architecture/format/README.md

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# D4 encapsulation protocol version 1 (DRAFT)
![Overview of the D4 encapsulation protocol](https://raw.githubusercontent.com/D4-project/architecture/master/docs/diagram/d4-protocol-encapsulation.png)
## Headers
| Name | bit size | Description |
|---------------|-----------|:----------------------------------------------------------------------:|
| version | uint 8 | Version of the header |
| type | uint 8 | Data encapsulated type |
| uuid | uint 128 | Sensor UUID |
| timestamp | uint 64 | Encapsulation time |
| hmac | uint 256 | Authentication header (HMAC-SHA-256-128) |
| size | uint 32 | Payload size |
## Types
The type is the list of format encapsulated within the D4 protocol.
|Type| Description |
|----|:-----------------------------------|
| 0 | Reserved |
| 1 | pcap (libpcap 2.4) |
| 2 | meta header (JSON) |
| 3 | generic log line |
| 4 | [dnscap](https://github.com/DNS-OARC/dnscap) output |
| 5 | pcapng (diagnostic) |
| 6 | generic NDJSON or JSON Lines |
| 7 | generic [YAF](https://tools.netsa.cert.org/yaf/index.html) (Yet Another Flowmeter)|
| 8 | [passivedns](https://github.com/gamelinux/passivedns) CSV stream |
| 254 | type defined by meta header (type 2) |
The D4 type list is [available in JSON format](https://raw.githubusercontent.com/D4-project/architecture/master/format/type.json).
## Meta types (via meta header)
Sample meta type JSON (type 2). If a new session is open, before sending D4 packet type 254, a type 2 packet MUST be sent
to describe to the D4 server how to decode packets. A meta header payload contains a single JSON object which describes
the next packet to be decoded as type 254 in the stream. The JSON object MUST at least contain a `type` field.
~~~~json
{
"type": "ja3-jl",
"encoding": "utf-8",
"tags": [
"tlp:white"
],
"misp:org": "5b642239-4db4-4580-adf4-4ebd950d210f"
}
~~~~
|Type| Description |
|----|:-----------------------------------|
| ja3-jl | JA3 fingerprinting JL version |
| d4-telemetry | D4 project sensor telemetry |
| fascia | fascia JSON object |