Like the age of the Earth or of Hollywood stars, estimates on the age of the Internet depend on whom you ask. By the calculations of one industry pioneer, this week marks the twentieth birthday of the modern Internet. On Jan. 1, 1983, Internet-forerunner ARPANET (a system developed by the US Department of Defense's Advanced Research Projects Agency) fully switched to TCP/IP (Transmission Control Protocol/Internet Protocol). The transition came after a decade of development work on the new system, which replaced an earlier, clunkier setup, the Network Control Protocol (NCP). Transition plans for the NCP-to-TCP/IP move were published in 1981, and some administrators began migrating soon after. But New Year's Day 1983 was the deadline, and one quite a few techies found themselves cramming for, according to Bob Braden, a member of the original ARPA research group that designed TCP. "People sometimes question that any geeks would have been in machine rooms on January 1. Believe it! Some geeks got very little sleep for a few days," Braden wrote in a recent post to an Internet Engineering Task Force mailing list, drawing attention to the twentieth anniversary of the switchover. "There may still be a few remaining T-shirts that read, 'I Survived the TCP/IP Transition'." Of course, an Internet-like system was up and running long before 1983: Since 1969, researchers had been exchanging data over ARPANET, which connected hundreds of host machines at the time of the TCP/IP switchover. But the standardization of TCP/IP laid the groundwork for today's massive, decentralized network. Over on slashdot.org, the Net's water-cooler for tech-news discussions, a link to Braden's note prompted reminisces as well as wisecracks. As one US poster pointed out, "Just one more year, and the Internet can drink! Think of the fun we'll have then!"