Domain name resolution is the process of converting human-readable domain names into computer-recognizable IP addresses. On the Internet, every device has a unique IP address, which is assigned by ICANN (Internet Corporation for Assigned Names and Numbers). However, an IP address is a string of numbers that is difficult to remember and type, so domain names were created that convert IP addresses into readable strings, making them easier for people to remember and use.

The principle of domain name resolution is based on DNS (Domain Name System). DNS is a hierarchical, distributed naming system used to identify and locate devices on the Internet. The DNS server stores the mapping relationship between the domain name and the corresponding IP address. When the user enters the domain name in the browser, the DNS server will resolve the domain name into the corresponding IP address and send the request to the server corresponding to the IP address.

The process of domain name resolution can be divided into the following steps:

1. The user enters the domain name in the browser.

2. The browser sends a request to the local DNS server.

3. The local DNS server queries the cache. If the IP address corresponding to the domain name is in the cache, it is returned directly to the browser.

4. If the local DNS server does not cache the IP address corresponding to the domain name, send a request to the root DNS server.

5. The root DNS server returns the address of the top-level domain name server.

6. The local DNS server sends a request to the top-level domain name server.

7. The top-level domain name server returns the address of the secondary domain name server.

8. The local DNS server sends a request to the secondary domain name server.

9. The secondary domain name server returns the IP address corresponding to the domain name.

10. The local DNS server returns the IP address to the browser and stores the mapping relationship in the cache.

It should be noted that since the DNS system is distributed, domain name resolution may involve interactions between multiple DNS servers, which will cause a certain delay. Therefore, in order to improve access speed, it is recommended to use a local DNS server or a third-party DNS service provider to reduce delays and improve response speed.

In short, domain name resolution is the process of converting human-readable domain names into computer-recognizable IP addresses. It relies on the DNS system and involves interactions between multiple DNS servers. Understanding the principles and processes of domain name resolution can help us better understand the Internet infrastructure and optimize the network access experience.