OSI-RM and TCP/IP Model Comparison
Figure 13 depicts the relationship between the OSI-RM and the TCP/IP model.
The relationship between these two models at Layers 1, 2, and 3 is identical. While the diagram in Figure 13 shows a one-to-one correspondence at Layer 4, it should be noted that UDP does not perform all of the functions required by the OSI-RM Transport layer; we will explore this fact further in Chapter 7.
The Application layer of the TCP/IP model assumes responsibility for the Session, Presentation, and Application layer of the OSI-RM. This relationship will be detailed further in Chapter 8 and numerous subsequent chapters.
One of the advantages of depicting the TCP/IP model as a five-layer model is that we can refer to Layer 1, 2, and 3 of both models. We will do so throughout this book.
Figure 13 OSI-RM and TCP/IP Comparison