Notes of the first week of 2021 Chengdu Arts and Sciences cloud computing intensive training class

Xujiahao

1.OSI/TCP/IP Models are used to define the data generation process

2.OSI The layers are divided into seven layers The seventh application layer The sixth layer is the presentation layer The fifth layer is the conversation layer Layer 4 transport layer The third network layer The second layer is the data contact layer The first physical layer among 7 To 5 The layers are uniformly divided into Control level 4 To 1 The layers are uniformly divided into Data level

3. application layer ： receive User data , Human computer interface , Application oriented （ The first step in the first step of generating data , Act on receiving ）

4. The presentation layer ： Logic language （ Software language ） Convert to machine language （ Binary system ）, translate , encryption （ The second step in generating data , The function is to translate into a language that can be recognized by the computer ）

5. The session layer ： For each kind of data transmitted （ Traffic ） establish （ management : maintain 、 End ） A virtual connection （ In order to prevent different types of data from influencing each other ）（ The third step of generating data focuses on distinguishing data , Prevent data from mixing ）

6. Transport layer ： Distinguish traffic and define data transmission methods （ The fourth step of generating data , The role is focused on transportation data ）

The main means to distinguish traffic is through the port number （1-65535） Static port （ One to one correspondence and binding    1-1023） Dynamic port （    One to one correspondence but No binding       1024-65535）       

  Focus on common port numbers ：

http---80tcp             https---443tcp              telent--- Remote login service    23tcp           ssh--- Remote login （ High security   encryption   authentication ）,22tcp

Data transmission mode ： Unreliable transmission mode （1 Large flow 2 High real-time performance 3 Insensitive to data loss ）    Reliable transmission mode

Mechanism for ensuring reliable transmission mode ：1. Acknowledgement mechanism 2. Retransmission mechanism    

Transport layer encapsulation                                                                                                                                         tcp： Transmission control protocol , It's a connection oriented Reliable transport protocol                                                                         udp： User datagram protocol , It is a non connection oriented Unreliable transmission protocol

Three times mobile phone system ： Connection oriented assurance , also called tcp Three handshakes of

The confirmation mechanism is divided into Explicit confirmation and Implicit confirmation （ The information may not be fed back after the reception is confirmed ）

MTU: Maximum transmission unit , The default is 1500 byte       PDU： Protocol data unit     4 Time PDU：segment

7. The network layer ： Addressing   Addressing （ The fifth step of data generation , Function in the use of IP Protocol transfer ）

IPV4： use 32 Binary addressing , One of the binaries is called 1 position bit                                                                  Network mask ：32 It's binary , Continuous 1 and 0 form , Successive 1 On behalf of network bit , Successive 0 Represents the host bit

complete IP Address =IP Address + Network mask

A Class address ：0xxx xxxx Except for the special address, it is converted to decimal 1-126 The netmask defaults to 255.0.0.0

B Class address ：10xx xxxx---128-191, The netmask defaults to 255.255.0.0

C Class address ：110x xxxx---192-223, The netmask defaults to 255.255.255.0

D Class address ：1110 xxxx---224-239 Multicast address , No mask

E Class address ：1111 xxxx---240-255, Scientific research address

Three layers PDU:packet package

unicast ： One to one transmission （ABC class ）              Multicast ： One to many transmission mode （D class ）          radio broadcast ： One to all transmission modes

8. Data contact layer ： Define the data transmission medium , Define the two-layer package according to different physical packages （ The sixth step of data generation ）

Second floor address ：Mac Address （ Media access control ）

The data link layer is divided into two sub layers in Ethernet ：LLC layer （ Describe the upper layer usage protocol ）MAC layer

 MAC Address ：48 It's binary , Writing uses 12 Hexadecimal

On the second floor PDU：frame frame

9. The physical layer ： Pay attention to the mechanical characteristics of network hardware Optical properties Electrical characteristics （ The seventh step of data generation , The function is to ensure that the data is transmitted on the physical media ）

First floor pdu：bit Bit stream             Transmission medium ： Optical fiber   Twisted pair

Twisted pair ：568b Linear sequence ： Orange white   orange Green and white   blue     Bluish white     green     Brown and white   Brown （568A Line sequence will 568A in Change orange to green ）

Parallel lines ： Same line sequence , Use of equipment at different levels         Cross line ： The line sequence is different , Use of equipment on the same floor                                       All negative ： The line sequence is opposite Network equipment for user control .

10. Data encapsulation ： The process of generating data     7-6-5-4-3-2-1

      Data unpacking ： The process of receiving data for reading    1-2-3-4-5-6-7