In the UK, the telephone area code for cyberspace will be 056.
Fixed phone firms must give access to emergency numbers
Government regulator Ofcom has picked the prefix for customers who sign up to make calls via the internet. Users can also opt for geographic numbers.
The decision on numbers comes as Ofcom reveals how it plans to regulate services that use the net rather than the old fashioned telephone network.
Ofcom says it will use a light touch when regulating voice over net services to help the new market flourish.
"Broadband voice services are a new and emerging market," said Stephen Carter, Ofcom Chief Executive. "Our first task as regulator is to keep out of the way."
Services that route voice calls via the net, using a technology called voice over IP (Voip), are becoming increasingly popular as more and more people sign up for the broadband net services that they piggy back on.
As well as letting people talk via the net, voice over broadband services also let companies offer all kinds of sophisticated message handling options that are much trickier, and expensive, to do with the old-fashioned phone network.
Getting an 056 phone number will also mean that you can use it where-ever you are as long as you are connected to the internet.
Ofcom believes that the move to Voip will be broadly positive and could mean call costs drop sharply because it costs a lot less to offer such services than it does to set up an old-fashioned phone system.
Ofcom has also published a plain-English guide to Voip services to help consumers find out what benefits they could get from these services and what they need to do to sign up.
But as it was announcing the decision to adopt 056 for Voip users, Ofcom also kicked off a consultation period designed to find out what it should do to protect consumers using the new services.
There are a long list of obligations that anyone providing old-fashioned phone services must comply with. Ofcom wants to find out if the same set of obligations should apply to Voip suppliers.
For instance, phone suppliers must guarantee access to 999 emergency numbers and Ofcom wants to see if the same responsibilities should be placed on Voip firms.
The consultation period runs until 15 November.