Table of Contents
Application Layer
The application layer of the OSI from its name is quite self-explanatory. This layer sits on top of the OSI network model discussed thus far. Let us now briefly discuss its roles and responsibility to give have a completeness in the understanding of the OSI model.
Let's Drive in...
Most of our day to day network applications rely on the functioning and services of this layer. Thus, the application layer enables the user to achieve a variety of things. The way it works is, the layer acts as an interface to the user. Any input given to the layer is processed and accordingly an action is carried out. This is facilitated by pushing data down through the layers and consecutively receiving a response
Services
Let’s discuss the most common services offered by the layer
File Transfer, access and Management
The most common and interesting service is the file transfer service. Data sharing and manipulation over the network is very common these days and presumably the most used application feature . It enables the user to access remote data (data on another computer) and manipulate it as needed; this includes transfer, manipulation or management. A critical service indeed.
Mail Services
This is the ground basis for all Email related technology. It uses the SMTP protocol that runs on this layer to facilitate the same. The explanation of how these application and services work is beyond the scope of this article and would be covered separately.
Virtual Terminals
Another common application is the virtual terminal. A software that emulates and creates an environment where the user can talk to another remote computer and make it believe that it is talking to its own terminal thus achieving a real time view of the GUI. It is the software version of the real terminal. The user computer talks to the emulated terminal which in turn talks to the host’s terminal which is perceived as its own and thus permits access and control. Another very useful feature.
Directory Services
This service provides access to global information about different services. The common Directory access protocol X.500 sits at this layer ,which helps with fetching relevant data from the database. Similarly X.400 indicates message-handling services.
Other commonly used protocols at this layer are File Transfer Protocol(FTP), DNS, HTTP etc. HTTP as you all know or observed is the most widely used protocol for the connectivity into the World Wide Web.
This summarizes the application layer thus bringing an end to the OSI model.
Thanks for reading!
Reference
Data Communication and Networking by Forouzan
