The Interframe Space(IFS) is a priority control in the CSMA/ CA method that works with different durations. Distributed Interframe Space (DIFS) is used for the transmission of asynchronous data services in WLANs according to 802.11. It has the longest waiting times with about 50 µs plus the backoff and the lowest priority.
The DIFS period is used when the radio link is free and a station that is willing to transmit wants to transmit. Before it is allowed to transmit, it must wait for the DIFS period. After the station has transmitted and the radio link is free again, request and acknowledgement data packets can be sent after a shorter interframe space such as the SIFS has elapsed. The DIFS is also used by WLAN stations that operate with the Distributed Coordination Function( DCF). It is used before the transmission of service and management data packets.