How does the internet work?

The internet is a big part of our daily lives and we use it constantly. But how does it actually work?

We just published a course on the freeCodeCamp.org YouTube channel that will teach you how the internet works along with basic networking principles.

Ian Frost teaches this course. He is an experienced teacher and is excellent at creating diagrams to simply explain complex topics.

You don't need any prior knowledge to follow this course since it teaches you everything from scratch.

The internet is actually more than what it appears to be. In this course you will learn all the key concepts related to the internet in a very visual way. You will see exactly how the Internet works.

In this course you will learn:

• how the internet works
• fundamental network devices
• how electronic devices in different parts of the world communicate with each other.
• what is going on in the background when you watch a video on YouTube
• what is the ISP?
• fundamental networking concepts
• and more!

Watch the full course below or on the freeCodeCamp.org YouTube channel (2-hour watch).

Transcript

(autogenerated)

This course will help someone with no technical knowledge.

Understand how the internet works in frost teaches this course with tons of visuals, just like he hastaught 1000s of people on Udemy.

The internet is a part of our daily life, and we use it constantly.

But what is the internet? Have you ever really thought about it? Have you ever wondered what happens inthe background? Then you enter a web page? If your answer to all these questions is yes, you are definitely looking at the right course in this course, I assume you don't know anything.

And I am slowly explaining what the internet is, you don't need any prior knowledge to follow this course,since this course tells you everything from scratch, which mean abstractions, these abstractions will allow you to understand the subject without knowing details.

I think everyone who uses the internet should know its basic features.

Everyone who uses the internet needs to know the ISP, everyone who uses the internet needs to know thatthe internet is just cables spread all over developed.

And in this course, we will go on a journey together.

And we will look at all these concepts in a very visual way.

I mean, you will see exactly how the internet works, which are eyes.

In addition, at the end of the course, there are some questions related to this course.

And by answering them, you can benefit from this course, at the maximum level.

Okay.

regardless of your age or profession, this course is for everyone, you will absolutely understand what theinternet is when you finish this course.

So let's dive into it.

Now, we are going to talk about a scenario.

Let's say you are the system administrator of a small company, and your boss wants you to enable all thesecomputers to communicate with each other.

I'm in PC, one should be able to communicate with PC seven, our PC five should be able to communicate withPC four, and so on.

He's got the point.

But the question is, how do we do such a task.

And this is where the solution device comes into play.

The switch is the device we use for computers in the same environment to communicate with each other.

When I say in the same environment, what I mean is that I'm talking about computers in the same officehouse or at work close distance to each other.

And this scenario is a good example for such a situation, there is an office and in this office, we haveseven computers that communication of them is required.

Wonderful.

We have a switch to accomplish the communication of computers.

This is good.

However, the question is, Can these seven computers communicate with each other right now? And the answeris big.

Now, because first of all, these seven computers need to interact with the switch somehow.

But how can we do that? I know that you have some ideas and you are probably guessing right we must usecables to connect computers to the switch.

As you can see, we are connecting all the computers to the switch with the help of cables.

We generally use copper cables for this task.

And the type of these copper cables can generally be cat five cable or cat six cable in smallenvironments.

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

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

And it is important to note that fiber optic cables are generally much faster compared to copper cables indata transmission.

This is very important.

And for switch devices, there is a crucial point to be aware of.

Please note that if there is a switch in the environment, and if you want to connect computers to thatswitch, we must definitely use a cable that has generally a copper cable or fiber optic cable.

What I have tried to say is with wireless technology, you cannot connect computers to a switch switchesonly work with cables.

This is very vital guys.

If you want to use a switch device, you have to use cable to connect your devices to the switch.

It's that simple.

However, if you want to connect computers in the same environment to each other, by using all the wirelesstechnology, you can use an access point device in If I switch device, I mean, you can use both a switch device or an access point device.

In order to connect all the seven computers, both of them separately is acceptable for this purpose.

The only difference between these devices is access points use wireless technology while switches usecables.

Okay, there are seven computers in this environment.

And we can connect these seven computers.

By using switches and cables, just like you see in the picture.

Or in the same way, we can use an access point device instead of a switch device.

And if you use an access point device access point uses wireless technology instead of cables whilecommunicating with devices.

In summary, both the switch device or an access point device enable these seven computers to communicatethis is obvious, but one uses cable and the other one uses wireless technology.

Anyway, what I just want you to know right now is we generally use copper cables in order to connectcomputers to the switch in the environment such as a home or office.

By the way, I want to focus on the source device instead of the access point device in discourse,wherever.

And at this moment, all these computers can communicate with each other which is because they connected tothe switch by using cables.

And this means that they created a network.

In other words, the reason that these computers can communicate with each other is all of them are in thesame network and we call this special network as local area network or briefly, LAN.

A local area network is a collection of devices connected together in non physical location, such as abuilding, office or harm.

As I just said, if you want to create a LAN, this location must be a restricted location in terms of area,I mean, you cannot create a LAN between computers located in United States and computers located in Russia.

On the other hand, this area is very suitable area in order to create a LAN.

Therefore, these computers can communicate with each other because all of them are on the same land.

With the help of this search search, we can deduce that if you want to create a LAN, when it is the wishdevice.

By using a switch device, we can create a local area network.

And if we consider the millions of local area network all over the world, we can easily understand howimportant is swish device is, you might think that all the houses in the world are actually a local area network, you have a LAN in your house or your neighbor's home also has a LAN or there is also a LAN in the office where you work.

Okay, you catch the idea.

And now let's take a closer look at the communication of computers.

And what this event actually represent.

Let's say pc one was to send a message to the PCs six.

By the way, the messages generated by computers has a few special names, some people call them as packetand some people call them as frame both of them is okay but in this course, I prefer to use packet instead of frame.

Okay, PC one, you set a packet to the PC six.

As you see in Division, the packet first goes to the switch, and then the switch looks at the inside ofthe packet or learns the destination of the packet.

And finally, the switch sends the packet to its destination.

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

The logic is basically this if a computer can send a packet to another computer, this refers to these twocomputers are on the same network and they can communicate with each other.

This information is so crucial guys, okay.

However, maybe by looking at only this switch image, what the switch device actually is may not be fullyvisualized in your mind.

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

This is the real version of a switch device.

And as you can see, there are many ports on a switch device This is important also the number of portsvaries from one switch device to another switch device.

I mean different switches have different numbers of ports.

Some switches have 10 ports, while some switches have more than transports and of course, this generallyleads to an increase in price.

Okay.

By the way, these ports have a special name and they are called LAN ports.

This probably makes sense to you because as you know, we create lands by using 3g devices.

For this reason, I think it is so reasonable to call these ports LAN ports.

Because by connecting these computers to these ports, we can create a LAN.

And in addition to this, there are LAN ports on the back of our computers, or on the side of our laptops,just like these LAN ports, you can see the Related regionals on the right side.

And to establish a connection between computers and the switch, we connect the LAN port on the computerand the LAN port on the switch with the help of a cable.

So let's do this.

Let's start with this port and PC one, then, let's connect this port and P theater.

After that, let's connect this port and PC three.

And finally, I want to make a connection between this port and PC four.

Wonderful.

And currently, these computers can communicate with each other.

But how exactly does this communication happen? From a switch perspective, let's take a look at this,let's say pc one master communicate with PC far saw, it will send a packet to the PC far this packet will go to this part of the switch first.

