< b="" />Introduction: OSI and TCP/IP Models< />
The OSI (Open Systems Interconnection) model and the TCP/IP (Transmission Control Protocol/Internet Protocol) model are both conceptual frameworks that define how network protocols should function. While the OSI model consists of seven layers, the TCP/IP model comprises four layers. Each layer in both models is responsible for specific tasks and functions.

< b="" />Explanation: Additional Layer in OSI Model< />
The OSI model has three additional layers compared to the TCP/IP model. These three layers are:

< b="" />1. Session Layer:< />
The session layer is the fifth layer in the OSI model and is responsible for establishing, maintaining, and terminating connections between applications. It manages the communication sessions by establishing checkpoints, synchronizing data exchange, and handling session recovery in case of failures. The session layer ensures that data is transmitted securely and reliably by providing services like session establishment, data segmentation, and synchronization.

< b="" />2. Presentation Layer:< />
The presentation layer is the sixth layer in the OSI model and is responsible for data representation, encryption, and compression. It translates data from the application layer into a format that can be understood by the network. The presentation layer also handles data encryption and decryption, ensuring secure transmission across the network. Additionally, it handles data compression and decompression to optimize bandwidth usage.

< b="" />3. Application Layer:< />
The application layer is the seventh and topmost layer in the OSI model. It is responsible for providing network services to end-user applications. This layer interacts directly with software applications and enables communication between different systems. Protocols such as HTTP, FTP, SMTP, and DNS operate at the application layer.

< b="" />Conclusion< />
In comparison to the TCP/IP model, the OSI model includes the additional layers of session, presentation, and application. These layers enhance the functionality of the model by providing services such as session management, data representation, encryption, and network application support.