The Domain Name Service is a directory that contains the registered domain names of websites and references them to their official IP address. Web browsers use it to translate the domain name (e.g: www.virtualhostedpbx.net) into a public IP address that the computer can use to access the website. Domain names are only relevant to humans as they are easy for us to read and remember. Computers however use IP addresses that are unique and therefore can be routed across the internet. Therefore every time you click on a URL link or type in a domain name like the example above, the web browser has to connect to the primary DNS server and ask for translations of the domain name to the public IP. You can watch it do this by looking down in the left hand corner when clicking on a sites URL. You should see the browser status change to connecting too … this is actually when it is looking up the Domain Name Service to resolve the IP from the domain name.
DNS is actual a hierarchy of DNS servers which will look up and refer queries to other authoritative name servers. These are servers with direct responsibility for the update of certain domains. Authoritative name servers can assign responsibility for subdomains to other servers. This provides for a distributed and fault tolerant system that doesn’t require a central database.
Data can be quickly updated on a DNS server though it can take almost 12 hours to propagate throughout the internet due to the slow route redistribution of the BGP internet routing protocol. The DNS records held in the server database are the AAA records for the address, the NS record for the name server, and the MX record for the email exchange server name.