2) Network interconnection

(open system interconnection / reference model, OSI / RM), from the bottom to the top, there are seven layers of structure, namely, physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer. The name and main functions of the layer specify that the application layer processes network applications to directly serve end users, and provides interfaces of various application processes and data representation of user interface presentation layer so that the application layer can interpret the meaning of data according to its services.