|  | 9.1 | The TCP/IP Protocol Suite
| 9.1.1 |
The Internet TCP/IP protocols and the OSI model
The TCP/IP suite of protocols was developed as part of the research done by the Defense Advanced Research Projects Agency (DARPA). It was originally developed to provide communication through DARPA. Later, TCP/IP was included with the Berkeley Software Distribution of UNIX. Now, TCP/IP is the de facto standard for internetwork communications and serves as the transport protocol for the Internet, enabling millions of computers to communicate globally. This curriculum focuses on TCP/IP for several reasons: TCP/IP is a universally available protocol that you likely will use at work. TCP/IP is a useful reference for understanding other protocols because it includes elements that are representative of other protocols. TCP/IP is important because the router uses it as a configuration tool. The function of the TCP/IP protocol stack, or suite, is the transfer of information from one network device to another. In doing so, it closely maps the OSI reference model in the lower layers, and supports all standard physical and data link protocols. - The layers most closely affected by TCP/IP are Layer 7 (application), Layer 4 (transport), and Layer 3 (network). Included in these layers are other types of protocols with a variety of purposes/functions, all of which are related to the transfer of information. TCP/IP enables communication among any set of interconnected networks and is equally well suited for both LAN and WAN communication. TCP/IP includes not only Layer 3 and 4 specifications (such as IP and TCP), but also specifications for such common applications as e-mail, remote login, terminal emulation, and file transfer.