The VC label used in the outbound direction (i.e. toward
the PSN). It may be set up manually if owner is 'manual' or
automatically otherwise. Examples: For MPLS PSN, it
represents the 20 bits of VC tag, for L2TP it represent the
32 bits Session ID.
If the label is not yet known (signaling in process), the
object should return a value of 0xFFFF.