Explain the two categories ("end-to-end layers" and "chained layers") of the OSI model's seven layers

Question

What will be an ideal response?

Answer 1

With the OSI model, the seven layers can be divided into two categories: end-to-end layers and chained layers. The top four layers are the end-to-end layers: application, presentation, session, and transport. These four layers are "end-to-end" because the layers on the sender's "end" and receiver's "end" directly communicate with each other. The four top layers on each "end" establish a communication. This communication provides an "end-to-end" connectivity. The remaining three lower layers–network, data link, and physical–are the chained layers. These three layers are "chained" in that they are used to link, or chain, one physical device to another in a communication path. The number of devices that need to be linked, or chained, depends on the number of intermediary devices or networks between the sender and receiver of a communication. In a network or enterprise, there may be many intermediary devices or networks between a sender and receiver. The lower three layers provide the chain of links that permits the sender and receiver to have a communication.