And there we go.

Afterwards, that part, we will give the packet to the hardware inside the switch Okay.

Then, this switch, we look inside this packet, our loves his destination.

After that the switch give this packet to this port that is connected to PC far.

And finally, the switch says the packet to the PC far.

Okay, wonderful.

And to summarize, currently, we have connected these four computers to each other thanks to this switch.

This means we have created a local area network.

And these computers can easily communicate with each other.

Since they're on the same LAN.

I hope everything is quite good software.

And the switch device is visualized spreader in your mind, thanks to this slide.

But there is a little issue here.

Let me explain.

If you are aware, our computers were in the same network.

And we have only talked about the communication between dos devices.

We have never talked about how these computers can connect to the internet.

Right? So the question is, Can these computers communicate with the internet just by having a switchdevice? And this my friends will be the question that we are looking for an answer in the next lesson.

See you guys soon.

Bye.

In our previous lesson, we briefly talked about how to connect computers in our office, and how do wecreate a network and I said that we can create a LAN with the help of a service device.

But the problem is currently these computers can only communicate amongst themselves, they cannotcommunicate with the internet, because the all the task of the switch is to create a LAN and enable the communication of the devices in the same land.

Great.

And by the way, I would like to remove this lamp statement from the visual because you can understand thatthere is a LAN here, thus, we can work more comfortably.

Wonderful.

And the main question is, how do we connect these computers to the internet.

And this is where the router device comes into play.

Let me explain.

The main task of the router is to enable computers to connect to the internet.

Without a router it is impossible for us to connect to the internet.

And in order to provide this connection.

I mean, in order to provide a connection to the Internet.

First of all, we must connect this switch to this router.

And this cable is a copper cable.

Just like other cables.

This is good.

But currently, what we have to do isn't over we still can't connect to the internet in this situationbecause we need a connection between the water and the internet as well.

And as you know, a special cable comes to our homes or offices and this cable is given us by internetservice provider and takes to this cable.

We connect to the internet if you have never heard of internet service service provider.

Don't worry, we will talk about it in detail.

But for now, all you need to know is the internet service provider is giving us this cable for a certainamount of money so that we can connect to the internet easily.

Okay, so currently, we have everything necessary to connect to the internet.

By using these computers, hams, let's see the basic tasks of the switch and router one by one on theanimation.

These seven computers in the office can communicate with each other thanks to the switch.

For example, let's say pc one was to communicate with PC five, for this purpose, PC, one will send apacket to the PC five, sir, is you know, the packet firstly goes to the switch.

And afterwards, this switch learns the destination of the packet.

And finally, this switch sends the packet to its destination.

And there we go.

This is how two computers in the same land communicate with each other.

And please always remember, a switch device is enough for us in order for communication of devices in thesame land.

On the other hand, a router has no role in the communication of different devices in the same line, likePC One and PC five.

This is very vital.

Okay.

I hope I could explain the events.

And however guys, what if pc one was to communicate with the internet? In other words, what will happen ifpc one first to send a packet to the internet? Let's see.

First of all, you should remember this information.

If a computer can send packets to the internet.

This means that this computer communicates with the internet.

For the speaking I believe that you exactly understand the logic of this event anymore.

If we can send packets from one point to another point, these two points can communicate.

It's that simple.

But the question is, how will pc one send packets to the internet.

To be able to do this first PC, one must start its packet to the switch just like before, because there isno other way for PC one to be able to eat the router, right? I mean, if pc one was to send a packet to the internet, this packet must reach the router no matter what, because the router is a door to access the internet.

This is obvious.

Hence, if pc one wants to communicate with the router, it must start its packet to the switch first.

After that, the switch looks at inside of the packet and understand that the packet wants to go to theinternet.

So it sends the packet to the router.

And there we go.

And then the router firstly looks at the inside of the packet and understand that the packet wants to goto the internet.

And afterwards, it sends the packet to the internet over this part.

And there we go.

By the way, if you're aware, we have plucked this cable that we purchased from the ISP into this port,this is our base.

I believe that currently you can easily imagine in an intuitive manner, how the cables coming to routerlike this or like this are plugged into the ports.

I mean, there are some ports on router, and you need to put the cables into that box.

It's that simple.

I will not show this visually, because detailed information about the ports isn't important for you.

At this moment, you just must understand the logic behind the router.

Okay.

And as a result, PC one sent its packet to the internet.

In other words, PC one and the internet communicated.

And the device that helped us to connect to the internet is durata.

Wonderful.

I believe that you understand the most basic tasks of the sewage and water.

And I hope the information may be useful for better understanding.

However, I want to ask you two questions.

My first question is, can you visualize the internet in your mind? And the second question is, whatexactly does the internet meme and these will be the equations that we are going to discuss in the next lessons.

See you guys.

Before discussing the meaning of connecting to the internet, from a computer perspective, I think it ishelpful to know what the internet exactly stands for.

Because if you're really starting from scratch, I mean I assume that you are real newbies, you may notknow exactly what the internet is.

For this reason, I want to visualize the internet for a better understanding.

To do this, in this lesson, we are going to see how a packet moves on the internet.

By the way, keep in mind that this model USA is a simplified model designed to make the concept is thejohn deere stat.

So this structure in real life is much more complex than you see individual.

But with this simplified model, you will understand the logic of the event very well, I promise you.

And I believe that's all you need right now is you can see, there are many routers on the internet, right.

And there is a special reason for this.

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

irata is a device required for a computer or electronic device to connect to the internet, you know thisdefinition.

On the other hand, you can think of the router is the device we use to communicate with your computer inanother part of the world, or you can think of the router is the device we use to communicate with a computer in a different plan.

I mean, if you are aware, there is a LAN here, right.

And there is another LAN here, this is obvious.

Therefore, we can draw the following conclusion connecting to the internet actually can stand forconnecting to the another computer located anywhere in the world.

I mean, you can think of the internet is the structure that connects all the lands all over the world.

I want to repeat this again, you can think of the internet is a structure that connects all lamps, allover devout.

And as you know, there are millions of lamps connected to the internet, except these lands.

Wonderful.

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

So I want to ask you a question.

Why are there so many routers here? Let me explain it in a simple manner.

First, you should know that these routers are distributed around the world in an organized manner.

However, routers aren't the only devices in the structure.

This is important.

There are tons of routers, and other different devices in this structure, distributed pre divide layer.

But focusing on only routers is enough for us in order to understand the concept behind the internet.

And the first question that comes to your mind is probably why routers are so important to the internet.

As a matter of fact, the answer to this question is hidden in the core task of errata.

The device we use to enable different lands to communicate with each other is dhiraj.

Right? And text to the internet, we can connect all the laughs in the world to each other.

You know, for this reason, it makes perfect sense to use many routers to connect millions of local areanetworks together.

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

In summary, if the internet must connect millions of local area networks, it is obvious that it needsrouters.

I hope you got this.

And once you understand the importance of the router for the internet, you probably think of anotherquestion.

And the second question that probably comes to your mind is why there are so many routers instead of justone router.

And I think this is a more critical question than the first question and let me answer it on the ratio.

But before answering this question, there is something in this picture that should catch your attention.

Please look carefully at the picture and try to find this difference.

As you can see these last on the visual one device instead of a switch and a router.

So if there is no switch in the environment, how can there be a LAN or if there is no router in theenvironment? How can it be connected to the Internet, and this is where the home router comes into play.

