Domain name resolution is the process of converting a human-readable domain name to an IP address that can be understood by machines. When a user types a domain name into their web browser, the following steps occur:
1. The browser checks its own cache to see if it has already resolved the domain name before. If it has, it retrieves the IP address from the cache and proceeds to the next step.
1. If the domain name is not in the cache, the browser sends a query to the local DNS resolver (usually provided by the Internet Service Provider) asking for the IP address of the domain name.
1. The local DNS resolver checks its cache to see if it has already resolved the domain name recently. If it has, it sends the IP address back to the browser.
1. If the domain name is not in the cache, the local DNS resolver sends a query to the Root Name Server (there are 13 of them globally) asking for the IP address of the Top Level Domain (TLD) associated with the domain name (e.g., .com, .org, .net).
1. The Root Name Server responds to the query with the IP address of the TLD server responsible for the domain name’s TLD (e.g., Verisign for .com).
1. The local DNS resolver sends a query to the TLD server asking for the IP address of the authoritative name server for the domain name.
1. The authoritative name server is responsible for storing and managing the DNS records for the domain name. The local DNS resolver sends a query to the authoritative name server asking for the IP address of the domain name.
1. The authoritative name server responds with the IP address of the domain name, which the local DNS resolver caches and sends back to the browser.
1. The browser receives the IP address and can now establish a connection with the web server hosting the domain name.
Overall, domain name resolution is a hierarchical process that involves multiple steps and servers to translate a human-readable domain name to an IP address.
