Which of these is not a layer in the OSI model for data communications?

The OSI model for data communications includes seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. Each layer has a specific function and contributes to the overall communication process. However, the Connection Layer is not a layer in the OSI model. The correct term is the Session Layer, which is responsible for establishing, maintaining, and terminating connections between devices. This layer facilitates the coordination of communication sessions and manages session establishment, synchronization, and authentication. Thus, the Connection Layer is not a valid layer in the OSI model for data communications.