When a user enters a URL on a browser, the DNS resolution process is as follows:
- The browser will check whether there is a parsed IP address corresponding to this domain name in the cache, and if so, the parsing ends.
- If not, the browser will check whether there is a DNS resolution result corresponding to the domain name in the operating system cache.
- If the machine cannot complete the resolution of the domain name, it will actually request the domain name server to resolve the domain name. The operating system will send the domain name to the LDNS (domain name server in this area), and about 80% of the domain name resolution has ended here, so the LDNS undertakes the main domain name resolution task.
- If LDNS is not hit, it will directly go to the Root Server domain name server to request resolution.
- The root domain name server returns a primary domain name server (gTLD Server international top-level domain name server) to the local domain name server for the queried domain.
- The Local DNS Server sends a request to the gTLD server returned in the previous step.
- The gTLD server that accepts the request finds and returns the address of the Name Server domain name server corresponding to this domain name.
- The Name Server domain name server will query the stored domain name and IP mapping relationship table. Under normal circumstances, it will obtain the target IP record according to the domain name, and return it to the DNS Server domain name server together with a TTL.
- Returns the IP and TTL value corresponding to the domain name. Local DNS Server will cache the corresponding relationship between the domain name and IP. The cache time is controlled by the TTL value.
- The result of the resolution is returned to the user, and the user caches it in the local system cache according to the TTL value, and the domain name resolution process ends.
