A DNS name server is a server on the internet that computer programs use to lookup domain names, and convert them to IP addresses. This information is most commonly looked up automatically by web browsers and email programs. The internet’s domain name system consists of an extensive network of DNS name servers which share domain name records and request records from each other.

The Name Server Process

When you click a link or type an address into the address bar, your web browser contacts a DNS server and sends it the domain it wants an IP address for. For most people, your computer will contact the DNS server which belongs to your Internet Service Provider, which will have been set in your modem or operating system when you setup your internet. You can use whichever DNS server you like if you go to the trouble to set it up. .

When the DNS server receives a request, it searches a massive database looking for the entry that matches the domain name. These entries are called DNS records. If it finds the correct record, it sends back the IP address of the server hosting the website you want to visit. If it cannot find the correct record it asks other DNS servers, moving up the DNS hierarchy until the result needed is found.

If necessary the DNS server will send a request to one of the root nameservers, the highest DNS servers in the hierarchy. There are just 13 of these servers on the entire internet. The root nameserver will look up the definitive registry for the top level domain you are asking for. So if it is looking for phoenixweb.com.au, it will look at the definitive .au registry. If the domain cannot be found even here, then it doesn’t exist and your browser will show an error. If the domain does exist in the definitive registry, the root nameserver will reply to say which name server holds the authoritative DNS records for that domain. The DNS retrieves the authoritative record from that name server and sends the browser the IP address.

Finally, your web browser receives the correct IP address. It took around 500ms for your browser to get it. Your browser now contacts that IP address and the server at that IP address sends back the web page.

External Resources

Read more about DNS servers at the Wikipedia name server article and this Znet article about name servers.