How does the internet work? (Full Course)

0:00This course will help someone with no technical knowledge. Understand how the

0:04internet works in frost teaches this course with tons of visuals, just like he has taught

0:101000s of people on Udemy. The internet is a part of our daily life, and we use it constantly.

0:18But what is the internet? Have you ever really thought about it? Have you ever wondered what

0:24happens in the background? Then you enter a web page? If your answer to all these questions

0:30is yes, you are definitely looking at the right course in this course, I assume you don't know

0:35anything. And I am slowly explaining what the internet is, you don't need any prior knowledge

0:42to follow this course, since this course tells you everything from scratch, which mean abstractions,

0:48these abstractions will allow you to understand the subject without knowing details. I think

0:55everyone who uses the internet should know its basic features. Everyone who uses the internet

1:02needs to know the ISP, everyone who uses the internet needs to know that the internet is

1:08just cables spread all over developed. And in this course, we will go on a journey together.

1:15And we will look at all these concepts in a very visual way. I mean, you will see exactly how the

1:21internet works, which are eyes. In addition, at the end of the course, there are some questions

1:27related to this course. And by answering them, you can benefit from this course, at

1:32the maximum level. Okay. regardless of your age or profession, this course is for everyone, you will

1:40absolutely understand what the internet is when you finish this course. So let's dive into it.

1:56Now, we are going to talk about a scenario. Let's say you are the system administrator of a small

2:02company, and your boss wants you to enable all these computers to communicate with each other.

2:08I'm in PC, one should be able to communicate with PC seven, our PC five should be able to

2:15communicate with PC four, and so on. He's got the point. But the question is, how do we do such a

2:21task. And this is where the solution device comes into play. The switch is the device we use for

2:28computers in the same environment to communicate with each other. When I say in the same

2:34environment, what I mean is that I'm talking about computers in the same office house or at work

2:42close distance to each other. And this scenario is a good example for such a situation, there is an

2:49office and in this office, we have seven computers that communication of them is required. Wonderful.

2:56We have a switch to accomplish the communication of computers. This is good. However, the question

3:03is, Can these seven computers communicate with each other right now? And the answer is big. Now,

3:12because first of all, these seven computers need to interact with the switch somehow. But

3:18how can we do that? I know that you have some ideas and you are probably guessing right we must

3:25use cables to connect computers to the switch. As you can see, we are connecting all the computers

3:32to the switch with the help of cables. We generally use copper cables for this task. And the

3:38type of these copper cables can generally be cat five cable or cat six cable in small environments.

3:45By the way, cat six cables are faster than cat five cables and cat represents category okay.

3:53On the other hand, in addition to copper cables, some switches support fiber optic cables as well.

4:00And it is important to note that fiber optic cables are generally much faster compared to

4:06copper cables in data transmission. This is very important. And for switch devices,

4:14there is a crucial point to be aware of. Please note that if there is a switch in the environment,

4:21and if you want to connect computers to that switch,

4:24we must definitely use a cable that has generally a copper cable or fiber optic cable. What I have

4:31tried to say is with wireless technology, you cannot connect computers to a switch switches

4:38only work with cables. This is very vital guys. If you want to use a switch device,

4:43you have to use cable to connect your devices to the switch. It's that simple. However, if you want

4:51to connect computers in the same environment to each other, by using all the wireless technology,

4:57you can use an access point device in If I switch device, I mean, you can use both a switch device

5:03or an access point device. In order to connect all the seven computers, both of them separately is

5:09acceptable for this purpose. The only difference between these devices is access points use

5:16wireless technology while switches use cables. Okay, there are seven computers

5:22in this environment. And we can connect these seven computers. By using switches and cables,

5:28just like you see in the picture. Or in the same way, we can use an access point device

5:34instead of a switch device. And if you use an access point device access point uses wireless

5:41technology instead of cables while communicating with devices. In summary, both the switch device

5:48or an access point device enable these seven computers to communicate this is obvious,

5:53but one uses cable and the other one uses wireless technology. Anyway, what I just want you to know

6:00right now is we generally use copper cables in order to connect computers to the switch

6:07in the environment such as a home or office. By the way, I want to focus on the source device

6:13instead of the access point device in discourse, wherever. And at this moment, all these computers

6:21can communicate with each other which is because they connected to the switch by using cables.

6:28And this means that they created a network. In other words, the reason that these computers

6:34can communicate with each other is all of them are in the same network and we call this special

6:40network as local area network or briefly, LAN. A local area network is a collection of devices

6:48connected together in non physical location, such as a building, office or harm. As I just said,

6:55if you want to create a LAN, this location must be a restricted location in terms of area, I mean,

7:02you cannot create a LAN between computers located in United States and computers located in Russia.

7:10On the other hand, this area is very suitable area in order to create a LAN. Therefore, these

7:17computers can communicate with each other because all of them are on the same land. With the help of

7:24this search search, we can deduce that if you want to create a LAN, when it is the wish device. By

7:31using a switch device, we can create a local area network. And if we consider the millions of local

7:39area network all over the world, we can easily understand how important is swish device is,

7:46you might think that all the houses in the world are actually a local area network, you have a LAN

7:53in your house or your neighbor's home also has a LAN or there is also a LAN in the office where you

8:00work. Okay, you catch the idea. And now let's take a closer look at the communication of computers.

8:07And what this event actually represent. Let's say pc one was to send a message to the PCs six. By

8:15the way, the messages generated by computers has a few special names, some people call them as packet

8:22and some people call them as frame both of them is okay but in this course, I prefer to use packet

8:30instead of frame. Okay, PC one, you set a packet to the PC six. As you see in Division, the packet

8:39first goes to the switch, and then the switch looks at the inside of the packet or learns the

8:45destination of the packet. And finally, the switch sends the packet to its destination.

8:52And if pc one can set a packet to the PC six, this means that PC One and PC six can communicate with

9:00each other. The logic is basically this if a computer can send a packet to another computer,

9:07this refers to these two computers are on the same network and they can communicate with each other.

9:13This information is so crucial guys, okay. However, maybe by looking at

9:20only this switch image, what the switch device actually is may not be fully visualized in your

9:26mind. For this reason, we will now examine this slide for you to understand the event better.

9:33This is the real version of a switch device. And as you can see, there are many ports

9:39on a switch device This is important also the number of ports varies from one switch device to

9:46another switch device. I mean different switches have different numbers of ports. Some switches

9:52have 10 ports, while some switches have more than transports and of course, this generally leads to

10:00an increase in price. Okay. By the way, these ports have a special name and they are called

10:09LAN ports. This probably makes sense to you because as you know, we create lands by using

10:163g devices. For this reason, I think it is so reasonable to call these ports LAN ports. Because

10:23by connecting these computers to these ports, we can create a LAN. And in addition to this,

10:30there are LAN ports on the back of our computers, or on the side of our laptops,

10:37just like these LAN ports, you can see the Related regionals on the right side.

10:54And to establish a connection between computers and the switch, we connect the LAN port on the

10:59computer and the LAN port on the switch with the help of a cable. So let's do this. Let's

11:06start with this port and PC one, then, let's connect this port and P theater. After that,

11:13let's connect this port and PC three. And finally, I want to make a connection between this port

11:20and PC four. Wonderful. And currently, these computers can communicate with each other. But

11:28how exactly does this communication happen? From a switch perspective, let's take a look at this,

11:34let's say pc one master communicate with PC far saw, it will send a packet to the PC far this

11:42packet will go to this part of the switch first. And there we go. Afterwards, that part, we will

11:50give the packet to the hardware inside the switch Okay. Then, this switch, we look inside this

11:56packet, our loves his destination. After that the switch give this packet to this port that

12:03is connected to PC far. And finally, the switch says the packet to the PC far. Okay, wonderful.

12:13And to summarize, currently, we have connected these four computers to each other

12:18thanks to this switch. This means we have created a local area network. And these computers can

12:25easily communicate with each other. Since they're on the same LAN. I hope everything is quite good

12:30software. And the switch device is visualized spreader in your mind, thanks to this slide. But

12:37there is a little issue here. Let me explain. If you are aware, our computers were in the

12:43same network. And we have only talked about the communication between dos devices. We have never

12:49talked about how these computers can connect to the internet. Right? So the question is, Can these

12:56computers communicate with the internet just by having a switch device? And this my friends

13:04will be the question that we are looking for an answer in the next lesson. See you guys soon. Bye.

