Defining Networks with the OSI Model
Crystal Panek · 2019
This chapter defines each of the Open Systems Interconnection reference model (OSI model) layers using hands-on labs and theory. The OSI model is a reference model used to define how data communications occur on computer networks. It is divided into layers that provide services to the layers above and below. These layers are associated with protocols and devices. The OSI model was created and ratified by the International Organization for Standardization (ISO), and is represented in the United States by the American National Standards Institute (ANSI). The OSI model was created as a set of seven layers, or levels, each of which houses different protocols within one of several protocol suites, the most common of which is TCP/IP. The OSI model categorizes how TCP/IP transactions occur. It is invaluable when it comes to installing, configuring, maintaining, and, especially, troubleshooting networks. Sometimes, a protocol suite such as TCP/IP is referred to as a protocol stack. The OSI model shows how a protocol stack works on different levels of transmission (that is, how it stacks up against the model). Because it is the most tangible, let's start with the Physical layer. Later, when you view the model, it will be from the seventh layer on top to the first layer on bottom. As mentioned previously, a LAN requires computers with network adapters. These must be connected in some way to facilitate the transfer of data.