1-3 Iso/osi Seven-storey model detailed

First, the physical layer

1. Responsible for the transmission of the bit stream between the equipment, physical interface, electrical characteristics and so on.

<1> Physical Interface: Cable interface model, audio cable interface model, video cable interface model, etc.

<2> Electrical Characteristics: For example, a total of 8 cable lines, these 8 lines are used to transfer data?

It's not, it's only 1, 3, 2, 64 lines for transmitting data, the rest of the line doesn't matter,

Similar functions are controlled by the physical layer.

2. Most common devices in the physical layer

<1> Cable

<2> Network card

Second, Data link layer

1. The main function of data link layer is to encapsulate frame, access media with MAC address, error detection and correction

<1> frame contains the sender and receiver's MAC address

<2> detection by means of carrier monitoring and multi-channel access

Third, the network layer

1. The main functions of the network layer are: providing logical address (ie IP address), routing

The <1> package also contains the IP addresses of the sender and receiver

<2> can also select the appropriate transmission path

<3> The network layer determines the IP address

Iv. Transport Layer

1. The main functions are reliable and unreliable transmission, error detection before transmission, flow control

<1> to determine whether the transport protocol is reliable or unreliable, there are two types of transport protocols,

One is TCP, also called Transmission Control Protocol, (reliable)

Another is called UDP, which is the user Digital Datagram Protocol (faster, but unreliable)

The <2> Transport layer also features error control and flow control

<3> Transport layer is determined by the port number

The <4> port number is used to identify the process,

The port number of the Web service is 80, and the mail Service has 25 or 110 ports, and the file Transfer Protocol is 21.

V. Session Layer

1. Managing and synchronizing Application sessions

<1> Determine if network data is going through a remote session

<2> if it is local, direct delivery of the hard drive does not need to be passed to the transport layer

Six, the presentation layer

1. Data representation, implementation of specific functions such as-encryption

<1> digital representation of data such as English via ASCII conversion to binary

<2> can also implement encryption, compression and other functions

VII. Application Layer

1. Provide user interface

　　

1-3 Iso/osi Seven-storey model detailed