The home router is a common device consisting of a router and switch combination hands these devices inthe last hour mix of the switch and router.

This means that if we have a home router, we don't need an additional switch.

And Roger, this device is enough for small and moments like a home or small office.

This is important.

I won't repeat this again, a home router is enough for us in small environments, or if there are very fewdevices in the environment, okay, I showed you home router, because most of you have these devices in your home, and you connect to the internet by using home routers.

For this reason, I wanted to tell you what these devices are in order to avoid confusion.

However, please note that if there are too many devices in the environment, the home router will beinsufficient.

And you may need additional switch and router, you catch the idea.

And now let's go back to our question, why there are so many routers, instead of just a single router.

Imagine that there is a single router in the middle of the world, instead of 1000s of routers distributedall over the world.

In this case, millions of electronic devices around the world will tell to be connected to the samerouter.

This is obvious, this means that this single router needs millions of parts, isn't it.

And it is impossible to design such a device.

But this is not done the problem.

In addition to it, if there was only one router, the entire lot of the all devices in the world won't beon that router.

And this is another problem.

Because in computer science, we don't want to give all too lot on a single point.

We even call this problem, the single point of failure.

And this is a problem that needs to be considered to be able to teach it better.

Let me give you an example.

Imagine this router is broken somehow.

This means that the Internet of the whole world is crashing down at the same time, right? Because we onlyuse a single router to connect all this around the world.

Rule two broke down and the whole internet crashed down.

It's that simple.

Just think about the consequences of this problem.

In a second, this will be terrible, right.

And so far, we have talked about two vital problems.

But it isn't our another major problems is the cable length problem.

Imagine how long the cable must be if there was all one giant router in the middle of the world,especially LANs that are the furthest from the giant router will need very long cables.

This is obvious, right? Therefore, this design is a very problematic design.

And the solution for all these problems is this distributed structure all over developed, you catch theidea.

But to make sure you fully understand the main logic of this structure, I want you to do an exercise, Iwant you to determine why such a structure eliminates the problems we talked about shortly before, I'm sure that you can handle this.

Just do it guys.

I asked you a question at the end of the previous lesson.

And I know that you were all analyzing the situation.

But let's do it together just in case is you know, if he used a single router in the middle of the world,we will have problems with the overloading of the router.

On the other hand, we will need made alone cables for less that are the furthest from the giant router.

But as you can see in this structure, the cables don't have to be that long.

And this is an important advantage.

Actually, of course, we can need long cables in this structure too, but not as much as in the otherstructure.

After all in this structure, there can be many kilometers between two routers, this is reasonable However,this is by no means laying cables from one end of the world to the other end right.

And while we only connect two routers with one cable in this structure, we will connect millions of lampsto the giant router in the other structure.

So we will need a lot of Furlong cables to a single point and it creates a huge mess.

Imagine cables coming to the giant router from millions of lamps that locate in the farthest area.

He got the point by using this structure.

we minimize the cable mess and be avoid overloading of errata everything is good.

But what about a lot of rodding since there are many routers load balanced process is very efficient inthe distributed structure, I mean, this system works very well.

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

For example, this router, this router, this router and this router are broken somehow, in this case, theinternet continues to work properly, right? Only its efficiency decreases a bit.

On the other hand, when there is only one router, and if this router is broken, the whole internet crushesdown and this was very bad.

So I believe that consistency is very important for such a huge structure, like the internet.

And now, I want to show you a visual that shows the cables between different countries and differentcontinents.

With this visual, you will understand much better what the internet is.

These cables are very important, especially for the communication of countries that there is an oceanbetween them.

And this visual represents real life itself.

Unlike the simplified model, we use 99% of all international communication on the internet is provided bythese 468 cable lies late under the water.

This is very crucial guys.

Some of these cables are only 131 kilometers long, while others are around 20,000 kilometers long, and soon.

And the funny thing is breaking one of these cables can cause the Internet of a whole continent to go awayin a flash time.

In fact, it was happen such an event in 2018.

And I want to show this on a different image.

Okay, I want you to focus on this red cable.

This is an almost 17,000 blog cable that starts in France or reaches third Africa.

And this cable connects down to two countries on the west coast of Europe and Africa to each other and tothe internet.

And the Internet of 10 of these countries crashed down when efficient port accidently cut the cable.

And I think this was a definitely a tragic karmic event.

In addition to this is you can imagine this is not the only problem that happens to cables, because we aretalking about 4 million kilometer long cables spread all over the world.

So, there must be something more as a matter of fact, nearly 200 problems are encountered each year.

And these are substantially related to shifts or natural disasters.

And there is a fun reason that I prefer to use substantially words, let me explain in 2007, see piratesstall 11 kilometers of a cable connecting Thailand, Vietnam and Hong Kong to each other.

And they sold this long cable as scrap by dividing it.

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

Now, I have back to the first slide, because there is something I want to show here.

These colorful cables generally represent intercontinental connections under waters.

But for example, if you look at Russia, land cables are not visible on this image.

Please don't be confused about it.

Of course, there are cables and routers distributed all over Russia, they are just ignored in this image.

I mean, the main purpose of this image was to show you how devices from different continents areinterconnected under the water, okay.

Also not that all of these cables under waters are fiber optic cables.

Because the fastest data transmission cable type is fiber optic cables.

And intercontinental data transmission must occur at the highest speed, right.

And another reason of why we don't use copper cables is well the length of the copper cables increases,the probability of errors in data transmission increases as well.

On the other hand, even if the fiber optic cables are very long, they transmit the data to its destinationalmost without error.

And this is another reason that why fiber optic cables are used over long distances.

Great.

I think it is important for you to understand what the internet really is.

It is very vital to be able to visualize it in your Might, because no matter what area of it you aredealing with, you need to grasp this basic subject.

Actually, there was something else I wanted to show in this lesson.

But I don't want to extend this lesson any further, we will continue where we left off in the next lesson,that will be a very important lesson.

See you guys in a moment.

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

In this way, you will understand how to devices in different countries communicate with each other, wewill see this on an example, let's say this computer in LAN one was to communicate with this computer in Atlanta.

Okay.

In other words, let's assume that this computer first to send a special packet to this computer.

So, this packet must go to this router to exit from the land one you know, because our destination is theart of land one I mean it is a different network, our destination is Atlanta, and we can set our packet over the Internet to land and now, we are going to do this exactly first, this computer sends the packet to the switch after the switch receives the packet, this switch looks at the destination address of the packet and understand that it has to send the packet to the router and after the raw to receive the packet.

Reuter looks at the content of it and learns his destination address.

Hence, it understand that it must send the packet to the internet because the destination of the packet isin a different network than LAN one.

So, router must start the packet to this router that is connected because this router is the key routerfor LAN one to connect to the internet, I mean, if this router needs to send a packet to the internet, it must send the packet to this router no matter what there is no other option right and you can think of this link is the connection of land one to the internet.

And if this link is cut somehow the devices in land one cannot access the internet.

It's that simple.

After this point, things will get a little complicated.

So please listen to me very carefully.

After packet reaches this router, the packet has three options to go this path, this path or this pathright this is obvious but the question is which path is better option to go for the packet? And in order to answer this question, first we need to discuss what what the table is each router must have a special table inside called routing table.

And after receiving a packet, a router looks at its routing table to learn which path it must send thepacket.

