A bit mask with 1 bit indicating the positions in the
effective destination address from which embedded SNPA
information is to be extracted. For the extraction, the
first octet of the isisRASNPAMask object value is aligned
with the first octet (AFI) of the NSAP Address. If the
isisRASNPAMask object value and NSAP Address are of
different lengths, the shorter of the two is logically
padded with zeros before performing the extraction. This
object follows the ManualOrAutomatic behavior.