Which two statements are correct with regard to route distinguisher as defined in RFC 4364-AKA IP-VPN（MPLS-VPN）？（）

• A、The configuration to define Route-Distinguisher is Ip vrf bulle Rd 1：1
• B、A route distinguisher can be imported and exported to and from a VRF
• C、Route-Distinguisher is an 8 byte BGP attribute value used in influencing BGP best path algorithm.
• D、Route-Distinguisher is an 8 byte value used in creating unique VPNv4 address.