For this router, it should be this path, this path or this path.

right this is obvious.

And if you're aware, firstly, draw to receives the packet from one of its ports.

I hope that you can imagine all these cables that come to the router are plugged into a port on therouter.

And after the raw to receive the packet rotor learns the destination of the packet and sends the packet toan appropriate port according to the information on the routing table.

And we call this operation forwarding is the result every router needs to look at its routing table tolearn which part it must forwards the packet.

In other words, we can easily understand that routing tables need to have information that which part apacket will got okay.

It is very important to know this fundamental task of the rhotic table.

Each router has a special processor.

And information in the routing table is created by this special processor using many different algorithms.

These algorithms determine the path that's a packet mascar.

And the results of these algorithms are added to the routing table.

Okay, is the result.

This router will look at its routing table or learn which path the packet must be forwarded one, two, orthree.

Meanwhile, when a router makes this decision, it always ignores the path that the packet came from,because it makes no sense to forward the packet back the way it came from.

Right.

And let's say according to the routing table of this router, the packet must be forwarded over path tree.

And there we go.

After that, this router needs to look at its routing table to decide Which paths the packet mascot? Assumethat routing table save the packet must be forwarded over patter.

So the packet will go to this route, right.

And there we go.

If you are aware, the event is always the same.

And it will continue to be the same in every router until the packet reaches lanter.

Anyway, let's get going very left off this router must look at its routing table to determine which paththe packet will be forwarded, let's say router choose patwon.

So the packet will go to this route, right? Wonderful.

And at this moment, please listen to me very carefully because there is a tricky part here.

When you look at the packets for the current position of the packet, you probably think of the mostreasonable option as pactor.

Because the shortest path to be able to access this router that is connected to this router seems to bepatter, right.

And if we choose path one, for example, we have to go to this router first.

From here, we can go to this route.

Or if we choose path three, we will go to this router first.

And from here, we can go to this router similarly.

But if we choose path two, we can go directly to this router.

And this is what we want.

But is this really the case? Let's see together.

First of all, never forget that routers always want to deliver the packet to its destination as fast aspossible.

So if this router chooses path three, instead of patter, it may seem unreasonable to you at the beginning,I understand that because you decide with a very simple logic, you are just using your eyes.

However, routers use many algorithms when creating the routing tables.

And these algorithms have many variables, I mean, routers have to take into account many situations whenthey are creating routing tables, for example, let's call every router is a point in this structure, okay.

So when routers create the routing tables, they are not only concerned with the number of points whenchoosing the shortest route to the destination, this is really, really important.

And I want to give an example to you to understand this subject better.

In some cases, routers control the traffic of the links they are connected to.

And if a path is still busy in terms of packet density, rotor will not set the packet over that part.

I mean, for instance, there may be an excessive density on the path to line, even if it seems the bestoption.

Okay.

And syst Road who knows this line is too busy that creating its routing table, it may decide that it ismore convenient set the packet or pantry instead of Patra.

And we call this situation congestion control.

Okay, I think that I could get to the point.

As a result, the router says the packet over pantry.

And here we go.

As you can see, the number of points that the packet went through has increased.

However, with the selection of path three, the packet can probably reach its destination faster.

Don't forget this.

And after this moment, let the packet go to this right and there we go.

And this router knows that the packet will go to the lamp and it sends the packet to the router in thehalf.

Okay, by the way you can think of this line is a straight line like that.

And this router knows that the packet came to this computer.

So it sends the packet to the related computer.

Wonderful.

As you can see, two devices located in this study areas basically communicate with each other.

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

I'm talking about milliseconds, guys, this is a huge thing.

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

I hope I was able to explain intuitively what the internet represents.

However, there is also something else very important that I have to say.

I want to tell you the bookish definition of the internet.

The internet is the network of networks.

Let me repeat the internet is the network of networks.

I believe that you got this but I would like to make this definition more meaningful to you.

Firstly Think about your own heart, maybe you have a lot of devices that can connect to the internet, forexample, computers, mobile phones, televisions, game consoles, tablets, and many, many more.

Similarly, most people have many devices with an internet connection in their home, just like you, right?In the same way, you can think about a company or an enterprise that has a huge number of devices.

And you know that there are many companies and enterprises in all over the world.

So as you notice, there are many small or medium sized labs spread all over developed.

And all these lands on the visual represent these networks.

As a result, the combination of all these networks stand for the internet itself, this is very important,the combination of all these networks stands for the internet itself.

In other words, we are talking about a huge system in which almost all electronic devices in the worldused to communicate with each other.

By the way, there is a very important part here to understand on the visual, we call this the structurethat is in the middle of the visual as the Internet, and you will see such a representation.

In many resources, you can usually see a club logo in order to represent the internet.

But in fact, the internet is the spec structure, you say, formed by a combination of all these networksand this structure in the middle.

Okay, this is very crucial guys.

What I'm trying to say is, when you only see such a representation, you should think that there aremillions of ladders that are connected to it, even if these lands don't appear individual, okay.

And the internet is a huge system that includes all lands in the world.

So I hope that you understand better reason have to bookish definition of the internet, the internet isthe network of networks.

Wonderful.

And you can think of this attractor is the heart of the internet.

For example, when we connect this land, to the heart of the internet, with this cable, this LAN will beincluded in the internet, and it can communicate other devices that are connected to the internet, you catch the idea.

So far we have learned what the internet is and how important routers are.

But what exactly does connecting to the internet look like from a computer's perspective? And we are goingto discuss this question in the next lesson.

See you guys soon.

Bye.

Now, we are going to discuss the meaning of connecting to the internet from the computer's perspective.

And I believe that it is very important to understand this event, assume that we are in a home instead ofan office and we have only one computer.

Therefore, to be able to connect to the internet.

What we only need is a home router, isn't it, there is no need for a switch.

Since we don't have other devices to connect to each other in this home.

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

Because if you are aware, we want to use only the router feature of the home router.

We don't need to use the switch feature of the home router right because there is only one computer in theenvironment.

I believe currently you know which device actually does what this should be logical to you.

Therefore, I will assume that you know what basic networking devices are doing from now on.

And so far, you have learned that the connection situation of the internet is determined by whetherrelated computer can send a packet to the internet or not.

And now, I will try to make this situation more meaningful to you.

You are watching this video on the udemy.com website.

Right? I mean, let's say you are turning on your computer and entering udemy.com on your favorite webbrowser.

Then you click on the video you are watching right now or any video you want to watch.

And as soon as you click on one of these videos, your computer creates a packet and says this packet toudemy.com over the internet.

The packet firstly is sent to home router.

And then the home router says the packet is To udemy.com over the Internet, and we can think of this greenpacket as your request message to use the.com request message gives information to udemy.com about, you want to watch the related video, okay, this is very crucial.

And after udemy.com receives your request message about watching a specific video, it's naturally realizesthat you want to watch every year hands you the muscles, the related video to you over the internet.

And there we go.

These red Packers represent the pieces of the video that you may sell to you.

In other words, the video you are watching right now, by the way, there is a very important thing aboutthis process.

Let me explain.

While you are watching any video on Udemy Udemy sells it to you piece by piece.

And we call this process streaming.

I think you have heard of this concept before.

And with the help of streaming technology you can most videos uninterruptedly are without any problem.

And to be able to solve this piece by piece sunning process better.

