1. Physical layer – Deals with physical attachment to communications lines.
2. Data link layer – Provides transfer and control of data over communications lines, error correction, etc.
3. Network layer – Adds destination switching, routing, and relaying functions and presents them independently of the network in use.
4. Transport layer – Provides user-to-user services, including multiplexing, to make the most effective use of network facilities. It enhances the quality of service.
5. Session layer – Controls the dialogue between users and supports synchronisation of their activity.
6. Presentation layer – Allows for the selection of the representation of data, resolving differences between systems.
7. Application layer – Provides the interface to user applications and common services, such as file transfer and terminal support.