The Tcpip Protocol Architecture

TCP/IP defines a large collection of protocols that allow computers to communicate. TCP/IP defines the details of each of these protocols inside document called Requests For Comments (RFCs). By implementing the required protocols defined in TCP/IP RFCs, a computer can be relatively confident that it can communicate with other computers that also implement TCP/IP.

An easy comparison can be made between telephones and computers that use TCP/IP. I can go to the store and buy a phone from one of a dozen different vendors. When I get home, I plug the phone in to the wall socket, and it works. The phone vendors know the standards for phones in their country and build their phones to match those standards. Similarly, a computer that implements the standard networking protocols defined by TCP/IP can communicate with other computers that also use the TCP/IP standards.

Like other networking architectures, TCP/IP classifies the various protocols into different categories. Table 2-2 outlines the main categories in the TCP/IP architectural model.

Table 2-2 TCP/IP Architectural Model and Example Protocols

TCP/IP Architecture Layer

Example Protocols







Network interface

Ethernet, Frame Relay

The TCP/IP model represented in column 1 of the table lists the four layers of TCP/IP, and column 2 of the table lists several of the most popular TCP/IP protocols. If someone makes up a new application, the protocols used directly by the application would be considered to be application layer protocols. When the World Wide Web (WWW) was first created, a new application layer protocol was created for the purpose of asking for web pages and receiving the contents of the web pages. Similarly, the network interface layer includes protocols and standards such as Ethernet. If someone makes up a new type of LAN, those protocols would be considered to be a part of the networking interface layer. In the next several sections, you will learn the basics about each of these four layers in the TCP/IP architecture and how they work together.

TCP/IP application layer protocols provide services to the application software running on a computer. The application layer does not define the application itself, but rather it defines services that applications need - like the ability to transfer a file in the case of HTTP. In short, the application layer provides an interface between software running on a computer and the network itself.

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