When a data frame is sent and confirmed, what is the time interval before the next data frame is sent?

Question

Options

• ASIFS
• BIFS
• CDIFS
• DPIFS

• A
  17% (5)
• B
  7% (2)
• C
  72% (21)
• D
  3% (1)

Explanation

After a data frame is sent and confirmed with an ACK, a station must wait a DIFS (Distributed Inter-Frame Space) before transmitting the next data frame, as DIFS governs standard contention-based access under the Distributed Coordination Function (DCF) in 802.11 networks. SIFS (option A) is incorrect because it is the shortest spacing, reserved for high-priority, immediate responses such as ACK and CTS frames - it keeps an ongoing exchange flowing without allowing other stations to interrupt. IFS (option B) is a generic umbrella term for all inter-frame spacing types, not a specific operational interval, so it is never the answer to "which spacing is used." PIFS (option D) is the PCF Inter-Frame Space used only by the Point Coordinator in Point Coordination Function mode, which is a different, centrally managed access method.

Memory tip: Associate the D in DIFS with Data - DIFS is the delay a station waits before sending a new Data frame into a contention-based channel.

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