Which layers of the OSI model do not exist in the current TCP/IP model?

The layers of the OSI model that do not exist in the current TCP/IP model are the Session and Presentation Layers. In the TCP/IP model, functionality typically associated with these layers is integrated into the Application Layer.

The Session Layer is responsible for establishing, maintaining, and terminating sessions between applications, while the Presentation Layer is responsible for data translation and formatting, ensuring that data is presented in a readable format for the application. In the TCP/IP model, these responsibilities are mostly handled by the Application Layer, which can implement session and presentation functions as needed without the need for dedicated layers.

This consolidation into the Application Layer simplifies the model and reflects the practical use of TCP/IP in networking environments, where the distinction between session management and data presentation can often be managed within the applications themselves.