Layer 1

Physical Layer

• "Physics layer" - the rules of physics actually apply
• Not always something you can touch
• Frequently updated
• First stop when troubleshooting
• Signal
• Bits

Signal

• Can you hear me now?
• Electrical voltage
• Optical (glass cables)
• Radio wave (wireless)
• Audible - morse code
• Avian (birds)
  • Pigeon racing
  • People using pigeons to send messages
  • There's an RFC (Request for comment), this is the white paper of the IT world which says how things should work.
  • There's a standard for IP over Avian Carrier, it was a joke but it expanded to be IP and have quality of service which means that certain packets can be ahead of others.
• All we try to do is to send 1s and 0s
  • Analogically or Digitally

Bits & Binary

• Base 2 numbering system
• 2 state model

In hex:

• 10 = A
• 11 = B
• 12 = C
• 13 = D
• 14 = E
• 15 = F

Copper vs. Fiber

• Copper cables usually have a bundle of 8 different wires together inside of one sheathing
  • Less expensive (cost effective)
  • Easy to implement
• Fiber is Glass
  • Strong against Interference
  • Reach very Far
  • Go very Fast
  • Implementation is more expensive and more difficult to implement

Wired vs. Wireless

• Wired
  • The fastest solution
  • No interference
  • More security
    • If they want to attach to my wired network they would need to to physically have access to the network
• Wireless
  • Can have good speed but not quite as fast
  • Very susceptible to interference
  • Less security
    • If they want to attach to my wireless network they would just need a bigger antenna.
  • More convenient
    • Especially with devices with usually move around.