1 00:00:02,130 --> 00:00:02,880 Hello, everyone. 2 00:00:03,510 --> 00:00:08,880 So in this video, we're going to see how do we find a website on the Internet? 3 00:00:09,930 --> 00:00:11,430 So we are going to take an example. 4 00:00:12,480 --> 00:00:15,340 Let's say Rohit wants to use a Facebook. 5 00:00:15,990 --> 00:00:21,670 So how does Rohit's computer identify the Facebook server? 6 00:00:21,960 --> 00:00:22,950 How the system. 7 00:00:23,850 --> 00:00:26,760 So DNS comes to the help. 8 00:00:29,290 --> 00:00:37,760 DNA stands for domain name service or sometimes referred as domain name server or domain name system. 9 00:00:39,910 --> 00:00:47,850 So with the help of DNS only any client is able to reach to a particular server. 10 00:00:48,550 --> 00:00:58,000 For instance, Rohit is able to reach to the Facebook server and is able to serve the content into his 11 00:00:58,180 --> 00:01:01,960 browser and the client side and is able to use the application. 12 00:01:03,310 --> 00:01:05,570 So how does this actually work? 13 00:01:06,100 --> 00:01:07,150 So we are going to see. 14 00:01:08,770 --> 00:01:16,390 I highly recommend coming onto this particular website, which is how DNS works, which is beautifully 15 00:01:16,390 --> 00:01:21,890 illustrated, the functioning of DNS in a cartoonist manner. 16 00:01:22,900 --> 00:01:28,080 So let us start this and see over here. 17 00:01:28,360 --> 00:01:31,340 Episode one, the website is unknown. 18 00:01:31,540 --> 00:01:37,220 So we do not know how are we going to reach to that particular Web site. 19 00:01:38,110 --> 00:01:45,940 So this is Rohit and he's going to type dnssimple.com into his browser and it's going to hit enter 20 00:01:47,320 --> 00:01:53,980 Freeze computers and other devices, communicate using IP addresses to identify each other on the Internet. 21 00:01:54,190 --> 00:01:59,920 And we know this, but humans can't remember IP addresses, so they use words. 22 00:02:01,360 --> 00:02:08,230 So in case I asked you guys, can you tell me 10 shopping websites name? 23 00:02:08,620 --> 00:02:14,880 You will quickly tell me Amazon, Flipkart, Jabong, Myntra and so on. 24 00:02:15,910 --> 00:02:25,600 But if I ask you 10 website IP address, which contains a shopping or I can buy some electronics from 25 00:02:25,600 --> 00:02:28,350 there, you won't be able to tell me the IP address. 26 00:02:28,960 --> 00:02:29,380 Why? 27 00:02:29,830 --> 00:02:35,610 Because we cannot remember numbers, but we can easily remember names. 28 00:02:36,310 --> 00:02:40,660 So for our help there is DNS. 29 00:02:41,140 --> 00:02:44,790 DNS brings together both of them. 30 00:02:45,100 --> 00:02:53,410 That is the name and the number, but is the domain name and the IP address and gets us to our destination. 31 00:02:53,770 --> 00:02:56,290 So this is how DNS works. 32 00:02:56,510 --> 00:03:01,610 It was very simple, but let us understand something in more depth. 33 00:03:02,920 --> 00:03:12,400 So whenever you type any particular address into your browser, for example, Rohit wants to use Facebook 34 00:03:12,400 --> 00:03:15,290 and he will type Facebook dot com into his browser. 35 00:03:16,090 --> 00:03:24,970 The first thing that will happen is the first request that has been checked is into the browsers. 36 00:03:25,210 --> 00:03:25,710 cache. 37 00:03:26,590 --> 00:03:35,400 So once the browsers cache is checked and if the website is not open earlier into the browser ever or 38 00:03:35,440 --> 00:03:40,030 saved into the cache, then the request goes to the OS. 39 00:03:40,840 --> 00:03:43,750 And OS also has its own cache. 40 00:03:44,710 --> 00:03:56,950 Once it is not able to find into the browser or the OS cache, then the request will now go to a round 41 00:03:56,950 --> 00:04:08,260 trip as the request will move or will leave the computer and now it is going to start its round trip. 42 00:04:09,370 --> 00:04:20,250 All right, let's go to the next episode and see ,so the request moves out of arrowheads, computer and Rohit 43 00:04:20,260 --> 00:04:22,020 house and goes out. 44 00:04:22,840 --> 00:04:26,890 Now the request reaches to the resolvers inbox. 45 00:04:27,490 --> 00:04:28,630 Who is the resolver? 46 00:04:29,140 --> 00:04:36,760 Resolver is none other than your ISP, which is your Internet service provider that gives you Internet 47 00:04:36,760 --> 00:04:37,260 service. 48 00:04:37,930 --> 00:04:45,890 So once your request reaches to the ISP, that is because you want to open Facebook dot com ,sure Rohit 49 00:04:46,120 --> 00:04:46,960 you can open it. 50 00:04:47,620 --> 00:04:52,930 So the ISP is going to check its own cache first again. 