Summary: Interframe spaces play an important role in 802.11 medium contention. They are used as additional medium contention protocols in addition to CCA and NAV. An interframe space, or IFS, is a quiet period access points and stations must wait before transmitting a frame.<br> There are shorter interframe spaces used for higher priority data transmissions. Think about QoS in that regard.<br> There are four rules that define which IFS will be used before frame transmission:<br> <br> * If arbitration is complete, then reduced IFS (RIFS) or short IFS (SIFS) will be used.<br> * If arbitration has not been determined, then arbitration IFS (AIFS) or DCF IFS (DIFS) will be used. DIFS is used for 802.11 WLANs that don’t support 802.11e QoS.<br> * If AP or station received a corrupted frame, then extended IFS (EIFS) will be used.<br> * PCF IFS (PIFS) is part of PCF and not used in the real world.<br> <br> <br> <br> <br> Links and Resources Mentioned<br> <br> * <a href="http://www.cleartosend.net/41">CTS 041: 802.11 Medium Contention</a><br> * <a href="https://www.cwnp.com/uploads/802-11_arbitration.pdf">802.11 Arbitration White Paper</a> from CWNP<br> * <a href="https://mrncciew.com/2014/10/12/cwap-802-11-medium-contention">CWAP – 802.11 Medium Contention</a> from mrn-cciew<br> <br>
