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