【My Study Note】OSI Model
OSI (Open Systems Interconnection) Model
OSI model is important to understand with the five-layer model because it’s the most rigorously defined. That means it’s often used in academic settings or by various network certification organizations.
The OSI model has seven layers, and introduces two additional layers between our transport layer and our application layer. The fifth layer in the OSI model is the session layer.
Session Layer
The concept of a session layer is that it’s responsible for things like facilitating the communication between actual applications and the transport layer.
It’s the part of the operating system that takes the application layer data that’s been unencapsulated from all the layers below it, and hands it off to the next layer in the OSI model, the presentation layer.
Presentation Layer
The presentation layer is responsible for making sure that the unencapsulated application layer data is actually able to be understood by the application in question. This is the part of an operating system that might handle encryption or compression of data.
While these are important concepts to keep in mind, you’ll notice that there isn’t any encapsulation going on. That’s why in our model we lump all of these functions into the application layer.
We believe a five-layer model is the most useful when it comes to the day-to-day business of understanding networking, but the seven-layer OSI model is also prevalent. No networking education would be complete without understanding its basics.