Which interframe space provides the highest level of priority control over the medium for a short time period?

Which interframe space provides the highest level of priority control over the medium for a short time period?

• A. Long Interframe Space (LIFS)
• B. Short Interframe Space (SIFS)
• C. Medium Interframe Space (MIFS)
• D. Power Interframe Space (PIFS)

Answer: (B)

The key idea is how interframe spaces regulate who can use the wireless medium and when. The shorter the interframe space, the higher the priority for the transmission that follows it. SIFS is the shortest of all interframe spaces, so it gives the highest level of priority for a brief window to send a response right after a frame has been received. This is why ACKs and CTS frames, which must be exchanged quickly to confirm reception and keep the channel flowing, are sent after a SIFS. By minimizing the waiting time, SIFS helps the successful, speedy completion of the exchange and reduces the chance that another station will contend for the medium.

Other interframe spaces are longer, which means lower immediate priority. For example, DIFS is used for regular contention-based access and is longer than SIFS, giving stations more opportunity to defer. PIFS is used in PCF contexts and is longer than SIFS but shorter than DIFS, providing a different tier of access. EIFS and LIFS are even longer in their respective contexts, further reducing immediate priority.