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How a DNS Server (Domain Name System) works.

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May 26, 2016

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How a DNS Server (Domain Name System) works.
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Transcription

  • In the world of networking, computers don't go by names like humans do, they go
  • by numbers, because that's how computers and other similar devices talk and
  • identify with each other over a network, which is by using numbers such as IP
  • addresses. Humans on the other hand are accustomed to using names instead of
  • numbers,
  • whether is talking directly to another person or identifying a country,
  • place, or thing, humans identify with names instead of numbers. So in order to
  • bridge the communication gap between computers and humans and make the
  • communication of a lot easier
  • networking engineers developed DNS, and DNS stands for a domain name system. And DNS
  • resolves names to numbers, to be more specific
  • it resolves domain names to IP addresses. So if you type in a web address in your
  • web browser, DNS will resolve the name to a number because the only thing
  • computers know are numbers. So for example if you wanted to go to a certain
  • website you would open up your web browser and type in the domain name of
  • that website, so for example let's use yahoo.com. Now technically you really
  • don't have to type in yahoo.com to retrieve the Yahoo web page, you can just
  • type in the IP address instead if you already knew what the IP address was, but
  • since we are not accustomed to memorizing and dealing with numbers,
  • especially when there are millions of websites on the internet, we can just
  • type in the domain name instead and let DNS convert it to an IP address for us.
  • So back to our example, when you typing yahoo.com your web browser
  • the DNS server with search through its database to find a matching IP address
  • for that domain name, and when it finds it it will resolve that domain name to
  • the IP address of the Yahoo web site, and once that is done then your computer is
  • able to communicate with a Yahoo web server and retrieve the webpage. So DNS
  • basically works like a phone book, when you want to find a number, you don't look
  • up the number first, you look up the name first then it will give you the number.
  • So to break this down into further detail let's examine the steps that DNS
  • takes.
  • So when you type in yahoo.com in your web browser and if your web browser
  • or operating system can't find the IP address in its own cache memory, it will
  • send the query to the next level to what is called the resolver server to resolver
  • server is basically your ISP or Internet service provider, so when the resolver
  • receives the query, it will check its own cache memory to find an IP
  • address for yahoo.com, and if it can't find it it will send the query to the
  • next level which is the root server.
  • The root servers are the top or the root of a DNS hierarchy. There are 13 sets of
  • these root servers and they are strategically placed around the world,
  • and they are operated by 12 different organizations and each set of these root
  • servers has their own unique IP address. So when the root server receives the
  • query for the IP address for yahoo.com, the root server is not going to know
  • what the IP address is, but the root server does know where to send the
  • resolver to help it find the IP address. So the root server will direct the
  • resolver to the TLD or top-level domain server for the dot-com domain. So the
  • resolver will now ask the TLD server for the IP address for yahoo.com.
  • The top level domain server stores the address information for a top-level
  • domains, such as.com and.net dot org and so on. This particular TLD server manages
  • the dot-com domain which yahoo.com is a part of.
  • So when a TLD server receives the query for the IP address for yahoo.com, the
  • TLD server is not going to know what the IP addresses for yahoo.com. So
  • the TLD will direct the resolver to the next and final level, which are the
  • authoritative name servers.
  • So once again the resolver will now ask the authoritative name server for the IP
  • address for yahoo.com.
  • The authoritative name server or servers are responsible for knowing everything
  • about the domain which includes the IP address. They are the final authority. So
  • when the authoritative name server receives the query from the resolver, the
  • name server will respond with the IP address for yahoo.com. And finally the
  • resolver will tell your computer the IP address for yahoo.com and then your
  • computer can now retrieve the Yahoo web page.
  • It's important to note that once the resolver receives the IP address, it will
  • store it in its cache memory in case it receives another query for yahoo.com so
  • it doesn't have to go through all those steps again.

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Description

This is an animated DNS tutorial showing what a DNS server is and how it works. It explains the different levels of DNS, such as the resolver, root server, domain server, and authoritative name server.

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