 In 1969, packet-switching technology was introduced in the US Defense Department's ARPANET computer network. Its first node was deployed at the University of California, Los Angeles, in September, with nodes at three more universities by the end of the year. Email was invented by Raymond Tomlinson, who sent the first message between two co-located computers. By 1973, email accounted for some three-quarters of the activity on ARPANET. In France, in 1972, under the leadership of Louis Poisain, development began of a packet-switch network called CICLAD. It showed that hosts could be given the role of delivering data, resulting in a simpler design for packet switches. The transmission control protocol TCP was designed in 1973 by Robert E. Kahn and Vinton G. Surf in the United States. It enabled different packet networks and the computers on them to inter-communicate. The combination with the internet protocol was defined in the name TCP-IP in 1978. Reputedly, the world's first unsolicited email was received by 600 users of ARPANET on 3 May 1978. It came from Gary Turk, a marketing manager for a US computer firm. The domain name system had its first successful test in 1983 with the domain .ARPA. In 1984, seven more generic top-level domains were added, .com, .net, .org, .edu, .gov, .mil and .int. In 1989, at the European Organization for Nuclear Research, CERN, Tim Berners-Lee, working with Robert Cahill, proposed a distributed hypertext system that became known as the World Wide Web. The necessary software was developed in 1990 and, crucially, the system was used not only within CERN, but also made freely available to all. The first widely available web browser, Mosaic, was made public in 1993. Some of its authors produced the browser, Netscape Navigator, in 1994, and soon after, Microsoft used Mosaic as the basis for Internet Explorer. The World Wide Web, a search engine for the World Wide Web, was created in 1993, soon followed by others, including Yahoo, Altavista and Lycos. Google was established in 1998. The first commercial mobile service for Internet access was offered in 1996 by Nokia in Finland. In Japan in 1999, NTT Dokomor launched iMode, a browser-based mobile web service. In 2007, the iPhone created by Apple Inc provided a new type of interface, and Google launched the Android operating system. Online chat rooms began in the mid-1980s and instant messaging was introduced by AOL in the 1990s. Many regional networking sites now exist around the world. In 2006, Facebook had its global opening and Twitter was launched. Image and video sharing websites also took off. Flickr was founded in 2004 and YouTube in 2005. ITU statistics indicate that in 2012 more than a third of the world's population are Internet users and numbers continue to climb.