Karteikarten
Chapter 10
Karten in diesem Stapel (19)
- 1What is the definition of Medium Access?It's the process of determining which device is allowed to transmit
- 2What does CA stand for and mean?Collision Avoidance. Detects collisions and clients start random back off timers
- 3Can a WiFi radio transmit & receive at the same time?No.
- 4What are the four parameters of Collision Avoidance?Physical Carrier Sense (CCA)
Virtual Carrier Sense (NAV)
Backoff
Interframe Spacing - 5What is CCA and what is analogy for it?Clear Channel Assessment
Similar to if you pick up a phone and you have a dial tone, it means you can go ahead and make a call - 6Physical Carrier Sense is made up by two parts. CS & ED, what are they?CS: Carrier Sense
ED: Energy Detect
Both indicate the state of the Wireless Medium - 7We have had Physical, what is Virtual Carrier Sense?Duration/ID - indicates how long to complete the present frame
(Clients can see this to see how long until they can then send themselves) - 8Easy way to remember Interframe Spaces?Real Sane People Dont Argue Ever
- 9List, prioritise & say the full name of all the Interframe Spaces1. RIFS - Reduced
2. SIFS - Short
3. PIFS - Point Co-ordinated Function
4. DIFS - Distrubuted Co-ordinated Funcition
5. AIFS - Arbitratory (Used by QoS)
6. EIFS (Used by retransmissions) - 10What is CW? and what does it do?Contention Window - randomly selects the back-off value (in slots)
- 11Draw and example of different back off times for 802.11 a/g and also b802.11a/g
0----CW----15
802.11b
0----------------CW----------------31 - 12What are the four Access Categories?Voice
Video
Best Effort
Background - 13What does a random back-off timer do?Allows fair access to the medium
- 14What actually is Interframe Space?It's the time between transmissions
- 15What is 802.11e?QoS which uses PCF & HCF
- 16What are PCF & HCF?Point Coordination Function (Contention free services for non QoS stations)
Hybrid Coordination Function (Prioritised QoS) - 17What is EDCA?Enhanced Data Channel Access (part of HCF)
- 18What does WMM mean?WiFi Multi Media (QoS Categories)
- 19What is airtime fairness?Proprietary fair usage based on connectivity
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- CWNA CWNA Online Karteikarten am Chapter 10, erstellt von Michael Gleeson am 13/02/2017.
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