1. Position on the seventh floor
The OSI Model Layers from Physical to Application 
https://www.lifewire.com/layers-of-the-osi-model-illustrated-818017 (Foreign website drawing seven-layer model)
2. Simple understanding
OSI Layer 5: Session Layer Functions and Functions_dream_uping's Blog-CSDN Blog_Session Layer Original Link: http://www.hcie.me/203OSI Seven-Layer Model Layer 5: Session Layer, Session LayerOSI Session Layer, Mainly The function is used to manage the session connection of network devices, which is subdivided into three major functions: Establishing a session: Two network devices A and B need to communicate and establish a session for them to use. During the process of establishing a session, there will also be Authentication, authority verification, etc.; Maintaining the session: After the communication session is established, the two communicating parties begin to transfer data. When the data transfer is completed, the OSI session layer will not necessarily immediately transfer the two... https://blog.csdn 
. net/weixin_42859280/article/details/86512490 3. Supplementary knowledge (general review)
Seven-layer network model_ShaYX1991's blog-CSDN blog_Seven-layer network model I saw this seven-layer model again recently. I have never been able to remember this seven-layer model. Even if I memorize it, I will forget it quickly. The main reason is that there is no real usage scenario and the principle cannot be understood. But this thing is the basis of computer network. Since I happen to see it, I will sort it out by the way. A lot of knowledge can be understood through articles, so when it comes to the application of technology in computer development, you can write code; if you write more articles about abstract knowledge, you will naturally understand it. ... https://blog.csdn.net/a369189453/article/details/81193661
4. Agreement
