How VoIP Works

Definition of VoIP

VoIP stands for Voice over Internet Protocol. It is today’s digital substitute for the analog telephone communications that have been in use for the past century. VoIP calls are made using an Internet connection instead of the dedicated communications lines of a telecommunications carrier. VoIP can be set up to allow communication with anyone with a telephone, including those with telephone numbers that may be wireless, local, national or international.

Switching Networks

Analog telephone systems are based on circuit-switching networks; VoIP telephone systems are based on packet-switching networks. In both analog and VoIP telephone systems, the sound waves of your voice are picked up by a telephone handset or computer microphone and changed to an electrical signal. Analog systems maintain that signal as a continuous stream; the computer on which the VoIP software runs breaks that signal into digital packets.

How Packet Switching Works

Here are the steps that occur with packet switching:

  1. The sending computer places on each digital packet a header that contains the IP address of the receiving computer and instructions for reassembling the packet back into a whole.
  2. The sending computer sends all the packets to the router by which the sending computer accesses the Internet.
  3. That router sends the packets on to another router whose IP address is determined by the rules of the network protocols to be closer to the recipient’s IP address.
  4. That router sends the packets on to another router closer to the recipient, the path set according to a dynamic network routing protocol that picks the least congested path at the time.
  5. All the packets eventually arrive at the router that handles the recipient’s IP address and are delivered to the recipient computer.
  6. The recipient computer uses the information contained in the header of each packet to reassemble the original electrical signal generated via the sender’s telephone handset or computer microphone.
  7. The electrical signal is converted back to sound waves.

Using VoIP

All the packet switching steps above are transparent to a VoIP caller and the recipient of a VoIP call. Also, using VoIP does not restrict the caller to only making calls to other VoIP users. If a caller’s VoIP service allows assignment of a telephone number, then a VoIP setup can also receive calls from anyone. A company offering VoIP services may also provide services not available on analog systems.