What is IP-telephony and how does it work?


Operators of mobile and fixed communication usually offer their users attractive conditions for calls «inside the network», but when it comes to communication with distant cities and foreign countries, the cost of such services can seriously damage the wallet. However, the solution to this problem has long existed, and it is called «IP-telephony».

This is a technology of voice communication, in which computer networks, network communication protocols and special technological methods are used for conversations. In simple words, the Internet (or a local network, for communication within the company or enterprise) is used to make calls, which makes their cost significantly smaller.

History of IP-telephony development

The date of the first appearance of technology can be considered 1993. It was then that the American Charlie Klein created a unique program of his kind called Maven, which allowed to broadcast voice over the Internet without delays. In 1994, Maven implemented in one of the first CU-SeeMe video communications programs from Macintosh and successfully implemented a joint project with NASA to broadcast audio and video during the flight of the space shuttle Endeavor.

In 1995, VocalTec entered the global consumer market with the Internet Phone for Windows application. Thanks to the use of all the advanced technologies at that time (conversion of digital signals, use of codecs and routing protocols), the level of delays and quality loss has significantly decreased. The rest of the companies immediately evaluated the market’s prospects and began working on their own analogues.

1996 is considered the official birthday of IP-telephony. VocalTec together with Dialogic (a major manufacturer of software for telephony on PC) launched a truly revolutionary project — Internet Telephone Gateway. Their goal was to combine conventional phones with the ability to make calls over IP networks. The success of the idea is evidenced by the fact that a year later the use of this technology on standard phones has become a common thing.

It is noteworthy that Russia was one of the first countries in which the gateway for IP-telephony was put into operation. It happened in November 1996.

Major definitions

When it goes about IP telephony, terms are often used, which may not be particularly understandable for the average person. Let’s figure it out together.

  • Gateway is a device that is an «intermediary» between a telephone line and a computer network, that is, it performs the function of pairing them.
  • IP-networks — a system of interconnected subnets, providing the interaction of autonomous systems, which in turn are combined with the help of routers.
  • VoIP is a technology for voice transfer over the Internet and / or computer networks. The definition is very similar to IP telephony, but the key difference is the fact that in VoIP, data transmission does not need to be connected with people’s communication. That is, VoIP can be used, for example, for video surveillance, online broadcasts on the Internet, etc.
  • SIP is a session management protocol that supports voice, multimedia, instant text messages, and the like. In VoIP, it can be responsible for connecting and disconnecting subscribers, as well as responding to changes in real time (for example, including redirection).

Principles of IP Telephony

In traditional telephone communication, where the only purpose is to talk directly between subscribers, a special telephone exchange is responsible for the connection. That is, there is a dedicated connection, through which the voice is transmitted over the telephone line. However, voice communication over the Internet works differently.

First of all, the telephone signal is transmitted to the gateway. If the signal is not digital, then the process of digitizing it is mandatory. After that, the data is compressed, divided into packets and transmitted to the endpoint using the TCP / IP protocol. At this point, IP packets are decoded so that the recipient subscriber can hear the original signal (voice).

All operations occur almost simultaneously, because users do not notice any delays or interrupts of sound. However, there are also bad providers, who still have similar problems. The quality of communication also depends on the speed and reliability of connecting users to the Internet.

Depending on the method of communication, IP-telephony can be divided into the following types:

  • Computer-to-computer is the simplest option, which requires a special program (Skype, SIPNET, etc.) and a working headset for the computer;
  • Computer-phone — almost no difference from the previous method, except that one of the subscribers is not tied to the computer — he uses a regular phone;
  • Phone-to-phone — except for individual services, the service of IP-telephony is not neglected even by ordinary cellular operators, which helps reduce the cost of calls;
  • Surf & Call — ability to make calls directly from the site, which is often used in commercial companies.

Advantages of IP-telephony

The main advantage is that such a link is profitable in financial terms. And both for ordinary subscribers, and for large operators. Technologies of voice packets compression allow to use the power of telephone lines optimally and without unnecessary loads, and the globalization of Internet access constantly increases the range of potential users of the service.

To date, it is possible to connect IP-telephony to its usual number (fixed or mobile). This service is increasingly at the level of telecom operators. In addition, encryption protocols ensure high security of voice traffic.

Internet telephony is often used in corporate networks. In this case, the communication functionality lends itself to flexible settings and constant improvements. Finally, thanks to this connection, you can call without leaving your computer, which can be a very significant factor for business people.

Our service uses a hybrid technology, which uses both telephone and cellular lines, and IP-telephony. The telephone signal is transmitted between the countries via the main Internet channels, and to them is delivered via telephone communication. This completely removes the dependence on the quality of the connection to the Internet and in some cases helps to avoid additional costs. You can use the service with almost any phone.