SIP phones using Avaya SBC
The Avaya Session Border Controller (Avaya SBC) sits on the edge of customer’s network with both internal and external IP interfaces. Using these IP interfaces, Avaya SBC functions as the gateway for SIP traffic into and out of the network. When used internally, SIP clients register to the IP Office directly. When used externally, the SIP clients connect to the Avaya SBC. This is achieved using Split DNS, which automatically resolves the FQDNs to the internal IP address of the IP Office or the public IP address of the Avaya SBC depending on where the clients are currently located. Apart from acting as a gateway, Avaya SBC also provides protection against any external SIP-based attacks. For privacy over the public internet, the public side of the Avaya SBC facing the remote workers must be configured to use the recommended values of TLS for signaling and SRTP for media encryption, as long as they are supported by the endpoints.