What is DNS

Q: What is "DNS”? What is its Chinese?

A: DNS, simply put, is the Domain Name System, which is translated into Chinese is "Domain Name System".

Q: What is the use of DNS?

A: 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, which is easy to remember, with the IP Address, which is not easy to remember. The network host that performs the DNS service above can be called a DNS Server. Basically, we usually think that DNS just converts the Domain Name to an IP Address, and then uses the IP Address found to connect (commonly known as "forward resolution”). In fact, the function of converting IP Address to Domain Name is quite often used. When login to a Unix workstation, the workstation will do a reverse check to find out where you came from. (commonly known as &ldquo ; reverse analysis & rdquo;).

Q: How does DNS work?

A: DNS works by using layers. For example, the Domain Name of the Harbin Institute of Lilacs is bbs.hit.edu.cn. This Domain Name is of course not out of thin air and is assigned from .edu.cn. .edu.cn is also granted from .cn. Where did .cn come from? The answer is from “.”, the so-called "root domain" (root domain). The root field is already the top level of the Domain Name. And this layer is managed by InterNIC (Internet Information Center). The Domain Name of the world is like this, and it is granted layer by layer.

Q: When I check a Domain Name, how does DNS find out its IP?

A: For example, suppose that the Domain Name we checked today (as a dns query) is bbs.hit.edu.cn, the DNS Server will handle this:

(1) The computer you are using (may be a PC or a workstation) sends a question to the DNS Server set up by this computer. Question: What is the IP of bbs.hit.edu.cn?

(2) This DNS will first check if it is in its cache, and if so, throw the answer. If not, look up from the top. There must be a setting on the DNS Server “.” who to ask. So, this time it goes to any DNS on the layer of "." (currently "13"). Who is the .cn to ask?

(3) “.” The layer of DNS will answer .cn to whom to check (and the DNS you use will cache this answer).

(4) Next, the DNS you use will ask the DNS of .cn layer: Who is the .edu.cn?

(5) This layer of .cn will answer .edu.cn to whom to check (and the DNS you use also caches this answer).

(6) Until bbs.hit.edu.cn replies: the IP of bbs.hit.edu.cn is 202.118.224.2 (cached up again).

After so many processes, I finally got this IP, and then I can make further connections. It's important to note that you will ask a question at each level, and write down the answer (cache), and you will forget it (see how long the layer is set to cache).

Q: How to set up DNS?

A: If you just want to use DNS, you only need to set it in the network properties of TCP/IP. The method of setting is related to the operating system used. For example: Windows 9x in the "Control Panel" & rdquo; & rarquo; Network & rdquo; & rarr; & ldquo; TCP /IP & rdquo; & rarr; & ldquo; attributes & rdquo;, find the DNS part and then set. Unix is ​​set in the /etc/resolv.conf file (if you are setting up a DNS Server, it is not discussed here).

Q: Which DNS information is the latest?

A: If you know that DNS is operating in a hierarchical structure, you should know that the DNS closest to you is the best.