Voice Over IP

Taken a look at your company’s telephone
bills lately? What if you could cut down your telephone bills, particularly for
long-distance calls? That is exactly what Voice over IP (VoIP, in short) promises. It uses
your company’s existing computer network and Internet connectivity for voice
communication, instead of using the normal POTS (Plain Old Telephone System) lines. The
network can be a combination of anything, including your LAN/WAN, fiber optic cables,
VSATs, and of course, the Internet, as long as you have IP as one of the protocols.

How Does It Work?
If you have PCs with a sound card, and software like Cool Talk, NetMeeting or Video Phone,
you are ready to get going. If you are connecting over the Internet, you could use
Internet Phone or similar software. The sound card converts the analog input from a
microphone/telephone handset to digital data. The software then compresses, encodes, and
breaks this data into small ‘packets’. These packets are transmitted over an IP network to
the receiving end, where they are put together, decoded, uncompressed to digital form, and
then converted back to analog sound.

On long-distance calls, particularly ISD
calls, you only need to pay for the local calls to your ISP. Similarly, at the other end
also, the called party needs to pay only for a local call. And you are actually talking to
someone half way across the globe! There are many companies, like Micom, who specialize in
providing IP-based telephony services. They have a large set of solutions for easy set-up
and maintenance of such networks.

It Sounds Nice, But What Are The

As with any new technology, VoIP also has some drawbacks. The first and foremost being
that IP is a slightly unreliable protocol when transmitting data over large distances and
involving the Internet. Some of the voice ‘packets’ may get lost or may reach out of order
in which they were sent. With digital data, this does not pose much of a problem, since
the receiving end can always request for the missing data to be sent again and wait for
them to reach before putting all the packets together. With voice, which is real-time,
this cannot be done as the data no longer exists on the sending side either.

There is, however, a solution for this.
Researchers have pointed out that humans need to hear only 80-90 percent of what is said
to be able to reconstruct the whole data. This means some tolerance comes into play
because of the human factor and some missing data is acceptable.

Another problem faced with VoIP is network
congestion. Normal PSTN line carry 8000 bytes per sec. A 28.8 Kbps modem gives around 3000
bytes per sec. When sending voice over this sort of network, there is bound to be a lot of
congestion and distortion. This is one area in which research is still going on.

Legality is another issue faced by VoIP.
Presently in India, sending voice over VSNL’s Internet service is prohibited. However, in
many countries, telephone companies have taken the lead in offering voice over IP

Instead of trying to fight the technology,
phone companies are themselves turning into ISPs to provide these facilities to users. The
day will not be far off when youwill have a smartly dressed sales executive sitting in
front of you, urging you to replace your archaic EPABX with ‘state-of-the-art’ and cheap
Internet telephony!

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