. Stands for Domain Name System.
. Humans communicate to various websites using domain names like yahoo.com and google.com etc.
. But computers are addressed with numbers called IP addresses.
. To bridge communication gap between humans and computers, DNS resolves domain names to IP addresses.
. Humans communicate to various websites using domain names like yahoo.com and google.com etc.
. But computers are addressed with numbers called IP addresses.
. To bridge communication gap between humans and computers, DNS resolves domain names to IP addresses.
Why is it important?
. It acts like phone book. If we don't know person's number but only their name, we look up in phone book using their names.
. If DNS is not there, we would have to view websites using IP Address instead of names which is very complicated.
How it Works?
Step 1:
. When you type any website name in browser, your computer looks in it local DNS cache.
. Local DNS cache stores information that your computer already retrived.
. If it founds, it returns IP Address and computer connects to that website.
. If not found, it sends query to next level called Resolver Server.
Step 2:
. Resolver server is basically ISP (Internet Service Provider) server.
. When it receives query, it will check in its cache memory to find IP Address.
. If not found, it sends query to next level called Root Server.
Step 3:
. Root Servers are top or root of DNS hierarchy.
. There are 13 sets of root servers strategically placed around world.
. Operated by 12 different organizations.
. When it receives query from resolver, it doesn't know IP address.
. But it knows to direct resolver to find IP address.
. It directs resolver to Top Level Domain (TLD) for .com domain.
Step 4:
. Resolver sends query to TLD server which is directed by Root Server.
. TLD server stores address information of all top level domains like .com , .org and .in etc.
. This particular TLD server manages .com domain addresses.
. It doesn't know IP Address requested by resolver but it directs to final level called Authoritative name servers.
Step 5:
. Now Resolver sends query to Authoritative Name Servers.
. These are responsible for knowing everything about domain which includes IP Address.
. So when it receives query for any domain like abc.com, it responds with IP address.
. Now finally, Resolver can tell your computer the IP address for abc.com.
Note:
. Once Resolver receives IP Address, it stores it in the local cache memory so that it doesn't need to repeat all process again.
. Entire process from start to finish takes only milliseconds to complete.
. Entire process from start to finish takes only milliseconds to complete.