Create 2025-10-30-tcp-rtt-and-tcp-fields.mdx

Change log for TCP fields

Author: mbullock1986

src/content/changelog/rules/2025-10-30-tcp-rtt-and-tcp-fields.mdx

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+---
+title: New TCP based fields available in Rulesets
+description: Cloudflare Rulesets now support evaluating TCP connections and TCP RTT as part of request logic.
+date: 2025-10-30
+---
+
+## Build Rules Based on TCP Transport and Latency
+
+Cloudflare now provides two new request fields in the Ruleset engine that let you make decisions based on whether a request used TCP and the measured TCP round trip time between the client and Cloudflare. These fields help you understand protocol usage across your traffic and build policies that respond to network performance. For example, you can distinguish TCP from QUIC traffic or route high latency requests to alternative origins when needed.
+
+---
+
+### New Fields
+
+| Field | Type | Description |
+| --- | --- | --- |
+| `cf.edge.client_tcp` | Boolean | Indicates whether the request used TCP. A value of true means the client connected using TCP instead of QUIC. |
+| `cf.timings.client_tcp_rtt_msec` | Number | Reports the smoothed TCP round trip time between the client and Cloudflare in milliseconds. For example, a value of 20 indicates roughly twenty milliseconds of RTT. |
+
+Example Ruleset expression:
+
+```
+cf.edge.client_tcp && cf.timings.client_tcp_rtt_msec < 100
+```
+
+More information can be found in the [Ruleset fields reference](https://developers.cloudflare.com/ruleset-engine/rules-language/fields/)