DNS
Before HTTPS/HTTP connection is done, how does it find the target's address over the internet... just like any street address? How does it find with just the name?
Why DNS was needed?
DNS stands for Domain name server.
We all know our system understands machine language and it is hard for a human to understand that language ...Comm'n we all are trying to be sane who are we kidding? That's why each device connected on the internet has a unique public IP. So that the identification becomes simplified and faster. Let's say I type hamleys.com on my browser, it won't understand it needs a machine-friendly address to look on to internet's street ....thus it will find the IP address of hamleys.com firs then carries out further connection i.e. HTTP/HTTPS connection with hamleys.com site. The process of resolving the domain name to machine-friendly address i.e. IP address...is where DNS routing picture comes in! Let's have an even better understanding as we go further.
DNS basic
Top-level domain (TLD):
The part after the dot
EX: .com/.net/.org
Naked domain:
The name followed by TLD
EX: hamleys.com
Subdomain/fully qualified domain:
Anything that is added in front of the naked name becomes a subdoamin/ fully qualified domain.
Ex: www.hamleys.com (completely different than hamleys.com we understand it with an example)
or server1.yada.ghost.example.com
Understand with an example
There are certain people on the internet whose sole purpose is to mainatin the addresses and each one of them does Only One thing.
When I say people it means: set of servers around the world
The following are those people and That one thing!
ISP/resolving DNS
-The job of this person is to find the IP address of whatever domain user is looking for instead of the system.
-This will user's internet service provider. It will talk to through the following people.
Root DNS
-Holds information about all the TLD.
-i.e. It knows the IP address that holds .com / .net / .org
TLD DNS
-He is the authorized person for the naked domain
-i.e. He knows who owns these naked domains...i.e. Name Server's address.
Authoritative DNS
-Has all the domain record
-It knows the IP addresses of the nameservers that are holding the target Ip address.
-for example, it could be Cloudfare/Route53...
FLOW
For the first time I am trying to connect Hamleys's site, i.e. for the first time I type hamleys.com in my browser.
It first connects to my Internet service provider DNS i.e. airtel.
Asks: Hey! my girl wants to buy some soft toys from hamleys.com. Do you know where it is?.
ISP DNS: Give me a sec, I will ask around and will tell you
ISP DNS will contact Root DNS
ISP DNS: Hey, do you happen to know the address of hamleys.com?
Root DNS: Sorry buddy. But I do know the address of a person who maintains the record of domains that ends up with .com (i.e. TLD). He can help you.
He takes the address of TLD and rushes to it.
ISP DNS will contact to TLD DNS
ISP: Hey lad! please help me with the address hamleys.com
TLD DNS: I know the servers who holds the authority for this domain.
They can definitely of great help.
here is where the name server comes into the picture. It will receive the address of name servers who hold the target's IP address
ISP DNS will contact to Authoritative DNS
ISP: Ghosh! it's so sunny and I'll treat you with SMOOR's desserts if you can help me out with this address: hamleys.com. Will ya??
Authoritative DNS: Hell yeah !! make that two for me. This is the address you are looking for, buddy. (chuckles)
ISP: Aaahaa!!! You are a savior.
ISP DNS goes back. Feeds the system i.e. it tells the IP address.
The system will make a call to webserver i.e. hamleys.com with IP address xx.xx.xx.xx. Then HTTPS/HTTP connection happens another story goes behind the scene click here to understand this encryption.
And tadaaaa! thats how the name resolving happens and the connection is established. :) You guys did a great job read this silly script. :P
By the way, I forgot to tell the IP address xx.xx.xx.xx is stored in the cache of the user's system. And along with IP address of hamleys.com Authoritative DNS also gives something called as TTL value i.e. Time To Live value. Which mean...TTL defines how long the IP address is supposed to live in the user's cache whether its 2 sec or a day...could be anything. Once that TTL time expires the entire process of resolving DNS and connection establishment happens. Thus going through the entire process and bribing people on the way with SMOOR's desserts... :P
DNS record types
Listed out the common once which we kinda see in our daily life
A: IP of a domain address
ex: hamleys.com is mapped to xx.xx.xx.xx IP
NS: IP of Name Servers
Maps domain to a nameserver, which acts as authoritative for the domain.
CNAME: one domain's address points to another domain.
Also known as Alias
ex: hamleys.com is map to xx.xx.xx.xx IP
www.hamleys.com is map to hamleys.com
So when hit on either of the domain it will point to the same destination.
MX: IP address of mail servers, like an A record.
if hosting your own mail server this comes into play.
SOA: Start of authority, record indicting who is the owner of the domain. Usually, it will be one of the nameservers.
TXT: Additional domain information/validation
One can add their own domain in google maps, with help of this does some verification stating the user is the actual owner of this domain none is just dumping some random crap. Benefits of it are pretty good if I explore about this in future ill definitely post it :)
Happy Learning
