Internet telephony – What is it and how does it work?

The terms IP telephony (IP = Internet Protocol) and Voice over IP (in short: VoIP) refer to making telephone calls via a computer network, whereby the data is transferred according to the IP Standard. This form of telephony is better known as internet telephony. It is necessary to prepare data for transfer via the internet to comply with the rules of the Internet Protocol. The transfer routes used here are the same as those employed for standard data transferral via the internet.

With internet telephony from NFON it is possible to integrate Unified Communication (UC) as well as fax solutions via XCAPI.

Internet telephony hardware

In order to use internet telephony one requires the appropriate hardware. Four different alternatives are available here. The first option is to use a standard computer with microphone for user voice capturing, as well as a loudspeaker or headphones in order to listen to the conversation participants. Added to this comes the application and installation of special software on the PC. Secondly, it is possible to use specific VoIP end devices as well as IP and SIP telephones. These only differ from a standard telephone in terms of the technology that enables the data transfer via the internet. As a further option it is possible to use the conventional telephone and connect this to a special adapter, which converts the analogue telephone data into digital signals. Finally, it is also possible to use a mobile phone by connecting through the telephone system via an FMC client. The advantage of the last three options lies in the operation of the device, which can be used in the same way as a conventional telephone. A further benefit is that the user is also attainable when the PC is switched off.

How VoIP works

First, the acoustic signals are digitalised during the data transfer, and divided up into individual data packages. These data packages are subsequently labelled with a so-called header. These headers contain information about the identity of the sender and recipient, or regarding the status of the message. It is now necessary to establish a connection. To do so one uses a Session Initiation Protocol Address (in short: SIP address). This is only assigned once, so that it is possible to uniquely identify the address. Activating the device results in this logging into a server. The server then registers the login. If this SIP address is called up by another participant then this request is passed on to the server that the user is registered with. The server passes the call on to the end device and therefore establishes a telephone conversation. Because the SIP address is not bound to a certain connection - in the manner of a standard telephone number - the user is connected with the internet by means of the corresponding end device and is therefore attainable anywhere in the world. It is now also possible to connect internet telephony with the standard telephone network. This takes place via certain gateways. This provides the user with the option of using a conventional telephone in order to call a VoIP telephone and vice versa. The so-called Media Gateway can be used for example with an ISDN connection or likewise with an analogue telephone connection.

The advantages of VoIP

The first noteworthy advantage here is that internet telephony is a particularly low-cost option, because almost every household has flat rate internet nowadays. Therefore, no further costs arise because IP telephony simply accesses this. This means that the standard telephone connection is superfluous and can even be removed. The costs of the individual telephone calls are usually also lower here than with analogue telephony. Telephone conversations with participants using the same VoIP provider are usually free of charge. It is also often the case that calling participants using alternative VoIP providers is also free; only in a few cases are fees charged here. However, calls placed within the standard telephone network are always subject to charges, although these are very low with many providers.