Physical Layer¶

The physical layer sends and receives bits between adjacent stations on the link and handles the following specifications:

physical
- connectors
- type of medium
  - wired (gerichtet, copper cable, fibreglass)
  - wireless (ungerichtet, radio waves)
electrical
- voltage
- current level
procedural
- signal encoding
- modulation
- bit rate control
- frame delimiting
- error detection
- frame ordering
- collision detection

loss of power
loss of environmental control \(\rightarrow\) air conditioning failure
physical theft of hw or data
physical damage or destruction of hw or data
unauthorized changes to the functional environment \(\rightarrow\) employee installing unapproved modem
disconnection of physical data links
undetectable interception of data \(\rightarrow\) scanning electromagnetic radiation, Van-Eck-Phreaking
key logging

geographical separated datacenters and redundant connections
use of link and data storage cryptography \(\rightarrow\) TLS for transit, AES for data at rest
uninterruptible power supplies (UPS) and emergency generators
monitored (thermal) environment, use of cooling systems
electromagnetic shielding
locked and monitored perimeters and enclosures using:
- electronic lock mechanisms for logging & detailed authorization
- PIN & password secured locks
- biometric authentication systems
- video & audio surveillance