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Bharat Kumar

To understand why Net telephony is cheaper, we need to know how it works: When you send e-mail from Nagpur to your cousin in Los Angeles, this is how your e-mail travels: the whole file is broken down into small bits called "packets". These packets choose different routes to reach your cousin's ISP server in LA. Some packets may take the Nagpur-Mumbai-France-Washington-LA route, while the rest may reach LA via Seoul and Tokyo (Remember, the Internet is a network of networks and packets travel across the globe through these networks at will!). At the destination server in LA, the packets are reassembled and your cousin can read the e-mail without trouble.

If data can be sent this way, why not voice? Thus came Net telephony. If the data packets containing your e-mail get jammed at, say, a server in Seoul, the packets that took the Paris route will reach LA earlier but wait for the other packets coming via Seoul. Only then is reassembling done. Till then your cousin does not even know that an e-mail has reached him.

However, with voice, that is not possible. The packets containing, "are you?" may reach before the "How" you started off with! If the conversation waits for all packets to be assembled before the listener can hear the sentence, the delay may become intolerable.

Why is it cheaper? In a "Nagpur-Paris-Washington" route, your ISP has a link to say, Dubai. That pipe jointly belongs to both traffic carriers - one at each end. From Dubai to say, Paris, the two respective carriers own that pipe. Similarly for Paris and Washington. Your ISP may also have a direct tie-up with a pipe provider in the US to avoid delays. The costs are distributed among several entities that have millions of customers.

And if your ISP does not have direct connectivity with Hong Kong, it's okay since the packets could travel to the US, and from the US travel via Paris to Hong Kong.

Whereas, with our good old telephone system, a separate channel must be established between two points that communicate to provide the quality of service that a voice conversation demands.

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