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The Domain Name System

2:15 with Joy Kesten

The Domain Name System or DNS is made up of domain name servers, a special type of server that looks up the IP address of other servers once you give it a domain name.

Jason Seifer's course on DNS

Domain Name System (DNS)

Fun Fact: Paul Mockapetris and Jon Postel figured out the Domain Name System.

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    A domain name server is a special type of server that connects domain

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    names with IP addresses, and it's a good thing we have them.

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    Thanks to DNS,

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    you don't have to keep your own address book of IPs to your favorite websites.

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    Instead, you just connect through DNS,

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    which manages a massive database that maps domain names to IP addresses.

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    You can always bypass DNS by typing an IP directly in your browser,

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    which you saw in the last video.

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    But could you imagine doing that every time?

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    And what if your favorite website gets a new IP address?

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    As you can probably already see, DNS is a really important part of the web.

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    Let's see how it works.

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    When it comes to DNS, proximity matters.

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    Depending on where you are and when you log onto the Internet,

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    you may use a different DNS to find websites.

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    [SOUND]. Meaning the DNS that looks up

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    teamtreehouse.com when you're at home, may not be the same DNS at work or school.

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    Say, for example, you hit up your local library for some free WiFi.

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    When you log onto the Internet,

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    the library's internet service provider tells your computer

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    what DNS to start with when looking up IP addresses for domain names on the web.

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    Although, not every DNS server knows every domain name.

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    For example, when I type in teamtreehouse.com into my address bar,

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    the DNS system begins by looking at the top level domain or

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    .com in the case of teamtreehouse.com.

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    It will then ask which server the domain teamtreehouse is on,

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    if it doesn't already know.

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    Within DNS there's a hierarchy of servers, so if one doesn't know, it sends a request

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    to the next server, and the next, until the correct website is located.

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    If all goes well, the server sends a short message back to the client,

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    your computer, saying that everything is okay, followed by the web page itself.

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    The DNS system is quite complex, but

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    the important takeaway is that DNS is the address book for the Internet,

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    and it's what connects domain names with IP addresses.

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    If you're interested in learning more about DNS, check out the teacher's notes.

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