13:16In our previous lesson, we briefly talked about how to connect computers in our office, and how

13:22do we create a network and I said that we can create a LAN with the help of a service device.

13:28But the problem is currently these computers can only communicate amongst themselves,

13:34they cannot communicate with the internet, because the all the task of the switch is to create a LAN

13:41and enable the communication of the devices in the same land. Great. And by the way, I would like to

13:48remove this lamp statement from the visual because you can understand that there is a LAN here, thus,

13:55we can work more comfortably. Wonderful. And the main question is, how do we connect these

14:01computers to the internet. And this is where the router device comes into play. Let me explain. The

14:08main task of the router is to enable computers to connect to the internet. Without a router it

14:15is impossible for us to connect to the internet. And in order to provide this connection. I mean,

14:20in order to provide a connection to the Internet. First of all, we must connect this switch to this

14:26router. And this cable is a copper cable. Just like other cables. This is good. But currently,

14:33what we have to do isn't over we still can't connect to the internet in this situation

14:39because we need a connection between the water and the internet as well. And as you know,

14:46a special cable comes to our homes or offices and this cable is given us by internet service

14:53provider and takes to this cable. We connect to the internet if you have never heard of

14:59internet service service provider. Don't worry, we will talk about it in detail. But for now,

15:04all you need to know is the internet service provider is giving us

15:09this cable for a certain amount of money so that we can connect to the internet easily. Okay,

15:15so currently, we have everything necessary to connect to the internet. By using these computers,

15:23hams, let's see the basic tasks of the switch and router one by one on the animation. These seven

15:30computers in the office can communicate with each other thanks to the switch. For example, let's say

15:36pc one was to communicate with PC five, for this purpose, PC, one will send a packet to

15:42the PC five, sir, is you know, the packet firstly goes to the switch. And afterwards, this switch

15:50learns the destination of the packet. And finally, this switch sends the packet to its destination.

15:55And there we go. This is how two computers in the same land communicate with each other. And please

16:02always remember, a switch device is enough for us in order for communication of devices

16:08in the same land. On the other hand, a router has no role in the communication of different devices

16:16in the same line, like PC One and PC five. This is very vital. Okay. I hope I could explain the

16:23events. And however guys, what if pc one was to communicate with the internet? In other words,

16:31what will happen if pc one first to send a packet to the internet? Let's see. First of all,

16:39you should remember this information. If a computer can send packets to the internet.

16:45This means that this computer communicates with the internet. For the speaking I believe that

16:51you exactly understand the logic of this event anymore. If we can send packets from one point to

16:58another point, these two points can communicate. It's that simple. But the question is,

17:04how will pc one send packets to the internet. To be able to do this first PC, one must start

17:12its packet to the switch just like before, because there is no other way for PC one to be able to eat

17:19the router, right? I mean, if pc one was to send a packet to the internet, this packet must reach

17:26the router no matter what, because the router is a door to access the internet. This is obvious.

17:33Hence, if pc one wants to communicate with the router, it must start its packet to the switch

17:40first. After that, the switch looks at inside of the packet and understand that the packet

17:46wants to go to the internet. So it sends the packet to the router. And there we go.

17:54And then the router firstly looks at the inside of the packet and understand that the packet wants

18:01to go to the internet. And afterwards, it sends the packet to the internet over this part. And

18:09there we go. By the way, if you're aware, we have plucked this cable that we purchased from the ISP

18:17into this port, this is our base. I believe that currently you can easily imagine in an intuitive

18:23manner, how the cables coming to router like this or like this are plugged into the ports. I mean,

18:30there are some ports on router, and you need to put the cables into that box. It's that simple.

18:37I will not show this visually, because detailed information about the ports

18:42isn't important for you. At this moment, you just must understand the logic behind the router. Okay.

18:50And as a result, PC one sent its packet to the internet. In other words, PC one and the internet

18:58communicated. And the device that helped us to connect to the internet is durata. Wonderful.

19:06I believe that you understand the most basic tasks of the sewage and water. And I hope

19:13the information may be useful for better understanding.

19:17However, I want to ask you two questions. My first question is, can you visualize the internet

19:24in your mind? And the second question is, what exactly does the internet meme

19:31and these will be the equations that we are going to discuss in the next lessons. See you guys.

19:44Before discussing the meaning of connecting to the internet,

19:47from a computer perspective, I think it is helpful to know what the internet exactly stands for.

19:54Because if you're really starting from scratch, I mean I assume that you are real newbies,

20:00you may not know exactly what the internet is. For this reason, I want to visualize the internet

20:07for a better understanding. To do this, in this lesson, we are going to see how a packet moves

20:14on the internet. By the way, keep in mind that this model USA is a simplified model designed

20:21to make the concept is the john deere stat. So this structure in real life is much more

20:28complex than you see individual. But with this simplified model, you will understand the logic

20:35of the event very well, I promise you. And I believe that's all you need right now

20:42is you can see, there are many routers on the internet, right. And there is a special reason for

20:49this. So at this moment, I would like to give you another piece of information about errata. irata

20:57is a device required for a computer or electronic device to connect to the internet,

21:03you know this definition. On the other hand, you can think of the router is the device we use to

21:10communicate with your computer in another part of the world, or you can think of the router is

21:16the device we use to communicate with a computer in a different plan. I mean, if you are aware,

21:23there is a LAN here, right. And there is another LAN here, this is obvious. Therefore,

21:29we can draw the following conclusion connecting to the internet actually can stand for connecting to

21:36the another computer located anywhere in the world. I mean, you can think of the internet

21:42is the structure that connects all the lands all over the world. I want to repeat this again,

21:49you can think of the internet is a structure that connects all lamps, all over devout. And as you

21:56know, there are millions of lamps connected to the internet, except these lands. Wonderful. I

22:05hope that everything is good so far, but there's a thing that we need to consider. So I want to

22:12ask you a question. Why are there so many routers here? Let me explain it in a simple manner. First,

22:19you should know that these routers are distributed around the world in an organized manner. However,

22:27routers aren't the only devices in the structure. This is important. There are tons of routers, and

22:34other different devices in this structure, distributed pre divide layer. But focusing on only

22:41routers is enough for us in order to understand the concept behind the internet. And the first

22:48question that comes to your mind is probably why routers are so important to the internet.

22:55As a matter of fact, the answer to this question is hidden in the core task of errata. The device

23:02we use to enable different lands to communicate with each other is dhiraj. Right? And text to the

23:08internet, we can connect all the laughs in the world to each other. You know, for this reason,

23:14it makes perfect sense to use many routers to connect millions of local area networks together.

23:21These last few see are just two of the millions of local area networks all over the world. In

23:27summary, if the internet must connect millions of local area networks, it is obvious that

23:33it needs routers. I hope you got this. And once you understand the importance of the

23:40router for the internet, you probably think of another question. And the second question that

23:46probably comes to your mind is why there are so many routers instead of just one router.

23:53And I think this is a more critical question than the first question and let me answer it

23:59on the ratio. But before answering this question, there is something in this picture that should

24:05catch your attention. Please look carefully at the picture and try to find this difference.

24:28As you can see these last on the visual one device instead of a switch and a router. So if there is

24:36no switch in the environment, how can there be a LAN or if there is no router in the environment?

24:44How can it be connected to the Internet, and this is where the home router comes into play.

24:51The home router is a common device consisting of a router and switch combination hands these

24:58devices in the last hour mix of the switch and router. This means that if we have a home router,

25:05we don't need an additional switch. And Roger, this device is enough for small and moments

25:11like a home or small office. This is important. I won't repeat this again, a home router is

25:19enough for us in small environments, or if there are very few devices in the environment, okay,

25:27I showed you home router, because most of you have these devices in your home,

25:32and you connect to the internet by using home routers. For this reason, I wanted to tell you

25:39what these devices are in order to avoid confusion. However, please note that if

25:46there are too many devices in the environment, the home router will be insufficient. And you

25:52may need additional switch and router, you catch the idea. And now let's go back to our question,

26:00why there are so many routers, instead of just a single router. Imagine that there is a single

26:07router in the middle of the world, instead of 1000s of routers distributed all over the world.

