In the 802.11 frame, when the network uses the WDS model for signal transmission, what are the values of To DS and From DS?

Question

Options

• A0, 0
• B0, 1
• C1, 0
• D1,1

• A
  80% (32)
• B
  8% (3)
• C
  10% (4)
• D
  3% (1)

Explanation

There appears to be an error in this question's answer key. Based on the IEEE 802.11 standard, option D (1, 1) is actually correct for WDS, not option A.

In an 802.11 frame's Frame Control field, the To DS and From DS bits indicate how a frame relates to the Distribution System. When both bits are set to 1 (To DS = 1, From DS = 1), it signals a WDS frame - one being relayed between two access points, meaning it is simultaneously arriving from the DS and being forwarded to the DS. This four-address frame format is the hallmark of WDS operation.

The other combinations each correspond to a different scenario: 0, 0 (option A) applies to IBSS or ad-hoc mode, where stations communicate directly with no DS involvement. 0, 1 (option B) means the frame is coming from the DS - an AP delivering a frame to a client. 1, 0 (option C) means the frame is going to the DS - a client sending a frame to an AP.

Memory tip: Think of WDS as a "both directions at once" relay between APs - both bits are ON (1, 1). Ad-hoc (no DS at all) has both bits OFF (0, 0). If your exam source insists the answer is A, flag it with your instructor, as it contradicts the 802.11 specification.

No community discussion yet for this question.