Question: How does Block Ack Request (BAR) work in Aruba OS?
Environment: Product & Software : This article applies to Aruba OS 5.x and above.
As per IEEE 802.11n Protocol
Scenario 1: A BlockAckReq sent using HT-immediate operation shall be sent as a non-A-MPDU frame.
Scenario 2a: A BlockAckReq sent using HT-delayed operation may be transmitted within an A-MPDU provided that its BAR Ack Policy field is set to No Acknowledgement.
Scenario 2b: The originator may send a BlockAckReq when a data MPDU that was previously transmitted within an AMPDU that had the Ack Policy field set to Normal Ack is discarded due to exhausted MSDU Lifetime.
The BAR was sent by Aruba AP to progress the BA window when AP didn’t receive BA for a set of aggregates.
In rare event, BAR are sent to set correct sequence of the BA.