TCP/IP Network Model
The TCP/IP network model was developed back in the 1970s and was adopted as the standard network model when the internet was officially launched on January 1, 1983.
Unlike the OSI model, which is a seven-layer model, TCP/IP has four layers, as shown in Figure 1.32:
Figure 1.32: TCP/IP network model
When you compare TCP/IP with the OSI reference model, you will see that the Application layer of TCP/IP combines the role and function of the Application, Presentation, and Session layers of the OSI model. However, the role and function of the Transport layer in both TCP/IP and the OSI models remain the same. The Internet layer of TCP/IP is responsible for the Internet Protocol (IP) and routing, whereas the Network layer of the OSI model encompasses a broader range of Layer 3 protocols. Lastly, the Network Access layer of TCP/IP combines the roles and functions of the Data Link and Physical layers of the OSI model.
Figure 1.33 shows how the layers of the OSI reference model aligned with the layers of TCP/IP:
Figure 1.33: TCP/IP network model
Lastly, keep in mind that TCP/IP is implemented on all network-connected devices, such as your computers, servers, laptops, IoT devices, smartphones, and networking devices. Next, you will learn about the role and function of common networking devices.
