An extension of the VLAN Identifier for the port,
as defined in IEEE 802.1P-1998.
A value of 1 through 4094 is used to define a valid PVID.
A value of 0 shall be used if the device is using priority tagged
frames, meaning that only the 802.1p priority level is significant
and the default VID of the ingress port is being used instead.
A value of 4095 is reserved for implementation use.