Add L4 stats docs for Rulesets and Workers

Author: Jannes Timm

src/content/docs/workers/runtime-apis/request.mdx

@@ -227,6 +227,14 @@ All plans have access to:
 
   * If Cloudflare replaces the value of the `Accept-Encoding` header, the original value is stored in the `clientAcceptEncoding` property, for example, `"gzip, deflate, br"`.
 
+* `clientQuicRtt` number | undefined
+
+  * The smoothed round-trip time (RTT) between Cloudflare and the client for QUIC connections, in milliseconds. Only present when the client connected over QUIC (HTTP/3). For example, `42`.
+
+* `clientTcpRtt` number | undefined
+
+  * The smoothed round-trip time (RTT) between the client and Cloudflare for TCP connections, in milliseconds. Only present when the client connected over TCP (HTTP/1 and HTTP/2). For example, `22`.
+
 * `colo` string
 
   * The three-letter [`IATA`](https://en.wikipedia.org/wiki/IATA_airport_code) airport code of the data center that the request hit, for example, `"DFW"`.
@@ -235,6 +243,12 @@ All plans have access to:
 
   * Country of the incoming request. The two-letter country code in the request. This is the same value as that provided in the `CF-IPCountry` header, for example, `"US"`.
 
+* `edgeL4` Object | undefined
+
+  * Layer 4 transport statistics for the connection between the client and Cloudflare. Contains the following property:
+    * `deliveryRate` number - The most recent data delivery rate estimate for the connection, in bytes per second. For example, `123456`.
+
+
 * `isEUCountry` string | null
 
   * If the country of the incoming request is in the EU, this will return `"1"`. Otherwise, this property is either omitted or `false`.
@@ -454,4 +468,4 @@ Incoming `Request` objects passed to the [`fetch()` handler](/workers/runtime-ap
 * [Examples: Modify request property](/workers/examples/modify-request-property/)
 * [Examples: Accessing the `cf` object](/workers/examples/accessing-the-cloudflare-object/)
 * [Reference: `Response`](/workers/runtime-apis/response/)
-* Write your Worker code in [ES modules syntax](/workers/reference/migrate-to-module-workers/) for an optimized experience.
+* Write your Worker code in [ES modules syntax](/workers/reference/migrate-to-module-workers/) for an optimized experience.

src/content/fields/index.yaml

@@ -898,13 +898,47 @@ entries:
     example_value: |-
       true
 
+  - name: cf.edge.l4.delivery_rate
+    data_type: Integer
+    categories: [Request]
+    keywords:
+      [request, l4, delivery rate, bandwidth, network, performance, transport]
+    summary: The most recent data delivery rate estimate for the client connection, in bytes per second.
+    description: |-
+      This metric reflects the rate at which data is being successfully delivered over the connection.
+
+      Returns `0` when L4 statistics are not available for the request.
+    example_value: |-
+      123456
+    example_block: |-
+      # Match requests where the delivery rate is below 100 KB/s
+      cf.edge.l4.delivery_rate < 100000
+
   - name: cf.timings.client_tcp_rtt_msec
     data_type: Number
     categories: [Request]
     keywords: [request, timing, tcp, rtt, performance, latency]
-    summary: The smoothed TCP round-trip time (RTT) from client to Cloudflare in milliseconds.
+    summary: The smoothed TCP round-trip time (RTT) between Cloudflare and the client in milliseconds.
+    description: |-
+      This field is only populated for TCP (HTTP/1, HTTP/2) connections. For QUIC connections, the value is `0`.
     example_value: |-
       20
+    example_block: |-
+      # Match requests over TCP where the RTT exceeds 200 ms
+      cf.timings.client_quic_rtt_msec > 200
+
+  - name: cf.timings.client_quic_rtt_msec
+    data_type: Integer
+    categories: [Request]
+    keywords: [request, timing, quic, rtt, performance, latency, http3]
+    summary: The smoothed QUIC round-trip time (RTT) between Cloudflare and the client in milliseconds.
+    description: |-
+      This field is only populated for QUIC (HTTP/3) connections. For TCP connections, the value is `0`.
+    example_value: |-
+      42
+    example_block: |-
+      # Match requests over QUIC where the RTT exceeds 200 ms
+      cf.timings.client_quic_rtt_msec > 200
 
   - name: cf.timings.edge_msec
     data_type: Integer
@@ -2205,4 +2239,4 @@ entries:
 
       You can use this field to customize the response for a specific type of error (for example, all 1XXX errors or all WAF block actions).
 
-      **Note**: This field is only available in [Response Header Transform Rules](/rules/transform/response-header-modification/) and [Custom Errors](/rules/custom-errors/).
+      **Note**: This field is only available in [Response Header Transform Rules](/rules/transform/response-header-modification/) and [Custom Errors](/rules/custom-errors/).