LENGTH, the subfield in the legacy Signal field of every 802.11 WiFi frames legacy preamble is more important than you maybe think.
Remarks: This is primarily for the 802.11 5GHz band
During CWNA, and other wireless studies, the Duration value (also called Network Allocation Vector, NAV) in the MAC header gets a lot of attention because it is used to protect the transmission. But this is only half the truth. The Duration value is only to protect the rest of the transmission after the frame currently been sent. In many of the 802.11 frames, this duration value is either 0 or a very small value. The only place it has real value is in a TXOP with protection, with RTS and CTS. In the RTS and CTS frames, this Duration value includes the duration of the rest of the transmission, including the QoS frame, the ACK-frame, and all the SIFS.
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