You should be familiar with the OSI model, because it is the most widely used method for talking about network communications. However, remember that it is only a theoretical model that defines standards for programmers and network administrators, not a model of actual physical layers.
Using the OSI model to discuss networking concepts has the following advantages:
Provides a common language or reference point between network professionals
Divides networking tasks into logical layers for easier comprehension
Allows specialization of features at different levels
Aids in troubleshooting
Promotes standards interoperability between networks and devices
Provides modularity in networking features (developers can change features without changing the entire approach)
However, you must remember the following limitations of the OSI model.
OSI layers are theoretical and do not actually perform real functions.
Industry implementations rarely have a layer-to-layer correspondence with the OSI layers.
Different protocols within the stack perform different functions that help send or receive the overall message.
A particular protocol implementation may not represent every OSI layer (or may spread across multiple layers)