Patent ID: 7450564

Claim:
A head end apparatus used in a voice over Internet protocol network providing a voice over Internet protocol service to subscribers using data communication terminals together with voice over Internet protocol terminals, by using a media gateway control protocol and including a call agent and a gateway connected to an Internet with an authorized Internet protocol address for providing voice over Internet protocol service to the voice over Internet protocol terminals, the head end apparatus comprising: a dynamic host configuration protocol server assigning the authorized Internet protocol address to the data communication terminals and a private Internet protocol address to the voice over Internet protocol terminals; a router accommodating a routing of an Internet protocol packet transmitted between the data communication terminals and the Internet and blocking the Internet protocol packet when the Internet protocol packet includes a user datagram protocol packet with having a destination address identical to an Internet protocol address of the call agent or the gateway; and a media gateway control protocol network address translator router transmitting the Internet protocol packet to the Internet by changing a source Internet protocol address of the Internet protocol packet to the authorized Internet protocol address while assigning a new user datagram protocol port number when the Internet protocol packet having the user datagram protocol packet with the source Internet protocol address identical to the private Internet protocol address and the destination Internet protocol address identical to the Internet protocol address of the call agent or the gateway is received from the voice over Internet protocol terminal, for registering the Internet protocol addresses and the user datagram protocol port numbers to a translation table, and for transmitting the Internet protocol packet by changing the destination Internet protocol address and user datagram protocol port number of the Internet protocol packet to a registered private Internet protocol address and a registered user datagram protocol port number when it receives from the Internet the Internet protocol packet having the source Internet protocol address identical to the Internet protocol address of the call agent or the gateway and the user datagram protocol port number registered in the translation table.