26:14In this case, millions of electronic devices around the world will tell to be connected

26:20to the same router. This is obvious, this means that this single router needs millions of parts,

26:27isn't it. And it is impossible to design such a device. But this is not done the problem. In

26:34addition to it, if there was only one router, the entire lot of the all devices in the world

26:40won't be on that router. And this is another problem. Because in computer science,

26:46we don't want to give all too lot on a single point. We even call this problem, the single

26:52point of failure. And this is a problem that needs to be considered to be able to teach it better.

26:59Let me give you an example. Imagine this router is broken somehow. This means that the Internet of

27:06the whole world is crashing down at the same time, right? Because we only use a single router to

27:12connect all this around the world. Rule two broke down and the whole internet crashed down. It's

27:19that simple. Just think about the consequences of this problem. In a second, this will be terrible,

27:27right. And so far, we have talked about two vital problems. But it isn't our another major problems

27:35is the cable length problem. Imagine how long the cable must be if there was all one giant router

27:43in the middle of the world, especially LANs that are the furthest from the giant router will need

27:50very long cables. This is obvious, right? Therefore, this design is a very problematic

27:56design. And the solution for all these problems is this distributed structure all over developed,

28:04you catch the idea. But to make sure you fully understand the main logic of this structure,

28:09I want you to do an exercise, I want you to determine why such a structure eliminates

28:16the problems we talked about shortly before, I'm sure that you can handle this. Just do it guys.

28:30I asked you a question at the end of the previous lesson. And I know that you were all analyzing the

28:37situation. But let's do it together just in case is you know, if he used a single router in the

28:44middle of the world, we will have problems with the overloading of the router. On the other hand,

28:51we will need made alone cables for less that are the furthest from the giant router. But as you can

28:58see in this structure, the cables don't have to be that long. And this is an important advantage.

29:04Actually, of course, we can need long cables in this structure too, but not as much as in

29:12the other structure. After all in this structure, there can be many kilometers between two routers,

29:18this is reasonable However, this is by no means laying cables from one end of the world to the

29:24other end right. And while we only connect two routers with one cable in this structure,

29:32we will connect millions of lamps to the giant router in the other structure. So

29:37we will need a lot of Furlong cables to a single point and it creates a huge mess. Imagine cables

29:45coming to the giant router from millions of lamps that locate in the farthest area. He got the point

29:53by using this structure. we minimize the cable mess and be avoid overloading of errata

30:01everything is good. But what about a lot of rodding since there are many routers load balanced

30:08process is very efficient in the distributed structure, I mean, this system works very

30:14well. And in addition to load balancing, it solves the single point of failure problem as well. For

30:21example, this router, this router, this router and this router are broken somehow, in this case, the

30:28internet continues to work properly, right? Only its efficiency decreases a bit. On the other hand,

30:36when there is only one router, and if this router is broken, the whole internet crushes down and

30:42this was very bad. So I believe that consistency is very important for such a huge structure, like

30:50the internet. And now, I want to show you a visual that shows the cables between different countries

30:58and different continents. With this visual, you will understand much better what the internet is.

31:05These cables are very important, especially for the communication of countries that there is an

31:12ocean between them. And this visual represents real life itself. Unlike the simplified model,

31:19we use 99% of all international communication on the internet is provided by these 468 cable lies

31:29late under the water. This is very crucial guys. Some of these cables are only 131 kilometers long,

31:37while others are around 20,000 kilometers long, and so on. And the funny thing is breaking one of

31:45these cables can cause the Internet of a whole continent to go away in a flash time. In fact,

31:53it was happen such an event in 2018. And I want to show this on a different image. Okay,

32:00I want you to focus on this red cable. This is an almost 17,000 blog cable

32:06that starts in France or reaches third Africa. And this cable connects down to two countries

32:12on the west coast of Europe and Africa to each other and to the internet. And the Internet of

32:1910 of these countries crashed down when efficient port accidently cut the cable.

32:25And I think this was a definitely a tragic karmic event. In addition to this is you can imagine this

32:32is not the only problem that happens to cables, because we are talking about 4 million kilometer

32:38long cables spread all over the world. So, there must be something more as a matter of fact,

32:45nearly 200 problems are encountered each year. And these are substantially related to shifts

32:53or natural disasters. And there is a fun reason that I prefer to use substantially words,

33:00let me explain in 2007, see pirates stall 11 kilometers of a cable connecting Thailand,

33:09Vietnam and Hong Kong to each other. And they sold this long cable as scrap by dividing it.

33:16And I think this event is more surprising than the incredible infrastructure of the internet.

33:24Now, I have back to the first slide, because there is something I want to show here. These colorful

33:31cables generally represent intercontinental connections under waters. But for example,

33:38if you look at Russia, land cables are not visible on this image. Please don't be confused about it.

33:46Of course, there are cables and routers distributed all over Russia,

33:51they are just ignored in this image. I mean, the main purpose of this image was to show

33:57you how devices from different continents are interconnected under the water, okay.

34:04Also not that all of these cables under waters are fiber optic cables. Because the fastest

34:11data transmission cable type is fiber optic cables. And intercontinental data transmission

34:18must occur at the highest speed, right. And another reason of why we don't use copper cables

34:26is well the length of the copper cables increases, the probability of errors in data transmission

34:32increases as well. On the other hand, even if the fiber optic cables are very long,

34:38they transmit the data to its destination almost without error. And this is another reason that

34:45why fiber optic cables are used over long distances. Great. I think it is important

34:53for you to understand what the internet really is. It is very vital to be able to visualize it

34:59in your Might, because no matter what area of it you are dealing with,

35:04you need to grasp this basic subject. Actually, there was something else I wanted to show in this

35:10lesson. But I don't want to extend this lesson any further, we will continue where we left

35:16off in the next lesson, that will be a very important lesson. See you guys in a moment.

35:28In this lesson, we are going to discuss how a packet moves over the internet. In this way,

35:34you will understand how to devices in different countries communicate with each other,

35:39we will see this on an example, let's say this computer in LAN one was to communicate with this

35:45computer in Atlanta. Okay. In other words, let's assume that this computer first to send a special

35:52packet to this computer. So, this packet must go to this router to exit from the land one you know,

36:00because our destination is the art of land one I mean it is a different network, our destination

36:05is Atlanta, and we can set our packet over the Internet to land and now, we are going to do this

36:13exactly first, this computer sends the packet to the switch after the switch receives the packet,

36:21this switch looks at the destination address of the packet and understand that it has to send

36:26the packet to the router and after the raw to receive the packet. Reuter looks at the

36:33content of it and learns his destination address. Hence, it understand that it must send the packet

36:40to the internet because the destination of the packet is in a different network than LAN one. So,

36:47router must start the packet to this router that is connected because this router is the key router

36:53for LAN one to connect to the internet, I mean, if this router needs to send a packet to the

37:00internet, it must send the packet to this router no matter what there is no other option right and

37:06you can think of this link is the connection of land one to the internet. And if this link is

37:13cut somehow the devices in land one cannot access the internet. It's that simple. After this point,

37:21things will get a little complicated. So please listen to me very carefully. After packet

37:27reaches this router, the packet has three options to go this path, this path or this

37:33path right this is obvious but the question is which path is better option to go for the packet?

37:39And in order to answer this question, first we need to discuss what what the table is each

37:46router must have a special table inside called routing table. And after receiving a packet,

37:53a router looks at its routing table to learn which path it must send the packet. For this router,

38:01it should be this path, this path or this path. right this is obvious. And if you're aware,

38:08firstly, draw to receives the packet from one of its ports. I hope that you can imagine

38:14all these cables that come to the router are plugged into a port on the router. And after

38:22the raw to receive the packet rotor learns the destination of the packet and sends the packet to

38:29an appropriate port according to the information on the routing table. And we call this operation

38:36forwarding is the result every router needs to look at its routing table to learn which part

38:43it must forwards the packet. In other words, we can easily understand that routing tables

38:50need to have information that which part a packet will got okay. It is very important to know this

38:57fundamental task of the rhotic table. Each router has a special processor. And information in the

39:06routing table is created by this special processor using many different algorithms. These algorithms

39:13determine the path that's a packet mascar. And the results of these algorithms are added

39:20to the routing table. Okay, is the result. This router will look at its routing table or learn

39:27which path the packet must be forwarded one, two, or three. Meanwhile, when a router makes

39:35this decision, it always ignores the path that the packet came from, because it makes no sense

39:41to forward the packet back the way it came from. Right. And let's say according to the routing

39:47table of this router, the packet must be forwarded over path tree. And there we go. After that,

39:56this router needs to look at its routing table to decide Which paths the packet mascot? Assume that

40:03routing table save the packet must be forwarded over patter. So the packet will go to this route,

40:10right. And there we go. If you are aware, the event is always the same. And it will continue

40:17to be the same in every router until the packet reaches lanter. Anyway, let's get going very left

40:25off this router must look at its routing table to determine which path the packet will be forwarded,

40:32let's say router choose patwon. So the packet will go to this route, right?

