What is the IEEE standard for Wireless LAN’s ?
802.11
It was first established in 1997
What is Ad-Hoc mode ?
Also known as IBSS (independent Basic Service Set).
Devices directly connect to each other without an Access Point or central router.
What is infrastructure mode ?
Also known as BSS (Basic service set).
Devices connect to a central Access point which manages the traffic and connects them to a wired network.
ESS (Extended service set) is when multiple BSSs are connected to cover a larger area.
Why cant WiFi use CSMA/CD (collision detection) like Ethernet ?
A wireless radio cant receive and send data at the same time (its half-duplex) so it cannot “hear” the collision while sending the data.
How does CSMA/CA (Collision avoidance) work ?
Listen: The device listens to the channel.
Wait: If the channel is clear, it waits a random amount of time.
Transmit: It sends the data.
Ack: It waits for an acknowledgement from the reciever. If no ack is recieved then it assumes there was a collision.
What is the difference between Passive and Active Scanning ?
Passive mode: The client just listens for Beacon frames broadcast periodically by the access point contianing the SSID.
Active mode: The client broadcasts a Probe Request and waits for a probe response from an AP.
Compare the 2.4GHz and 5 GHz bands.
2.4GHz: - Better range
- High interference
- Only 3 non-overlapping channels
5GHz: - Shorter range
- Faster speeds
- 24 non-overlapping channels
Define the types of Signal Interference issues.
Reflection: Signal bounces of larger objects.
Refraction: Signal bends as it passes through a medium.
Diffraction: Signal bends around an object.
Scattering: Signal hits uneven surfaces and scatters in many directions.
Absorption: Signal energy is converted to heat as it passes through material.
Compare the Wireless Security Protocols.
WEP (Wired Equivalent Privacy): Original. Uses static RC4 keys. Highly insecure.
WPA (Wi-Fi Protected Access): Uses TKIP (Temporal Key Integrety Protocol) which changes the key for every packet.
WPA2: Uses AES (advanced encryption standard).
WPA3: Disallows legacy protocols, uses PMF (Protected Management Frames) for better security.
