How does the internet work? (Full Course)

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.

Channel: freeCodeCamp.org

Views: 165,218

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Id: zN8YNNHcaZc

Length: 102min 42sec (6162 seconds)

Published: Mon Aug 02 2021