In the Cisco Unified WLAN QoS, which two aspects create the need for collision avoidance mechanisms? (Choose two.)

Question

Options

• AShared media: Multiple nodes share the frequency and only one can successfully transmit at a
• BCongested plant floors: Workers must maneuver without running into each other.
• CHalf-duplex communication: A radio cannot transmit and receive at the same time.
• DSmart routing: Traffic is directed automatically according to priority.
• ELimited budgets: Manufacturers will not spend the money to install enough designated channels.

• A
  90% (43)
• B
  2% (1)
• D
  6% (3)
• E
  2% (1)

Explanation

Wireless LANs require collision avoidance (CSMA/CA) for two fundamental technical reasons: all nodes share the same radio frequency spectrum (A), meaning simultaneous transmissions corrupt each other; and radios operate half-duplex (C), so a device cannot hear a collision while transmitting - unlike wired Ethernet's CSMA/CD, which detects collisions after the fact. Together, these two constraints make avoidance the only viable strategy.

Why the distractors are wrong:

• B is a physical-world analogy that has nothing to do with RF transmission.
• D describes QoS traffic prioritization, which is a separate concept layered on top of the collision avoidance mechanism.
• E is a business/budget concern, not a technical driver of wireless protocol design.

Memory tip: Think of wireless as a walkie-talkie - everyone shares the same channel (shared media) and you can't talk while listening (half-duplex). Those two walkie-talkie limitations are exactly why "over-and-out" courtesy rules (collision avoidance) exist.

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