Answer: DNS, simply put, is Domain Name System, translated into Chinese as "domain name system".
Q: What is the purpose of DNS?
Answer: In a TCP/IP architecture network (such as the Internet) environment, DNS is a very important and commonly used system. The main function is to convert the Domain Name that is easy for people to remember with the IP Address that is difficult for people to remember. The network host that performs DNS services above can be called DNS Server. Basically, we usually think that DNS just converts Domain Name to IP Address, and then uses the found IP Address to connect (commonly known as "forward resolution"). In fact, the function of converting IP Address to Domain Name is also quite commonly used. When logging into a Unix workstation, the workstation will do a reverse check to find out where you came in (commonly known as "reverse analysis").
Q: How does DNS work?
A: DNS operates using the layer method. For example: The Domain Name of the Lilac Station of Harbin Institute of Technology is, of course, this Domain Name did not come out of thin air, but was assigned from. . is granted from .cn again. Where did .cn come from? The answer is from ".", which is the so-called "root domain". The root domain is already the top level of Domain Name. And the "." layer is managed by InterNIC (Internet Network Information Center). This is how Domain Names around the world are granted layer by layer.
Q: When I check a Domain Name, how does DNS find out its IP?
Answer: For example, if we check the Domain Name (dns query) today, the DNS Server will handle it like this:
(1) The computer you are using (maybe a PC or a workstation) sends a question to the DNS Server set by this computer and asks: What is the IP?
(2) This DNS will first check whether it is in its cache, and if so, throw out the answer. If not, start from the top. There must be a setting of "." on DNS Server. Who should I ask. So, at this time, it will go to any DNS in the "." layer (there are currently 13 ".") and ask: Who should I ask.cn?
(3) The DNS of the "." layer will answer whom to.cn should be checked (at the same time, the DNS you use will cache this answer).
(4) Next, the DNS you use will ask the DNS at the .cn layer: Who are you going to ask?
(5) The .cn layer will answer. Who should I check (at the same time, the DNS you use will also cache the answer).
(6) Until the answer: The IP is 202.118.224.2 (and cached again).
After so many processes, I finally got this IP, and I can only make further connections. It should be noted that you will ask a question on each layer, write down the answer (start cache), and forget it (see how long it takes to cache the setting of this layer).
Q: How to set up DNS?
Answer: If you just want to use DNS, just set it in the network properties of TCP/IP. The setting method is related to the operating system used. For example: In Windows 9x, in "Control Panel" → "Network" → "TCP/IP" → "Properties", find the DNS part and set it. Unix is set in the /etc/ file (if you want to set up a DNS Server, it is not discussed here).
Q: Which DNS data is the latest?
Answer: If you know that DNS operates using a hierarchical architecture, you should know that the DNS closest to you is the best.