Overview of computer Networks (OSI)

Computer network is divided into two parts: software and hardware.

The functions of computer network: data communication, resource sharing, increasing data reliability, improving system processing capacity.

The protocol of the network is divided into three elements: syntax, semantics and synchronization.

There are two types of services: 1) connection-oriented services

First establish a connection and then transmit data to ensure the reliability of data transmission.

2) Connectionless services:

There is no need to establish a connection in advance, and the reliability of message transmission is not guaranteed.

Service elements are divided into: request, indication, response, confirmation.

ISO is the International Organization for Standardization.

OSI is the reference model of open systems interconnection.

OSI is an open architecture that divides the network into seven layers:

Physical layer-- > data link layer-- > network layer-- > transport layer-- > session layer-- > presentation layer-- > application layer.

Tcp/ip four-layer model: network interface layer-> network layer-- transport layer-- > application layer.

Tcp/IP five-layer protocol: physical layer-> data link layer-- > network layer-- > transport layer-- > application layer.

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