Now, I have opened a random video on udemy.com you can see that the video is being sent to my computerfrom udemy.com piece by piece.

Thanks to the ability to send videos piece by piece, we can most video without requirement for all thevideo to reach our computer.

For example, imagine you want to watch a one hour video and assume that your internet speed is so slow.

If you couldn't watch this video, before the whole video reached your computer, it will be very bad foryou, right? Fortunately, the process doesn't work like that.

Okay.

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

The first or our internet speed is, the sooner the video will reach our computer.

It's that simple.

I hope in this way you have a better understanding of what these red packets are great is a resultconnecting to the internet refers to you can send some packets to the Internet, and you can receive some packets from the internet.

And here, the water or home router in this situation plays a very important role.

The home router gives the packets it receives from the computer to the Internet, and gives the packets itreceives from the internet to the computer.

In summary, packet transmission is the basis of connecting to the internet or communicating with acomputer on the other side of the world.

Meanwhile, when we enter udemy.com, we communicate with very powerful computers that actually belong tothe udemy.com.

And we call these special computers, server servers do not differ fundamentally from normal computers.

However, since the servers will exchange packets with 1000s of normal computers at the same time, serversmust be much more powerful computers in terms of hardware compared to normal computers.

Because as you know, too many people access udemy.com at the same time.

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

And at this moment, let me tell you what I mean, when I say servers after you demand, if you remember, wetalked about the importance of the single point of failure and load balancing before.

And this is true for servers, a few Demeter, there is not a single Udemy server in the world.

Udemy has a lot of servers distributed around different parts of the world, the location of one of theseservers is the best for you and you communicate with this best suited server.

It's that simple is the result, when you want to enter udemy.com you are actually communicating with oneof the suitable Udemy servers for you.

So while some of you communicate with the same server, some of you will communicate with a differentserver.

But at the end of the day, you will all get the same content, therefore takes the distributed serversUdemy prevents single point of failure and provide load balancing.

Please think about it lol.

Okay.

By the way, of course, there are many details behind the transmission of packets.

But you can think of it in this way is the simplest logic and That's all I need to say in this lesson.

See you guys soon.

Bye.

In this lesson, we will shortly talk about the white area network or briefly van, which is a veryimportant type of network for the internet in a simple manner, you can think of van is a network consisting of a combination of different plants.

For example, with the combination of these two lands, we can create a van, or combination of this land,this land, and this lesson, we can create another van.

Okay.

And in order to understand better the logical van, we can talk about the company example.

Let's say we have a growing company, and reopened some offices in different parts of the world.

And we want these offices to be in the same network, even if they are far apart.

And this is where the wide area network comes into play.

By using van, we can create a special network for our requirements.

Let's say this is one of our land.

And this is our another land.

And they are located in different parts of the world.

And we want to create a van for our company by using these two lands.

But the question is, how do we do that? Let's see.

Let's say our boss wants us to establish a special network for these lands.

I mean, he wants the computers in these two different offices to work as if they are in the sameenvironment.

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

But there's an important point to consider here.

Thanks to the internet, we can already enable these last two communicate right? If you know the internetstands for the network of networks.

This means that the internet itself represents connecting millions of flats together.

Hence, if these last are already connected to the internet, computers in land one and computers in landtwo can already communicate over the internet.

This is obvious, sir, the question is if these offices can already communicate with each other over theinternet, why we need another special network is a van.

Please be careful communication over the internet directly.

And communication over a special van belongs to a company is a whole different tank.

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

If you have noticed, the internet is a public network.

I mean, the internet has no owner and it belongs to everyone.

Any person can connect to the internet whenever and wherever he wants.

For this reason, it is obvious that this public and huge network can have security related problems ininformation transfer between different locations.

You know, hackers are everywhere, and they are in this public and huge network.

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

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

And after the file is sent to this computer, there will be no problem.

Because this transmission process took place within this land.

This land is a private network for this office, an outsider cannot read access this land without yourpermission.

This is very important.

Hence, file transmission operation in this land is a secure operation.

in general.

Everything is good so far.

But what will happen if this file was sent to the other office over the internet.

Let's see.

Now the scenario is the same again, we need to send a file related to the company but this time, we mustsend this file to the other office of the company.

As we can see the file persists through the public network, isn't it? And this is where the problemsappear.

Just think about it.

This part of the internet is an absolute public network.

This means that if you sell the file over the internet like that, there is no guarantee that no one fromthe outside sight can't see this file or worst, no one from the outside can change this file.

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

Hence, it is important to remember that there is a possibility for a problem when you send this file aboutthe company over the internet directly, especially, if it is a very important file about the company, it is very vital to be careful, and a special man for the company is a solution to such problems.

In general, setting up a van is a costly and not easy task.

But fortunately, there are various methods of setting up a van.

And now, we will only talk about the most popular and cost effective van methods and this method is van byusing VPN.

I am sure that you have heard of VPN before.

It stands for virtual private network.

And people usually use VPN to access restricted websites, because we pn ensures our anonymity, and itencrypts our data before sending the packet Hance.

This gives us high security in general.

And while creating grants by using VPN technology, we take advantage of these features of VPN.

But the most important feature you should know about VPN is the tunneling.

This feature of VPN provides privacy and anonymity and security to us by creating a special networkconnection over a public network.

This is really, really important.

I want to repeat this again.

VPN tunnel link provides privacy, anonymity and Security Trust by creating a special network connectionover a public network.

However, frankly speaking, a physical tunnel isn't created here.

This is very crucial.

tunneling technology makes the packet acts as if it is going through a physical tunnel.

But I won't repeat it.

Again, this is not a physical tunnel.

This tunnel visual just represents the high security connection between land one and lanter.

You can think of it in this way.

This tunnel visual just stands for the high security for the connection between these routers.

It's that simple.

By the way, of course, the packet will pass through many routers on the internet in order to reach itsdestination, just as you have learned before.

However, since VPN uses tunneling, it will be almost impossible to interfere with this packet from theoutside.

Great.

I hope that you get the tunneling conceptually, but I want to take a closer look at it.

So first, we start our file to the right.

And there we go.

And at this moment, there will be some changes on the packet.

But before doing these changes, first of all, you should know that VPN tunneling is set up between theserouters, this is very crucial.

And we call this site to site VPN.

This method is very popular while creating a van between offices and take the tunneling our file safereaches lanter.

You know, but the question is, if tunneling is not a physical tunnel, as shown in the picture, whatexactly is it? Let's see, I will use an analogy.

To explain this.

Let's say you need to send a letter from land one to lanter.

So, you should give the letter you wrote to a postman, right, the postman can take this letter to itsdestination.

And suppose you are not putting this letter in an envelope.

This means that the postman can read the letter if he wants.

This is obvious, you can think of the postman in this example, is the public Internet.

On the other hand, if you had put this letter in an envelope first and gave it to the postman in this way,the postman wouldn't be able to read it.

This is obvious.

Hence, the process of putting the letter in an envelope represents the tunneling itself.

So in the real scenario, we had to put this yellow packet into another packet.

And there we go.

Assume that the yellow packet is in the red packet is just like putting glitter in an envelope.

That's the whole idea about tunneling wanderful.

And in this moment, I want to ask you a question.

And my question is that is this packet, really in safe right now? I mean, kept the postman open theenvelope and find out the information in it.

If he really wants to just think about it.

He got the point right.

