This attribute shall specify the mandatory maximum size, in
octets, of the MPDU that may be delivered to the PHY. An MSDU
shall be broken into fragments if its size exceeds the value
of this attribute after adding MAC headers and trailers. An
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 2346 or the
aMPDUMaxLength of the attached PHY and shall never exceed the
lesser of 2346 or the aMPDUMaxLength of the attached PHY. The
value of this attribute shall never be less than 256.