40:38Wonderful. And at this moment, please listen to me very carefully because there is a tricky

40:46part here. When you look at the packets for the current position of the packet,

40:51you probably think of the most reasonable option as pactor. Because the shortest

40:56path to be able to access this router that is connected to this router seems to be patter,

41:02right. And if we choose path one, for example, we have to go to this router first. From here,

41:08we can go to this route. Or if we choose path three, we will go to this router first. And

41:15from here, we can go to this router similarly. But if we choose path two, we can go directly

41:23to this router. And this is what we want. But is this really the case? Let's see together.

41:30First of all, never forget that routers always want to deliver the packet to its destination

41:36as fast as possible. So if this router chooses path three, instead of patter, it may seem

41:43unreasonable to you at the beginning, I understand that because you decide with a very simple logic,

41:50you are just using your eyes. However, routers use many algorithms when creating the routing

41:57tables. And these algorithms have many variables, I mean, routers have to take into account many

42:04situations when they are creating routing tables, for example, let's call every router is a point in

42:12this structure, okay. So when routers create the routing tables, they are not only concerned with

42:19the number of points when choosing the shortest route to the destination, this is really, really

42:25important. And I want to give an example to you to understand this subject better. In some cases,

42:32routers control the traffic of the links they are connected to. And if a path is still busy

42:38in terms of packet density, rotor will not set the packet over that part. I mean, for instance,

42:45there may be an excessive density on the path to line, even if it seems the best option.

42:52Okay. And syst Road who knows this line is too busy that creating its routing table,

42:59it may decide that it is more convenient set the packet or pantry instead of Patra. And

43:06we call this situation congestion control. Okay, I think that I could get to the point.

43:13As a result, the router says the packet over pantry. And here we go. As you can see,

43:20the number of points that the packet went through has increased. However,

43:26with the selection of path three, the packet can probably reach its destination faster.

43:31Don't forget this. And after this moment, let the packet go to this right and there we go.

43:38And this router knows that the packet will go to the lamp and it sends the packet to the router in

43:46the half. Okay, by the way you can think of this line is a straight line like that. And this router

43:53knows that the packet came to this computer. So it sends the packet to the related computer.

44:01Wonderful. As you can see, two devices located in this study areas basically communicate with each

44:08other. Thanks to the internet, we can communicate in milliseconds with a device on the other side of

44:14the belt text to the internet. I'm talking about milliseconds, guys, this is a huge thing. And

44:22that's the main reason of why the internet is one of the most important things that mankind created.

44:30I hope I was able to explain intuitively what the internet represents. However, there is also

44:37something else very important that I have to say. I want to tell you the bookish definition of the

44:43internet. The internet is the network of networks. Let me repeat the internet is the network

44:52of networks. I believe that you got this but I would like to make this definition more meaningful

44:58to you. Firstly Think about your own heart, maybe you have a lot of devices that can connect to

45:05the internet, for example, computers, mobile phones, televisions, game consoles, tablets,

45:13and many, many more. Similarly, most people have many devices with an internet connection in their

45:19home, just like you, right? In the same way, you can think about a company or an enterprise

45:26that has a huge number of devices. And you know that there are many companies and enterprises

45:32in all over the world. So as you notice, there are many small or medium sized labs

45:39spread all over developed. And all these lands on the visual represent these networks. As a result,

45:47the combination of all these networks stand for the internet itself, this is very important,

45:54the combination of all these networks stands for the internet itself. In other words,

46:00we are talking about a huge system in which almost all electronic devices in the world

46:07used to communicate with each other. By the way, there is a very important part here to understand

46:13on the visual, we call this the structure that is in the middle of the visual as the Internet,

46:20and you will see such a representation. In many resources, you can usually see a club logo in

46:27order to represent the internet. But in fact, the internet is the spec structure, you say,

46:34formed by a combination of all these networks and this structure in the middle. Okay,

46:41this is very crucial guys. What I'm trying to say is, when you only see such a representation,

46:48you should think that there are millions of ladders that are connected to it,

46:53even if these lands don't appear individual, okay. And the internet is a huge system

47:00that includes all lands in the world. So I hope that you understand better

47:07reason have to bookish definition of the internet, the internet is the network of networks.

47:14Wonderful. And you can think of this attractor is the heart of the internet. For example,

47:22when we connect this land, to the heart of the internet, with this cable, this LAN will be

47:28included in the internet, and it can communicate other devices that are connected to the internet,

47:35you catch the idea. So far we have learned what the internet is and how important routers are.

47:43But what exactly does connecting to the internet look like from a computer's perspective? And

47:49we are going to discuss this question in the next lesson. See you guys soon. Bye.

48:02Now, we are going to discuss the meaning of connecting to the internet from the

48:06computer's perspective. And I believe that it is very important to understand this event,

48:12assume that we are in a home instead of an office and we have only one computer.

48:19Therefore, to be able to connect to the internet. What we only need is a home router, isn't it,

48:25there is no need for a switch. Since we don't have other devices to connect to each other in

48:31this home. Wherever it by the way, if you want, we could use a router device instead of a home router

48:39device. Because if you are aware, we want to use only the router feature of the home router. We

48:46don't need to use the switch feature of the home router right because there is only one computer

48:52in the environment. I believe currently you know which device actually does what this should be

48:59logical to you. Therefore, I will assume that you know what basic networking devices are doing

49:05from now on. And so far, you have learned that the connection situation of the internet

49:13is determined by whether related computer can send a packet to the internet or not. And now,

49:21I will try to make this situation more meaningful to you. You are watching this video

49:26on the udemy.com website. Right? I mean, let's say you are turning on your computer

49:33and entering udemy.com on your favorite web browser. Then you click on the video you are

49:40watching right now or any video you want to watch. And as soon as you click on one of these videos,

49:47your computer creates a packet and says this packet to udemy.com over the internet. The

49:54packet firstly is sent to home router. And then the home router says the packet is To udemy.com

50:01over the Internet, and we can think of this green packet as your request message to use the.com

50:08request message gives information to udemy.com about, you want to watch the related video, okay,

50:15this is very crucial. And after udemy.com receives your request message about watching a specific

50:22video, it's naturally realizes that you want to watch every year hands you the muscles, the

50:28related video to you over the internet. And there we go. These red Packers represent the pieces of

50:35the video that you may sell to you. In other words, the video you are watching right now,

50:41by the way, there is a very important thing about this process. Let me explain. While you

50:47are watching any video on Udemy Udemy sells it to you piece by piece. And we call this process

50:54streaming. I think you have heard of this concept before. And with the help of streaming technology

51:02you can most videos uninterruptedly are without any problem. And to be able to solve this piece

51:09by piece sunning process better. Now, I have opened a random video on udemy.com you can see

51:17that the video is being sent to my computer from udemy.com piece by piece. Thanks to the ability

51:25to send videos piece by piece, we can most video without requirement for all the video to reach our

51:33computer. For example, imagine you want to watch a one hour video and assume that your internet speed

51:41is so slow. If you couldn't watch this video, before the whole video reached your computer,

51:48it will be very bad for you, right? Fortunately, the process doesn't work like that. Okay.

51:55And in addition, this transmission time varies depending on the speed of our internet.

52:02The first or our internet speed is, the sooner the video will reach our computer. It's that simple.

