Add TURN server configuration documentation

docs/configuring-playbook-turn.md

@@ -0,0 +1,33 @@
+# TURN server
+
+The playbook installs a [Coturn](https://github.com/coturn/coturn) TURN server by default, so that clients can make audio/video calls even from [NAT](https://en.wikipedia.org/wiki/Network_address_translation)-ed networks.
+
+By default, the Synapse chat server is configured, so that it points to the Coturn TURN server installed by the playbook.
+
+
+## Disabling Coturn
+
+If, for some reason, you'd like to prevent the playbook from installing Coturn, you can use the following configuration:
+
+```yaml
+matrix_coturn_enabled: false
+```
+
+In that case, Synapse would not point to any Coturn servers and audio/video call functionality may fail.
+
+
+## Using your own external Coturn server
+
+If you'd like to use another TURN server (be it Coturn or some other one), you can configure the playbook like this:
+
+```yaml
+# Disable integrated Coturn server
+matrix_coturn_enabled: false
+
+# Point Synapse to your other Coturn server
+matrix_synapse_turn_uris:
+- turns:HOSTNAME_OR_IP?transport=udp
+- turns:HOSTNAME_OR_IP?transport=tcp
+- turn:HOSTNAME_OR_IP?transport=udp
+- turn:HOSTNAME_OR_IP?transport=tcp
+```

docs/configuring-playbook.md

@@ -46,6 +46,8 @@ When you're done with all the configuration you'd like to do, continue with [Ins
 
 - [Using your own webserver, instead of this playbook's nginx proxy](configuring-playbook-own-webserver.md) (optional, advanced)
 
+- [Adjusting TURN server configuration](configuring-playbook-turn.md) (optional, advanced)
+
 
 ### Server connectivity