Chapter 15. How Skype and VoIP Work

The Internet has pioneered many new ways to communicate, such as email, live chat, and newsgroups. But it can be used to enable some old-fashioned communication as well: You can make telephone calls using the Internet. When you do so, the sound of your voice and that of the person you're talking to are broken down into packets. Those packets are delivered using the Internet's TCP/IP protocol.

The technique for making a phone call using the Internet is referred to as Voice over Internet Protocol (VoIP), because it uses TCP/IP for delivering voice information.

There are a myriad of ways for using VoIP. In perhaps the most revolutionary technique, you call directly from one computer to another. You don't actually use your telephone with any of them. Instead, you speak into a microphone attached to your computer and listen through speakers and a sound card, or else use a headset or a phone attached to your computer through a USB port.

When you make a computer-to-computer call, you don't actually have to pay for the phone call itself. In addition, you can make calls anywhere in the world, without paying. The only catch is that both parties need to be using the same VoIP software, such as the popular Skype, or VoIP capabilities built into many instant messenger programs such as Yahoo Messenger or America Online Instant Messenger. The software is available for free.

Skype and similar services also allow you to make calls from your PC to landline phones or mobile phones. When you make calls this way, your call mostly travels over the Internet, and only at the end does it enter the normal telephone network. These calls are not free, but they are very inexpensive, especially when compared to international phone rates. Not uncommonly, they are two cents a minute between most places in the world.

VoIP does not have to be used only on computers. Increasingly, the technology is used in concert with special telephone headsets that do not need to be connected to a computer. The popular Vonage service uses this type of technology. With Vonage and similar services, a telephone connects via an Ethernet port to a network connection, such as a cable modem, home router, or corporate network. The call uses TCP/IP to travel over the local network, then through the Internet, and then finally goes to the normal phone network closest to the call location. These calls are less expensive than normal phone calls. Often, a low-cost monthly service includes all phone calls.

VoIP is not only used at homeit increasingly is becoming common at big corporations. The reason is simplecost. A company need not maintain separate telephone and data networks; a single network can handle all calls. And any calls inside the network, including another company location across the world, can be made for free.