On Mon, 2012-02-20 at 16:33 +0530, Mohammed Shafi wrote: > > Don't know much about other AP software. But hostapd sends them > > to check if a station is still in range and active. > > > > quote from hostapd.conf: > > > > # Station inactivity limit > > # > > # If a station does not send anything in ap_max_inactivity seconds, an > > # empty data frame is sent to it in order to verify whether it is > > # still in range. If this frame is not ACKed, the station will be > > # disassociated and then deauthenticated. This feature is used to > > # clear station table of old entries when the STAs move out of the > > # range. > > i think also in this path in mac80211 > sta_notify (driver call back) for AP mode > ieee80211_sta_block_awake > sta_unblock -> > ieee80211_sta_ps_deliver_poll_response -> > ieee80211_sta_ps_deliver_response -> > ieee80211_send_null_response > > also in UAPSD path. i don't know much about the technical details Yes, this is true, it happens when the station sends a PS-Poll but we timed out the frame in the meantime -- should be uncommon. In the uAPSD case it's more common, if nothing is pending and the station sends a trigger frame. In any case, it's perfectly normal for an AP to send null data frames. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
