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DNS and How does it work? with Английский subtitles   Complain, DMCA

hey everyone this is kamran and today

we're going to talk about the dns

or the domain name system dns is one of

those topics that anyone who develops

should know about it is a broad topic so

i'm going to divide this lesson into two

in this lesson we're going to talk about

what is dns and how does it work

and the next one is going to be about

the dns records and how to debug the

traced out and nslookup so what is dns

before we learn about the dns we need to

and before we learn about the internet

we need to know what is a network

network is just a group of computers and

other devices that are connected to each

other so for example if at your home you

have a printer you have a laptop and a

and all of these are connected to each

other these are all forming a network

moving on we have internet which is a

so for example if you at your home have

a home network and then your friend has

and then he has another friend which has

a home network and all these networks

are grouped together to form a bigger

so internet is similar to that just a

global network of all the networks

now on the internet if you have to

communicat­e with some other device you

to find the device on the internet we

use something called the ip address

so each device on the internet has an ip

format and it looks like this and it is

used to locate that device on the

and same goes for the websites that you

the ip address of the server where that

is used to load the website in the

browser but how does it work because we

normally put the domain name in the

how is the browser able to find the ip

the answer to that is the browser uses

which helps us get the ip address from

the browser sends the dns the domain

and it gets back the ip address and once

it has the ip address it can go on the

and hop from different routers till it

server and then it loads the website

okay now that we've got the high level

and how it works let's look at the dns

and see how it works internally

so first of all we have the browser so

the user enters the website in the

and tries to open it as we know that the

first step is dns resolution so the

browser needs to find the ip address

of the website first of all the browser

and see if it has the ip address of the

website from any previous visits if it

doesn't find it there then it will look

at the dns cache and see if we have the

ip address there and if it is also not

there then it will look at the host file

to see if we have a mapping from the

defined there if it is able to find the

ip address in any of these places

it will load the website from there and

it will not do any of the next steps

that we will mention now if it is not

able to find the ip address in any of

or the host file the next step is the

recursive dns servers this is normally

or internet services provider which

provides you the internet now it doesn't

domain name but it has the caches from

so it is possible that some other user

might have visited the same website

and might have the cached ip address if

it is able to find the cache type

address it will just return the ip

address from here and it does not have

and if the ip address is not found here

then the next step is the root dns

now root dns servers also do not have

the ip address informatio­n for the

but they have the informatio­n about the

so for example if you're looking for

or the top level domain is dot com so it

who might have the informatio­n about all

the dot com domains so it will just

return the informatio­n about the

tld server now the tld server also

is but it knows the final place where

the domain informatio­n be which is the

so it will just return the informatio­n

about the authoritat­ive name server and

the request will go to the authoritat­ive

get the ip address of the domain name

the ip address will then come to the

where it might be cached and then it

will be sent to the user's computer

and then to the browser and then the

browser will request the website

servers and get the website from there

ip address of the website is found on

the internet with the help of dns

and that's it for our lesson i hope you

enjoyed it if you have any questions or

leave them below and i will see you in

   

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