This table contains a read-only display of the interface
stack in indented format. The first row will correspond to one
of the system's physical interfaces. The following rows will
be in order of which interfaces are stacked on top of which
with blank space at the beginning of the
xsysIfStackDisplayString values to show the hierarchy. (Note
that several rows may be indented to the same level if they
are stacked on top of the same lower-layer interface.) When
the top of one stack is reached, the next physical interface
will start at the left again.