51 00:04:53,890 --> 00:05:00,490 And if he is not able to identify the website, then we are going to ask the Root! 52 00:05:01,030 --> 00:05:08,710 So a road trip is going to get continued because even the resolver, which is our ISP, does not know 53 00:05:09,220 --> 00:05:10,710 where is Facebook dot com. 54 00:05:12,100 --> 00:05:16,000 So there is always a server is usually your ISP and we know that now. 55 00:05:16,730 --> 00:05:24,040 Now our request is going to the route server the route server knows where to locate the dot com 56 00:05:24,040 --> 00:05:24,670 TLD. 57 00:05:25,330 --> 00:05:28,300 So dot com is basically what is added. 58 00:05:28,930 --> 00:05:40,360 Behind our website, for example, Google dot com, Facebook dot com, and there are more such top-level 59 00:05:40,360 --> 00:05:45,970 domains like edu.gov.in etc 60 00:05:48,440 --> 00:06:00,340 Now, next, when the request reaches to the root servers, then the root server ask, what do you want? 61 00:06:01,130 --> 00:06:07,090 And we are going to say here what we want to open Facebook dot com. 62 00:06:08,870 --> 00:06:10,640 Do you know where can I find it? 63 00:06:11,510 --> 00:06:13,830 So the root says "sorry" resolver. 64 00:06:13,850 --> 00:06:19,180 I do not know where to find Facebook dot com, but I can tell you where to find them. 65 00:06:19,190 --> 00:06:21,620 Dot com, top level domain server. 66 00:06:22,160 --> 00:06:26,390 So now a request is going to the dot com TLD server. 67 00:06:27,320 --> 00:06:34,910 So a route has different different DNS hierarchies of TLD's. 68 00:06:35,330 --> 00:06:42,230 For example, as you can see a little zoom out a little bit .com , .org, .net. 69 00:06:42,230 --> 00:06:44,840 And there are many such like that. 70 00:06:45,710 --> 00:06:53,810 So root checks for whatever the request has came of the client, for example, as it wants to see 71 00:06:53,990 --> 00:06:55,090 Facebook dot com. 72 00:06:55,910 --> 00:06:58,940 So the route is only going to check the TLD. 73 00:06:59,120 --> 00:07:03,680 That is the top level domain in the dot com hierarchy. 74 00:07:04,460 --> 00:07:08,530 And here the route will be able to find it. 75 00:07:08,820 --> 00:07:09,230 Why? 76 00:07:09,830 --> 00:07:20,380 Because all the domain names which are registered has all its database saved to the root server. 77 00:07:20,930 --> 00:07:29,900 So anytime you buy any domain from GoDaddy, Namecheap or anywhere in this world, always a small fee has 78 00:07:29,900 --> 00:07:35,060 been taken from you, which we generally call it, as I can fee. 79 00:07:36,290 --> 00:07:45,920 So your particular domain name or your particular website name are added into the root servers 80 00:07:45,920 --> 00:07:50,190 hierarchy this is compulsory and that has to happen. 81 00:07:50,210 --> 00:07:58,130 So basically the root root knows if any website has been made or deployed with any particular domain 82 00:07:58,130 --> 00:07:58,460 name. 83 00:07:59,180 --> 00:08:08,600 And finally we are able to see the particular website how once route is able to identify. 84 00:08:08,630 --> 00:08:17,060 OK, Facebook dot com lies and the dot com tlt and it is pointing to IP address, let's say it points 85 00:08:17,060 --> 00:08:23,570 to the IP address 10.10.10, and then route is going to say, Ok Rohit,this 86 00:08:23,750 --> 00:08:25,940 I have identified Facebook. 87 00:08:25,940 --> 00:08:28,040 Dot com is pointing to this IP address. 88 00:08:28,190 --> 00:08:30,290 Now you can fetch Facebook. 89 00:08:30,950 --> 00:08:40,040 So now Rohit is going to come back, which is taking the request or the response back to his computer. 90 00:08:40,910 --> 00:08:47,450 Once he is coming back, he will keep on saving the particular response that he have got from the root 91 00:08:47,450 --> 00:08:47,960 server. 92 00:08:48,140 --> 00:08:55,460 In all the cases, for example, that resolver is going to say it into its cache first, then the browser 93 00:08:55,460 --> 00:09:03,770 will save it as well as the OS will save it into its cache why so that the whole process or the 94 00:09:03,770 --> 00:09:06,890 whole round trip does not happen again. 95 00:09:07,550 --> 00:09:10,640 So I hope you guys understood how actually DNS works. 96 00:09:11,060 --> 00:09:19,370 And whenever you type anything into your browser, how the request goes from your browser cache to your 97 00:09:19,370 --> 00:09:24,530 OS cache, then to your resolver, then to the root and then to the server. 98 00:09:25,280 --> 00:09:25,820 Thank you.