A DNS (Domain Name System) lookup is a process used to translate a human-readable domain name (like www.example.com) into a machine-readable IP address (like 192.0.2.1), which computers use to locate each other on the internet.
In more technical terms:
Query Generation: When you type a URL into your browser, it generates a DNS query for the domain’s IP address if it’s not already stored in its cache. This query is then sent to a DNS resolver.
Resolver Role: The DNS resolver is usually provided by your Internet Service Provider (ISP), or it might be a third-party service. If the resolver does not have the IP address cached, it will query other DNS servers.
Recursive DNS Lookup: The resolver performs a recursive DNS lookup by querying various DNS servers, starting from the root DNS servers, moving to the top-level domain (TLD) servers (like those for .com, .net), and finally to the authoritative DNS servers for the domain. Each of these servers provides part of the pathway to finding the final IP address.
Response: Once the IP address is found, it’s sent back to your device’s DNS resolver, which in turn sends it back to your browser.
Caching: The resolver caches the DNS query results for a specific duration, known as the Time-To-Live (TTL). This helps in reducing latency for future requests to the same domain and reduces the load on DNS servers.
Essentially, DNS lookup is a fundamental process that allows us to use easy-to-remember domain names instead of numerical IP addresses when using network services over the internet.