DNS/DNS SERVERS

DNS Servers

Every Zone on the previous page (., com., example.com., robots.example.com., cecelia.robots.example.com.) needs a nameserver to answer authoritatively for it, A nameserver is a database of records (More about records further in this tutorial) that point a name to a number, so that robots.example.com can be resolved to 75.125.124.243 for example.

So, let us for a minute imagine that your web browser is also a resolver (It is not, but let us not get into where the resolver lives just yet).

And Cecelia's mother wants to see how Cecelia is doing, And would like to leave her a message on her website telling her that she has prepared delicious snacks and that she should visit home and enjoy along.

So, Cecelia's mother opens her mom-web-browser application (Also known as internet explorer 6) and in the address bar, Cecelia's mother types in "cecelia.robots.example.com" knowing that this is her daughter's website.

So the browser does not know where the server that has Cecelia's files is, all our browser knows up to this minute is, that cecelia.robots.example.com points to the address where the information is.

So, the browser starts by contacting the root servers, remember that "." we said the ICANN manages ? that is called the root, and the nameservers that answer authoritatively for the root are called the root nameservers, There are currently 13 root nameservers in the world, our magical resolver-enabled-browser simply knows the address of the root nameservers so it asks any of them for directions. (As a side note, the 13 root namservers are proxies for thousands of behind the scene nameservers, but that is irrelevant at the minute).

The root namservers will respond, Oh, You are trying to locate a .com, i don't know where Cecelia.robots.example.com is, but i can tell you one thing, the .com nameservers can guide you, and so the root nameservers now point Cecelia's mother to the .COM nameservers and goes back to sleep.

So, our resolving-browser now goes to the .COM nameservers, and asks them about cecelia.robots.example.com, and the .COM nameservers answer, Oh, you want to know where to find a robots.example.com, all i can tell you is that there is a nameserver in the cyberwoods that can guide you, and the .COM namservers send Mark's mother to the nameservers responsible for example.com.

So, yet another trip to ask about the address where we can find Cecelia's website (Let alone finding Cecelia), Now we arrive at the namesevrvers that answer for example.com. And those responsible for example.com point us yet again to the ones responsible for robots.example.com.

So now, Cecelia's mother is at the server that is responsible for robots.example.com, but now, if you remember from the last chapter, where Mark (The person responsible for robots.example.com) had 2 choices, he had the choice to delegate cecelia.robots.example.com to Cecelia or to manage the zone for her.

So here is how it will go depending on what Mark the robotics guy dealt with giving Cecelia a name,

The first option is that mark created the A, MX, and other records for Cecilla and did not delegate the zone to her, in that case, the servers responsible for robots.example.com are also the ones responsible for cecilia.robots.example.com, and the name servers will answer with the address of the web server we are looking for.

The second option mark had was to delegate Cecelia.robots.example.com to Cecilia, In this case, Cecelia's mother needs to visit yet another Nameserver and ask about the address of cecilia's website, and that last nameserver will give her the actual address of the "Web Server" where Cecilia keeps everyone updated on where she is and what she is doing.

Now is probably the best time to tell you that the browser did not ask all the nameservers, it actually asked a resolver (Usually belonging to your ISP), and that resolver did all the asking and returned the final result.

You can also install a resolver on your own computer and let it do the domain name resolution, but why would we do that when our ISP is already providing s with a resolver (Some like to be able to clear the DNS cache, so they might want to manage there own resolvers) As a side article, i will tell you how to install a resolver on a web page separate from this tutorial here.. DNS resolver setup