DNS recursive Resolution Process

This title is too big to be written, but I am afraid to forget it. Simply remember a bit and let's talk about the whole process of DNS resolution. The DNS resolution process is like this. First, we request the DNS server we entered. The server first queries its own cache. If no, we directly ask the top-level domain name. What about the top-level domain name, if you do not directly tell you the answer, an IP address is returned to allow you to access this IP address. This IP address is not the real IP address of the domain name you want to request, the server corresponding to this IP address may know the IP address of the I domain name you want to request.
Www.2cto.com is actually like this. You ask where your server A is, where it asks the top-level domain name B, and B says you go to the IP address C, and it will tell you, then I asked C and C, and I may ask D, and D will know that it continues until a DNS server tells you the answer. This method is called recursive resolution. There are 13 top-level domain names, and the domain names will go on layer by layer until they are resolved. This is not intuitive. Let's use the dig command to see the effect.
First, the DNS server accesses the top-level domain name. 13 In total, from a ~ J.root-servers.net. The figure tells us that through our own DNS server 10.0.0.1, it tells us that we have accessed the top-level domain name to find the domain name we requested to resolve. Www.2cto.com
Then, return N entries from the B .root-servers.net, telling us that through these entries you can know the answer you want, in turn, all of the following, our request is mediated by it, I asked A, but A asked B. let's take a look at the final result. Finally, through dns.uestc.edu.cn, we know that the domain name address is 202.112.14.184. it should be noted that there may be multiple addresses that the domain name on the machine returns to us for our query. From the above example, we can see that we may send a request to multiple servers, finally, these addresses are returned. From the last entry, we can see that a server returns an ns record, which is dns.uestc.edu.cn. this address is exactly the server we accessed last time. That is to say, some servers have already given us the answer, while some may still be slow in parsing, and they are constantly giving NS records. Www.2cto.com
Finally, I posted a strange figure. I went to dig to find a non-existent domain name with the suffix zzq. Finally, I got an IP address of Guangdong Telecom and attached the whole process of resolution, in addition, the record type is an SOA that has never been seen. This is used for later research on the AD domain.