Broadband Internet connection usage have created increased interest in VoIP and Internet telephony--after all, if an always-on connection to the Internet for a fixed cost is present, it stand to reason that telephone calls over it would be free. Well, no - here's more information:
It's cheaper--and sometimes free
If calling family or friends overseas who also have broadband and VoIP ability, it is a very attractive option. Video-telephony is no extra cost, except for a camera. The quality isn't so much of a concern. Even calling a PSTN phone the costs can still be less if you use VoIP. A subscription, with pay-per-minute costs, to the commercial Internet/PSTN gateway connection and local call cost at the other end.
Is It Good Enough For Business?
The bottom line is what level of quality and reliability you demand for business calls. At this point, VoIP can drop out, not be available for some period of time. Quality can cause jittery, broken or delayed speech in times of congestion. Other ADSL users in your area can affect the VoIP connection depending on how many are on at the same time, or if they are downloading streamed video.
So it comes back to level of service and quality.
The Following Technical Explanation Is Taken Directly From the Telecoms Advice site
So how can vendors demonstrate the high quality systems in operation? Firstly differentiate between VoIP on a local, wide area 'managed', network and Internet telephony over the largely unmanaged (in a prioritised traffic sense) public Internet.
IP, Internet Protocol, allows computers and similar devices with different operating systems to communicate with each other using an 'open' common protocol--a language and way of doing things--rather than their own 'closed' proprietary protocols. It is the basis of the Internet where Windows PCs, Macs, Unix, Linux, PDAs, mobile phones and various other machines and systems can communicate transparently. It has become the networking protocol of choice for local area and wide area networks, becoming intranets and extranets and using Internet developed applications.
Internet Protocol allows for some data packets to be prioritised over others so routers can be configured to recognise certain types of packet, real-time voice or video packets, for example, and give them priority over more 'bursty' data traffic. It doesn't matter if a data transfer is a bit jittery as long as the file eventually arrives within a reasonable time. With recorded streamed audio and video the packets can be buffered and local presentation started when seamless delivery is predicted. But with real-time voice and video telephony buffering would not be appropriate and jittery delivery would mean poor or even unusable quality.
So, on a local or wide area network owned by one company, or several networks run on an agreed commercial basis, standard configuration of routers and prioritisation of voice packets is feasible. But that degree of cooperation on the thousands, if not hundreds of thousands, of networks which makes up the public Internet is some time away.
Voice and data convergence
Now all the above may put you off Internet telephony as your full-time, single-solution telephony service. But the applications enabled by a converged voice and data network over IP are many and varied. The savings made, particularly if new network cabling and hardware is being installed should make a look at VoIP worthwhile. IP handsets can plug directly into a computer or enabled versions through the LAN sockets, and a VoIP gateway from your LAN to the PSTN allows you to utilise the best of both technologies as appropriate.
Internet telephony can be trialed free using Skype