The Internet's origins in the United States began in the 1960s. The Advanced Research Projects Agency (ARPA) of the Department of Defense was doling out a great deal of research money to universities and other research centers around the country. ARPA quickly realized that having some sort of data network that would connect the various research sites would make it much easier for research scientists and ARPA officials to share information.
A great deal of theory related to packet-switching networks was developed (much of this early research was done at MIT) and then tested by ARPA by the late 1960s. Two issues that were of supreme importance in developing the packet-switching network envisioned by ARPA scientists were the protocol that would provide the rules and transmission scheme for data on the network and the devices that would actually switch the data along a particular path as it moved from a sending to a receiving device.
The development of the hardware switches, called Interface Message Processors (IMPs), actually preceded the finalization of the network host-to-host protocol, and these switches were tested as early as 1969. The IMP was actually the precursor to the router. In 1970 work was completed on the host-to-host protocol that would be used on the ARPA network, now called ARPAnet . This protocol, the Network Control Protocol , was further developed and eventually rehabilitated into the much more robust TCP/IP protocol suite.
The number of computers on the ARPAnet grew rapidly in the 1970s, as the ARPAnet infrastructure was expanded throughout the United States. Networks designed to serve research and higher education institutions such as BITnet (used to send out electronic postings using LISTSERV software), Usenet (a huge electronic bulletin board full of newsgroups, still in use today and discussed in this chapter), and NSFnet (developed by the National Science Foundation) were developed, thus further expanding the range and number of devices on the packet-switching network that began as ARPAnet.
With the expansion of the Internet backbone by for-profit companies beyond the infrastructure built for educational and research facilities, the Internet has become as integral to business and personal communication as the telephone. You would have to go a long way to find a company of any size without a connection to, and a presence (a Web site) on, the Internet. The number of home connections to the Internet is growing daily at a very rapid pace worldwide.
On a personal level, most people use the Internet to send and receive email and to browse information on the World Wide Web. As far as companies and institutions go, email is also important to corporate communications, as is the presence of companies on the Web.
One thing you should keep in mind as you read through the information in this chapter is that the technology developed to make the Internet a reality is also often used on private networks that do not allow public access. This use of Internet protocols and Internet technology to provide networking services on a private network creates what is called an intranet . Therefore, an intranet would be the private equivalent of what we see on the public Internet. A company simply uses the TCP/IP protocol, Web servers, FTP servers, and other Internet technologies to exchange information on the corporate network.
Let's take a look at some of the different Internet services available, such as FTP and the Web. We can then take a look at some of the other onramps to the Internet, which can also be used for data communication.