All language subtitles for [English] How does the internet work (Full Course) [DownSub.com]

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 has taught

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 in the 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 that the 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 the internet 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
these computers 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 with PC 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 office house 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 have seven 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 answer is 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

use cables 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 small environments.

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 in data 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 that switch,

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 switches

only 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 wireless technology,

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 use
cables. 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 while communicating
with devices. In summary, both the switch device

or an access point device enable these seven
computers to communicate this 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 connect computers 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 to the 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 the same 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 a building, 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 wish device. 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 how important 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 packet

and 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 of the 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

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

this refers to these two computers 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 fully visualized 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 ports varies 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 generally leads 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

computer and 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 switch device? 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 we create 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 cannot communicate 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 that there 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 situation

because 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 internet service

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 certain amount 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 the animation. 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 a packet 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 the same land. On the other hand, a router has
no role in the communication of different devices

in the same line, like PC 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 if pc 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 is no 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 the internet. 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 go to 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 router like 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, what exactly 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 is helpful
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 not know 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 the john 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 this definition. On the other hand, you
can think of the router is the device we use to

communicate with your computer in another 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 for connecting 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, all over 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 area networks 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 needs routers. I hope you got this. And
once you understand the importance of the

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

probably comes to your mind is why there are
so many routers instead of just one 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 the environment?

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 in the 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 few devices 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 be insufficient. 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 distributed all over the world.

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

to the same router. 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 be on 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 only use 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 the idea. But to make sure you fully
understand the main logic of this structure,

I want you to do an exercise, I want 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 other structure. 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 lamps to 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 in the 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, the

internet 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 crushes down 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 different continents. 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

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

we use 99% of all international communication on
the internet is provided by these 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 so on. And the funny thing is breaking one of

these cables can cause the Internet of a whole
continent to go away in 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 to the 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 are talking 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 pirates stall 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
are interconnected 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 destination almost
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 are dealing 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,

we will 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 the art 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 is in a different network than LAN one. So,

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

for 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

path right 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 the packet. 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 the router. And after

the raw to receive the packet rotor learns the
destination of the packet and sends the packet to

an 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 to learn which part

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

need to have information that which part a packet
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, or three. 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? Assume that

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 path the 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 most reasonable
option as pactor. Because the shortest

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

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 as possible. 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 when they 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 when choosing 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 best option.

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

it may decide that it is more 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

the half. 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 belt text 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, for example, 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 world

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

on the visual, we call this the structure that
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 networks
and 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 are millions
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 is the 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 be

included 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 going to 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 of
an 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 the environment. 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 whether related 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 web
browser. 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 to udemy.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 green
packet 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 realizes that 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
about this 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 computer from
udemy.com piece by piece. Thanks to the ability

to send videos piece by piece, we can most video
without requirement for all the video 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 for you, 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 result connecting 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 it receives
from the internet to the computer. In summary,

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

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

computers that actually belong to the 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, servers must 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, we talked 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 these servers 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 one

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

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

get the same content, therefore takes the
distributed servers Udemy 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 very important 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 same environment. 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 internet stands 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 land two can already communicate
over the internet. This is obvious, sir,

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

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 in information 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
your permission. 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 must send 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 problems appear.

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 from

the 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

about the 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 by using 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 it encrypts 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 network connection 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 connection over
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 its destination, just as you have
learned before. However, since VPN uses tunneling,

it will be almost impossible to interfere
with this packet from the outside. 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 these routers, 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

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

as shown in the picture, what exactly 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 its destination. 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 the envelope

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 some problems. 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 will see 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 into another 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 private tunnel. 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

decrypt the 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 and says 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
both budget 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 internet in 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 the servers of amazon.com. We absolutely

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

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 cards except 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 different plans

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

to your mind rapidly isn'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

from the 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
to each 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 the same 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 of networks 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 see the 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 always moves

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

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

100% security, even if the packet is protected
with tunnel link 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 of fan. 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,

his private 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, you know,

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

glass can 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 the same 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 other thanks to the router device.

Suppose that one of these networks is
related to the marketing unit of the company,

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

networks to communicate with each other,
we should use erasure in the 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 the router. 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 the

cables 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 the router 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 increases
hierarchy 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 I haven'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 one location to another. If you remember,

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

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 ISVs
This is very crucial. Think of it as of each ISP

controls specific routers, and packets are sent
from one location to another location over these

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

understanding this situation 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 that

every 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 single structure. There

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

you see 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 of two 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 this local 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 can also 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 got the 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 we

must 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, separate over 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 SB three. 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 to be 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 four paths.

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

localized space 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 in a country. It's that simple.

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

areas and regionally 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, combined
in 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 must purchase 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 is where

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

devices in the same countries, but in different
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 SB three, 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 middleclass peace,
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 number of 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 in different 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 that

provides 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

ISP one. 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 is determined

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 next time. 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 global SB 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

from global 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 local SB 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
a faster 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 money must 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 local SB 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 the internet. 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 is obvious,
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 a response 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 a

simplest 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 the request 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
on the 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 all information

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 in your 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 complex operations 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 all around the world.

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

to its customers. 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 will probably 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 the world.
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 the servers 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 direct connection 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 Google servers
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 the period, 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 package

from 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 around the world. And you are all

aware that YouTube works very efficiently by you
want to watch a video on YouTube, you can watch

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

quality and speed a lot. But I can say that Udemy
did a significantly Good job overall, because

serving millions of people at the same 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 so on. He's got the point. And finally, I
want to give you some general information about

ISP is you know, global ASB are responsible for
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 And efficiency. 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 honor a lot of money. You know what
I'm saying, right? If you have a lot of money,

establishing a global ASB company is a good
choice, 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 other

familiarity 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

to work 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 these ISP 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 is possible. What I am trying to say is

if you want to get your ISP service from a certain
company, and if this company doesn'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 the service you want

that set. But for normal users, this is where
unnecessary normal users only need to choose one

of two ISP services in 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.