52:09I hope in this way you have a better understanding of what these red packets are great

52:16is a result connecting to the internet refers to you can send some packets to the Internet, and you

52:24can receive some packets from the internet. And here, the water or home router in this situation

52:31plays a very important role. The home router gives the packets it receives from the computer to the

52:38Internet, and gives the packets it receives from the internet to the computer. In summary,

52:45packet transmission is the basis of connecting to the internet or communicating with a computer

52:52on the other side of the world. Meanwhile, when we enter udemy.com, we communicate with very powerful

53:00computers that actually belong to the udemy.com. And we call these special computers, server

53:08servers do not differ fundamentally from normal computers. However, since the servers will

53:15exchange packets with 1000s of normal computers at the same time, servers must be much more powerful

53:22computers in terms of hardware compared to normal computers. Because as you know, too many people

53:30access udemy.com at the same time. I mean, too many people access servers of udemy.com at the

53:37same time. And at this moment, let me tell you what I mean, when I say servers after you demand,

53:44if you remember, we talked about the importance of the single point of failure and load balancing

53:51before. And this is true for servers, a few Demeter, there is not a single Udemy server in

53:58the world. Udemy has a lot of servers distributed around different parts of the world, the location

54:05of one of these servers is the best for you and you communicate with this best suited server. It's

54:12that simple is the result, when you want to enter udemy.com you are actually communicating with one

54:20of the suitable Udemy servers for you. So while some of you communicate with the same server,

54:28some of you will communicate with a different server. But at the end of the day, you will all

54:34get the same content, therefore takes the distributed servers Udemy prevents single point

54:41of failure and provide load balancing. Please think about it lol. Okay. By the way, of course,

54:51there are many details behind the transmission of packets. But you can think of it in this way

54:57is the simplest logic and That's all I need to say in this lesson. See you guys soon. Bye.

55:11In this lesson, we will shortly talk about the white area network or briefly van,

55:16which is a very important type of network for the internet in a simple manner, you can think of van

55:23is a network consisting of a combination of different plants. For example, with the

55:28combination of these two lands, we can create a van, or combination of this land, this land,

55:35and this lesson, we can create another van. Okay. And in order to understand better the logical van,

55:43we can talk about the company example. Let's say we have a growing company, and reopened some

55:50offices in different parts of the world. And we want these offices to be in the same network, even

55:56if they are far apart. And this is where the wide area network comes into play. By using van, we

56:03can create a special network for our requirements. Let's say this is one of our land. And this is our

56:10another land. And they are located in different parts of the world. And we want to create a van

56:16for our company by using these two lands. But the question is, how do we do that? Let's see.

56:23Let's say our boss wants us to establish a special network for these lands. I mean, he wants

56:31the computers in these two different offices to work as if they are in the same environment. So

56:38our guy is van, if we create a van, these lads can communicate as if they're in the same environment.

56:46But there's an important point to consider here. Thanks to the internet,

56:51we can already enable these last two communicate right? If you know the internet stands for the

56:58network of networks. This means that the internet itself represents connecting millions of flats

57:06together. Hence, if these last are already connected to the internet, computers in land one

57:14and computers in land two can already communicate over the internet. This is obvious, sir,

57:21the question is if these offices can already communicate with each other over the internet,

57:28why we need another special network is a van. Please be careful communication over the internet

57:36directly. And communication over a special van belongs to a company is a whole different tank.

57:44So I want you to think about that question for a short time and try to answer it.

58:03If you have noticed, the internet is a public network. I mean, the internet

58:08has no owner and it belongs to everyone. Any person can connect to the internet whenever

58:15and wherever he wants. For this reason, it is obvious that this public and huge network can have

58:23security related problems in information transfer between different locations. You know, hackers

58:30are everywhere, and they are in this public and huge network.

58:35And to be able to answer the question I just asked better, I want to give you a very good example.

58:42Let's say this computer wants to send an important file related to the company to this computer.

58:49And after the file is sent to this computer, there will be no problem. Because this transmission

58:56process took place within this land. This land is a private network for this office,

59:03an outsider cannot read access this land without your permission. This is very important. Hence,

59:10file transmission operation in this land is a secure operation. in general. Everything is

59:17good so far. But what will happen if this file was sent to the other office over the internet.

59:26Let's see. Now the scenario is the same again, we need to send a file related to the company

59:34but this time, we must send this file to the other office of the company. As we can see

59:40the file persists through the public network, isn't it? And this is where the problems appear.

59:46Just think about it. This part of the internet is an absolute public network. This means that

59:53if you sell the file over the internet like that, there is no guarantee that no one from

59:59the outside sight can't see this file or worst, no one from the outside can change this file.

1:00:06As I said before, hackers are everywhere and the possibility of these issues are generally not low.

1:00:14Hence, it is important to remember that there is a possibility for a problem when you send this file

1:00:21about the company over the internet directly, especially, if it is a very important file

1:00:27about the company, it is very vital to be careful, and a special man for the company is a solution

1:00:35to such problems. In general, setting up a van is a costly and not easy task. But fortunately,

1:00:43there are various methods of setting up a van. And now, we will only talk about the most popular

1:00:50and cost effective van methods and this method is van by using VPN. I am sure that you have heard of

1:00:58VPN before. It stands for virtual private network. And people usually use VPN to access restricted

1:01:06websites, because we pn ensures our anonymity, and it encrypts our data before sending the packet

1:01:14Hance. This gives us high security in general. And while creating grants by using VPN technology,

1:01:22we take advantage of these features of VPN. But the most important feature you should know

1:01:28about VPN is the tunneling. This feature of VPN provides privacy and anonymity and security to

1:01:36us by creating a special network connection over a public network. This is really, really important.

1:01:42I want to repeat this again. VPN tunnel link provides privacy, anonymity and Security Trust

1:01:49by creating a special network connection over a public network. However, frankly speaking,

1:01:56a physical tunnel isn't created here. This is very crucial. tunneling technology makes

1:02:02the packet acts as if it is going through a physical tunnel. But I won't repeat it. Again,

1:02:09this is not a physical tunnel. This tunnel visual just represents the high security connection

1:02:14between land one and lanter. You can think of it in this way. This tunnel visual just stands

1:02:21for the high security for the connection between these routers. It's that simple.

1:02:27By the way, of course, the packet will pass through many routers on the internet in

1:02:32order to reach its destination, just as you have learned before. However, since VPN uses tunneling,

1:02:39it will be almost impossible to interfere with this packet from the outside. Great.

1:02:46I hope that you get the tunneling conceptually, but I want to take a closer look at it. So first,

1:02:53we start our file to the right. And there we go. And at this moment, there will be some changes

1:03:02on the packet. But before doing these changes, first of all, you should know that VPN tunneling

1:03:08is set up between these routers, this is very crucial. And we call this site to site VPN.

1:03:15This method is very popular while creating a van between offices and take the tunneling our file

1:03:23safe reaches lanter. You know, but the question is, if tunneling is not a physical tunnel,

1:03:30as shown in the picture, what exactly is it? Let's see, I will use an analogy. To explain this. Let's

1:03:38say you need to send a letter from land one to lanter. So, you should give the letter you wrote

1:03:44to a postman, right, the postman can take this letter to its destination. And suppose you are

1:03:51not putting this letter in an envelope. This means that the postman can read the letter if

1:03:57he wants. This is obvious, you can think of the postman in this example, is the public Internet.

1:04:04On the other hand, if you had put this letter in an envelope first and gave it to the postman

1:04:10in this way, the postman wouldn't be able to read it. This is obvious. Hence, the process

1:04:17of putting the letter in an envelope represents the tunneling itself. So in the real scenario,

1:04:23we had to put this yellow packet into another packet. And there we go. Assume that the yellow

1:04:30packet is in the red packet is just like putting glitter in an envelope. That's the whole idea

1:04:37about tunneling wanderful. And in this moment, I want to ask you a question. And my question

1:04:44is that is this packet, really in safe right now? I mean, kept the postman open the envelope

1:04:51and find out the information in it. If he really wants to just think about it. He got the point

1:04:58right. Even though We have increased the security of the packet by applying tunneling, there are

1:05:05still some problems. And this is where encryption comes into play. Suppose that you encrypt your

1:05:12letter in a way that only people working in your company can understand. In this case,

1:05:18even if the postman opens the envelope, he cannot obtain the information, because he will see none

1:05:25understandable data, he will not understand the encrypted information. So, what we have to do is

1:05:32very simple, right, we must encrypt the original packet before putting it into another packet.

1:05:39So, let me back one step on Dynamesh. And for this scenario, we encrypt the yellow packet

1:05:46before putting it in the red packet. And then we put this encrypted packet into the red packet.

1:05:53Now, finally, this packet is sent to them to over the internet safely. And there we go.

