The difference between the TCP/IP model and the OSI reference model is that the TCP/IP model combines the presentation layer and session layer into the application layer.

When the device encapsulates data, the TCP/IP protocol stack sets a data check mechanism at each layer.

When sending data, a device adds a specific protocol header to the data according to the TCP/IP model. This action is called encapsulation.

When receiving data, the device removes the protocol header according to the TCP/IP model and analyzes the payload information. This action is called decapsulation.