Introduction to OSI reference model

OSI reference model

Introduction: Open System Interconnection (OSI) is an open reference model for interconnection of traffic systems. It is a well-defined protocol specification. The OSI model has a layer-7 structure, and each layer can have several child layers. The top layers, namely Layer 7, layer 6, layer 5, and Layer 4, define the functions of the application. The bottom three layers, namely Layer 3, Layer 2, and Layer 1, are mainly oriented to end-to-end data streams through the network.

7. Application Layer: Provides network service access interfaces for operating systems and applications. Protocol representatives: ftp http snmp telnet, etc.

6. Presentation Layer: Transform upper layer data and information to ensure that application layer information can be understood by another host application (data transformation includes, compression, encryption, and so on)

5 Session Layer: Manages session processes between hosts, such as creating sessions and closing sessions.
4. Transmission Layer: implements data segmentation at the upper layer and achieves end-to-end reliable or unreliable transmission such as TCP and UDP
3. Network Layer: Implements packet routing, such as the IP protocol.
2. data link layer: implements data frame transmission on physical media, such as PPP and frame relay.
1 physical layer: physical media for data transmission, such as RJ45

Introduction to OSI reference model