Webmaster Community at iTalkWebs.com

Voice Over IP, also known as VoIP, is a protocol that in the past few years has revolutionized the world of telecommunications by making it possible to call a landline from your personal computer with programs such as the notorious Skype for a much cheaper price than regular cell or land lines.  But how does it all work?

To understand it, we first need to understand how the plBut how does it all work?ain old telephone network (POTS) operates.In the telephone network, as soon as you finish dialing the number you want to contact, a circuit is established to create a physical, dedicated connection from the caller to the person called. A dedicated connection means that no external unit can interfere with your communication nor interrupt it — the line will be freed again only once the call has finished. However, since in a normal conversation only one person at a time will speak, this translates into a 50% waste of resources. This technique is known as ‘circuit commutation’.

VoIP, on the other hand, doesn’t use circuits, but rather ‘packets’ (small units of information) traveling independently from one another until they reach the common destination. This technology is suitable to transmitting data relative to different, independent transactions over the same cable, and this results in a much more efficient use of the resources available. This technique is known as ‘packet commutation’, which is also the fundamental way in which the Internet works.

Then, what happens when I make a VoIP call? That depends on the kind of call you want to make. If you’re calling from computer to computer, nothing special is really happening because all packets are traveling into the standard Internet: the mechanism is very similar to when you’re watching a video stream on YouTube, that is, data is being buffered for a short time and then played back to the receiver.

If you’re calling from a computer to a landline (or vice versa), though, things get just a little bit more difficult, since you have to pass from packet commutation to circuit commutation (and vice versa, since phone communication travels both ways). The beauty of the protocol is that it doesn’t require any additional hardware or filters of sorts installed on your line for it to work: in a few words, once packets arrive to the last switch that connects them to the phone, they are ’sequentialized’ so to become in a format that is decodable by the landline — the opposite happens when data travels from the phone to the Internet.

One of the drawbacks of VoIP is that quality of service is not always acceptable nor controllable. Internet packets can travel in two different ways, with two main different formats, TCP or UDP: the first is apt to relatively slow but highly reliable transmission, while the latter emphasizes speed but is also prone to errors, which happen much more often than in TCP. VoIP has to use UDP to provide a smooth communication, but this means that data will be sometimes distorted (depending on how congested the network is).

Moreover, the nature of packet commutation relies on packets traveling independently, so this could mean there is no guarantee that they will arrive in the order they were sent. Once again, this problem can be partially solved by buffering data on the receiver side (only if the receiver is a computer with a software apt to provide that function!), but that means additional delays in the conversation are being added.

Even despite these drawbacks, VoIP seems to be gradually affirming because of its lower costs: companies and privates are starting to adopt it to save on their phone bills, while its technology, together with the worldwide adoption of broadband Internet connections, is helping making the quality loss less noticeable.

Tags: pots, skype, voice over ip, voip

(2 votes, average: 5 out of 5)

 Loading ...

This entry was posted on Thursday, May 1st, 2008 at 8:22 pm. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.