Patent ID: 8346962

Claim:
A method for routing a session initiation protocol (SIP) message between a local network and a public network, the method comprising: receiving the SIP message from one of the local network and the public network; determining a transmitting subject and a transmission method identifier of the received SIP message, wherein the transmitting subject is one of the local network and the public network, and wherein the transmission method identifier includes information relating to whether the SIP message includes one of a request message and a response message; extracting, from the received SIP message, information relating to a media receiving port, information relating to a media receiving Internet Protocol (IP) address, and information relating to a real time control protocol (RTCP) receiving IP address and port; applying a network address translation to the extracted information based on the determined transmitting subject and the determined transmission method identifier; using a result of the applied network address translation to specify a node address relating to performing routing on the SIP message, wherein when the determined transmitting subject is the local network, a public IP address used by the public network is specified, and wherein when the determined transmitting subject is the public network, a private IP address used by the local network is specified; and using the extracted information and the specified node address relating to performing routing to route the SIP message to a destination address which belongs to a same network as the specified node address.