Today, I reviewed the network architecture and recorded it for later review.
As shown in the figure, the network architecture is divided into 7 layers:
1. Physical layer: Mainly defines physical equipment standards, such as the interface type of network cable, the interface type of optical fiber, and the transmission rate of various transmission media. Its main role is to transmit the bit stream. The data in this layer is called bits.
2. Data link layer: The data received from the physical layer is mainly encapsulated and decapsulated by the MAC address (the address of the network card). The equipment working at this layer is a switch, and data is transmitted through the switch. The data in this layer is called frame.
3. Network layer: Mainly encapsulate and decapsulate the data received by the lower layer. The device working at this layer is the router. The data at this layer is called a data packet.
4. Transport layer: defines some data transmission protocols and port numbers, such as TCP and UDP. The main purpose is to transmit the data received from the lower layer in segments and reassemble it after reaching the destination address. The data at this level is called a segment.
5. Session layer: Establish a data transmission path through the transport layer. Initiate a conversation or accept a conversation request between systems. (The devices need to know each other, either IP, MAC or host name)
6. Presentation layer: it mainly interprets, encrypts and decrypts received data, compresses and decompresses the received data, and converts what the computer recognizes into something humans can recognize (such as pictures and sounds).
7. Application layer: mainly some terminal applications, such as FTP, WEB, QQ, etc., which can be understood as what we can see on the computer screen.