VoIP Cookbook: How VoIP Works for Dummies
A overly simplified figure on how VoIP network work is shown in the Figure. The heart of VoIP network is the softswitch. It stores all information on the subscribers. In a simple view, a VoIP softswitch basically has a table mapping the phone number of the subscriber and the computer or IP address of the subscriber.
Everytime, a subscriber wants to make a call to another subscriber. The client equipment will ask the softswitch the destination address of the other subscriber. The destination address can be an IP address. Thus, the softswitch basically store in its table, the phone number of the subscriber and their IP address.
VoIP will be more fun, as we can use IP Phone instead of a computer as subscriber equipment. IP Phone looks similar to normal phone. However, it is much smaller than a computer. Thus, the client equipment may be run 24 hours without consuming too much electricity.
For more advanced user, we may insert an an Analog Telephone Adapter (ATA) into the network. An ATA is another type of client equipment. It may act as gateway between VoIP network and legacy phone network. Thus, anyone on VoIP network may call to the old phone network.