Introduction
OSI / RM protocol is developed by ISO (International Standardization Organization), which has three basic functions: provide a developer a must, universal concept for development is perfect It can be used to explain the framework for connecting different systems.
OSI divides the computer network architecture to the following seven layers:
Physical layer: convert the data into the handling of the electronic signal transmitted by physical media Worker.
Data Link Link: Decide how to access the network media.
The data is divided on this layer and the stream control is processed. This layer specifies the topology and provides hardware addressing, which is equivalent to unpacking workers in the post office.
Network Layer: Use the right data route is equivalent to the sorting worker in the post office.
Transportation layer: Provides a reliable connection of the terminal to the terminal equivalent to the sending staff of the company's mutual post office.
Conference Layer: Allows users to establish a connection to establish a connection to send a letter, write envelopes and dismantling envelopes.
Repayment: The negotiation data exchange format is equivalent to the company's briefing boss, the assistant written by the boss.
Application layer: The interface between the user's application and the network.
History
In the development of computer network standards, two major international organizations play a major role are: International Telecommunications Alliance Telecom Standardization Department, International Standards Organization (ISO), although they The work is different, but with the development of science and technology, the boundaries between communication and information processing becomes more vague, which has become the field of international telecommunications alliance telecommunications standardization departments and ISO. In 1984, ISO issued a famous ISO / IEC7498 standard, which defines the 7-layer framework of the network interconnection, which is an open system interconnect reference model.
Hierarchical division
According to the recommendation X.200, OSI divides the computer network architecture into the following seven layers, labeled 1 to 7, and the first layer is at the bottom. Now "OSI / RM" is an abbreviation of English "OpenSystemsInterConnectionReference".
Layer 7 Application Layer
Main entry: Application layer
Application layer (ApplicationLayer) provides an interface set to the application to set with another Communication between applications. For example: HTTP, HTTPS, FTP, Telnet, SSH, SMTP, POP3, etc.
Layer 6 Expression Layer
Main entry: Expression layer
Expression layer (PresentationLayer) converts data to compatible with the recipient's system format and suitable Transfer format.
Fifth Layer 5 Session Layer
Main Enterprise: Session Layer
Conference Layer (sessionlayer) is responsible for setting up and maintaining two computers in computer networks in data transfer Communication connection between.
Layer 4 Transport Layer
Main Entry: TransportLayer Adds Transmission Header (TH) to data to form a packet . The transfer header contains sending information such as the protocol used. For example: Transmission Control Protocol (TCP), etc.
Layer 3 Network Layer
Main entry: Networklayer
Network layer (Networklayer) determines the path selection and forwarding of the data, and puts the network header ( NH) Add to the packet to form a packet. The web header contains network data. For example: Internet Protocol (IP), etc..
Layer 2 Data Link Layer
Main entry: Data Link Layer
Data Link Layer (Datalinklayer) Responsible for Network Addressing, Error Detection And let go. When the head and the tail are added to the packet, frames are formed. Data Linksheet Head (DLH) is a method that contains physical addresses and error detection and inclination. Data Link Tail (DLT) is a string indicating the end of the data package. For example, Ethernet, Wireless LAN (Wi-Fi), and General Packet Wireless Service (GPRS), etc.
is divided into two sub-layers: LogicLinkControl, LLC) sublayer and media access control (Mac) sub-layers of MediaAccessControl, Mac.
Layer 1 Physical Layer
Main Items: PhysicalLayer Transport Data Frames (DataFrame) on local LAN, it is responsible for managing Interoperability between computer communication devices and network media. Including pin, voltage, cable specification, hub, repeater, network card, host adapter, etc.
Effects
OSI is a set of well-defined protocol specification, and there are many optional sections to complete similar tasks. It defines the hierarchies, hierarchical relationships between the hierarchies, and the possible tasks included in the layers, as a framework to coordinate and organize the services provided by each layer. The
OSI reference model does not provide a method of implementing, but describes some concepts to coordinate the development of inter-process communication standards. That is, the OSI reference model is not a standard, but a conceptual framework used when setting standards.
See
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DOD model (departmentofdefensemodel) four floors is the model developed by Arpanet.
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Network Transfer Protocol
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TCP / IP, the existing network model with the OSI model has similar structure
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