1:06:00It's that simple guys. We encrypted the origin of packets and put it in another packet. Thus,

1:06:07we maximized the security of the pact, okay. The term of tunneling comes from here,

1:06:13because packet is safe is if it was moving in your own private tunnel. I hope that I made this

1:06:19concept understandable to you. And at this moment, the writer needs to get the original packet.

1:06:26And to be able to do this router first eliminates the outside packed right and then it needs to

1:06:33decrypt the encrypted packet so that it cannot be in the original packet. And after the router

1:06:40gets the original packet, it looks inside the packet and loves his destination and says the

1:06:46packet to his destination. And there we go is the result with the help of the van. By using VPN,

1:06:54we can securely search company related information from one LAN to another. But never forget that

1:07:01there is no such thing as 100% security. This means there may be always a security vulnerability

1:07:08for every system. However, currently, Van networks built by using VPN technology

1:07:15are quite satisfactory, in terms of both budget and sacred. Okay. I believe

1:07:22everything is good so far. But some of you curious can think about equation, you probably think like,

1:07:29I constantly use the internet in daily life. I sent mail to my friends, I use e commerce website,

1:07:36and I do all of these over the internet. So since the internet is a public network,

1:07:42are all these operations insecure? The answer is both Yes. And now, let me explain.

1:07:50Assume that you want to make an operation on amazon.com. And let's say you had to enter

1:07:56some information about your credit card. While purchasing a product says this information will

1:08:02be sent as a packet over the Internet to one of the servers of amazon.com. We absolutely

1:08:08don't want anyone from the outside to see the information about our credit card is a solution

1:08:15to this. And add to add encryption method is used between our computer and the destination server.

1:08:21And since the packet is encrypted, nobody from the outside can see the information about our

1:08:28credit cards except the server of amazon.com. This is the main logic behind the answer and

1:08:34encryption. All of the endpoints can decrypt the packet and obtain to original data. Okay.

1:08:41However, this kind of encryption was not used in the past. And this situation made it easy for

1:08:48hackers. Imagine that the information about your credit card was directly obtained by a hacker in

1:08:55pure text. This is terrible, right? But text to add to add encryption, we eliminate this problem.

1:09:03And finally, I'm going to ask you a question. And then I'm going to finish the lesson. Now, you know

1:09:10what when is right, in summary van repossessed the networks we create by combining different plans

1:09:18in this case. My question is, what is the largest wide area network in the world? The answer comes

1:09:25to your mind rapidly isn't it? The internet itself is the largest wide area network in the world.

1:09:33However, I want to remind you again, please note that a company's van created with VPN is different

1:09:42from the internet. While one of these vans is completely special to the company. The internet is

1:09:48owned by everyone in the world. And yeah, that's all I will say about Ron. See you guys soon.

1:10:03We have learned a lot of information about network devices until now. And in this lesson,

1:10:09we will look at a few more cases, by using these devices. Let's say we have two

1:10:14offices belongs to the same company. And suppose that there are 100 meters between these offices.

1:10:22If you are aware, this distance is very short. In this case, what I'm wondering is whether or not

1:10:30we can connect switch one and switch two directly to each other to create a LAN. And the answer is,

1:10:36we can definitely do this because as you know that we use switches to create a class. Therefore,

1:10:43we can create a LAN by connecting these switches to each other, even if they are

1:10:48not in the same environment. But please note that the distance is very short between these offices.

1:10:55If this distance, were not too short, it is impossible to connect these switches and create

1:11:01a LAN. Meanwhile, these types of lands can be called campus Area Network, or briefly can since

1:11:10these types of networks are generally used on university campuses, okay. On the other hand, you

1:11:17know that we can also connect these two offices by using van with VPN. But please note that

1:11:24when our LAN or different kinds of network types, this is important, and you can see the packet sent

1:11:31with tunneling in the animation. And there we go. Yep, I believe so far, everything is good. But I

1:11:42want to ask you a question. Which one do you think is more secure? When which VPN or LAN created by

1:11:50connecting villages directly? Please think about that for a short time and try to answer it.

1:12:04The answer is source. Simple, isn't it? a LAN is always more secure than a van. Because in the

1:12:11communication within the land, the packet never passes over the internet, the packet always moves

1:12:18on our own cable. On the other hand, even if the packet is protected in the van,

1:12:24the packet still persists over the internet. And as you know, there is never such a thing as

1:12:30100% security, even if the packet is protected with tunnel link and encryption. So to summarize,

1:12:38both of these methods are secure. But LAN is more secure. This is obvious.

1:12:44However, there is a condition that event is almost a secure SLR and we call private van

1:12:52for this type of fan. By the way, we haven't talked about this van type before. I mean,

1:12:58this is different from manmad VPN, because the line between offices is dedicated for the company,

1:13:06you request this line from the ISP and give a special money for this line does. The ISP

1:13:13gives you a private line that only your company can use? We call the van created in this way,

1:13:20his private van. Okay. And please remember that we were using public internet network environment

1:13:27VPN. And that's why we also call them each VPN is public van This is very crucial. In addition,

1:13:35even if private van sounds great, it the first glance, it can be quite costly. For this reason,

1:13:41it makes sense for an average company to prefer a public van instead of private van, you know,

1:13:48public van provides us security that we definitely cannot underestimate right, wonderful. Now,

1:13:56I want you to pay attention to one point. Some of you may have already noticed this, but it will be

1:14:02good to mention. In any case, we will switch devices to create a LAN while we use routers

1:14:10to create a van. This is very vital. I want to repeat this again, we use switches to create a LAN

1:14:17while we use Rogers to create a van. This means we cannot create a van by using service devices.

1:14:25Because a van fundamentally represents connection of different plans with the help of Van different

1:14:32glass can act as if they are in the same environment. And you know that if you want

1:14:38to connect different plants, we definitely need a router for this task. He's got the point.

1:14:45And now I want to talk a little bit about ratar o until now. I have always explained the router is

1:14:53an internet related device. However, it isn't the main task of the router is to connect different

1:15:00networks. That said, you should realize that these networks may be in different parts of the world,

1:15:06or maybe in the same office, it really doesn't matter. And in this slide, you can see that two

1:15:13different plants in the same office are connected to each other thanks to the router device.

1:15:19Suppose that one of these networks is related to the marketing unit of the company,

1:15:24and the other relate to the software unit. And as you know, if we want different

1:15:29networks to communicate with each other, we should use erasure in the animation,

1:15:35you can see that land one Outland, through communicate through Roger, and there we go.

1:15:46Great. And here, I want to give you additional information about Roger, I want you to focus on

1:15:54the cables of the router. If you are aware, each cable is connected to a different network. I mean,

1:16:01one of the cables is connected to LAN one, one of the cables is connected to and to and one of the

1:16:08cables is connected to the internet. This is the case for the router. The router connects different

1:16:14networks, you know, for this reason, each cable connected to a port on the router represents a

1:16:20different network. Okay. By the way, you may have wondered why different networks are needed within

1:16:27the same office. As a matter of fact, this is a common situation in real life. I mean,

1:16:33you may want different units in the office to be in different networks. This might be absurd

1:16:39for an office suite for computers. However, imagine an office with 50 computers in it,

1:16:46dividing these computers into units increases hierarchy and order never forgot. That

1:16:53is you can see the basic principles are the same everywhere. By using these basic principles,

1:17:00we can enable devices in different parts of the world to communicate. And we can enable devices

1:17:07in the same office to communicate, both of them represent the same task. I think you

1:17:13understand this concept very well. And that's all I want to say in this lesson. See you guys soon.

1:17:26In one of our previous lessons, I told you, we purchased this cable that came to our home from

1:17:33ISP, but I haven't mentioned what exactly ISP is. And in this lesson, we are going to discuss

1:17:40what is the ISP and why it is so important. The internet service provider or briefly ISP

1:17:48is responsible for the transmission of packets from one location to another. If you remember,

1:17:54we have learned that there are a lot of routers in the heart of the internet and talking about

1:18:01this structure. And you can think of the ISP as the mechanism that controls all these routers

1:18:08in this structure. For example, there are actually many routers in this globalized.

