Thirty-one years after the first internet protocol structure was put in place, the internet is in danger of running out of free IP addresses - according to the man who created the system, Vince Cerf.

Cerf, these days an internet evangelist for Google, says that there are 4.2 billion possible IP addresses, and only around 600 million left. Coupled with the expected explosion in mobile internet use, Cerf predicts that we will run out of IP addresses by early 2010.

IPV6 can provide up to 340 undecilion (340,000,000,000,000,000,000,000,000,000,000,000,000) IP addresses, and Cerf is urging ISPs to inform customers of the upcoming switchover.

"They are persisting in the 'nobody is asking for this' mentality, and are not valuing business continuity as they should," he told The Times.

"When they finally wake up, there is going to be a mad scramble for IPv6 and they won't implement it properly."

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