In the earlier days, the voice data was typically carried over the public switched telephone network (PSTN), which consisted of telephone lines, fiber optic cables, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by switching centers. The arrival of the Internet added another dimension to the movement of voice from one part of the globe to another. In an Internet Protocol-based network (IP network) data packets (containing, for instance, voice, video, etc.) are used to communicate between two nodes. To connect diverse networks like the PSTN and an IP-based network, “gateways” have been developed that as links between them. A gateway is a network point that acts as an entrance to another network.