In our last class, we had a brief introduction to the OSI model—the seven-layer model used to help application developers design applications that can run on any type of system or network. Each layer has its special jobs and select responsibilities within the model to ensure that solid, effective communications do occur.
In this tutorial class, you’ll get to know the functions defined at each layer of the upper layer of the OSI model.
The Application Layer
The Application layer of the OSI model is the layer where users actually communicate to the computer. This layer only comes into play when access to the network is going to be needed soon. It’s just like browsing the internet with Internet Explorer or Mozilla Firefox. The browser will respond to requests such as using HTTP by attempting to access the Application layer.
The Application layer acts as an interface between the actual application program and the next layer (presentation layer) by providing ways for the application to send information down through the protocol stack. This means that the browser doesn’t truly reside within the Application layer—it interfaces with Application layer protocols when it needs to deal with resources on the network.
The Application layer is also responsible for identifying and establishing the availability of the intended communication partner and determining whether sufficient resources for the intended communication exist.
The Application layer acts as an interface between the actual application programs. Simply put, applications like Microsoft Word do not reside at the Application layer but instead interfaces with the Application layer protocols, such as FTP and TFTP.
The Presentation Layer
The Presentation layer gets its name from its purpose: It presents data to the Application layer and is responsible for data translation and code formatting.
The Presentation layer ensures that data transferred from the Application layer of one system can be read by the Application layer of another one. The data received from the application layer is translated into a language (code) that the presentation layer understands. Computers receive this generically formatted data and then convert the data back into its native format for actual reading (for example, EBCDIC to ASCII). Data compression, decompression, encryption, and decryption are associated with this layer.
The Session Layer
The Session layer basically keeps different applications’ data separate from other applications’ data. It sets up, manages, and then tears down sessions between Presentation layer entities. This layer also provides dialog control between devices, or nodes.
So, now you know the three upper layers of the OSI model; the application, presentation and session layer and the respective roles they play in information and communication transfer.
In summary, the following services are available at the layers:
• Application layer: File, print, message, database and application services.
• Presentation layer: Data encryption, compression and translation services.
• Session layer: Dialog control.
In our next tutorial class, you’ll get to know the functions defined at each layer of the lower layer of the OSI model.
In this tutorial class, you’ll get to know the functions defined at each layer of the upper layer of the OSI model.
The Application Layer
The Application layer of the OSI model is the layer where users actually communicate to the computer. This layer only comes into play when access to the network is going to be needed soon. It’s just like browsing the internet with Internet Explorer or Mozilla Firefox. The browser will respond to requests such as using HTTP by attempting to access the Application layer.
The Application layer acts as an interface between the actual application program and the next layer (presentation layer) by providing ways for the application to send information down through the protocol stack. This means that the browser doesn’t truly reside within the Application layer—it interfaces with Application layer protocols when it needs to deal with resources on the network.
The Application layer is also responsible for identifying and establishing the availability of the intended communication partner and determining whether sufficient resources for the intended communication exist.
The Application layer acts as an interface between the actual application programs. Simply put, applications like Microsoft Word do not reside at the Application layer but instead interfaces with the Application layer protocols, such as FTP and TFTP.
The Presentation Layer
The Presentation layer gets its name from its purpose: It presents data to the Application layer and is responsible for data translation and code formatting.
The Presentation layer ensures that data transferred from the Application layer of one system can be read by the Application layer of another one. The data received from the application layer is translated into a language (code) that the presentation layer understands. Computers receive this generically formatted data and then convert the data back into its native format for actual reading (for example, EBCDIC to ASCII). Data compression, decompression, encryption, and decryption are associated with this layer.
The Session Layer
The Session layer basically keeps different applications’ data separate from other applications’ data. It sets up, manages, and then tears down sessions between Presentation layer entities. This layer also provides dialog control between devices, or nodes.
So, now you know the three upper layers of the OSI model; the application, presentation and session layer and the respective roles they play in information and communication transfer.
In summary, the following services are available at the layers:
• Application layer: File, print, message, database and application services.
• Presentation layer: Data encryption, compression and translation services.
• Session layer: Dialog control.
In our next tutorial class, you’ll get to know the functions defined at each layer of the lower layer of the OSI model.
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