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Network layer 7 protocol
2022-07-06 13:15:00 【wx5caecf2ed0645】
- The physical layer :
Solve the problem of how to communicate between two hardware , Common physical media are optical fibers 、 cable 、 Repeater, etc . It mainly defines physical equipment standards , Such as the interface type of network cable 、 Interface type of optical fiber 、 Transmission rate of various transmission media, etc .
Its main function is to transmit bitstreams ( Is the 1、0 It's converted into current to transmit , After arriving at the destination, it is transformed into 1、0, That is to say, we often talk about analog-to-digital conversion and analog-to-digital conversion ). The data in this layer is called bit .
- Data link layer :
Because of all kinds of interference in the computer network , Physical links are unreliable . The main function of this layer is : Through various control protocols , Change the physical channel with errors into error free 、 A data link that can reliably transmit data frames .
Its specific work is to receive data in the form of bit stream from the physical layer , And encapsulate it into frames , Send to the next level ; Again , It will also come from the upper data frame , Data in the form of bitstream is forwarded to the physical layer . The data in this layer is called frames .
- The network layer :
If there are multiple computers in the computer network , How to find the one to send ? If there are multiple nodes in the middle , How to choose the path ? That's what routing does .
The main task of this layer is : Through routing algorithm , For message ( The data unit of this layer , Packaged from the upper layer of data ) Select the most appropriate path through the communication subnet . This layer defines IP Address , adopt IP Address addressing , That's why IP agreement .
- Transport layer :
When sending large amounts of data , Packet loss is likely to occur , The other computer wants to tell whether all the packets have been received completely . If there is a lack of , Just tell me which bags are missing , Then send it again , Until all are received .
Simply speaking , The main function of the transport layer is : Monitor the quality of data transmission services , Ensure the correct transmission of messages .
- The session layer :
Although it can be implemented to the right computer , Send the correct encapsulated information . But we can't always call the transport layer protocol to package every time , Then call IP Protocol routing , So we need to set up an automatic receiving and contracting system , Automatic addressing function . So the conversation layer appears : Its role is to establish and manage communication between applications .
- The presentation layer :
The presentation layer is responsible for data format conversion , Convert the information processed by the application into a format suitable for network transmission , Or convert the data from the next layer into a format that the upper layer can process .
- application layer :
The application layer is the computer user , And interfaces between various applications and networks , Its function is to provide services directly to users , Complete all kinds of work that users want to accomplish on the network . Front end students must be the most familiar with the application layer .
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