This object is used to specify the ifIndex of the ETHERNET
port associated with this VC for point-to-point Ethernet
service, or the ifIndex of the virtual interface of the VPLS
instance associated with the PW if the service is VPLS. Two
rows in this table can point to the same ifIndex only if:
1) It is required to support multiple COS on a MPLS PSN
for the same service (i.e.: a combination of ports and
VLANs) by the use of multiple VC, each with a different
COS.
2) There is no overlap of VLAN values specified in
cpwVcEnetPortVlan that are associated with this port.
A value of zero indicate that association to an ifIndex is
not yet known.