Copyright 2006 Dave Markel
To make your VoIP (Voice over Internet Protocol) work good enough you need to have broadband internet connection. Internet broadband connections are represented with cable or DSL modems with bandwidth of 56 kbits and higher.
The main idea of VoIP is voice connection using computers. All you need is appropriate software installed on your computer and microphone with a headset or speakers connected. Do not forget that using such software is free and easy to download.
Unlike computer-to-computer calls which are free of charge VoIP software is also used as simple trunk-line. But even so such calls are still cheaper then phone-to-phone ones.
Remember- to make computer-to-computer calls you should run the same software at both sides. But in case of making cellular or land-line call via VoIP no extra software or equipment is needed.
How does it work?
All internet transmissions including VoIP appear to be digital data that travels through the telephone, optical fiber or even satellite lines. To transmit the voice signal VoIP software must convert human (analog) voice to the set of 1s and 0s (digital data). It is done with the help of ADC (analog-to-digital converters) and codecs which compress and decompress (on receive) data to make it more compact during transfer.
Compressed data is divided into packets. Without going into details i can say that these packets consist of the header and the body. Headers contain source and destination addresses and other system data. And the body is the spitted and compressed audio file.
All data transmitted over internet follows the set of rules gathered in the models (OSI, TCP/IP). Models consist of layers that represent particular network function.
Video and audio transmission use the set of protocols originally developed or changed for faster work over the internet. Transport layer in VoIP is usually represented with User Datagram Protocol (UDP). And the application layer is Real-time Transport Protocol (RTP).
Drop of delayed packets is the main advantage of RTP. By doing so the VoIP software skips the delayed packets that must be reassembled and decoded. It is quite preferable because it prevents undesirable pauses in the conversation. Even if the amount of dropped packets is big enough the conversation is still legible. Of course, the better internet connection you possess- the better conversation you'll be having after the remote software will receive, reassemble and decode data into the analog signal (human voice). |
