diff --git a/docs/setup/turn/eturnal.md b/docs/setup/turn/eturnal.md
new file mode 100644
index 0000000000..2e5a45673e
--- /dev/null
+++ b/docs/setup/turn/eturnal.md
@@ -0,0 +1,170 @@
+# eturnal TURN server
+
+The following sections describe how to install [eturnal](<https://github.com/processone/eturnal>)
+(which implements the TURN REST API).
+
+## `eturnal` setup
+
+### Initial installation
+
+The `eturnal` TURN server implementation is available from a variety of sources
+such as native package managers, binary packages, installation from source or
+[container image](https://eturnal.net/documentation/code/docker.html). They are
+all described [here](https://github.com/processone/eturnal#installation).
+
+Quick-Test instructions in a [Linux Shell](https://github.com/processone/eturnal/blob/master/QUICK-TEST.md)
+or with [Docker](https://github.com/processone/eturnal/blob/master/docker-k8s/QUICK-TEST.md)
+are available as well.
+
+### Configuration
+
+After installation, `eturnal` usually ships a [default configuration file](https://github.com/processone/eturnal/blob/master/config/eturnal.yml)
+here: `/etc/eturnal.yml` (and, if not found there, there is a backup file here:
+`/opt/eturnal/etc/eturnal.yml`). It uses the (indentation-sensitive!) [YAML](https://en.wikipedia.org/wiki/YAML)
+format. The file contains further explanations.
+
+Here are some hints how to configure eturnal on your [host machine](https://github.com/processone/eturnal#configuration)
+or when using e.g. [Docker](https://eturnal.net/documentation/code/docker.html).
+You may also further deep dive into the [reference documentation](https://eturnal.net/documentation/).
+
+`eturnal` runs out of the box with the default configuration. To enable TURN and
+to integrate it with your homeserver, some aspects in `eturnal`'s default configuration file
+must be edited:
+
+1. Homeserver's [`turn_shared_secret`](../../usage/configuration/config_documentation.md#turn_shared_secret)
+ and eturnal's shared `secret` for authentication
+
+ Both need to have the same value. Uncomment and adjust this line in `eturnal`'s
+ configuration file:
+
+ ```yaml
+ secret: "long-and-cryptic" # Shared secret, CHANGE THIS.
+ ```
+
+ One way to generate a `secret` is with `pwgen`:
+
+ ```sh
+ pwgen -s 64 1
+ ```
+
+1. Public IP address
+
+ If your TURN server is behind NAT, the NAT gateway must have an external,
+ publicly-reachable IP address. `eturnal` tries to autodetect the public IP address,
+ however, it may also be configured by uncommenting and adjusting this line, so
+ `eturnal` advertises that address to connecting clients:
+
+ ```yaml
+ relay_ipv4_addr: "203.0.113.4" # The server's public IPv4 address.
+ ```
+
+ If your NAT gateway is reachable over both IPv4 and IPv6, you may
+ configure `eturnal` to advertise each available address:
+
+ ```yaml
+ relay_ipv4_addr: "203.0.113.4" # The server's public IPv4 address.
+ relay_ipv6_addr: "2001:db8::4" # The server's public IPv6 address (optional).
+ ```
+
+ When advertising an external IPv6 address, ensure that the firewall and
+ network settings of the system running your TURN server are configured to
+ accept IPv6 traffic, and that the TURN server is listening on the local
+ IPv6 address that is mapped by NAT to the external IPv6 address.
+
+1. Logging
+
+ If `eturnal` was started by systemd, log files are written into the
+ `/var/log/eturnal` directory by default. In order to log to the [journal](https://www.freedesktop.org/software/systemd/man/systemd-journald.service.html)
+ instead, the `log_dir` option can be set to `stdout` in the configuration file.
+
+1. Security considerations
+
+ Consider your security settings. TURN lets users request a relay which will
+ connect to arbitrary IP addresses and ports. The following configuration is
+ suggested as a minimum starting point, [see also the official documentation](https://eturnal.net/documentation/#blacklist):
+
+ ```yaml
+ ## Reject TURN relaying from/to the following addresses/networks:
+ blacklist: # This is the default blacklist.
+ - "127.0.0.0/8" # IPv4 loopback.
+ - "::1" # IPv6 loopback.
+ - recommended # Expands to a number of networks recommended to be
+ # blocked, but includes private networks. Those
+ # would have to be 'whitelist'ed if eturnal serves
+ # local clients/peers within such networks.
+ ```
+
+ To whitelist IP addresses or specific (private) networks, you need to **add** a
+ whitelist part into the configuration file, e.g.:
+
+ ```yaml
+ whitelist:
+ - "192.168.0.0/16"
+ - "203.0.113.113"
+ - "2001:db8::/64"
+ ```
+
+ The more specific, the better.
+
+1. TURNS (TURN via TLS/DTLS)
+
+ Also consider supporting TLS/DTLS. To do this, adjust the following settings
+ in the `eturnal.yml` configuration file (TLS parts should not be commented anymore):
+
+ ```yaml
+ listen:
+ - ip: "::"
+ port: 3478
+ transport: udp
+ - ip: "::"
+ port: 3478
+ transport: tcp
+ - ip: "::"
+ port: 5349
+ transport: tls
+
+ ## TLS certificate/key files (must be readable by 'eturnal' user!):
+ tls_crt_file: /etc/eturnal/tls/crt.pem
+ tls_key_file: /etc/eturnal/tls/key.pem
+ ```
+
+ In this case, replace the `turn:` schemes in homeserver's `turn_uris` settings
+ with `turns:`. More is described [here](../../usage/configuration/config_documentation.md#turn_uris).
+
+ We recommend that you only try to set up TLS/DTLS once you have set up a
+ basic installation and got it working.
+
+ NB: If your TLS certificate was provided by Let's Encrypt, TLS/DTLS will
+ not work with any Matrix client that uses Chromium's WebRTC library. This
+ currently includes Element Android & iOS; for more details, see their
+ [respective](https://github.com/vector-im/element-android/issues/1533)
+ [issues](https://github.com/vector-im/element-ios/issues/2712) as well as the underlying
+ [WebRTC issue](https://bugs.chromium.org/p/webrtc/issues/detail?id=11710).
+ Consider using a ZeroSSL certificate for your TURN server as a working alternative.
+
+1. Firewall
+
+ Ensure your firewall allows traffic into the TURN server on the ports
+ you've configured it to listen on (By default: 3478 and 5349 for TURN
+ traffic (remember to allow both TCP and UDP traffic), and ports 49152-65535
+ for the UDP relay.)
+
+1. Reload/ restarting `eturnal`
+
+ Changes in the configuration file require `eturnal` to reload/ restart, this
+ can be achieved by:
+
+ ```sh
+ eturnalctl reload
+ ```
+
+ `eturnal` performs a configuration check before actually reloading/ restarting
+ and provides hints, if something is not correctly configured.
+
+### eturnalctl opterations script
+
+`eturnal` offers a handy [operations script](https://eturnal.net/documentation/#Operation)
+which can be called e.g. to check, whether the service is up, to restart the service,
+to query how many active sessions exist, to change logging behaviour and so on.
+
+Hint: If `eturnalctl` is not part of your `$PATH`, consider either sym-linking it (e.g. ´ln -s /opt/eturnal/bin/eturnalctl /usr/local/bin/eturnalctl´) or call it from the default `eturnal` directory directly: e.g. `/opt/eturnal/bin/eturnalctl info`
|
