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How does the internet work

6 min read

What is the switch?

  • The switch connects the computers and allows them to communicate
  • It creates a LAN and it has LAN ports for the computers to connect
    • connected using wires, typically Cat5 or Cat6 cable
    • *local area network (LAN) = a group of devices connected within a physically close area. A home WiFi network is a common example of a LAN.
  • The switch looks at the packet (the msg) and sees where it should be headed, then sends the packet accordingly
  • The computers so far can only communicate with themselves and not with the internet
  • Campus Area Network (CAN)
    • You can also create a LAN by CONNECTING SWITCHES (if the distance is close between the switches)

What is the router?

Used to connect to the internet

  • A router is required to connect a computer/network (like LANs) to the internet (enables computers to connect to internet)
  • The connection between the router and the internet
    • the cable is given to us by the ISP (Internet Service Provider)
  • If a computer can send packets to the internet, this means that this computer can connect to the internet w/o any problem
    • The router receives the packet and sends it to the internet

Used to connect different networks

  • 2 different LANs are connected through a router
  • commonly different networks are used in different offices irl

Internet Service Provider (ISP)

Companies that enable us to connect to the internet (for money)

  • Responsible for packets from one location to another
  • Each ISP is responsible for specific routers
  • The 1st step to connecting to the internet is the local ISP, which are responsible for small area communications
    • If a PC in a village wants to connect to another PC in the same village, it will directly use the local ISP
    • every home/office must purchase a cable to connect your router to the internet
    • some local ISP can connect directly to the global ISP
  • The routers represent POPs (Point of prescence)
    • a physical location where networks and communication devices connect
    • There are many POPs distributed and routers are in this POP
  • Local ISPs connect neighborhoods and Regional ISPs connect cities
  • Network of a country = all local ISPs + regional ISPs
  • You don’t have to connect to a local ISP to connect to the internet → you can directly connect to a regional/global ISP → it’s your decision to choose the provider you want!

The Wide Area Network (WAN)

  • network consisting of different LANs
  • companies that has different LANs across the globe might want a WAN instead of just using the Internet for information security reasons

WAN + VPN

  • can set up a WAN using a VPN (virtual private network)
    • ensures our anonymity and encrypts our data before sending the packet
    • The tunneling feature of the VPN provides privacy and anonymity and security
      • creates a special network connection over a public network
      • not a physical tunnel ofc, the tunnel is a high security for the connection bet. the 2 routers → encryption + encapsulation (when packet is received, it goes through decapsulation and decryption)
    • Site to Site VPN
  • (WAN + VPN) or LAN? Which is more secure?
    • A LAN is always more secure because the packet never moves through the internet

Private WAN

  • different with wan + vpn
  • ISP gives you a private line ONLY your company can use
  • Private WAN can be quite costly exp over long distances

The Internet!

  • Many routers in the internet!
    • since routers connect with other networks/computers, connecting to the internet can also stand for connecting to any other computer in the world
  • Home router
    • The LANs have 1 home router → switch + router
    • Most home routers nowadays also have an access point feature (enables wireless technology)
    • enough for small environments (home, office, etc)
  • If you use 1 giant router for the internet instead of many (like the diagram)
    • Single point of failure (the router will be overloaded)
    • huge mess in connecting all computers in the world to a single router with cables
    • if some router fails, efficiency decreases only a lil bit (if its a giant one, if it fails, then all fails)
  • Each router has a special processor that create a “Routing Table” using algorithms
    • The router looks this table up when it receives a package to see which router it should forward the package
  • A router always wants to deliver the packet to the destination ASAP
  • each router in the diagram actually represents a POP

With servers

  • After the server of the website receives the request message, it sends a response msg (info about the webpage (img, vids, html files, and everything else))
  • For big comapnies like google, its servers are distributed around the world
    • distributed server structure
  • Peering
    • a direct connection established between two separate networks, allowing them to exchange traffic with each other directly without going through a third-party provider

Other NOTES

  • The internet is a structure that connects ALL LANs and computers in the WORLD

    • Massive undersea cables are connecting all continents on Earth
    • https://www.submarinecablemap.com/
    • Each cable is HUGE, consisting of 100s of optic fibers, each using lasers to transmit up to 400 GB of data per second
    • Tiny electric signals travel at the speed of light through oceans

  • Every single computer/device that’s connected to the Internet has an IP address

  • A server is a computer that’s directly connected to the internet, and webpages are files stored on that hard drive

    • ex: udemy.com has many diff servers around the globe

  • Every server has a unique IP (Internet Protocol) address

    • But we use domain names instead of IP addresses

  • Your computer at home is NOT a server, because it’s not connected directly to the Internet. They’re called clients because they’re connected indirectly through an ISP

    • ISP are the people you pay to be able to access the internet
    • ISP gives the IP address of your device

  • When client makes a request to the web browser google.com

    • Client → ISP → Domain Name System (DNS) → server → data is sent
    • Browser sends the message google.com to your ISP
    • ISP will relay the msg to the DNS server
      • DNS server looks up its database to find the exact IP address of that website you’re trying to access
    • DNS server finds that IP address and gives to browser
    • Browser sends that IP address to the server and fetch the necessary data back to your browser
    • Data flow starts, transferred in digital format via optical fiber cables
    • Data (light pulse) flows into the router where the cables are connected, and are changed into electric signals, then an ethernet cable if it’s connected to your laptop
      • But if you’re using cellular data, the light pulse is sent to a cell tower, then the signal reaches your device in electromagnetic waves

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