Even though We have increased the security of the packet by applying tunneling, there are still someproblems.

And this is where encryption comes into play.

Suppose that you encrypt your letter in a way that only people working in your company can understand.

In this case, even if the postman opens the envelope, he cannot obtain the information, because he willsee none understandable data, he will not understand the encrypted information.

So, what we have to do is very simple, right, we must encrypt the original packet before putting it intoanother packet.

So, let me back one step on Dynamesh.

And for this scenario, we encrypt the yellow packet before putting it in the red packet.

And then we put this encrypted packet into the red packet.

Now, finally, this packet is sent to them to over the internet safely.

And there we go.

It's that simple guys.

We encrypted the origin of packets and put it in another packet.

Thus, we maximized the security of the pact, okay.

The term of tunneling comes from here, because packet is safe is if it was moving in your own privatetunnel.

I hope that I made this concept understandable to you.

And at this moment, the writer needs to get the original packet.

And to be able to do this router first eliminates the outside packed right and then it needs to decryptthe encrypted packet so that it cannot be in the original packet.

And after the router gets the original packet, it looks inside the packet and loves his destination andsays the packet to his destination.

And there we go is the result with the help of the van.

By using VPN, we can securely search company related information from one LAN to another.

But never forget that there is no such thing as 100% security.

This means there may be always a security vulnerability for every system.

However, currently, Van networks built by using VPN technology are quite satisfactory, in terms of bothbudget and sacred.

Okay.

I believe everything is good so far.

But some of you curious can think about equation, you probably think like, I constantly use the internetin daily life.

I sent mail to my friends, I use e commerce website, and I do all of these over the internet.

So since the internet is a public network, are all these operations insecure? The answer is both Yes.

And now, let me explain.

Assume that you want to make an operation on amazon.com.

And let's say you had to enter some information about your credit card.

While purchasing a product says this information will be sent as a packet over the Internet to one of theservers of amazon.com.

We absolutely don't want anyone from the outside to see the information about our credit card is asolution to this.

And add to add encryption method is used between our computer and the destination server.

And since the packet is encrypted, nobody from the outside can see the information about our credit cardsexcept the server of amazon.com.

This is the main logic behind the answer and encryption.

All of the endpoints can decrypt the packet and obtain to original data.

Okay.

However, this kind of encryption was not used in the past.

And this situation made it easy for hackers.

Imagine that the information about your credit card was directly obtained by a hacker in pure text.

This is terrible, right? But text to add to add encryption, we eliminate this problem.

And finally, I'm going to ask you a question.

And then I'm going to finish the lesson.

Now, you know what when is right, in summary van repossessed the networks we create by combining differentplans in this case.

My question is, what is the largest wide area network in the world? The answer comes to your mind rapidlyisn't it? The internet itself is the largest wide area network in the world.

However, I want to remind you again, please note that a company's van created with VPN is different fromthe internet.

While one of these vans is completely special to the company.

The internet is owned by everyone in the world.

And yeah, that's all I will say about Ron.

See you guys soon.

We have learned a lot of information about network devices until now.

And in this lesson, we will look at a few more cases, by using these devices.

Let's say we have two offices belongs to the same company.

And suppose that there are 100 meters between these offices.

If you are aware, this distance is very short.

In this case, what I'm wondering is whether or not we can connect switch one and switch two directly toeach other to create a LAN.

And the answer is, we can definitely do this because as you know that we use switches to create a class.

Therefore, we can create a LAN by connecting these switches to each other, even if they are not in thesame environment.

But please note that the distance is very short between these offices.

If this distance, were not too short, it is impossible to connect these switches and create a LAN.

Meanwhile, these types of lands can be called campus Area Network, or briefly can since these types ofnetworks are generally used on university campuses, okay.

On the other hand, you know that we can also connect these two offices by using van with VPN.

But please note that when our LAN or different kinds of network types, this is important, and you can seethe packet sent with tunneling in the animation.

And there we go.

Yep, I believe so far, everything is good.

But I want to ask you a question.

Which one do you think is more secure? When which VPN or LAN created by connecting villages directly?Please think about that for a short time and try to answer it.

The answer is source.

Simple, isn't it? a LAN is always more secure than a van.

Because in the communication within the land, the packet never passes over the internet, the packet alwaysmoves on our own cable.

On the other hand, even if the packet is protected in the van, the packet still persists over theinternet.

And as you know, there is never such a thing as 100% security, even if the packet is protected with tunnellink and encryption.

So to summarize, both of these methods are secure.

But LAN is more secure.

This is obvious.

However, there is a condition that event is almost a secure SLR and we call private van for this type offan.

By the way, we haven't talked about this van type before.

I mean, this is different from manmad VPN, because the line between offices is dedicated for the company,you request this line from the ISP and give a special money for this line does.

The ISP gives you a private line that only your company can use? We call the van created in this way, hisprivate van.

Okay.

And please remember that we were using public internet network environment VPN.

And that's why we also call them each VPN is public van This is very crucial.

In addition, even if private van sounds great, it the first glance, it can be quite costly.

For this reason, it makes sense for an average company to prefer a public van instead of private van, youknow, public van provides us security that we definitely cannot underestimate right, wonderful.

Now, I want you to pay attention to one point.

Some of you may have already noticed this, but it will be good to mention.

In any case, we will switch devices to create a LAN while we use routers to create a van.

This is very vital.

I want to repeat this again, we use switches to create a LAN while we use Rogers to create a van.

This means we cannot create a van by using service devices.

Because a van fundamentally represents connection of different plans with the help of Van different glasscan act as if they are in the same environment.

And you know that if you want to connect different plants, we definitely need a router for this task.

He's got the point.

And now I want to talk a little bit about ratar o until now.

I have always explained the router is an internet related device.

However, it isn't the main task of the router is to connect different networks.

That said, you should realize that these networks may be in different parts of the world, or maybe in thesame office, it really doesn't matter.

And in this slide, you can see that two different plants in the same office are connected to each otherthanks to the router device.

Suppose that one of these networks is related to the marketing unit of the company, and the other relateto the software unit.

And as you know, if we want different networks to communicate with each other, we should use erasure inthe animation, you can see that land one Outland, through communicate through Roger, and there we go.

Great.

And here, I want to give you additional information about Roger, I want you to focus on the cables of therouter.

If you are aware, each cable is connected to a different network.

I mean, one of the cables is connected to LAN one, one of the cables is connected to and to and one of thecables is connected to the internet.

This is the case for the router.

The router connects different networks, you know, for this reason, each cable connected to a port on therouter represents a different network.

Okay.

By the way, you may have wondered why different networks are needed within the same office.

As a matter of fact, this is a common situation in real life.

I mean, you may want different units in the office to be in different networks.

This might be absurd for an office suite for computers.

However, imagine an office with 50 computers in it, dividing these computers into units increaseshierarchy and order never forgot.

That is you can see the basic principles are the same everywhere.

By using these basic principles, we can enable devices in different parts of the world to communicate.

And we can enable devices in the same office to communicate, both of them represent the same task.

I think you understand this concept very well.

And that's all I want to say in this lesson.

See you guys soon.

In one of our previous lessons, I told you, we purchased this cable that came to our home from ISP, but Ihaven't mentioned what exactly ISP is.

And in this lesson, we are going to discuss what is the ISP and why it is so important.

The internet service provider or briefly ISP is responsible for the transmission of packets from onelocation to another.

