Call and connect

Enum, or Telephone Number Mapping, aims to do for phone numbers of any kind what the Domain Name System did for the World Wide Web.

The DNS is a giant distributed directory your computer consults when it does not know the location of a website you want to visit.

The UK's Enum directory will be run by Nominet - which administers the .uk internet domain.

Jay Daley, technology director at Nominet, said the directory would be populated with numbers for the UK's voice over IP (voip) networks that route telephone calls through the net.

Although voip was widely used in business, said Mr Daley, it was typically only used within firms rather than between them.

Before now, he said, it was not easy for the various voip servers of companies or net telephony firms to find each other and connect callers between them.

"That bit of magic is missing," he said. "There's no way for one to find another if it only has a telephone number."

While interconnect agreements did exist between voip suppliers, said Mr Daley, they were ad hoc agreements. Most relied on a caller knowing which voip supplier someone used so they could add extra digits before dialling.

In contrast to that stood the directory systems behind websites and e-mail which will get a person to a website or deliver a message by looking up the domain or address.

Enum, he said, would try to do the same for telephone numbers.

Having an easy way for those networks to interconnect could prompt a boom in net telephony, said Mr Daley adding that the situation was comparable to the moment when mobile phone operators let text messages travel between their networks.

He said: "It's going to change the business model for communication providers quite seriously."

Mr Daley said many other nations, such as Germany, Australia and Ireland, had already started work on their national Enum directories.

Work had also begun to get hi-tech firms, such as voip hardware makers, net service providers and handset makers, to include the Enum technology in their products.

Once those global Enum directories were in place, he said, many other applications were likely to spring up.

Although it was hard to predict, he said, the directories could one day list all the ways that someone can be contacted so calls, e-mails or other messages always get through.

But, said Mr Daley, work would have to be done to ensure that personal privacy is preserved.

"Do I really want people to find out which of my devices I am on at the moment?" he asked "Or which IP address I'm on at any one time?"