Seven frequently asked questions about VoIP
VoIP stands for Voice over Internet Protocol. It is a way of making telephone calls over the internet.
Fairly soon even the telephone network will use the Internet Protocol to send messages. In essence, there will be no distinction between the internet and the telephone system.
Until then, VoIP calls may be free or cheaper than ordinary phone calls.
It works much the same way as the telephone system, except for how the message gets from your handset to the person you are calling.
The phone system sets up an exclusive circuit between you and the person you dial for the duration of the call. (That's why you get an engaged signal when you dial someone who is already on the line.) You speak into a microphone which converts the sound into electrical waves that pass along the wires to the receiver, where they are turned back into sound. With ISDN, a digital telephone technology, the sounds are converted into digital packets but the network sets up the exclusive circuit while the call lasts.
With VoIP, the sounds are converted into packets of digital information, each with the internet address of the person you want to speak to. Devices called network routers (rather than telephone exchanges) send the individual packets around the network using the easiest, quickest route. At their destination, the packets are put back into the correct order and converted back into sound.
Skype is probably what most people think of when they think of VoIP. Although Skype uses VoIP to route data packets, it relies on peer-to-peer links between end users' computers rather than network servers. How it does this is a company secret.
The telecommunications industry is going for an international standard, the Session Initiation Protocol (SIP). This is likely to become the global standard for all digital multimedia calls. Despite its millions of users, Skype will have to coexist with SIP rather than the other way round. But Skype is free, so there's no harm in trying it out.
SIP and Skype both allow this. Under SIP, you will probably pay for the entire call unless it is to a subscriber on the same network as yours. All Skype calls are free as long as they are to other Skype users. Skype charges a small fee for calls to phones outside its family.
E-numbers is this context are not shorthand for permissible food additives.
The internet community is finalising its E-Numbers plan. This will give all VoIP devices a real telephone number that you can call from any other phone.
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Other useful VoIP links
ITSPA: The trade industry website for the Internet Telephony Service Providers Association
Voip-Info.org - a reference site for all things VoIP. A wiki-style website which covers everything to do with VOIP, including software, hardware, service providers, reviews, configurations, standards, tips & tricks and everything else related to voice over IP networks, IP telephony and Internet Telephony.
CommsWatch: A telecoms blog written by Roger Darlington
VoIP Watch: Andy Abramson's VoIP blog
Voice Over Internet Protocol - a US government website that is a great resource
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This was first published in August 2008