DCF InterFrame Spacing (DIFS)

Computer EngineeringComputer NetworkMCA

Distributed coordination function (DCF) is a mandatory technique used to prevent collisions in IEEE 802.11-based WLAN standard (Wi-Fi). It is a medium access control (MAC) sublayer technique used in areas where carrier-sense multiple access with collision avoidance (CSMA/CA) is used.

Using DCF technique, a station needs to sense the status of the wireless channel before it can place its request to transmit a frame. The time interval that a station should wait before it sends its request frame is known as DCF Interframe Spacing (DIFS).


  • When a station has a frame to transmit, it waits for a random backoff time.
  • At the end of the backoff period, if the channel is clear, the station will wait for an amount of time equal to DIFS and sense the channel again.
  • If the channel is still clear, the station transmits a RTS (request to send) frame.
  • The destination station responds using a CTS (clear to send) frame if it is available.
  • Then the transmitting station sends the data frames.

The technique is shown in the following diagram −

Published on 19-Nov-2019 10:56:51