Introduction to Voice Over IP

by: Dave Markel

VoIP is probably something you have heard about if you are keen of new computer technologies. VoIP allows telephone calls over the Internet and due to the constantly improving Internet connections it is starting to replace traditional phone networks. VoIP is mainly used by businesses as they are more likely to have access to fast Internet connections, needed by this type of telephony.

Although the initial use of VoIP systems was to allow communication between computer users located in different places, the idea was developed even further and is now on its way to becoming a stand alone telephone network. VoIP has made calling any phone in the world as well as receiving phone calls from users connected to Local Area Networks or the Internet possible.


The idea dates back in 1995 and it was started by an Israeli computer enthusiast who managed to establish the first phone call between two computers. Later that year a software package called Internet Phone Software was developed and released and it was essential for a VoIP connection. VoIP users needed this software, a modem, sound card, microphone and speakers in order to be able to use the Voice over Internet Protocol.

The Internet Phone Software was responsible for the digitalization and compression of the audio signal prior to sending it over the Internet. It was also needed for its decompression and therefore VoIP communications were only possible between people using this software. Due to the fact that the whole system was at its beginnings, the sound quality was very poor and far from that of traditional telephony.

The potential behind this idea was easily understood so the technology was developed further in the following years. Gateways that allowed PC-to-phone connections were established as well as designated VoIP connections later that year. Calls using this protocol were even possible from standard phone sets once the connection had been established from a computer.

The protocol today

Quite a few VoIP services are available today, suiting any type of needs. While some are still computer dependent, phone-to-phone and PC-to-phone services are also available.

Although special USB compatible Internet phones were developed, the computer can be completely bypassed by Internet phones that link directly to a cable or DSL broadband connection via a modem.

The principles behind VoIP

In order to be able to send your voice over the Internet, it has to be transformed into digital data. The digitalization process is called 'sampling' and involves 'breaking' the sound into very small pieces that can be characterized by a number value. After this process has ended, the digital result is compressed and divided into small 1500 bytes packets that will be send over the Internet. Packets contain not only the voice but also data regarding their order needed for a correct reconstruction and data about their origin. Once the packets have reached the destination they will be reconstructed and the resulting digital data will be transformed back into analogue sound and played by the speakers.

A broadband connection is required due to the large amount of data that has to be transmitted over the Internet in a short time to avoid noticeable delays. This is the reason why the system is more popular among companies that already use and can easier afford such connections.