The current development on telecommunications industry is changing the use of
telecommunications networks remarkably. People use telephone lines more and more
for data transfer instead of ordinary voice calls. At the moment the data
traffic is estimated to be equal to voice traffic but the estimate by the year
2001 is that the data traffic will be one hundred times greater than voice
IP telephony, or voice over IP, means that voice and fax calls are
transmitted over an IP network such as the Internet, rather than over the
familiar public switched telephone network (PSTN). During the last three years
IP telephony has become a hot topic. Five years ago IP telephony was virtually
unknown technology but at the moment it seems that IP telephony will
revolutionize voice call business and technology used to transport voice calls.
Since access to the Internet is available at local phone connection rates, an
international or other long distance call will be much less expensive than
through the traditional call arrangement.
On the Internet, three new services are now or will soon be available:
The ability to make a normal voice phone call (whether or not the callee is
immediately available; that is, the phone will ring at the location of the
The ability to send faxes at very low cost (at local call prices) through a
gateway point on the Internet in major cities.
The ability to leave voice mail to a called number.
There were research activities of transmission of voice signals over packet
networks in the late 70's and early 80's. In the late 70's there was discussion
and experiments with packetized voice over ARPANET, the predecessor of the
Internet using IP and specialized coding and packetizing equipment .
The real development in IP telephony started in 1995. VocalTec pioneered the IP
telephony market in 1995 with PC software which opened a voice connection
between two PCs over IP-based network. The product was ideally suited for the
Internet. After that, several other competing software packages were launched
consecutively. In 1996 first internetworking trials between IP network and PSTN
were made. In 1997 the Delta Three launched the first phone to phone service for
The development of IP telephony is summarized in the following :
1995 - The year of the Hobbyist
1996 - The year of the IP Telephony Client
1997 - The year of the Gateway
1998 - The year of the Gatekeeper
1999 - The year of the Application
In the beginning of the next millennium IP telephony will be used over mobile
IP network such as GPRS (General Packet Radio Service) or UMTS (Universal Mobile
Telecommunications System). This is an opportunity to the new mobile telephony
operators because they do not have to build separate networks or parts of
networks for voice and data. It also offers opportunities for new mobile
Advantages of IP telephony include lower cost long distance call
and reduced access
charges, more efficient backbones and compelling new services. The benefits of
shifting traditional voice onto packet networks can be reaped by businesses,
Internet Service Providers (ISP), traditional carriers etc. Business benefits
from IP telephony because it takes advantages of existing data networks,
reducing operating costs by managing only one network and enables them to enjoy
almost-toll quality voice.
The communication industry is going through a period of explosive change.
Data is becoming a more significant proportion of traffic compared to voice. IP
is today considered the most promising platform on which to build new services.
IP telephony service shapes the Internet for real-time services.
PC to PC
PC to Phone
Phone to Phone
IP telephony can be used in three basic situations: PC to
PC, PC to phone (and vice versa) and phone to phone. IP
telephony market is growing very rapidly at the moment. The prices of IP
telephony call are essentially lower than in PSTNs.