If you remember, we have learned that there are a lot of routers in the heart of the internet and talkingabout this structure.

And you can think of the ISP as the mechanism that controls all these routers in this structure.

For example, there are actually many routers in this globalized.

Similarly, there are many routers in this region last year.

But to simplify the concept, I didn't visually show routers within the ISP s.

However, I want you to imagine that the routers distributed around the world are controlled by these ISVsThis is very crucial.

Think of it as of each ISP controls specific routers, and packets are sent from one location to anotherlocation over these routers.

We previously talked about how the packet travels from one point to another era others understanding thissituation is the first condition to understand the ISP.

What I am trying to say is certainly SPS are responsible for certain routers, I want you to imagine thatevery ISP you see in this picture is responsible for certain routers, okay, but I am removing them from the visual for the simplicity of the concept.

In addition, the ISP model you see here is a simplified model.

But even if the model is simple, it is enough to understand the most important parts of the concept.

Let's start with basic definition of the ISP.

ISP s represent companies that serve us so that we can connect to the internet.

And of course, they charge a certain fee for this service.

You cannot connect to the internet without an ISP.

Think of ISP is the structure that allows you to connect to the internet and ISP is not a singlestructure.

There are hundreds of 1000s of ISVs in the world, and all these isbs come together to form structure yousee individual, there is few ISP individual I know that.

But I can say that there are hundreds of 1000s of ISP s in real life.

The most common ISP type in default is local ISP.

And now, I want to start with it.

The first step of connecting to the internet is to communicate with the local ISP.

And local ISPs are generally responsible for small area communications, for example, the communications oftwo different plants in the same neighborhood, or communication of less located in neighborhoods close to each other.

Let's say we live in the USA, and these two homes are located in the same neighborhood.

If this computer wants to communicate with this computer, the connection is provided directly over thislocal ISP.

This is obvious, you can see this on the animation.

The packet passes through different routers at local ISP and reaches its destination.

But in general, since the local ISP is responsible for the communication of small areas, the packet canalso pass through all the one router before reaching its destination.

You can think of this local ISP is the ISP that only connects lands within a neighborhood.

Of course, a local ISP can connect different neighborhoods.

But in this scenario, let's say it doesn't, therefore, one router can be enough to connect them, you gotthe point.

And in this visual, you can see an example of a small local ISP office.

And we call these offices Point of Presence or briefly pop.

In fact, effect routers distributed over the internet are included in these paths.

And in this fab.

In other words, in this office, routers are on the left side.

In addition, you have probably noticed that there are other devices than routers, because sometimes wemust do different configurations with different devices.

Hence, EPA must save routers, switches, servers, and so on.

But the device we use to connect different networks to each other is the right you know, for this reason,we will only focus on routers.

And in our previous lessons, Reuters on the internet visual, were actually representing paths, separateover divulge.

And in order to explain this better, I want to talk on a different image.

But in this image, I want to think of different houses and offices connected to local SB two and local SBthree.

I mean, you both talk about the thoughts, you got the point.

And there we go.

As you can see, a home and small office connect to a pop over local SB saw this pop is the first point tobe able to connect to the internet for this home.

And this office.

This should be clear to you.

By the way, if you are aware, locally, SB two has four paths, you might think that takes to these fourpaths.

Locally SB two connects different neighborhoods.

And in this way, lands in different neighborhoods can communicate over local SB two effectively.

And from here, we can draw the following conclusion.

Some local asbs can have more than one path.

However, some localized space can only have one path.

This depends on the size of the localized sphere.

For example, if a local ISP connects four different neighborhoods, it may have four different paths.

But if a local ISP connects all the one neighborhood, it has all the vamp up, you catch the idea.

And if you want to do more detailed studies on this topic, you will see many resources on the internet.

with raw trackers, you should be aware that these icons actually represent water within the pop.

There are many pops distributed all of our developers and routers are in these paths.

It's that simple.

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

And these local SPS Connect regionally space that are larger than this means that different localizedspace communicate over regionalized space.

For example, local SP to communicate with local SP three over the regional SP one.

As a matter of fact, you can think of local asbs Connect neighborhoods and regional SPS Connect cities ina country.

It's that simple.

I want to repeat this again, you can think of localized space, connect neighborhoods or small areas andregionally space Connect cities.

In a country, okay.

Meanwhile, there is one regional SP in this simplified model we use.

But in real life, a country can have many regional airspace and all local SPS and regional SPS, combinedin order to create a network of a country.

In summary, the first step to connecting to the internet is local ISP.

And this line represents the line we purchased from the local ISP, right? every home or office mustpurchase such a line from the relevant ISP to connect to the internet.

And if you examine your home router carefully, you can see the cable coming from your ISP.

Wonderful.

Now, let's suppose that this computer and this computer want to communicate with each other.

By the way, these two homes are located in the USA, but they are in different cities.

As a result, they are connected to different local ISP.

So this is our base.

so in this situation, how will this local SV communicate with this local ISP, let's say in fact, this iswhere the regional SB one comes into play.

In general, the regional SP is engaged in the communication of devices in the same countries, but indifferent cities.

If you look carefully at the animation, local asbs communicate over the region laceby is obvious, right?And there we go.

And at this moment, some of you may be wondering why there is no direct link from local SB two to local SBthree, this is not expected question.

Just think about it.

If we connect, localize these directly, the hierarchy is broken.

I mean, you see very few localized these in the scenario, but in real life, there can be middleclasspeace, even in the same city.

And if we connect them all together, complexity will definitely occur.

And we don't want to increase the complexity of this system, it is already quite complex, isn't it.

And that's why we use a central hierarchical ISP structure is you see individual with the minimum numberof connections between ISP s, we ensure that all ISP is communicate with each other.

It's that simple.

So far, we have talked about the local ISP, and regionalised.

Also, the computers that communicate with each other, were always in the USA.

But what if computers in different countries want to communicate with each other.

And this is where the global SP comes into play, you may think that the global ISP connects devices indifferent countries in general, is, you know, there is an ocean between the USA and China.

So if a device in the USA, and a device in China wants to communicate, it must be a global ISP thatprovides this connection, you cannot connect these two devices with only local ISP, and regional ISP.

And as you can see in the image, there are multiple global asbs.

And these globalists, these are the part of the hierarchy.

And by using them, these two computers can communicate with each other.

Let's assume that this computer wants to communicate with this computer.

In this case, the packet will first go to the local ISP, Peter, you know, and then go to the regional ISPone.

And the packet has two options at this moment, this path or this path.

In other words, globally, SB one or global SB three, I hope you understand that this selection isdetermined by the routers in the regional SP one, each router makes a choice.

And as a result of these choices, the Reuters path is determined.

Let's say the packet will be forwarded to global SB one.

And there we go.

By the way, another packet that will pass through regionalize v one may go to the global SB three nexttime.

Who knows you catch the idea.

Anyway, afterwards, let's say that the packet will be sent from global SB one to global SB two.

And there we go.

And at this stage, the packets can be sent to local ISP six, or directly to the regional SB two or globalSB three.

Either way, it will reach its destination.

What I'm trying to say is the packet can follow different paths.

And I won't show you some of these paths.

For example, from global SB two to local SB six, regional SB two, local SB seven and this nation or fromglobal SB two to three regionally SB two, locally SB seven and this nation or from globally SB two To globally SB three, regional SB two, local SB seven and this nation again all of them are suitable paths.

