VoIP or Voice over Internet Protocol or Voice over IP is a technology of delivering (or sending) audio and voice data packets over Internet Protocol (IP), for example the Internet. VoIP allows people to make a long distance call, bypassing most or all of their provider’s charges. Voice over broadband (VoBB), broadband phone, broadband telephony, Internet telephony and IP telephony are the synonyms of VoIP.
Alon Cohen and Lior Haramaty, co-founders of Israeli company, VocalTec, introduced the first VoIP software. Internet Phone was the name of that software, which used the H.323 Protocol. This software was able to handle packet data loss and reordering them, but the quality of voice was not so good as compared to a telephone call, due to the lack of broadband availability. In 1998, there were several companies offering computer to phone service. Till 2000, VoIP traffic covered 3 % of voice traffic. The use of VoIP has been increased rapidly from the year 2000 to date.
The growth of VoIP technology really exploded when hardware companies like Cisco and Nortel started producing equipment for switching. As the cost of this hardware became less, companies began using VoIP over their IP Network. This technology has changed the face of communications.
Many computer users use Microphone to record a human voice in a sound file, these sound files are stored on the computer. Sound files are created by sampling the sound at a very high rate (about 8000 times per second); each sample of sound containing tiny bit of human voice. VoIP uses the same idea, but instead of storing a sound file on the computer, it transmits the sound files in a form of packets over the Internet Protocol (IP) network.
Human voice or voice signal is converted from analog form to digital form, so that it can be transmitted through fiber optic cables with a transmission speed of 16 kbps or more in a binary form. Circuit or Path is used for transmitting the data over a complex network. The devices which make the path are called nodes like switches, routers or any other network devices.
VoIP uses a packet-switching circuit for transmission of voice data over the IP network. Before transmission of data over the Internet, TCP/IP breaks the data into small pieces, these pieces are called packets, sometimes referred as segment or datagram. These packets contain the information about the source and destination IP address, number of bits, sequence number, starting and ending bit etc., so that it can be easily reassembled at the destination. In packet-switching, packets are transmitted over the IP network as they are generated.
Working of packet-switching involves the following steps–
a) The computer breaks the data into the small packets.
b) Each packet contains the destination IP address and the information about file being transmitted.
c) These packets are then transmitted to the router; at this point, the router starts its work.
d) The router checks the destination IP address, whether the receiver is connected to it or not, if not then it sends the packets to another router. This process is continuing until all the packets are delivered.
e) When all the packets are delivered, the receiver reassembles the packets into the original file using the information given in the packet.
Each Packet takes the shortest route to reach at the destination address; there is no predetermined route or path. Packets are sometime delayed or lost, due to any network problem. Such packets are discarded, as it was never received. There are many methods or algorithm available to detect or rectify the packet loss.