Chapter 13. The TCP/IP Protocols This chapter introduces the TCP/IP protocol suite, which represents the basis of the popular Internet. Chapter 3 introduced the TCP/IP reference model. The sections in this chapter and the following chapters begin with an introduction of the tasks of each of these protocols and then describe how they operate and how they are implemented in Linux. The history of the Internet and its protocols began in 1961, when Leonard Kleinrock developed packet-switching theory at MIT. His work was based on the idea of splitting data into many small packets and sending them to the destination separately, without specifying the exact path. After initial skepticism, the principle was eventually used in a research project of ARPA (Advanced Research Projects Agency), a division of the United States Department of Defense. In 1968, ARPA granted a budget of more than half a million dollars for a heterogeneous network, which was called ARPANET. In 1969, this experimental network connected the four universities of Los Angeles (UCLA), Santa Barbara (UCSB), Utah, and the Stanford Research Institute (SRI) and expanded very quickly. Later, satellite and cellular links were successfully connected to the ARPANET. In one impressive demonstration, a truck in California was connected with the next university over a radio link and used the satellite network to access a computer based in London, UK. This system was used intensively in the years following. On the basis of the knowledge gained from this system, a second generation of protocols was developed. By 1982, a protocol suite with the two important protocols, TCP and IP, had been specified. Today, the name TCP/IP is used for the entire protocol suite. In 1983, TCP/IP became the standard protocol for the ARPANET. The TCP/IP protocols proved particularly suitable for providing a reliable connection of networks within the continually growing ARPANET. ARPA was very interested in establishing the new protocols and convinced the University of California at Berkeley to integrate the TCP/IP protocols into its widely used Berkeley UNIX operating system. They used the principle of sockets to design applications with network functionality. This helped the TCP/IP protocols to soon become very popular for the exchange of data between applications. In the following years, the ARPANET had grown to a size that made the management of all computers IP addresses in one single file too expensive. As a consequence, the Domain Name Service (DNS) was developed and is used to hide IP addresses behind easy-to-remember computer and domain names. Today, the Internet protocol Version 4 is the most frequently used network-layer protocol. However, it was not designed for such an enormous proliferation and has already hit its capacity limits, so a new version had to be developed. The new Internet Protocol Version 6 is also called IPv6 or IPng. |