This object represents the framing type to be assigned to the
virtual tributaries in byte sync mapping mode.
notApplicable : If VT mapping is not byteSynchronous(2).
dsx1ESF : Extended Superframe Format
dsx1D4 : Superframe Format
Default is dsx1ESF(3) if csTributaryMappingType is
byteSynchronous(2). For asynchronous(1) mapping, the default is
notApplicable(1).
The value notApplicable(1) can not be set.