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7 layer OSI Model

The Application Layer

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If you are reading this tutorial then without doubt you have a browser running on which the page is displayed. The browser, I think I am repeating myself but I want to make it very clear, is the application and belong completely to the category called application layer.

It is the user interface the product of all the hula bulla which goes on behind the scenes is displayed on this browser for the user to see. Without a user friendly user interface Internet would be for the geek's and nerds of the world and a normal user would make no sense of it at all. Viewing websites can be accomplished through the use of utilities like Netscape and Internet Explorer, you can also have access to email gateway like mail.yahoo.com through you browser but may users prefer using utilities such as Outlook express which makes life a lot easier when you are inundated by a mails day in and day out. Outlook express of Microsoft would be an example of a Email gateway, again emails work on smtp protocol hence the front end is only used to display the mails and the graphics the connection and the rest would need to be taken care of by the layers below the Session layer.

Well so there it is the Application layer is nothing but the front end of any web based application. It might sometimes be required the the application layer checks for the presence of all the resources available before the application can kick start. For example , when you fire a outlook express application , it checks to determine if the email server (like MSN or Yahoo) is reachable.

Continue to: OSI Presentation Layer