editor)
Cloudflare
Email: lucas@lucaspardue.com
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