DNS

DNS - Domain Name System - translates easily memorized domain names to the numerical IP addresses. IP addresses are needed for locating computer services and devices worldwide. It would be too difficult to remember IP addresses, so the domain names have been introduced and the DNS founded. Thanks to DNS, you only need to remember the domain names, the DNS cares for the right connection with the requested web page.

How does DNS work? Each domain name has been given authoritative DNS servers, which save concrete DNS records of a specific IP address. The authoritative DNS servers are registered in the Whois database.

But how does your browser know them? For explanation see the picture underneath.

Your internet provider has assigned "local" DNS servers (caching servers) to your PC at home. The internet browser in your PC asks the local DNS servers if they know the IP address for requested domain (in this case www.forpsi.eu). The server searches its memory (caching), where it stores data about IP addresses, and when no record is found, it asks somewhere else:

1. First it asks the "root" DNS servers if they know the IP address for the requested domain www.forpsi.eu. The root DNS answers that it does not know the address for www.forpsi.eu, but it knows where the DNS records for . EU are stored and sends this information back to us.
    
2. The local server uses this information and asks the .EU domain name server if it knows the IP address for www.forpsi.eu. That server answers that it does not know address for www.forpsi.eu, but it knows which servers are authoritative for the domain forpsi.eu and sends this record back to us.
    
3. The server uses this information again and asks one of the authoritative servers for the address www.forpsi.eu. This server already knows the concrete IP address for such domain name and gives it to the local server. The local server returns this address to our internet browser.
    
4. The browser contacts directly the server given for the concrete IP address asking it to display the requested web page. The web page is shown on your PC screen.