TURN/STUN Server configuration

The estos UCServer facilitates a common TURN and STUN configuration of the estos ProCall clients. The configuration is used by the estos ProCall clients if the features "AudioChat" or "VideoChat" are enabled. TURN/STUN servers are typically located at the internet and are not an integral part of the estos UCServer package. The TURN/STUN configuration of the estos UCServer (at Services -> STUN/TURN) are used to set the parameters describing how to access TURN/STUN servers residing at the public internet.
TURN and STUN servers may be installed at the same system resulting in identical URLs, IP addresses and port numbers. But these servers may also be located on different systems having different URLs, IP addresses and port numbers. Web hosting companies providing TURN/STUN services are further on reffered to as "hoster".

• STUN server
  Please enter the URL or IP address of the STUN server (e.g. go.estos.com or 5.35.242.32).
• STUN server port
  Please enter the port number of the STUN server (e.g. 3478).
• TURN server
  Please enter the URL or IP address of the TURN server (e.g. go.estos.com or 5.35.242.32).
• TURN server port
  Please enter the port number of the TURN server (e.g. 3478).
• Password
  This parameter is provided by the hoster of the TURN server. Using passwords helps TURN server administrators to protect their system. Relaying media streams consumes internet bandwidth and processor performance limiting the TURN server capacity.
• TURN/STUN diagnostics
  The actual settings described above can be verified by pressing the "Start diagnostics" button. The test result appears in the text field near the button, for example "STUN test passed, TURN test passed".
  If a log file of the diagnostics tool exist and if the log file is accessible for the estos UCServer administrator program the "Open logfile" button is enabled. The diagnostic is done with a helper tool named "ICE-Test.exe". The "Start diagnostics" button stays disabled if the helper tool is not accessible for the estos UCServer administrator program.

What is a STUN server?
STUN (Session Traversal Utilities for NAT) is a client-server protocol which returns the public IP address to the client. It allows a client to discover its public IP address at the internet if the client is located in a LAN behind a NAT. Additional information is provided enabling the client to make conclusions about the type of NAT. Thus a STUN server shall not be accessible via internal IP addresses of a LAN, for example if the STUN server resides in the DMZ of an enterprise network. The STUN server need to be addressed by the client always by using IP addresses of the public address space.

What is a TURN server?
TURN (Traversal Using Relays around NAT) servers are used when direct peer-to-peer communication is disabled by a firewall. A TURN server relayes media streams between the endpoinds avoiding such direct peer-to-peer communication.
The usage of a TURN server is required when the NAT device (a device connecting a LAN with the public internet, for example a router) is very restrictive like symmetric NAT devices.

What is a NAT device?
NAT stands for "Network Address Translation" and translates the "internal" IP addresses (and ports) to the external IP addresses (and ports). A NAT device is for example a router connecting a LAN with the public internet.

What is a symmetric NAT?
A remote station at the internet may reply data back to a client only if the remote station replies from the same system (using the same IP address and port number). If the remote station answers from a different location it fails because the NAT device opens a new NAT table entry. Using symmetric NAT devices no VoIP connection can be established without using a TURN server.

When do I need STUN or TURN servers?
All Audio/VideoChat clients are at the same local network (LAN): there is no need for configuring STUN and TURN servers.
The Audio/VideoChat clients are using also the internet to communicate to each other. No symmteric NAT is used: a STUN server configuration is required, configuring a TURN server is optional.
The Audio/VideoChat clients are using the internet to communicate to each other. The NAT type is unknown or mobile devices are used over the public internet: a STUN server and a TURN server configuration is required.