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OSI Open System Interconnect

Layers

Layer Name Description Data Labels
1 Physical Bits Bits
2 Data Link MAC Frames
3 Network IP Packets
4 Tranport TCP or UDP Segments
5 Session Connection Controls DATA
6 Presentation Compression, Encryption controls DATA
7 Application App data DATA

Physical Layer

Physical medium: cables, fibre optics, wireless

Convert digital data to signals

Voltage, modulation and synchronization

Physical layer cannot be controlled from software as we cannot plugin or unplug from software.

But we can enable or disable network device from software

ip link set dev <interface> up to enable

ip link set dev <inetrfcae> down to disable

To know the interfaces: ip -br a show

It defines who should receive data

Function:

  • Organized data into frames
  • Add source and destination MAC

It has 2 sub layers

  1. Logical Link Control (LLC)
    1. Flow control and error detection
    2. It connects to network layer
  2. Media Access Control (MAC)
    1. Unique hardware addresses
    2. Understand who is sender and receiver

MAC

Hexadecimal