OSI seven layer model

One 、OSI

Open system interconnection communication reference model （ English ：Open System Interconnection Reference Model, Abbreviation for OSI）, Referred to as OSI Model （OSI model）, A conceptual model , Proposed by the international organization for standardization , A standard framework that attempts to interconnect computers worldwide as networks . Defined in ISO/IEC 7498-1.

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Two 、 Detailed explanation

1. application layer

Can generate network traffic 、 Applications that can interact with users .
for example ,QQ, browser , Video client and other online network communication 、 service .
notes ： Notepad does not generate traffic traffic , So it doesn't belong to the application layer .

2. The presentation layer

The representation of data ： Plaintext 、 encryption 、 Compression etc. . It's a developer's job .
Such as the encoding method of the browser ：

3. The session layer

Session established between service and client ： Check the Trojan horse session netstat -nb. Because the Trojan horse monitors your local computer , And send the data to the external computer remotely .

4. Transport layer

Reliable transmission （ Establish a conversation ）、 Unreliable transmission （ Don't set up a conversation ）、 flow control （ Don't set up a conversation ） etc. .

5、 The network layer

IP Address address 、 Choose the best path .

6、 Data link layer

How to encapsulate data 、 Add physical layer address MAC.

7、 The physical layer

Specified voltage standard 、 Interface standards .

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3、 ... and 、 summary

application layer 、 The presentation layer 、 The session layer , It belongs to the work scope of program developers .
Transport layer 、 The network layer 、 Data link layer , It belongs to the work scope of network engineer .