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College computer network class, the teacher said the commonly used hierarchical structure is 5-storey structure, training video is generally said to be 7 layers, computer network is how to divide the principle of hierarchy and stratification?
hierarchical structure of computer networks:
the so-called Network Architecture (Architecture) is a collection of computer network levels and their protocols. Hierarchies are generally represented by vertical hierarchical models.
1 . The main points of the hierarchy structure:
1) In addition to the actual communication on the physical media, the rest of the peers are virtual communication.
2) The virtual communication of the peer layer must follow the protocol of that layer.
3) N-layer virtual communication is achieved through the service provided by the N-1 layer at the N/n-1 layer interface and the communication of the n-1 layer (usually virtual communication).
2 . The principle of hierarchical structure Division:
1) Each layer of the function should be clear, and is independent of each other. When the specific implementation method of a layer is updated, it will not affect the neighbor as long as the upper and lower interfaces remain unchanged.
2) layer of indirection must be clear, the amount of information across the interface should be as small as possible.
3) The number of layers should be moderate. If the number of layers is too small, the protocol for each layer is too complex, and if the number of layers is too many, the architecture is too complex, making it difficult to describe and implement the functions of each layer.
3, the network architecture is characterized by:
1) function as the basis for dividing the hierarchy.
2) The nth-tier entity can only use the services provided by tier N-1 when implementing its own defined functions.
3) The service provided to tier n+1 by the nth tier includes not only the functionality of the nth tier itself, but also the functionality provided by the downlevel services.
4) There is an interface between adjacent layers only, and the specific implementation details of the service provided are completely shielded from the previous layer.
4. Iso/osi Reference Model
the basic Reference Model for Open Systems Interconnection (interconnection) is a standardized open computer network hierarchy model developed by the International Organization for Standardization (ISO), also known as the ISO s OSI Reference Model. The word "open" means that any two systems that adhere to the reference model and the relevant standards are interconnected.
The OSI includes architecture, service definition, and protocol specification level three abstraction. The OSI architecture defines a seven-tier model for inter-process communication and as a framework to coordinate the formulation of standards for each layer, and the OSI service definition describes the services provided by each layer, as well as the abstraction interface between layers and the service primitives used to interact with each other, and the protocol specifications of the OSI layers. Defines exactly what control information should be sent and what process to interpret the control information.
It should be emphasized that the OSI reference model is not a description of the implementation, but rather a conceptual framework for the development of standard machines. In the OSI, only a variety of protocols are achievable, and devices in the network can be interconnected only if they are consistent with the OSI and related protocols.
The TCP/IP model focuses on related terminology (SDU, PDU, Idu and SAP), comparing the similarities and differences between TCP/IP network architecture and OSI/RM, and osi/rm information flow process.
5 . The system structure of computer network
tiering, protocols, services
6 . Elements of network protocol: grammatical semantic synchronization
7. Architecture of the five-tier protocol (bottom-up):
the physical layer is responsible for transmitting the original binary data on the physical circuit;
The data link layer is mainly responsible for establishing the data link connection between the entities of the communication;
the network layer is mainly responsible for creating the logical link, and realizes the fragmentation and reorganization of the packet, and realizes the functions of congestion control and network interconnection.
Transport layer is responsible for providing users with end-to-end communication services, flow control and error control;
The application layer provides network services for the application.
9.OSI7 Layer System structure
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Dark Horse Programmer---Hierarchical structure and principle of computer network