1:18:14Similarly, there are many routers in this region last year. But to simplify the concept, I didn't

1:18:21visually show routers within the ISP s. However, I want you to imagine that the routers distributed

1:18:29around the world are controlled by these ISVs This is very crucial. Think of it as of each ISP

1:18:36controls specific routers, and packets are sent from one location to another location over these

1:18:43routers. We previously talked about how the packet travels from one point to another era others

1:18:50understanding this situation is the first condition to understand the ISP. What I am

1:18:56trying to say is certainly SPS are responsible for certain routers, I want you to imagine that

1:19:03every ISP you see in this picture is responsible for certain routers, okay, but I am removing them

1:19:10from the visual for the simplicity of the concept. In addition, the ISP model you see here

1:19:18is a simplified model. But even if the model is simple, it is enough to understand the most

1:19:24important parts of the concept. Let's start with basic definition of the ISP. ISP s represent

1:19:33companies that serve us so that we can connect to the internet. And of course, they charge a

1:19:39certain fee for this service. You cannot connect to the internet without an ISP. Think of ISP is

1:19:46the structure that allows you to connect to the internet and ISP is not a single structure. There

1:19:53are hundreds of 1000s of ISVs in the world, and all these isbs come together to form structure

1:20:00you see individual, there is few ISP individual I know that. But I can say that there are hundreds

1:20:07of 1000s of ISP s in real life. The most common ISP type in default is local ISP. And now, I want

1:20:15to start with it. The first step of connecting to the internet is to communicate with the local

1:20:21ISP. And local ISPs are generally responsible for small area communications, for example, the

1:20:28communications of two different plants in the same neighborhood, or communication of less located in

1:20:35neighborhoods close to each other. Let's say we live in the USA, and these two homes are located

1:20:42in the same neighborhood. If this computer wants to communicate with this computer, the connection

1:20:49is provided directly over this local ISP. This is obvious, you can see this on the animation.

1:20:56The packet passes through different routers at local ISP and reaches its destination.

1:21:06But in general, since the local ISP is responsible for the communication of small

1:21:11areas, the packet can also pass through all the one router before reaching its destination. You

1:21:18can think of this local ISP is the ISP that only connects lands within a neighborhood.

1:21:24Of course, a local ISP can connect different neighborhoods. But in this scenario,

1:21:30let's say it doesn't, therefore, one router can be enough to connect them, you got the point. And

1:21:38in this visual, you can see an example of a small local ISP office. And we call these offices

1:21:45Point of Presence or briefly pop. In fact, effect routers distributed over the internet are included

1:21:53in these paths. And in this fab. In other words, in this office, routers are on the left side. In

1:22:01addition, you have probably noticed that there are other devices than routers, because sometimes we

1:22:08must do different configurations with different devices. Hence, EPA must save routers, switches,

1:22:16servers, and so on. But the device we use to connect different networks to each other is the

1:22:21right you know, for this reason, we will only focus on routers. And in our previous lessons,

1:22:28Reuters on the internet visual, were actually representing paths, separate over divulge.

1:22:34And in order to explain this better, I want to talk on a different image. But in this image,

1:22:41I want to think of different houses and offices connected to local SB two and local SB three. I

1:22:48mean, you both talk about the thoughts, you got the point. And there we go. As you can see, a

1:22:56home and small office connect to a pop over local SB saw this pop is the first point to be able to

1:23:04connect to the internet for this home. And this office. This should be clear to you. By the way,

1:23:11if you are aware, locally, SB two has four paths, you might think that takes to these four paths.

1:23:18Locally SB two connects different neighborhoods. And in this way, lands in different neighborhoods

1:23:25can communicate over local SB two effectively. And from here, we can draw the following conclusion.

1:23:33Some local asbs can have more than one path. However, some localized space can only have

1:23:39one path. This depends on the size of the localized sphere. For example, if a local ISP

1:23:45connects four different neighborhoods, it may have four different paths. But if a local ISP

1:23:51connects all the one neighborhood, it has all the vamp up, you catch the idea. And if you want to do

1:23:58more detailed studies on this topic, you will see many resources on the internet. with raw trackers,

1:24:05you should be aware that these icons actually represent water within the pop. There are many

1:24:11pops distributed all of our developers and routers are in these paths. It's that simple.

1:24:18At this moment, I want you to imagine that there are hundreds of 1000s of local SPS in the world.

1:24:25And these local SPS Connect regionally space that are larger than this means that different

1:24:31localized space communicate over regionalized space. For example, local SP to communicate

1:24:38with local SP three over the regional SP one. As a matter of fact, you can think of local asbs

1:24:44Connect neighborhoods and regional SPS Connect cities in a country. It's that simple.

1:24:51I want to repeat this again, you can think of localized space, connect neighborhoods or small

1:24:56areas and regionally space Connect cities. In a country, okay. Meanwhile, there is one regional

1:25:04SP in this simplified model we use. But in real life, a country can have many regional airspace

1:25:11and all local SPS and regional SPS, combined in order to create a network of a country.

1:25:18In summary, the first step to connecting to the internet is local ISP. And this line represents

1:25:25the line we purchased from the local ISP, right? every home or office must purchase such a line

1:25:32from the relevant ISP to connect to the internet. And if you examine your home router carefully,

1:25:38you can see the cable coming from your ISP. Wonderful. Now, let's suppose that

1:25:46this computer and this computer want to communicate with each other. By the way,

1:25:51these two homes are located in the USA, but they are in different cities. As a result,

1:25:57they are connected to different local ISP. So this is our base. so in this situation,

1:26:02how will this local SV communicate with this local ISP, let's say in fact, this is where

1:26:08the regional SB one comes into play. In general, the regional SP is engaged in the communication of

1:26:15devices in the same countries, but in different cities. If you look carefully at the animation,

1:26:22local asbs communicate over the region laceby is obvious, right? And there we go.

1:26:32And at this moment, some of you may be wondering why there is no direct link from local SB two to

1:26:39local SB three, this is not expected question. Just think about it. If we connect, localize

1:26:45these directly, the hierarchy is broken. I mean, you see very few localized these in the scenario,

1:26:52but in real life, there can be middleclass peace, even in the same city. And if we connect them all

1:26:58together, complexity will definitely occur. And we don't want to increase the complexity of this

1:27:05system, it is already quite complex, isn't it. And that's why we use a central hierarchical

1:27:11ISP structure is you see individual with the minimum number of connections between ISP s,

1:27:18we ensure that all ISP is communicate with each other. It's that simple. So far, we have talked

1:27:26about the local ISP, and regionalised. Also, the computers that communicate with each other,

1:27:32were always in the USA. But what if computers in different countries want to communicate with each

1:27:37other. And this is where the global SP comes into play, you may think that the global ISP connects

1:27:45devices in different countries in general, is, you know, there is an ocean between the USA and China.

1:27:52So if a device in the USA, and a device in China wants to communicate, it must be a global ISP that

1:27:59provides this connection, you cannot connect these two devices with only local ISP, and regional ISP.

1:28:07And as you can see in the image, there are multiple global asbs. And these globalists,

1:28:12these are the part of the hierarchy. And by using them, these two computers can communicate with

1:28:18each other. Let's assume that this computer wants to communicate with this computer. In this case,

1:28:26the packet will first go to the local ISP, Peter, you know, and then go to the regional

1:28:32ISP one. And the packet has two options at this moment, this path or this path. In other words,

1:28:39globally, SB one or global SB three, I hope you understand that this selection is determined

1:28:46by the routers in the regional SP one, each router makes a choice. And as a result of these choices,

1:28:54the Reuters path is determined. Let's say the packet will be forwarded to global SB one. And

1:29:00there we go. By the way, another packet that will pass through regionalize v one may go to

1:29:07the global SB three next time. Who knows you catch the idea. Anyway, afterwards,

1:29:14let's say that the packet will be sent from global SB one to global SB two. And there we go.

1:29:22And at this stage, the packets can be sent to local ISP six, or directly to the regional

1:29:28SB two or global SB three. Either way, it will reach its destination. What I'm trying to say is

1:29:36the packet can follow different paths. And I won't show you some of these paths. For example,

1:29:43from global SB two to local SB six, regional SB two, local SB seven and this nation or

1:29:58from global SB two to three regionally SB two, locally SB seven and this nation or from globally

1:30:06SB two To globally SB three, regional SB two, local SB seven and this nation again all of them

1:30:08are suitable paths. You should also have noticed a situation here.

