This attribute shall specify the current 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.