In the mid-1960s the US Department of Defense decided that they wanted a command and control system that could survive attack by nuclear weapons. In order to do this they asked their research arm the Advanced Research Projects Agency to initiate a number of projects which looked at the possibility of using packet switching as a mechanism to connect a number of computers together. This led to the development of a network known as ARPANET which connected a number of universities, research organizations, and defence organizations. The early experiments with ARPANET indicated that the original protocols devised for the network were not adequate and this led to the development of TCP-IP. In order to encourage the use of these protocols a number of development contracts were awarded by ARPA to integrate them into a number of versions of the UNIX operating system. By 1983 there were hundreds of computers connected to ARPANET and the TCP-IP protocol set had become stable. In the late 1970s the US National Science Foundation, the major funding agency for research in the United States, decided to develop their own network which would connect US universities and research establishments. This network, named NSFNet, used the TCP-IP protocol from the start. It was a huge success and was immediately overloaded. In 1991 the US congress passed a bill authorizing the NREN network. This was a successor to NSFNET and was intended to be its gigabit successor. The major growth in the Internet started when ARPANET and NSFNET were connected together. Much of the growth has come from the fact that whole networks, for example the massive internal IBM network, joined the Internet, connecting thousands of computers at one fell swoop. The exponential growth of the Internet meant that the old, ad hoc methods of running it were not really adequate and the Internet Society was born. Commercial involvement in the Internet came in 1990 when a consortium of companies known as ANS took over NFSNET. Since then, a network which was previously mainly confined to researchers and academics has been rapidly commercialized to the point where the vast majority of users are commercial users or home-based users accessing the Internet via Internet service providers. There were a number of other developments which accelerated the growth of the Internet. Almost certainly the most influential was the development of the World Wide Web by Tim Berners-Lee at CERN and the development of the first browser called Mosaic.