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Building Blocks For OSI Model

How Data is transferred?

  • Data is transferred in small chunks called Packets

How do we know which server to connect to?

  • Through IP address
  • Every server connects with one another through IP addresses
  • Format:
    • **X.X.X.X**
      • (0-255).(0-255).(0-255).(0-255)

  • Types of IP addresses

    • Global IP addresses
    • Local IP addresses

  • DHCP (Dynamic Host Configuration Protocol) → used to dynamically assign an IP address to any device, or node, on a network so they can communicate using that IP address

  • Example:

    • Here ISP → Internet Service Provider
    • Example: Airtel, Jio etc.

  • NAT (Network Access Translator) → helps the router determines which Device sent the request (through which local IP address) ⇒ refer the example above

PORT Numbers

Q. Which application in a particular device (local IP address) is requesting the data?

  • This is determined using PORTS

  • a way to identify a specific process in a particular device

  • PORTS are **16-bit** numbers

    • Total PORT Numbers possible are = 2^16

  • PORT numbers defined for various networking protocols:

  • PORT Numbers from 0-1023 are reserved
    • You’ll not be able to use those for personel usage
  • PORT Numbers from 1024-4915 are reserved for some applications like MongoDB, mySQL etc.
    • Example → every SQL server you run, has a PORT of **1433**
  • PORT Numbers after 4916 are not reserved & can be used publicly

How do we measure the internet speed?

  • 1 mbps
    • mbps → Mega-bits per second
    • 1 bit → 0 or 1
    • Mega → 6 0’s
    • Therefore:
      • 1mbps = 10,00,000 bits/sec
  • Some common terms used here:
    • Upload → You are sending some data to another computer
    • Download → You are receiving some data in your computer

How are countries connected with each other?

  • Different mediums to connect:
    • Physical → Optical fibre cables etc.
    • Wireless → Bluetooth, Wifi, etc.

LAN, WAN, MAN

  • LAN (Local Area Network)→ Small houses/offices
    • via ethernet cables, wifi, etc.
  • MAN (Metropolitan Area Network) → Across a city
  • WAN (Wide Area Network) → Across countries
    • via Optical fibre cables
    • Types:
      1. SONET (Synchronous Optical Networking) → carries data using optical fibre cable (covers large distances)
      2. Frame Relay → way to connect LAN to a wider area (the internet)

⇒ Internet is a collection of all these 3 types of networks!

Resources Used