1. Physical LayerPhysicallayer: Transmission of the original bit stream (BIT)
(1) provide physical channels for data transmission
(2) Data Transmission
Main devices: relay, Hub
2. Data Link LayerDatalinklayer: Establish data link transmission (frame) for adjacent nodes)
(1) establish, maintain, remove, specify the topology of data links, and provide hardware addressing
(2) data frame Group
(3) control the sending and receiving sequence of frames
(4) error detection and recovery. Traffic Control
Main devices: L2 switches and bridges
3. Network LayerNetwork Layer: IP address-based routing data transmission (packet)
(1) Route Selection
(2) congestion control, error detection and recovery
(3) Network Interconnection
Main devices: Routers
4. Transport LayerTransport Layer:Conventional data transmission, connection-oriented or connectionless (Data Segment segment)
(1) Traffic Control
5. Session LayerSession Layer:Establish session relationships
6. Presentation LayerPresentation Layer: Unified Data Transmission Format
(1) data compression and decompression
(2) data encryption and decryption
7. Application LayerApplication Layer: Provides service interfaces for user applications