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Recap:
This article is only a personal study record and understanding, and there may be some errors.
Network protocols and domain names
We can use the website's URL to access the website, such as Baidu's URL
http://www.baidu.com
http:// is the network communication protocol used. The following www.baidu.com are three domain names (separated by dots). Each domain name will correspond to an IP address, just like a name in the phone book. Same as a phone call (disregarding the situation where a person has multiple phones).
We actually use the IP address to access the website.
List of network communication protocols
DNS protocol, DNS pollution
It is the DNS protocol that resolves domain names to IP. By the wayDNS pollution, when we resolve domain names, after parsing An IP address will be returned. If the DNS is contaminated, a different IP address will be returned after parsing (the same principle applies to being unable to access pornographic websites)
Ipv4、Ipv6
The IP address needs to be allocated, and both IPv4 and IPv6 can be allocated.
IPv4 is designated by the United States, so the United States holds the most IP addresses in the world. It is not that everyone is using the world's Internet, but that everyone is using the United States' Internet. This sentence is not unreasonable.
IPv6 can allocate more IPs than IPv4. It is said that every grain of sand in the world can be allocated its IP.
Although the number of IP addresses is limited, since ipv4 and ipv6 are completely different protocols, changing protocols requires changing hardware, so most people prefer ipv4.
NAT protocol, IP: port, link IP address exhaustion
The NAT protocol that appeared in 2008 delayed the exhaustion of IP addresses and also delayed the process of replacing ipv4 with ipv6 protocol.
Let me briefly introduce the NAT protocol as I understand it: for a device to access the Internet, we need to assign an IP to it, and each computer needs an IP address. But I don’t know if you have seen itIP：端口. Through this design, when many computers are connected to the same router or server, these computers will uniformly use the IP address of the server and then identify it through the port. The sending end and receiving end of data. This requires only one IP address, delaying the allocation of IP addresses.
This gives rise to the concepts of public network and private network. The public network is identified by IP address, and the private network is identified by port number internally.
Although the emergence of the NAT protocol has greatly delayed the depletion of IP addresses, with the development of world situations, such as the Prism Gate incident in 2013.
The NAT-PT protocol that appeared later greatly accelerated the process of ipv6.
NAT-PT protocol, accelerates Ipv6 application
IPv6 can be converted into IPv4 through this protocol, which can achieve a certain degree of compatibility and ease the pain of this technology iteration.
Now with the implementation of reforms in our country, more devices and software in our country now support ipv6. For example: On my mobile phone, open the settings, click on Dual SIM and mobile network, open the telecom, you can see that the APN protocol says IPv4 /ipv6.
When the future develops further, devices will not need to be accessed through ports, but will all use IP, and the data transmission speed will be further accelerated (resolving ports always takes a certain amount of time). It will be wonderful to think about the interconnection of everything.
Full concept overview study materials
This is the end.
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