Patent ID: 7752319

Claim:
A method for implementing a firewall application for communication data transmitted between terminal devices, comprising: disposing a first terminal device and a first interworking device in a first communication network; disposing a second terminal device and a second interworking device in a second communication network; initiating a data connection between the first terminal device and the second terminal device; sending data for authenticating the first terminal device from a first interworking device to a second interworking device with a known address; authenticating, by the second interworking device, that the first terminal is authorized to communicate with the second communication network; and in response to the first terminal being authorized: communicating, by the second interworking device, a further address to a firewall device, the further address is selected from an address of the first terminal device and the address of a first gatekeeper connected to the first terminal device; and activating the firewall device to allow signaling data to be sent by the first terminal device via the firewall device to the second terminal device.