The session layer’s responsibility is to take the services of the transport layer and build a service on top of it that manages user sessions.

As we will see shortly, the transport layer is responsible for transporting session layer messages across the network to the destination. The session layer must manage the mapping of messages delivered by the transport layer to the sessions.

A session is an exchange of information between local applications and remote services on other end systems.

For example, one session spans a customer’s interaction with an e-commerce site whereby they search, browse and select products, then make the payment and logout.

Abstracts: the session layer assumes that connections establishment and packet transportation is handled by the layers below it.