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The internet could face years of instability as it moves to a new addressing system, one of the network's original architects has warned.

Vint Cerf, one of the fathers of the internet, spoke as the UK was urged to begin using the new addressing system.

With current addresses due to run out in 2012, nations and businesses must get on with switching, said Mr Cerf.

During the switch internet links could become unreliable, making sites and services hard to reach, Mr Cerf said.

"This has to happen or the internet will stop growing or will not be growable," he said of the move to the addressing system.

The net has grown to its current size using version 4 of its addressing scheme (IPv4), which allows for about 4.3 billion addresses.

Estimates suggest that this pool of addresses will be exhausted by the end of January 2012.

A system with a far larger pool of addresses has been created, called IPv6, but progress towards using it has been sluggish.

"The business community needs to understand that this is an infrastructure they are relying on and it needs to change for them to continue to grow and to rely on it," Mr Cerf said.

He criticised global businesses, saying they were "short-sighted" for not making the shift sooner.

"They cannot grow their business if they do not have an address space to grow it into," he added.

The problem of the switchover will be exacerbated, said Mr Cerf, because the two addressing systems are not compatible.

As parts of the internet do eventually convert to IPv6 those trying to get at the parts still on IPv4 may not reach the site, resource or service they were after.

The net would not stop during the switch, said Mr Cerf, but access could get "spotty".

That instability could last years, he suggested, as even search giant Google - his current employer - took three years to get its IPv6 network up and running.

"There's work to be done," he said.

"It's not massive work but it is meticulous work."

Mr Cerf was the keynote speaker at a launch event for 6UK, a non-profit group set up to get UK businesses converting to the new addressing scheme.

Currently only about 1% of data sent over the internet is wrapped in IPv6 packets, said Mr Cerf, adding that moving to using the bigger address space should now be a global priority.

Some nations, such as China and the Czech Republic, had made great strides in using IPv6 but others had not even started.

"There is turbulence coming," said Nigel Titley, chairman of RIPE, the body that hands out Europe's allocation of IPv4 addresses.

He said it was only a matter of time before the shortfall of addresses started to hit business.

Attempts to get more people online, close digital divisions or to boost e-commerce could all be hampered by a lack of addresses, Mr Titley said.

The key to accelerating the shift to IPv6 would be making internet service providers (ISPs) offer the service to their customers, he said, something too few were doing at the moment.

"Sooner or later BT is not going to be able to provision a new broadband customer," said Mr Titley. "That's when the accountants might wake up."