You should also have noticed a situation here.

If the destination of the packet was this harm, the packet could reach his destination directly over localSB six without going over regionalist feature.

This means that some localized space can connect with global ad space.

Without a regional ISP.

This is very important is enough, local ad space represents small companies.

And in some cases, these small companies may want a direct connection with a global ASV to provide afaster internet experience to its customers.

Actually, there are two ways for this kind of connection.

in general.

If a local ISP connects directly with a global ISP, its location can be very suitable for this purpose.

I mean, related global ISP can already have an infrastructure on this location.

However, if the related global ISP doesn't have an infrastructure in this location, a lot of extra moneymust be paid for disconnection by the local ASB company to the global ASB company, you catch the idea.

And for this packet on the global ASB through, let's say it will go to the regional ISP instead of localSB six or global SB three.

Okay, from here, packet will go to the local SB seven.

And there we go.

As you can see, locally, SB seven is connected directly to the destination LAN.

Therefore, locally, SB seven knows that where it will send the packets.

And finally, to home rats receiving the packet sends it to the destination computer Wallah.

As a result, you have learned how computers in two different regions of the world communicate over theinternet.

You also learnt the relationship between the internet routers and ISP with each other.

And in the next lesson, we are going to cover two more scenarios related to the ISP concept.

See you guys in a moment.

Let's say we are in Belgium.

This is our home.

And we want to connect to enable establish website called ABC x.com.

The owners of the website have limited financial power.

For this reason, they have all the answer we're on the USA.

So to be able to reach ABC x.com our request message must pass over at least one global ASP This isobvious, you can see the whole process on the animation.

And after the server of the ABC x.com receives the request message in exchange for it, ABC x.com creates aresponse message.

This response message contains information about the web page we want to enter.

It includes images, videos, HTML file, and everything related to the web page.

Meanwhile, if you don't know what an HTML file is, you can think of it as the skeleton of a web page in asimplest manner, and after generating the response message, the server must send it to us.

However, the path preferred by the response message will be different from the path preferred by therequest message.

Please pay attention to this on the animation.

There is no way to know the exact path of a message beforehand.

Since routers can make different choices each time I'm in the park for a message is always determined onthe way.

Never forget that.

And as soon as we received the response message, the website appears in our web browser.

In summary, then you want to enter a website, you first sent a request message to the server off website.

And the web server receiving your request message sends you a response message which contains allinformation about the web page you want to enter.

And then this message comes to you.

your web browser learns all information from this response message and displays the related web page inyour web browser.

And the surprising thing is, every time you want to enter a website, this process happens again.

However, since this process takes place in milliseconds, you don't realize that there are complexoperations in the background.

And now let's try to enter google.com instead of ABC x.com and see what happens.

You know, Google is quite different from ABC x.com.

Since it is a giant company, for instance, unlike ABC x.com, Google has many servers distributed allaround the world.

And with this distributed server structure, Google provides a much more efficient and fast service to itscustomers.

And let's say one of these servers is not far from our heart.

Therefore, when you want to enter google.com, or when you want to get any service from Google, we willprobably connect to this server, which is close to us, okay? For this reason, the process failed way much faster.

In fact, this is the main reason why big companies put many servers in different locations around theworld.

They want customers to communicate with them in the fastest and most efficient way.

And the distributed server structure is a great solution for such a desire.

I believe you catch the idea.

So then we want to request a service from Google, our request message will go to this server clusters.

You'll know that how the packet reaches the related server with the help of ISP.

Yes.

And you know that what will happen after this stage, Google sends us a response message related to theservers we request.

However, the time for Google to communicate with the customers is sometimes not satisfactory for Google.

And Google wants to increase this a bit in general.

Fortunately, Google has a very good solution for this kind of issue called peering.

But what exactly is peering? Let's see, peering is the technique, which Google establishes a directconnection with an ISP to provide faster access to eat servers.

As you can see on the animation, Google connects directly with the local asbs.

Thus, when we want to get a service from Google, you will be able to communicate directly with Googleservers without using ISP infrastructures.

In this way, Google can communicate with the customers much more effectively and quickly.

At this moment, everything is good.

But what about security, since the number of public pop that packets pass through decreases, takes theperiod, security increase a saw much I'm in the packet goes directly to Google via local ISP.

In other words, the packet does not use public ISP infrastructures to communicate with Google.

Remember that security is very important to large companies.

And it is obvious that this direct connection decreases the possibility to be obtained for the packagefrom the outside.

Wonderful.

And last, but not least, I want to give you an example is you know, YouTube is owned by Google.

So when you want to watch a video on YouTube, you are actually using Google's distributed servers aroundthe world.

And you are all aware that YouTube works very efficiently by you want to watch a video on YouTube, you canwatch it very well, you will be interrupted whatsoever.

The main reason for this is the distributed server structure and the appearing infrastructure of Google.

On the other hand, you may sometimes see freezes and interruptions, while watching videos on Udemy.

Because Udemy infrastructure is not as strong as Google in general.

Of course, Udemy also uses a distributed server structure.

But this number is probably not as many as Google This is obvious.

In addition, Udemy doesn't use peering.

And you know that peering is a very efficient technology, especially it increases the streaming qualityand speed a lot.

But I can say that Udemy did a significantly Good job overall, because serving millions of people at thesame time is a really challenging engineering problem.

Okay.

In summary, peering is a very effective structure is used by giant companies like Google, Amazon, and soon.

He's got the point.

And finally, I want to give you some general information about ISP is you know, global ASB are responsiblefor the international communication.

I can't say that, although definitely not as many as the regional ISP.

There are a few global ISP in the world.

And you can guess that the technical reasons for not having only a single global ISP in the world.

We have talked about similar things before but in addition to these reasons, like load balancing Andefficiency.

There are also some financial reasons for this.

I mean, setting up a global ASB company is a very costly business at the beginning, but it makes its honora lot of money.

You know what I'm saying, right? If you have a lot of money, establishing a global ASB company is a goodchoice, it will probably make you smile with time.

By the way, we also call the internet backbone to the network that global ASB set up with each otherfamiliarity to internet backbone term can be useful for you in the future.

In addition, there are structures called internet exchange points, in order for the internet backbone towork synchronously for global a space to communicate with each other more efficiently.

And we brief the call these structures I XP, or I x never forgot that.

And the last thing I want to mention is that you don't have to connect to a local ISP.

In order to connect to the internet, you can directly connect to a regional ISP, or global ASB if theseISP have a service for your location.

This means that you can learn which ISP is our serving value live and make your choice.

According to this information, it is absolutely your decision to choose the ISP service you want.

Okay? For example, let's say this is our home and we connect to the internet via local ASB.

However, if you request, we can also connect directly to the internet via regional SP one, this ispossible.

What I am trying to say is if you want to get your ISP service from a certain company, and if this companydoesn't serve your location, you can contact the company and talk about what you can do.

If you give the required money to the ISP company, most regional ISP and global ISP can provide you theservice you want that set.

But for normal users, this is where unnecessary normal users only need to choose one of two ISP servicesin their location and benefit from it.

On the other hand, if you want to set up a local ISP company, such a move may make sense.

Wonderful.

And we talked about the ISP in general, I think you got a lot of good information.

But if you want you can do more research about the ISP on the internet.

However, that's all I have to say in this course.