This denotes the address type of the peer node maintenance protocol address if a PW maintenance protocol is used for VC creation, and it should be set to unknown if such a protocol is not used, that is, when cpwVcOwner is set to manual. This declares whether the far-end signaling peer address is IPv4 or IPv6, and the MIB is explicit that it should be left as unknown whenever this VC was configured manually rather than through signaling, so a real address type populated alongside a manual owner setting would reveal an inconsistent, likely leftover configuration. For example, a VC correctly configured for LDP-based signaling with cpwVcOwner set to maintenanceProtocol should show either ipv4 or ipv6 here matching the actual peer PE's signaling address family, never unknown.