Patent ID: 9203688
Filing Date: 2015-12-01
Classification: H04L

Abstract:
1. A Voice over Internet Protocol (VoIP) service system using Network Address Translation (NAT), comprising: a router to receive a call connection request from a first terminal connected to the Internet to a second terminal to look up a NAT table using port information in a packet transferred from the first terminal, and to determine a private address of the second terminal connected to a gateway using port information in a first packet transferred from the first terminal to the second terminal, the gateway comprising a call server and the NAT table comprising port information corresponding to the call server, wherein the router is configured to send a request message and the call server is configured to provide a private IP address of the call server to the router, wherein, in response to a second packet being transferred from the second terminal to the first terminal and a previously generated value stored in the NAT table, the router is configured to generate an IP conntrack comprising a private IP address of the call server as a source address and an address of the first terminal as a destination address, and wherein a source address of the second packet is changed from the private IP address of the call server to a public address of the router.