International Phone Card Review

        Exactly the narrowness of this method
so much extends his possibilities


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Using the Internet, it is possible to exchange digital information. The most known example is an e-mail. Moreover, it is technically possible to digitize and send sound as well. And in this sense, IP-telephony systems use the Internet for sending a fax or a voice between two users of computers in real time.

We can estimate connection quality using the following basic descriptions:
  • Level of distortion of a voice
  • Frequency of disappearing a vocal package
  • Delay length (between pronouncing of a phrase by the first user and moment when it will be heard by the second user).
On the first two characteristics, connection quality was considerably multiplied by comparison to the first versions of IP-telephony systems which assumed distortion and breaking of speech.

The improvement of voice encoding and renewal of the lost packages allowed attaining a level when users understand speech easily enough. The delays influence on the rate of conversation. It is known that the delay to 250 milliseconds is practically unnoticeable for a human. The IP-telephony solutions existing for today exceed this limit. Thus, a talk looks like one with an ordinary public-call network through a satellite. Even in such quality, connections through IP-telephony fully befit for many appendixes, including phone calls for international and domestic destinations with prepaid calling cards.

Except for it, the delays diminish due to the following factors:
  1. Public-call servers are perfected (their developers contest with the delays, improving the work algorithms).
  2. Private (corporate) networks are developing (their proprietors can control the width of key-in bar and sizes of delay).
  3. The Internet is developing. Together with the Internet service providers, the Internet Engineering Task Force (IETF) offers new technologies such as Reservation Protocol (RSVP), which allow reserving the key-in bar.
Although updating routers needs some time, the world of the Internet moves very quickly and in a correct direction.






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