The VC label used in the inbound direction (i.e. packets
received from 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.