VoIP, Voice over Internet Protocol and Internet telephone calls

by Crucible Multimedia

The increased availability and use of broadband Internet connections has created increased interest in VoIP and Internet telephony - after all, if you have an always-on connection to the Internet for a fixed cost then telephone calls over it would be free wouldn't they? Well yes - but.... there is always a but isn't there!

If you are calling your Granma in New Zealand and both you and she have always-on broadband connections to the Internet then Internet telephony is a very feasible and attractive option - even video-telephony at no extra cost (except for buying the cameras)! It doesn't matter too much if the quality of the call falters occasionally. Even if it is just you who has the Internet connection and she has an ordinary PSTN phone service then it is still feasible to make calls from your computer but you will have to subscribe to, and pay per minute for, the commercial Internet/PSTN gateway connection and local call cost at the other end.

Daisy Group plc is a commercial partner of Telecoms Advice, specialising in ip telephony within the business to business telecoms sector.

For a business call the technology would work just as well but would the overall reliability and voice quality be good enough? We have got used to very high reliability and good quality of service (QOS) in the PSTN and traditional telephone systems - what level of non-availability or dropped calls would you accept in you business calls to customers or key suppliers, or between your own managers and staff? 99.9% availability sounds good but that could be one hour every 42 days or one day every three years without a phone service. And what about audio quality - jittery, broken, delayed speech perhaps at times of congestion? If you are using ADSL broadband then you could be sharing a 512kbps connection with 50 residential users or 20 other businesses all with say 10 users - it only takes one user to be downloading streamed audio or video or some other intensive application to slow everything down for everyone.

Vendors can demonstrate high quality VoIP systems in operation so what is the problem. Well first of all we have to differentiate between VoIP on a local or 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 - that is even if the traditional telecoms operators who own much of the infrastructure which carries the Internet want to allow it to cannibalise their traditional PSTN business.

Now all the above may put you off Internet telephony as your full-time, single-solution telephony service, but the applications that are enabled by a converged voice and data network over IP are many and varied, and the savings you may be able to make particularly if you are having new network cabling and hardware installed should make you look at VoIP and a converged voice and data LAN to see what the wider benefits might be. IP handsets can plug directly into a computer or enabled verions 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 trialled free using Skype.

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Reviewed January 2011

last updated : 05/07/2011

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