Indicates the operational link type of a bridge port
for the RSTP protocol.
pointToPoint -- the port is operationally connected to
a point-to-point link.
shared -- the port is operationally connected to
a shared medium.
other -- none of the above.
This object is only instantiated when the object value of
stpxSpanningTreeType is mst(4) or rapidPvstPlus(5).