The task of each layer is to provide service to a higher (higher) layer. Two computers
in the communication between the layers respectively; At the same time, layers at the same level do not directly communicate, but a virtual communication occurs between them.
Figure: Between Two Computers; The relationship between layers real (vertical) and virtual (horizontal)
The data is divided into packets before data is transmitted from one layer to another. The packet is a volume of data used to transfer data from one device to another. Additional information (formatting or addressing) is added to the package in each layer.
The transmission of the data is from the upper layer to the lower layer. Data transmission via cable
by layer. On the other computer, the data that is met by the physical layer first moves to the upper layers.