OSI seven-layer model

ISO: International Organization for Standardization

OSI: Open Systems Interconnection model

iOS: In a computer network, iOS is the Internet operating system and is the operating maintenance system developed by Cisco for its network equipment

Seven-layer model introduction

1-7: Physical Layer--Data link layer--network layer--Transport Layer--session layer--presentation layer--Application layer

Data unit: Bit--frame--Message--TPDU--SPDU--PPDU--APDU

The most important information saved in the frame is the hardware MAC address of the network card, and the MAC address is responsible for LAN communication

The most important information stored in the message is the IP address, the IP address is responsible for the external network communication

The data unit of the transport layer is the segment, TPDU is the Transport Protocol data Unit

SPDU is a session protocol data unit

PPDU is the presentation Layer Protocol data Unit

APDU is the Application Protocol data unit

Tiering for easy management of data

Data is sent from the upper layer (7) to the lower layer (1), and then passed through the physical layer to the other side, when received from the lower layer to the upper layer

Layer 5-7 is used to provide services to users

1-4-tier service for actual data transfer

Seven-layer model action

Physical layer: The transmission of bitstream between devices, physical interface, electrical characteristics, etc. (8 network cable, 13,264 cable is responsible for transmitting data)

Data Link layer: Framing, Access media with MAC address, error detection and remediation

Network layer: Provides logical (IP) address, routing

Transport layer: reliable and unreliable transmission (TCP\UDP protocol), error detection before transmission, flow control

Session Layer: Managing and synchronizing Application sessions

Presentation layer: The representation of data, implementation of specific functions, such as encryption

Application Layer: User interface

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OSI seven-layer model