The internet has officially celebrated its 20th birthday.

On 1 January 1983 the Advanced Research Projects Agency Network (Arpanet) of the US Department of Defence - the forerunner of the internet - was switched to the TCP/IP protocol.

This enabled millions of computers to go online instead of the Network Control Protocol (NCP) which limited it to just 1,000 machines.

The TCP/IP protocol was designed by Vinton Cerf and Robert Kahn.

On the mailing list of the Internet Engineering Task Force, internet pioneer Bob Braden wrote: "The most logical date of origin of the internet is 1 January 1983, when the Arpanet officially switched from the NCP protocol to TCP/IP.

"Six months later, the Arpanet was split into the two subnets - Arpanet and Milnet [Military Network] - which were connected by internet gateways.

"There may still be a few remaining T-shirts about that read: 'I Survived the TCP/IP Transition'."

Braden added that some people would be surprised to discover that there were actually a few souls wanting to work on the TCP/IP changeover on 1 January. But they did.