Points to an entry in the diffServQTable to indicate the queue
that a drop algorithm is to monitor when deciding whether to drop
a packet. If the row pointed to does not exist, the algorithmic
dropper element is considered inactive.
Setting this to point to a target that does not exist results in
an inconsistentValue error. If the row pointed to is removed or
becomes inactive by other means, the treatment is as if this
attribute contains a value of zeroDotZero.