Learn DNS Series (10) Diagram, example detailed DNS recursive and iterative query principle and process (2)

In the last section, we use the form of text to describe the process of DNS parsing, in order to better help you understand the entire parsing process, I did a DNS domain name resolution of the step-by-step diagram, as follows:

In this diagram, the 8-step parsing process allows the client to successfully access the domain name of www.163.com, but in practical applications, the process is usually very rapid and is largely determined by several reasons. 1, the client network condition is good, 2, the speed of the local DNS connection is excellent, 3, the local DNS has access to the address of the cache, etc., if the above factors answer is affirmative, then access will be very rapid, the steps on the diagram will be reduced to 2, because there is a cache, so the local The DNS server will quickly inform the IP of the domain name and achieve rapid access.

There are 2 unfamiliar lists in the picture above, so let's talk about the origins of these two tables. Here we continue with the Nineth chapter to explain the advanced properties of DNS, as shown in the following figure:

As you can see, there are 13 root servers listed in the Root Hints tab, respectively

(a~m). root-servers.net and corresponding IP address, there are 2 IP, the latter is an alternative address, we can manually modify these addresses, but in general, it is recommended not to move it. If you accidentally change or delete, we still have a few ways to repair. Because the address lists for these servers are shared across the Internet, we can find the latest list of root servers on the network. Usually in this link:

Ftp://rs.internic.net/domain/named.root can also be replicated directly from the network. The following figure: