Give an example of the process of domain name switching. What is the role of caching in nameservers?

There are two ways to resolve the name server: the first is called recursive resolution, in which the resolver sends a recursive query request to the server, and the server first searches within its jurisdiction, and if it is found, the result is returned to the resolver; Otherwise, a request is made to the root server, which is made from the top down. The second type is called forwarding resolution, the resolver requests a name server each time, and when a name server cannot provide an answer to a query, the server that requests this time returns the address of the next request server, and the resolver sends a new request to another name server.

So, regardless of the resolution, each resolver knows how to access at least one name server, and each name server knows the address of at least one other name server.

During this process, if the domain name entered by the user is incorrect or cannot be found, the resolver will prompt an error message. The whole process seems quite cumbersome, but due to the caching mechanism, all recently found host addresses are stored in the cache, so the query process is very fast.

Same with your browser cache. The pages you have viewed will be stored in the cache. When I browsed it again, some of the content in the page was read from the cache, so it was very fast.

The same is true for the cache of the name server, the ** information you have recently accessed is stored in the cache, and it will be read from the cache when you visit it again, and it does not need to be re-parsed. This makes the domain name service more responsive.

You can go to a professional domain name provider with domain name transfer to consult, and they will give you a reasonable answer based on your actual situation.

Step 1: The client makes a DNS request and sends the request to the local name server.

Step 2: When the local nameserver receives the request, it will query the local cache first, and if there is such a record, the local nameserver will directly return the query result.

Step 3: If the local cache does not have the record, the local nameserver sends the request directly to the root nameserver, which then returns the address of the primary nameserver of the queried domain (a subdomain of the root) to the local nameserver.

Step 4: The local server sends a request to the nameserver returned to the previous step, and then the server receiving the request queries its own cache, and if there is no such record, it returns the address of the relevant subordinate nameserver.

Step 5: Repeat step 4 until you find the right record.

Let's take an example to elaborate on the process of resolving a domain name. Suppose our client wants to access the site: , the customer's local nameserver is , a root nameserver is , and the nameserver of ** to be accessed is , and the process of domain name resolution is as follows:

1) The client sends a packet requesting the domain name to be resolved.

2) After receiving the request, the local name server queries the local cache, assuming that there is no such record, the local name server sends a request to the root name server to resolve the domain name.

3) After receiving the request, the root nameserver queries the local record and obtains the following result ns (indicating that the nameservers in the domain are: ) and returns the result to the nameserver.

4) After receiving the response, the name server sends a packet requesting the domain name to be resolved.

5) Name server After receiving the request, start to query the local record, and find the following record A (indicating that the IP address of the name server in the domain is, and the result is returned to the customer's local name server.

6) The customer's local nameserver saves the returned results to the local cache and returns the results to the client.

This completes the domain name resolution process.