Domänuppslag

Domänuppslag, often referred to as DNS lookup, is the process of translating a human-readable domain name, such as www.example.com, into a machine-readable IP address, like 192.168.1.1. This translation is essential for the internet to function, as computers communicate using numerical IP addresses, not domain names.

When a user enters a domain name into a web browser, their computer initiates a series of queries to DNS servers. These servers are organized in a hierarchical system, starting with root servers, then top-level domain (TLD) servers (e.g., for .com, .org, .net), and finally authoritative name servers for the specific domain. Each server in the chain either knows the IP address or directs the query to another server that might.

This process typically involves recursive queries, where a DNS resolver (usually provided by an Internet Service Provider) handles the multiple steps to find the IP address. Alternatively, iterative queries can be used, where the client directly asks each server in turn. The result of a DNS lookup is then cached by the resolver and sometimes by the user's computer for a period, speeding up future requests for the same domain. Errors in domänuppslag can prevent users from accessing websites or online services.