You Are The System Administrator For A Large Network

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The Application layer is the topmost layer of the OSI model, and it provides services that directly support user applications, such as database access, email, and file transfers. It also allows applications to communicate with applications on other computers as though they were on the same computer. When a programmer writes an application that uses network services, this is the layer the application will access. For example, Internet Explorer uses CCNA Certification
the Application layer to make its requests for files and web pages; the Application layer then passes those requests down the stack, with each succeeding layer doing its job (as in Figure 1.9).

The Application layer is where the applications function, using lower levels to get their work done.

When a message is sent from one machine to another, it travels down the layers on one machine and then up the layers on the other machine, as shown in Figure 1.10.

As the message travels down the first stack, each layer it passes through (except the Physical layer) adds a header. These headers contain pieces ...
... of control information that are read and processed by the corresponding layer on the receiving stack. As the message travels up the stack of the other machine, each layer removes the header added by its peer layer and uses the information it finds to figure out what to do with the message contents (see Figure 1.11).

How Microsoft’s Network Components Work with the OSI Model

Because the OSI model is so abstract, it can be Mcsa Exams
hard to tell how its concepts relate to the actual network software and hardware you use in the real world. The following sections will make the link clearer. We will introduce you to some network protocols and show how they apply to the various layers of the OSI model.

In the following sections, we will discuss some protocols that Microsoft Windows Server 2008 no longer supports. We will talk about some of these protocols to help give you a wider range of networking knowledge and to help explain some of the networking concepts in previous Microsoft Windows Server versions.