This attribute shall specify the current maximum size, in octets, of the PSDU that may be delivered to the PHY. This maximum size does not apply in the case of A-MPDU. An MSDU, A-MSDU or MMPDU shall be broken into fragments if its size exceeds the value of this attribute after adding MAC headers and trailers. An MSDU, A-MSDU or MMPDU shall be fragmented when the resulting frame has an individual address in the Address1 field, and the length of the frame is larger than this threshold. The default value for this attribute shall be the lesser of 8000 or the aMPDUMaxLength or the aPSDUMaxLength of the attached PHY and shall never exceed the lesser of 8000 or the aMPDUMaxLength or the aPSDUMaxLength of the attached PHY. The value of this attribute shall never be less than 256.