How a DNS Server (Domain Name System) works.
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May 26, 2016
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- 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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