The increasing popularity of personal computers changed the basic model of computing in most organizations from a model based on central computing using mainframes or minicomputers with terminals to one based on personal computers connected in local area networks, which in turn were connected to central resources (i.e., the client/server model of computing). The adoption of the personal computer by consumers (which is correlated with the improving price/performance of computers and, in particular, increasing modem speeds at affordable prices) provided the household infrastructure for supporting widespread dial-in access to the Internet by the mid-1990s in the United States.35

To function on the Internet, a computer needs to have some basic information, such as its IP address, the IP address of at least one router,36 and the IP addresses of a few critical services.37 In the world of a relatively small number of large mainframes or minicomputers, such information was entered manually on each new computer when installed and, once configured, rarely changed. In such a world, IP addresses functioned as de facto stable identifiers, with the DNS (or its HOSTS.TXT predecessor) representing a convenience, not a necessity.38

However, as the number of computers increased sharply, such a custom approach became increasingly impractical. Thus, a mechanism to


According to the Current Population Survey (conducted by the U.S. Census Bureau), personal computer adoption in the United States continued to increase throughout the 1990s and demonstrated a 5-fold increase from 1984, the first year data was collected on computer ownership to the year 2000. By the year 2000, 51 percent, or 54 million households, had access to at least one computer at home, up from 36.6 percent in 1997. The percentage of households with Internet access more than doubled between these years, from 18 percent in 1997 to 41.5 percent, or 42 million households, by the year 2000. Computer access and Internet access were becoming synonymous: more than four in five households with computer access also had Internet access. For the full report, see Eric C. Newburger, “Home Computers and Internet Use in the United States: August 2000,” Current Population Reports, U.S. Department of Commerce, U.S. Census Bureau, Washington, D.C., September 2001, available at <http://www.census.gov/prod/2001pubs/p23-207.pdf>.


A router is a device that determines the next Internet Protocol (IP) network point to which a data packet should be forwarded toward its destination. The router is connected to at least two networks and determines which way to send each packet based on its current understanding of the state of the networks to which it is connected. Routers create or maintain a table of the available routes and use this information to determine the best route for a given data packet.


Examples include the address of an e-mail server (because most computers do not operate their own mail server) and the address of a DNS resolver (explained in Chapter 3).


Indeed, the IP addresses of certain important servers were well known to system administrators.

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