What are the functions of the OSI session layer?

Open Systems Interconnection model represents how the communication takes place. Each layer has a specific function to play within this model.

In case of Session layer, your devices communicates between each other are controlled in this layer. This layer establishes connection in between devices, manages the existing connection and also terminates it. This connection is established in multiple ways. Three most common ways for the connection are - simplex, full duplex and half duplex. Each of these connection types allow you to restart, termination and checkpoint establishment.

As for Presentation layer, ensures that the context between the relevant protocol is maintained. Think of it as HTTP protocol is served when asked for specific query. Just like when FTP protocol is not called and accessed when HTTP is called for. So the semantic part of the layer is managed in the presentation layer. This layer also takes care of the encryption, compression of data packets and decryption.

Transport Layer makes sure that the connection between the service requests are established, managed and maintained between entities.