|  |  | Summary
This chapter began by describing how layers are used for general forms of communication. In this section, you learned that data travels from a source to a destination over media and that a protocol is a formal description of a set of rules and conventions that govern how devices on networks exchange information. Following the discussion on layered communication, you learned that: The OSI reference model is a descriptive network scheme whose standards ensure greater compatibility and interoperability between various types of network technologies. The OSI reference model organizes network functions into seven numbered layers: Layer 7 -The application layer Layer 6 -The presentation layer Layer 5 -The session layer Layer 4 -The transport layer Layer 3 -The network layer Layer 2 -The data link layer Layer 1 -The physical layer Encapsulation is the process in which data is wrapped in a particular protocol header before it is sent across the network. During Peer-to-Peer Communications, each layer's protocol exchanges information, called protocol data units (PDUs), between peer layers. In the last section of the chapter, you learned about the TCP/IP model and it compares to the OSI model. Now that you have a basic understanding of the OSI model, you will start looking at each layer in more depth in the following chapters.