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However, the Internet has no obligatory hierarchy. Message passing is voluntary. Anyone can use these standards, and multiple connections are encouraged. Consequently, no person or organization owns or runs the Internet, and there is no headquarters or master control. Similarly, rather than get an account on the Internet or connect to the Internet itself, you get an account or connection from one of the organizations or companies that is currently connected to the other organizations that make up the Internet. Most portions of the Internet offer some combination of e-mail; access to the World Wide Web; remote login to any accounts you might have on other parts of the Internet, such as Telnet; and document retrieval, including gopher and FTP (File Transfer Protocol). Traditionally, financial charges at the system-to-system level have been based on the speed of the connection to the Net ("the size of the pipe"), rather than the amount of data exchanged or the distance involved. Individual users at companies and universities usually get their accounts without charge, while users connecting through dial-up Internet Service Providers and online services pay by the hour or month, sometimes paying an extra fee for extensive Web traffic or extra storage space. The current form of the Internet grew out of a project created by the U.S. military to link scientific laboratories and defense installations in a network that would survive an atomic war. Along the way, the Net's development was shaped by the Unix-to-Unix copy system for forwarding electronic mail that became popular in universities in the 1960s. The next stage added links to general users at universities and at the research departments of commercial enterprises. Finally, in the early 1990s, the Internet was opened up to full commercial traffic and open public access through Internet Service Providers.
