3.7: DNS Servers
Eduqas / WJEC
What is a DNS Server?
A DNS (Domain Name System) server stores a list of domain names and a list of corresponding IP addresses where the website is stored.
The first thing to understand is that every web page has a domain name that is easy for humans to remember and type in (such as www.csnewbs.com) as well as a related IP address (such as 126.96.36.199) which is a unique address for the device that the web page is stored on.
The steps taken to display a web page:
A domain name is typed into the address bar of a browser.
The browser checks a local (cached) host file to check if it already holds the IP address, but if it doesn't...
A query is sent to the local DNS server for the corresponding IP address of the domain name.
The local DNS server will check if it holds an IP address corresponding to that domain name. If it does it passes the IP address to your browser.
The browser then connects to the IP address of the server and accesses the web site.
If the local DNS server does not hold the IP address then the query is passed to another DNS server at a higher level until the IP address is resolved.
If the IP address is found, the address is passed on to DNS servers lower in the hierarchy until it is passed to your local DNS server and then to your browser.
3.7 - DNS Server:
1. What is a DNS server? 
2. Describe, using a mix of text and icons / images, how a DNS server is used to display a web page. 
3. Describe how a DNS server searches for an IP address if it is not found on the local DNS server.