DNS/intro

Introduction to DNS

In this introduction, i will explain how a DNS system works in the simplest way i can, but in order to keep it simple, Some inaccuracy had to be used, for example, avoiding terms that we will learn in later chapters forced us to use terms you are more likely to know.

First of all, the DNS system is distributed, So no one NameServer can give you the address of any computer you ask of it, if you ask a famous nameserver (ROOT NAMESERVERS that we will explain a bit about later) about the computer that goes by the name example.com, You call the top of the system (The root servers), they point you to the next address keeper, then to the next and so on until some address keeper (DNS server) says, i am responsible for this address, you can find the computer at this numerical location, so your browser goes and gets the data from that server (in case it was a web server).

Let me explain some more.

Let us assume the world has .com and .org and nothing more, ignoring the .net, .info, .us (For the united states), or .UK for (United kingdom), Let us pretend only .com and .org existed.

In reality, .COM and .ORG are nothing more than "Domain names" themselves, so when you have a domain like example.com you are in reality managing a sub-domain name under the .COM domain name, but to make it even more strange, the .COM and .ORG domains are also sub domains of the root "." domain !

If you have ever added CNAME or MX records to a DNS system, You would recall that you needed to add a dot "." right after the domain name, so to point mail to example.com to a certain mail server you would add a record such as

    MX 10 mailserver.myisp.com.

Notice the dot right after mailserver.myisp.com. this dot is a reference to the root domain name that .COM is under.

The root is managed by the ICANN (The Internet Corporation for Assigned Names and Numbers), the ICANN delegates (Under it's root domain) subdomains such as .COM and .ORG to others so that they can manage

So VeriSign got there domain name (com.) and Public Interest Registry got theirs (ORG.)

Now VeriSign is the owner of a domain name COM. and they can delegate authority over sub-domains under COM. to you, so you can have your website example.com.

The tree does not need to stop here though, Now you can give your friend Mark who is, in addition to being your friend, an excellent robot designer his own domain name (You can take money from him like VeriSign took money from you), or you can be a nice friend and avoid those tax complications and give him a domain like robots.example.com.

So there you have it, this is a Sub-tree demonstrating our example

Now, example.com. is called a ZONE rather than a domain, robot.example.com. is also a zone, and mark can even create more zones and give them to his friends if he wants to, for example he can give Cecilia a zone under his domain like cecilia.robots.example.com.

But if cecilia does not know how to manage a zone, Mark can simply create records for cecilia.robots.example.com. rather than actually giving cecilia a new zone, the difference between Zones and records i will explain in the next chapters.

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