1:30:13If the destination of the packet was this harm, the packet could reach his destination directly

1:30:19over local SB six without going over regionalist feature. This means that some localized space

1:30:26can connect with global ad space. Without a regional ISP. This is very important is enough,

1:30:33local ad space represents small companies. And in some cases, these small companies may want a

1:30:40direct connection with a global ASV to provide a faster internet experience to its customers.

1:30:46Actually, there are two ways for this kind of connection. in general. If a local ISP connects

1:30:53directly with a global ISP, its location can be very suitable for this purpose.

1:30:59I mean, related global ISP can already have an infrastructure on this location. However, if the

1:31:06related global ISP doesn't have an infrastructure in this location, a lot of extra money must be

1:31:13paid for disconnection by the local ASB company to the global ASB company, you catch the idea.

1:31:20And for this packet on the global ASB through, let's say it will go to the regional ISP instead

1:31:26of local SB six or global SB three. Okay, from here, packet will go to the local SB seven. And

1:31:34there we go. As you can see, locally, SB seven is connected directly to the destination LAN.

1:31:41Therefore, locally, SB seven knows that where it will send the packets. And finally, to home rats

1:31:49receiving the packet sends it to the destination computer Wallah. As a result, you have learned how

1:31:56computers in two different regions of the world communicate over the internet. You also learnt

1:32:02the relationship between the internet routers and ISP with each other. And in the next lesson,

1:32:08we are going to cover two more scenarios related to the ISP concept. See you guys in a moment.

1:32:22Let's say we are in Belgium. This is our home. And we want to connect to enable establish website

1:32:29called ABC x.com. The owners of the website have limited financial power. For this reason, they

1:32:37have all the answer we're on the USA. So to be able to reach ABC x.com our request message must

1:32:46pass over at least one global ASP This is obvious, you can see the whole process on the animation.

1:33:01And after the server of the ABC x.com receives the request message in exchange for it, ABC x.com

1:33:10creates a response message. This response message contains information about the web page we want

1:33:16to enter. It includes images, videos, HTML file, and everything related to the web page. Meanwhile,

1:33:25if you don't know what an HTML file is, you can think of it as the skeleton of a web page in a

1:33:31simplest manner, and after generating the response message, the server must send it to us. However,

1:33:38the path preferred by the response message will be different from the path preferred

1:33:44by the request message. Please pay attention to this on the animation. There is no way to know

1:33:50the exact path of a message beforehand. Since routers can make different choices each time

1:33:56I'm in the park for a message is always determined on the way. Never forget that. And as soon as we

1:34:05received the response message, the website appears in our web browser. In summary, then you want

1:34:12to enter a website, you first sent a request message to the server off website. And the web

1:34:18server receiving your request message sends you a response message which contains all information

1:34:25about the web page you want to enter. And then this message comes to you. your web browser learns

1:34:32all information from this response message and displays the related web page in your web browser.

1:34:39And the surprising thing is, every time you want to enter a website, this process happens again.

1:34:46However, since this process takes place in milliseconds, you don't realize that there

1:34:52are complex operations in the background. And now let's try to enter google.com instead of ABC x.com

1:35:01and see what happens. You know, Google is quite different from ABC x.com. Since it is a giant

1:35:08company, for instance, unlike ABC x.com, Google has many servers distributed all around the world.

1:35:16And with this distributed server structure, Google provides a much more efficient and fast service

1:35:22to its customers. And let's say one of these servers is not far from our heart. Therefore,

1:35:29when you want to enter google.com, or when you want to get any service from Google,

1:35:35we will probably connect to this server, which is close to us, okay? For this reason, the process

1:35:41failed way much faster. In fact, this is the main reason why big companies put many servers

1:35:48in different locations around the world. They want customers to communicate with them

1:35:53in the fastest and most efficient way. And the distributed server structure is a great solution

1:36:00for such a desire. I believe you catch the idea. So then we want to request a service from Google,

1:36:07our request message will go to this server clusters. You'll know that how the packet reaches

1:36:13the related server with the help of ISP. Yes. And you know that what will happen after this stage,

1:36:22Google sends us a response message related to the servers we request. However,

1:36:28the time for Google to communicate with the customers is sometimes not satisfactory for

1:36:33Google. And Google wants to increase this a bit in general. Fortunately, Google has a

1:36:40very good solution for this kind of issue called peering. But what exactly is peering? Let's see,

1:36:49peering is the technique, which Google establishes a direct connection with an

1:36:54ISP to provide faster access to eat servers. As you can see on the animation, Google connects

1:37:01directly with the local asbs. Thus, when we want to get a service from Google, you will be

1:37:07able to communicate directly with Google servers without using ISP infrastructures. In this way,

1:37:14Google can communicate with the customers much more effectively and quickly. At this moment,

1:37:21everything is good. But what about security, since the number of public pop that packets pass

1:37:28through decreases, takes the period, security increase a saw much I'm in the packet goes

1:37:34directly to Google via local ISP. In other words, the packet does not use public ISP infrastructures

1:37:42to communicate with Google. Remember that security is very important to large companies. And it is

1:37:49obvious that this direct connection decreases the possibility to be obtained for the package

1:37:55from the outside. Wonderful. And last, but not least, I want to give you an example

1:38:02is you know, YouTube is owned by Google. So when you want to watch a video on YouTube,

1:38:09you are actually using Google's distributed servers around the world. And you are all

1:38:14aware that YouTube works very efficiently by you want to watch a video on YouTube, you can watch

1:38:21it very well, you will be interrupted whatsoever. The main reason for this is the distributed server

1:38:28structure and the appearing infrastructure of Google. On the other hand, you may sometimes see

1:38:34freezes and interruptions, while watching videos on Udemy. Because Udemy infrastructure is not

1:38:42as strong as Google in general. Of course, Udemy also uses a distributed server structure. But this

1:38:49number is probably not as many as Google This is obvious. In addition, Udemy doesn't use peering.

1:38:57And you know that peering is a very efficient technology, especially it increases the streaming

1:39:03quality and speed a lot. But I can say that Udemy did a significantly Good job overall, because

1:39:11serving millions of people at the same time is a really challenging engineering problem. Okay.

1:39:18In summary, peering is a very effective structure is used by giant companies like Google, Amazon,

1:39:25and so on. He's got the point. And finally, I want to give you some general information about

1:39:32ISP is you know, global ASB are responsible for the international communication. I can't say that,

1:39:41although definitely not as many as the regional ISP. There are a few global ISP in the world. And

1:39:47you can guess that the technical reasons for not having only a single global ISP

1:39:53in the world. We have talked about similar things before but in addition to these reasons,

1:39:58like load balancing And efficiency. There are also some financial reasons for this.

1:40:04I mean, setting up a global ASB company is a very costly business at the beginning, but it

1:40:10makes its honor a lot of money. You know what I'm saying, right? If you have a lot of money,

1:40:16establishing a global ASB company is a good choice, it will probably make you smile with time.

1:40:23By the way, we also call the internet backbone to the network that global ASB set up with each other

1:40:31familiarity to internet backbone term can be useful for you in the future. In addition,

1:40:37there are structures called internet exchange points, in order for the internet backbone

1:40:44to work synchronously for global a space to communicate with each other more efficiently.

1:40:50And we brief the call these structures I XP, or I x never forgot that.

1:40:58And the last thing I want to mention is that you don't have to connect to a local ISP.

1:41:03In order to connect to the internet, you can directly connect to a regional ISP,

1:41:08or global ASB if these ISP have a service for your location. This means that you can learn

1:41:15which ISP is our serving value live and make your choice. According to this information, it is

1:41:22absolutely your decision to choose the ISP service you want. Okay? For example, let's say this is

1:41:29our home and we connect to the internet via local ASB. However, if you request, we can also connect

1:41:36directly to the internet via regional SP one, this is possible. What I am trying to say is

1:41:43if you want to get your ISP service from a certain company, and if this company doesn't serve your

1:41:49location, you can contact the company and talk about what you can do. If you give the required

1:41:56money to the ISP company, most regional ISP and global ISP can provide you the service you want

1:42:03that set. But for normal users, this is where unnecessary normal users only need to choose one

1:42:10of two ISP services in their location and benefit from it. On the other hand, if you want to set up

1:42:18a local ISP company, such a move may make sense. Wonderful. And we talked about the ISP in general,

1:42:26I think you got a lot of good information. But if you want you can do more research

1:42:32about the ISP on the internet. However, that's all I have to say in this course.