the OSI LAYERED model from ISO refers to a set of tasks that must be acomplished in order to make the telecommunications system works.
every LAYER groups a susbset of tasks that have things in common. The model is for abstraction, that is right, but every LAYER has well defined task to do. Studying this in function of the tasks helps to understand better the model....
the seven osi layer is a reference to design a network. But nowadays it usually used to understand the basic of the network design and how to troubleshooting. Nowadays we usually use tcp/ip layer. It's more practical than osi layer i quess.
Correct me if i'm wrong. Thanks
The OSI Model is just a reference model for making communication systems work. You can modify it according to your requirements. There is no exact working model as described by OSI. One example which tries to emulate OSI model is the model of TCP/IP. Some layers of OSI are combined to get one layer of TCP/IP.