7 Layer Osi Model

The OSI 7 layer model, what it is and what it does

The OSI 7 layer model is a concept that helps represent and show how it is possible for communication to take place on computers and networks. Starting with the lowest layer, or first layer, the names of each level are, physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer.

The highest level, the application layer allows information to interact with other layers of the OSI model as well as direct communication between two separate programs that may be sharing information with each other. It is essentially considered the graphical user interface now a day’s by many since most input that this level is coordinating around originates from a user via the GUI. This layer also has protocols defined that help it to properly clarify what type of data is trying to be sent and viewed, like HTTP, FTP, or Telnet.

The next layer down is the presentation layer; it is responsible for things like encryption/decryption as well as translation and compression. For instance if you were to be on a website purchasing goods, hopefully you would be on an SSL connection when entering your credit/debit card information. The presentation level will take your data and encrypt it prior to the session layer making a connection and being sent out to the transport layer. This layer can also compress and decompress files as well as transform information from the application layer into commonly known formats like avi, mpeg, mp4 etc.

The next layer down would be the session layer which is responsible for creating, maintaining, and terminating sessions. For instance, you logon to the Devry e-college website, you have now created a session with the Devry server on your computer that is kept open until you logout, or in some cases, if a connection is idle for a pre-defined amount of time, meaning no data has been transferred, the connection may be terminated automatically. This...