From its early days as a pet project in the Department of Defense to its infamous time nestled under Al Gore's wing, the history of the Internet is littered with dozens of so-called birthdays.

But, as Gore can surely attest, not everyone agrees when they are.

Wednesday is one of those days.

Some historians claim the Internet was born in 1961, when Dr. Leonard Kleinrock first published a paper on packet-switching technology at MIT.

Others cite 1969, when the Department of Defense commissioned the Advanced Research Projects Agency Network, known as ARPANET, to research a communication and command network that could withstand a nuclear attack.

The 1970s boast a slew of what could be pegged essential Internet milestones, including the advent of e-mail and the splintering off of ARPANET from military experiment to public resource.

But perhaps the most famous of the lot is the acclaimed Jan. 1, 1983, switch from Network Control Protocol to Transmission Control Protocol and Internet Protocol.

The transition from NCP to TCP/IP may not have been the sexiest moment in Internet history, but it was a key transition that paved the way for today's Internet.

Call it one small switch for man, but one giant switch for mankind.com.

Protocols are communication standards that allow computers to speak to one another over a network. Just as English speakers of different dialects and accents can often understand one another, protocols provide a lingua franca for all the different kinds of computers that hook into the Internet.

Until that fateful moment 20 years ago, the fewer than 1,000 computers that connected to ARPANET used the primitive Network Control Protocol, which was useful for the small community despite some limitations.

"NCP was sufficient to allow some Internetting to take place," said Kleinrock, now a computer science professor at UCLA. "It was not an elegant solution, but it was a sufficient solution.

"They saw a more general approach was needed."

Indeed, as ARPANET continued its exponential growth into the 1980s, the project's administrators realized they would need a new protocol to accommodate the much larger and more complicated network they foresaw as the Internet's future.

Vint Cerf, who is credited with co-designing the TCP/IP protocol with Robert Kahn, said, "It was designed to be future-proof and to run on any communication system."

The switch was "tremendously important," according to Ronda Hauben, co-author of Netizens: On the History and Impact of Usenet and the Internet.

"It was critical because there was an understanding that the Internet would be made up of lots of different networks," Hauben said. "Somehow the Internet infrastructure had to be managed in a way to accommodate a variety of entities."

But despite the need to take ARPANET to the next level, the decision to switch to TCP/IP was controversial.

Like the current Windows versus Linux debate, there were factions of the community that wanted to adopt different standards, most notably the Open Systems Interconnection protocol.

"A lot of people in the community – even though we had given them six months' to a year's notice – they didn't really take it seriously," Kahn said.

"We had to jam it down their throats," Cerf said.

It was worth the jamming, Hauben said.

"They had the vision," she said. "They understood that this was going to be something substantial, and that's what they provided for in a very special way."

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