So starting at the top of the OAS model we have Layer 7 or the application layer.
So we've started layer seven and then work down through the various layers towards Layer 1 the physical
layer layer 7 is once again the application layer and this layer provides a network processes to applications
it provides access for users and application processes to utilize it network services.
This is a layer that a lot of people are familiar with.
Applications such as FTB telnet and HDP are used at this layer.
Please note that when we talk about the application layer we are not talking about individual applications
such as Firefox Chrome or Safari.
We are discussing the application protocol.
In other words HDP which those web browsers use as another example when discussing telnet.
We are not talking about telnet applications such as Patty or terror term or other telnet applications.
We are talking about the protocol telnet.
The same applies to other applications applications such as Firefox Chrome or Safari can function correctly
because the applications are written to work with the HDP protocol.
So we refer to the application being HDP rather than being Firefox.
This layer provides the network services to the application such as Firefox or Chrome or whichever web
browser you're using.
This layer can identify communication partners determine resource availability and provide user authentication.
Another example would be Microsoft Outlook Microsoft Outlook is an application that works with protocols
such as eye map pop 3 and SMP.
Don't worry about the details of the individual protocols such as they seem T.P. or HDP or DP.
What you need to take note of here is that the various applications that you use such as party or Firefox
or Chrome use protocols to communicate with the lower layers of the OS on model.
A few other examples would include remote file access remote printer access resource sharing directory
services and there are many other examples.
So once again the application layer is the window for users and application processes to access and
network resources and services.