Lec-81: Domain Name System (DNS) in computer Networks transcript

Hello friends. Welcome to Gate Smashers. The topic is DNS. Domain Name System. Why we use is Domain Name System or Domain Name servers To map the Domain names With the IP address Means in real life environment on daily basis we open lots of websites and lots of web applications what we enter ? Lets say lets say Google Facebook YouTube Do we ever add IP address No. We always enter domain names So here the concept is that user always recalls by domain names not by IP address reason behind this is it is easy to remember pictures and name as our mind can easily capture names and pictures than capturing numbers is difficult for example as I have written an IP address Do we ever discuss with our friends or anyone to open this or any IP address No we never talk like this lets say This is an IP address and this IP address is of crickinfo As a cricket lover I take example of cricket It is an IP address of crickinfo.com So we never open with IP address we always use domain name So the very first use of domain name server or domain system that user always remember domain with name so it become very easy to search any website and we can also say that that it work like a phonebook in phonebook we never say that search anyone with number we remember person name and than by person name only we search alphabetically in dictionary or in phonebook we find out the particular value and second main reason to use DNS is is that IP address are dynamic they are never static Like if you made any web application lets say xyz.com you made a website and hosted it on amazon web services you purchased database and hosted and hosting means that you got your IP address but everyone will search you by which name ?

They will search you by xyz name not by your IP address Lets say after 1-2 years you or amazon decided to shift to other ip address or you find amazon a bit expensive so you decided to use any other web application or any other web provider lets say godaddygo when you shifted to other web application your database will remain same so there your name of website xyz Everyone remember you with you name xyz not by your IP address your Ip address in this case is changed but your name remains the same If you change the name of your website from xyz to abc than you have to start business with new way because everybody knows you by your name xyz so here IP address are changing from backend but the name of domain database remain same yes it keep on updating but the domain name should remain same so these are the major two reasons to use DNS Next , if we talk about that how we search by adding domain name Lets say in my system I opened browser and on browser I entered , lets take a example crickinfo.com when I typed Crickinfo.com what happen next is I have entered domain name so this domain name will first get mapped with IP address so this is not my responsibility for this we have this architecture and this is a hierarchical architecture In which there is Root server this is a root road from here request firstly will go to root server This also have 2 methods it can be recursive or iterative mode so here so firstly request goes to root server or basically it work as a resolver means in middle resolver is there work of resolver is to resolve this Domain name into ip address Root server will get request first for your knowledge I tell in this entire world there are 13 root servers all over the world so your request will go to root server first and from root server will give you a IP address You means to resolver it will give a IP address and that IP address and location will be of next level Now the next level is generic server level or country server level in which the domain which you have searched crickinfo.com so in this resolving will be done from right to left means it resolves from backsides to .com here the .com commercial non profitable organisation .in we use for India for military , for education , there are different different domain so your request will forward to which server they will forward to .com servers so here what we have done is distribution we have divided the traffic instead of going to one place traffic is we send the request to this load or to this link there is no need to move to rest . generally these .com servers are not single server they are multiple servers so that load balancing can be done easily after .com from second level we move to authoritative level Authoritative servers are are servers they store all IP address and names Name is crickinfo and crickinfo ip address is saved in authoritative server it can also happen that crickinfo have multiple ip address like Google , YouTube these are high level organisations they cannot work with single server like we talk about Facebook in Facebook only there is near about 70,000 servers so as every the so many servers there could be chance of having multiple ip address also So authoritative server will choose one of the ip address and that ip address you have to search so how your request is working firstly sent to resolver resolver to root server root server asking resolver to move to commercial than to commercial commercial is giving address to resolver and with that address move to authoritative server from there request is sent to authoritative server from here i get ip address and that ip address will be given to resolver and that resolver will bring back it to my browser So this is resolving name is mapped with ip now after this this crickinfo lets say crickinfo it is hosted in a Europe country so now your request will send to Europe that any data you have to check or check match score from there your data will come this is how from basic level i have explained i will explain recursive and iterative mode in more detailed in my next video but here i have explained the basic idea how DNS work and how many components are there how many components are there in hierarchal architecture from where the domain name is mapped into ip address although everytime we don’t require this because our ISP internet service provider is responsible and it always keep cache cache meaning it store in cache memory always your request is not sent to root server whenever we search any website for first time than it sent to root server next time the ISP will store it so the next time your request do not take this much time and it get resolved easily There is DNS caching concept also that we will discuss in next video and recursive and iterative mode will also be discussed in next video so here are the two reasons I have mentioned that why we use DNS thank you