Ip--- ia review

Static routing ：

What is the Internet : The network connects the devices and connects the network devices through the transmission medium , Share resources , Information transmission platform .

What is a router ： Router （Router） Is the connection of two or more networks Hardware equipment , Act as a gateway between networks , It is a network device that reads the address in each packet and then decides how to transmit it .

What is a switch ： Switch （Switch） Meaning for “ switch ” It's used for electricity （ light ） Signal forwarding Network devices . It can be any two of the access switches Network nodes Provide exclusive access to electrical signals .

OSI Seven layer model ：

application layer         Abstract language input and output     Abstract language --> code （ human-computer interaction ）

The presentation layer          code decode encryption Decrypt --> Binary system

The session layer          Inside the application , Internal distinguished address provided  

The upper three layers are application programs processing processing processing data , The above three are collectively referred to as the application flow layer

The lower four layers are responsible for data transmission , Collectively referred to as the data flow layer

Transport layer    Provide the port number , piecewise （ suffer MTU Limit ）  TCP/UDP（ Provide reliable transmission ）

             ---a. static state 1-1023  b. dynamic 1024-65535  c . special   0 

The network layer         Internet  agreement   -- IP Address  

Data link layer / Media access control layer --MAC    Control physical hardware

The physical layer

PDU Protocol data unit ---- The top three The data packet ; Transport layer   Data segment ; The network layer Data packets ; Data link layer Data frame ; The physical layer Bit stream .

tcp/ip Model ：

tcp： Reliable transmission ： On demand transmission 、 There is a confirmation mechanism 、 Lost retransmission 、 Strictly check .

udp: Unreliable transmission ： Just pass it on , Nothing else .

TCP Protocol transmission is reliable , and UDP Our transmission is best effort .

TCP It can carry out flow control and congestion control UDP You can't

TCP Data can be segmented

TCP It consumes a lot of resources , Relatively slow ;UDP Less resource consumption , Fast .TCP and UDP Application scenarios of

TCP It is more suitable for relatively low efficiency , But the scenes that require high accuracy .

UDP It is more suitable for relatively high efficiency , But the scene with low accuracy requirements （ Instant communication ）

UDP： Voice class , Real time transmission class （ video 、 game ）

TCP： File class , Pursue complete transmission of information

WeChat and qq The chat data of is udp

ipv4 The calculation of

32 Binary components

192.168.1.1 --> Point and point 10 Hexadecimal writing format

Address by 2 Part of it is made up of

Network bit

Host bit

VLSM And CIDR

No class address --- Instead of identifying network segments by numbers, use subnet masks to identify , The rule is to set the address subnet mask of the network bit 1

VLSM --- Variable length subnet mask ---- Subnet partition

The core idea ： By extending the subnet mask （ Borrow the host bit to the network bit ） To realize the division of network segments

CIDR --- No inter domain routing ---- Summary

Variable length subnet mask --- Take the same and go different