Patent ID: 8140707

Claim:
An interworking system, comprising: a simple traversal under user datagram protocol through network address translator (STUN) server configured to provide public IP binding information based on a private IP address; and an application layer gateway (ALG) server including: an IP masquerading performer configured to change header information of a public IP binding request into private media receiving address information extracted from a payload of a packet received from a call transmitting terminal; a STUN client performer configured to: transmit the public IP binding request with the header information, as changed by the IP masquerading performer, to the STUN server, and receive a binding request response included in the header information, as changed from the STUN server, wherein the header information includes global media receiving address information; an address translator configured to change the private media receiving address information of the packet received from the from the call transmitting terminal into global media receiving address information extracted from the binding request response; and a determiner configured to determine whether to drive the IP masquerading performer depending on whether a network of the destination specified in the header of a call connection request packet corresponds to a source network.