| DNS (Domain Name System) is what drives the | | | | your primary DNS server for the ip address of |
| internet, without it none of our favourite sites would | | | | google.com, the DNS server will then have the result |
| work, we wouldnt be able to check our email, check | | | | and return it your machine, your machine now knows |
| our facebook, in fact 99% of internet communications | | | | where google is, or at least its ip address which is the |
| would simply not work without DNS. So what exactly | | | | information it needs to be able to communicate with it. |
| is it? Well essentially DNS is what converts a Domain | | | | The hierarchy of DNS - Unfortunately not every DNS |
| Name (for example google.com) into a machine | | | | server has every result, a full DNS database is |
| readable IP Address. | | | | enormous, just think about how many millions and |
| What is an IP Address? - Well its pretty important that | | | | millions of websites there are out there! This is why |
| you understand what an ip address is if your going to | | | | there are several links in the chain for DNS. At the top |
| understand how DNS works. Basically every machine | | | | of the chain are what are called Root Servers, these |
| that communicates over the internet does so using an | | | | hold all the answers, they know every single Domain |
| IP address. It is a 4 block number that ranges from 0 | | | | Name that is globally accessible. However your |
| to 255 for each block, for example: 24.50.10.99 This is | | | | computer will not query these, instead if your primary |
| an ip address. I will not go into any specific details here | | | | DNS server does not know the answer it will then ask |
| but every machine that wants to communicate on the | | | | its next server in the chain, this is typically an ISP DNS |
| internet uses this address to identity itself. Routers do | | | | server. If this server does not know the answer then it |
| not understand domain names, they only understand ip | | | | will ask the next one in the chain, this will keep |
| addresses so it is essential that a Domain Name | | | | happening until a Root Server is queried which will |
| converts to one. | | | | always have the answer. |
| Note: Above I am referring to IPV4 and not IPv6 | | | | To speed things up a bit most DNS servers will hold a |
| So what does DNS do? - Everytime you type in a | | | | cache or a temporary store of DNS records, these |
| URL into your web browser your computer has to | | | | usually last around 24 hours but they will save the root |
| lookup the ip address of the Domain Name, it does this | | | | servers being constantly queried if the DNS server |
| by doing a DNS lookup. Your computer will query its | | | | before already knows the answer. |
| primary DNS server for the ip address (You can | | | | So there you have it, a basic introduction to DNS, as I |
| check your primary dns server by going into command | | | | said before it is indeed a massive subject and we've |
| prompt and typing ipconfig /all) | | | | only just scratched the surface here, however you |
| So far so good right? Well a basic DNS query will | | | | now know what DNS does and why it is so important. |
| typically be a host machine (you for example) asking | | | | |