This value indicates whether or not a top label
should be pushed onto the outgoing packet's label
stack. The value of this variable MUST be set to
true if the outgoing interface does not support pop-
and-go (for example an ATM interface) or if it is a
tunnel origination. Note that it is considered an
error in the case that mplsOutSegmentPushTopLabel is
set to false, but the cross-connect entry which
refers to this out-segment has a non-zero
mplsLabelStackIndex. The LSR MUST ensure that this
situation does not happen. This object cannot be
modified if mplsOutSegmentRowStatus is active(1).