TCP/ IP

Internetworking with TCP/IP has been around for many years-almost as many years as Unix has been available. TCP/IP, orTransmission Control Protocol/Internet Protocol, grew out of the work that was done with the Defense Advanced Research Projects Agency, or DARPA. In 1969, DARPA sponsored a project that became known as the ARPANET. This network mainly provided high-bandwidth connectivity between the major computing sites in government, educational, and research laboratories.

The ARPANET provided those users with the ability to transfer e-mail and files from one site to another, while DARPA provided the research funding for the entire project. Through the evolution of the project, it became clear that a wide range of benefits and advantages were available, and that it was possible to provide cross-country network links.

During the 1970s, DARPA continued to fund and encourage research on the ARPANET, which consisted chiefly of point-to-point leased line interconnections. DARPA also started pushing for research into alternate forms of communication links, such as satellites and radio. It was during this time that the framework for a common set of networking technologies started to form. The result was TCP/IP. In an attempt to increase acceptance and use of these protocols, DARPA provided a low-cost implementation of them to the user community. This implementation was targeted chiefly at the University of California at Berkeley's BSD Unix implementation.

DARPA funded the creation of the company Bolt Beranek and Newman Inc. (BBN) to develop the implementation of TCP/IP on BSD Unix. This development project came at the time when many sites were in the process of adopting and developing local area network technologies, which were based closely on extensions of the previous single computer environments that were already in use. By January 1983, all the computers connected to the ARPANET were running the new TCP/IP protocols. In addition, many sites that were not connected to the ARPANET also were using the TCP/IP protocols.

Because the ARPANET generally was limited to a select group of government departments and agencies, the National Science Foundation created the NSFNet that also was using the successful ARPANET protocols. This network, which in some ways was an extension of the ARPANET, consisted of a backbone network connecting all the super-computer centers within the United States and a series of smaller networks that were then connected to the NSFNet backbone.

Because of the approaches taken with NSFNet, numerous network topologies are available, and TCP/IP is not restricted to any single one. This means that TCP/IP can run on token ring, Ethernet and other bus topologies, point-to-point leased lines, and more. However, TCP/IP has been closely linked with Ethernet-so much so that the two were used almost interchangeably. Since that time, the use of TCP/IP has increased at a phenomenal rate, and the number of connections to the Internet, or this global network of networks, has also increased at an almost exponential rate. A countless number of people are making a living off the Internet, and with the current trends in information dissemination, it likely will touch the lives of every person in the developed world at some time.

TCP/IP, however, is not a single protocol. In fact, it consists of a number of protocols, each providing some very specific services. The remainder of this chapter examines how addressing is performed in TCP/IP, network configuration, the files controlling how TCP/IP can be used, and many of the various administrative commands and daemons.