[HCAI] learning summary OSI model

OSI（Open System Interconnect）, Open system interconnection . It's usually called OSI Reference model , yes ISO（ International Organization for Standardization ） Organized in 1985 Network interconnection model studied in .

​ ISO In order to better make the network application more popular , Launched OSI Reference model . The implication is to recommend that all companies use this specification to control the network . So all companies have the same specifications , You can connect .

OSI The seven layer reference model divides the necessary functions in the communication protocol into 7 layer . Through these layers , More complex network protocols can be simplified .

Use each tier independently , Even if some layers in the system change , It won't affect the whole system

application layer ： Accept user data , Interface of human-computer interaction , Application oriented .

The presentation layer ： Logic language （ Software language ） Convert to machine language （ Binary language ）, translate , encryption .

The session layer ： For each type of data transmitted （ management ： establish , maintain , End ） A virtual connection （ In order to prevent different types of data from imaging each other ）.

Transport layer ：

effect 1, Distinguish traffic

Port number ：port ID, Range of values 1-65535

Static port ： Also known as port , Range 1-1023

Dynamic port ： Range ：1024-65536

effect 2, Define the data transmission mode

TCP： Transmission control protocol , Is a reliable connection oriented transport protocol ;

UDP： User datagram protocol , It is a non connection oriented unreliable transmission protocol .

The network layer ：network         Organization         Addressing

Address ：

Addressing protocol ：IP（IPv4/IPv6）  IPX  apple  talk  novell   nsap

IPv4： use 32 Binary addressing .

Write a complete IP Address time ：IP Address + Network mask .

IP Address ：32 It's binary ,0 and 1 constitute For addressing .

Network mask ：32 It's binary , Successive 1 Plus continuous 0 form , Successive 1 On behalf of network bit , Successive 0 Represents the host bit .

Address classification ：

A Class address ： The first fixed is 0,0XXX XXX---128-191, The netmask defaults to 255,0,0,0

B Class address ： The first two fixed are 10,10XX XXX--128-191, The netmask defaults to 255,255,0,0

C Class address ： The first three fixed is 100,100X XXX-128-191, The netmask defaults to 255.255.255.0

Multicast address ：D Class address , One to many communication , No mask .

E Class address ： Reserved address , Special address .

A class ,B class ,C Class becomes a unicast address , Addresses that users can use . 

Special address ：

1.0.X.X.X Invalid address （ Reserved address ）,0.0.0.0 Invalid address         placeholder .

2.127.0.0.1 Local testing .

3. network number , The host bits with the same network bits are all 0 The address of .

4. Restricted broadcast address ,255.255.255.255

5. Directional address , The network bit remains unchanged , All hosts are 1

6. Local link address ：link-local {169.254.0.0 255.255.0.0}

Common address ： Globally unique identification address .

Private address ： Address without unique identification .

 

Data link layer ： LAN （ Ethernet Ethernet）  Wide area network （PPP  HDLC  ATM  FR）

Second floor address ：MAC Address （ Media access control ）--- Physical address   Hardware address   Burn address

LLC layer ：; Logical link control sublayer .

MAC layer ： Media access control sublayer .

MAC Address structure ：48 It's binary , Writing uses 12 Hexadecimal , How to write ： Subtractive hexadecimal or dotted hexadecimal .

60-F2-62-3C-E3-53———— terminal , host , mobile phone , The server

60F2.623C.E353———— Connect to the device     Router     A firewall   ASA......

The physical layer ：

The actual final signal transmission is realized through the physical layer . The main function is to use the transmission medium to provide physical connection for the data link layer , Transparent transmission of bitstream .

Transmitting bitstreams over physical media . Common devices are （ All kinds of physical equipment ） A hub 、 Repeater 、 modems 、 Ethernet cable 、 Twisted pair 、 Coaxial cable . These are the transport media of the physical layer .

568A Linear sequence ： Green and white , green , Orange white , blue , Bluish white , orange , Brown and white , Brown

568B Linear sequence ： Orange white , orange , Green and white , blue , Bluish white , green , Brown and white , Brown

Parallel lines , Cross line , All negative .