In this hour, you learned about the layers of the TCP/IP protocol stack and how those layers interrelate. You also learned how the classic TCP/IP model relates to the seven-layer OSI networking model. At each layer in the protocol stack, data is packaged into the form that is most useful to the corresponding layer on the receiving end. This hour discusses the process of encapsulating header information at each protocol layer and outlines the different terms used at each layer to describe the data package. Lastly, you got a quick look at how the TCP/IP protocol system operates from the viewpoint of some of its most important protocols: TCP, UDP, IP, ARP, and RARP.