IP address
On the network each host , each network device , each network are having only one IP address. Such as: 192.168.3.100 , 172.12.3.123
The IP address is equivalent to the ID number of each of us and is unique .
The computer can only recognize the IP address, but not the domain name ( www.baidu.com ) . How to convert the IP address and domain name? I'll talk about it later.
The IP address consists of 32 -bit binary, assuming 11111111100000000000000000000110101101010010
It consists of 4 segments of 8 -bit binary, separated by " . " In the middle of each segment .
The IP address consists of: abcd , where a , b , c , and d are numbers between 0-255
The usual IP address is expressed in decimal .
Special IP address: 127.0.0.1 represents theIPaddress ofthe machine. 127.0.0.1This machine'sIPaddress cannot be used by the outside world.
The domain DN (Domain Name)
For example: www. Baidu .com www.sina.com.cn
Because IP addresses are not easy to remember, a "domain name " composed of characters was invented .
The composition of the domain name : letters, numbers, -( underscore ) and other characters, the length of the domain name cannot exceed 255 characters. Domain names are case-sensitive.
www.care-jet.com Kerry Jebsen
Domain names are hierarchical:
www.sina.com.cn The lowest level is on the far left , and the highest level is on the far right
Sina is the main body of Sina domain name
com stands for commercial organization
cn stands for China ( the top domain name of the country )
Common institution codes
com commercial organization, generally refers to a company
gov government department www.gz.gov.cn www.henan.gov.cn www.beijing.gov.cn
mil military website
edu education website www.pku.edu.cn Peking University
org non-profit organization www.redcross.org.cn Chinese Red Cross
Commonly used country codes
cn China us United States jp Japan tw Taiwan hk Hong Kong
Special domain name: the domain name of this machine is localhost
Special IP : The IP address of this machine : 127.0.0.1