The Coturn TURN Server is a VoIP media traffic NAT traversal server and gateway. It can be used as a general-purpose network traffic TURN server/gateway, too.

This implementation also includes some extra features. Supported RFCs:

TURN specs:

• RFC 5766 - base TURN specs
• RFC 6062 - TCP relaying TURN extension
• RFC 6156 - IPv6 extension for TURN
• Experimental DTLS support as client protocol.

STUN specs:

• RFC 3489 - "classic" STUN
• RFC 5389 - base "new" STUN specs
• RFC 5769 - test vectors for STUN protocol testing
• RFC 5780 - NAT behavior discovery support

The implementation fully supports the following client-to-TURN-server protocols:

• UDP (per RFC 5766)
• TCP (per RFC 5766 and RFC 6062)
• TLS (per RFC 5766 and RFC 6062); TLS1.0/TLS1.1/TLS1.2
• DTLS (experimental non-standard feature)

Supported relay protocols:

• UDP (per RFC 5766)
• TCP (per RFC 6062)

Supported user databases (for user repository, with passwords or keys, if authentication is required):

• SQLite
• MySQL
• PostgreSQL
• Redis

Redis can also be used for status and statistics storage and notification.

Supported TURN authentication mechanisms:

• long-term
• TURN REST API (a modification of the long-term mechanism, for time-limited secret-based authentication, for WebRTC applications)

The load balancing can be implemented with the following tools (either one or a combination of them):

• network load-balancer server
• DNS-based load balancing
• built-in ALTERNATE-SERVER mechanism.