PLCP service data unit (802.11) (PSDU)
The PLCP Service Data Unit (PSDU) is a service data unit( SDU) of WLANs. It is essentially the same as the MSDU, except that it operates at the physical layer. It receives its data from the Data Link Layer and is embedded in the PLCP Protocol Data Unit( PPDU).
In the various WLANs, the PLCP Service Data Units (PSDU) have different lengths. For example, the frame length is 4,095 bytes for 802.11a, 65,535 bytes for 802. 11n and 4,692,480 bytes for 802.11ac.