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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.

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 0:00
    names with IP addresses, and it's a good thing we have them. 0:04
    Thanks to DNS, 0:08
    you don't have to keep your own address book of IPs to your favorite websites. 0:09
    Instead, you just connect through DNS, 0:14
    which manages a massive database that maps domain names to IP addresses. 0:18
    You can always bypass DNS by typing an IP directly in your browser, 0:23
    which you saw in the last video. 0:27
    But could you imagine doing that every time? 0:29
    And what if your favorite website gets a new IP address? 0:32
    As you can probably already see, DNS is a really important part of the web. 0:35
    Let's see how it works. 0:40
    When it comes to DNS, proximity matters. 0:42
    Depending on where you are and when you log onto the Internet, 0:45
    you may use a different DNS to find websites. 0:49
    [SOUND]. Meaning the DNS that looks up 0:52
    teamtreehouse.com when you're at home, may not be the same DNS at work or school. 0:55
    Say, for example, you hit up your local library for some free WiFi. 1:02
    When you log onto the Internet, 1:07
    the library's internet service provider tells your computer 1:08
    what DNS to start with when looking up IP addresses for domain names on the web. 1:12
    Although, not every DNS server knows every domain name. 1:18
    For example, when I type in teamtreehouse.com into my address bar, 1:23
    the DNS system begins by looking at the top level domain or 1:27
    .com in the case of teamtreehouse.com. 1:32
    It will then ask which server the domain teamtreehouse is on, 1:35
    if it doesn't already know. 1:39
    Within DNS there's a hierarchy of servers, so if one doesn't know, it sends a request 1:41
    to the next server, and the next, until the correct website is located. 1:47
    If all goes well, the server sends a short message back to the client, 1:52
    your computer, saying that everything is okay, followed by the web page itself. 1:56
    The DNS system is quite complex, but 2:01
    the important takeaway is that DNS is the address book for the Internet, 2:03
    and it's what connects domain names with IP addresses. 2:07
    If you're interested in learning more about DNS, check out the teacher's notes. 2:11

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