By Mark Ward Technology correspondent, BBC News website

New net domains are regularly being launched

If you created something that is used billions of times every day by millions of people, you might expect it to be around for a long time to come.

Yet Dr Paul Mockapetris, inventor of the net's Domain Name System (DNS), entertains few illusions about the longevity of his creation.

If ever your computer needs help finding out where a. com, .uk or any other website is on the net, the DNS is the system it consults for that address.

"I expect the DNS to be eventually replaced," he told the BBC News website.

"The internet is all perishable technology that is going to get replaced or extended."

Hidden value

Dr Mockapetris originally designed the DNS system to support around 50 million net names.

But numbers have soared. Figures for the exact number of registered domains are hard to come by but a survey in January 2006 showed that there were at least 394 million.

Even this mark of success is not enough to convince Dr Mockapetris that the naming and addressing system has a future.

The future of the internet is ahead of it Paul Mockapetris

"If you want to do work that potentially is going to live forever, work in music or art," he said.

In some respects, said Dr Mockapetris, the DNS is already starting to be hidden from net users.

For instance, he said, many popular e-mail programs hide the exact mail address in favour of a proper name, nickname or shortcut. Rarely do people have to spell out the full mail address which includes the domain where that person's e-mail account is administered.

Similarly, when people use search engines such as Google, navigating to a site is a matter of typing in a keyword and clicking on a link. It almost never requires someone to type in a full domain.

The technology forming the DNS is still in place but fewer and fewer people are encountering it directly, he said.

What is important about the Domain Name System, argues Dr Mockapetris, is not the way it is done now but the central idea behind it.

Spread bet

For him, what helps make the DNS a success and is likely to outlast the technology is the insight that allows a series of databases spread around a network give authoritative answers.

Even mobile phones are getting their own internet domain

In a centralised system, looking up an address involves repeatedly querying a single, authoritative database. Problems with that database mean everything grinds to a halt.

"I was firmly convinced that it was possible to do authority in a different way," said Dr Mockapetris.

By having copies of databases spread around the network and a principle of simply moving on to another if the first one you try does not respond, it is possible to build a very dependable addressing system.

Dr Mockapetris said this reliability will become more important as the net takes its next big step forward.

Reliable system

Moves are afoot to unite the worlds of telephone numbers and e-mail addresses in a system called ENum or the E.164 protocol that should make it much easier to contact someone, provided you have one reliable way of reaching them.

But, said Dr Mockapetris, creating an addressing system for such a unification involves much larger populations than the current DNS supports.

"You have domain name spaces that are very large, such as all of Germany," he said.

They also have to match the kinds of reliability that people expect from the telephone system.

"Telephone companies want never to have to re-start the server," he added.

Huge addressing systems that are reliable enough are now becoming available, said Dr Mockapetris, who is now chairman and chief scientist at Nominum.

Work is starting on unifying the big databases held by cable firms, telephone operators and net service firms.

"I think, long-term, it's going to change hugely. I really believe the future of the internet is ahead of it," he said.