docs: recommend TCP fq + BBR for validator nodes

src/pages/guide/node/system-requirements.mdx

@@ -50,6 +50,27 @@ We do not recommend using a cloud firewall / NAT gateway as it can introduce add
 - ratelimiting connections and messages in consensus and execution to prevent abuse
 - only accepting consensus connections from validators that can prove their identity
 
+## Network Tuning
+
+We recommend enabling TCP **BBR** congestion control with the **fq** packet scheduler for better P2P and consensus performance.
+
+Add the following to your sysctl configuration (e.g. `/etc/sysctl.d/99-tempo-network.conf` or equivalent):
+
+```ini
+net.core.default_qdisc = fq
+net.ipv4.tcp_congestion_control = bbr
+```
+
+Apply and verify:
+
+```bash
+sudo sysctl --system
+sysctl net.ipv4.tcp_congestion_control   # should print: bbr
+sysctl net.core.default_qdisc            # should print: fq
+```
+
+Restart the node after applying for the changes to take effect.
+
 ## Ports
 
 | Port | Protocol | Purpose | Expose |