table of Contents
2. Common network hierarchical model
2. Why network stratification?
1. Network layered structure
1. What is the network?
The network is composed of a number of nodes and links connecting these nodes, representing many objects and their interconnections.
2. Common network hierarchical model
3. TCP/IP four-layer model
Data link layer : The data link layer includes the interface between software and hardware , as well as the hardware of various network devices , that is, the lowest-level infrastructure in the entire network communication process.
Network layer : The network layer is used to process the flow of data packets, that is, if the corresponding data is routed to a designated location , the transmission route is selected for network transmission during communication.
Transport layer : The transport layer provides data transmission between two computers. There are two important protocols in the transport layer, namely TCP and UDP.
Application layer : The application layer determines the application type of this communication (that is, what kind of work this communication is used for), such as FTP, DNS, SMTP, etc. At the same time, the HTTP protocol also belongs to the scope of the application layer
2. Why network stratification?
1. After the network is layered, each layer is independent of each other . A specific layer does not need to know the specific implementation of the next layer, but only needs to know the interface between the layers, so the work of the previous layer does not affect The next level of work. As long as the interface remains unchanged, the functions inside can be adjusted at will.
2. Good flexibility . When a change occurs at any one time, as long as the inter-layer interface relationship remains unchanged, the layers above or below this layer will not be affected. When there is a technological innovation in one layer or a problem occurs in one layer, it will not affect the work of other layers. When troubleshooting, you only need to consider the individual problems of this layer.
3. The structure can be divided . Each layer can be implemented using the most appropriate technology. The development of technology is often asymmetrical, and the hierarchical division effectively avoids the barrel effect, and will not affect the overall work efficiency due to technical imperfections in one aspect.
4. Easy to implement and maintain . This structure makes it easier to implement and debug a large and complex system, because the entire system has been decomposed into several relatively independent subsystems. When debugging and maintenance, each layer can be debugged separately to avoid the situation that the problem is not found or the problem is solved.
5. Can promote standardization work . Because the functions of each layer and the services it provides have been accurately explained. The advantage of standardization is that one of the layers can be replaced at will, which is very convenient for use and scientific research.