The OSI model is a conceptual framework that divides the network communication process into seven layers, each with a specific function and protocol4.
The session layer is the fifth layer of the OSI model, and it is responsible for establishing, maintaining, and terminating sessions between applications on different devices45.
A session is a logical connection that allows two or more applications to exchange data for a certain period of time5.
For example, when two users on a LAN establish a video call, the session layer coordinates the initiation, synchronization, and termination of the call, using protocols such as SIP (Session Initiation Protocol) or H.32356.
The session layer also provides services such as authentication, authorization, encryption, and checkpointing5.
The other layers of the OSI model have different roles in the network communication process, such as:
The physical layer is the first layer, and it is responsible for transmitting and receiving bits over a physical medium, such as a cable or a wireless signal4.
The transport layer is the fourth layer, and it is responsible for ensuring reliable and error-free data transfer between devices, using protocols such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol)4.
The data link layer is the second layer, and it is responsible for framing and addressing data packets over a local network, using protocols such as Ethernet or Wi-Fi4. Reference:
4: CompTIA Network+ N10-008 Cert Guide, 1st Edition, Chapter 1: Introduction to Networks, pp. 22-29
5: CompTIA Network+ N10-008 Cert Guide, 1st Edition, Chapter 11: Network Services, pp. 443-444
6: CompTIA Network+ N10-008 Cert Guide, 1st Edition, Chapter 11: Network Services, p. 452