Overview

Introduction: What is VoIP?

Voice over Internet Protocol (VoIP) is the method of routing voice calls over the Internet, or other IP based data networks. In simple terms, this allows a user to call another user over the Internet for free, or for a fraction of the cost of a normal telephone call.

IP Telephony, or VoIP, is one of the fastest growing segments of the computer and telecommunications industry. Its success is inextricably linked with the phenomenal adoption of Transmission Control Protocol ("TCP") / and Internet Protocol ("IP") by the industry as the choice network protocol.

Traditional voice calls require a dedicated (bandwidth 64k) line to be open for the duration of the call and the whole channel is unavailable to any other users, regardless of whether a conversation is in progress or not. Once either caller puts the phone down, the line becomes free and another call can take place on that line.

VoIP eradicates this simple limitation by using packets, rather than circuits. VoIP gateways convert the voice from the originating PSTN network, into a digital signal, allowing it to be sent via an IP network, such as the Internet and 'chops the call up' into packets. By sending the voice in small packets at a time, many simultaneous calls can be sent over the same channel at the same time by the originating gateway. The receiving gateway ( the termination gateway) then re-assembles the packets into the correct order and the call is converted back to an analogue signal and sent to the receiving user - via the traditional local PSTN network. An average VoIP call uses just 8k of bandwidth, so using a 64k line can often handle up to 8 calls simultaneously.

As many organizations have invested heavily in IP networks over the past few years e.g. for web sites, email, Intranets, the basic infrastructure is already in place to make and receive calls over IP. But, as all that is required for simple VoIP is a PC connected to the Internet, over 500 million people world-wide can now exploit this technology

Digital technology is primarily used with new physical media such as fibre optic, leased lines, wireless and satellite transmission.