http://www.rfc-editor.org/rfc/rfc7024.txt
RFC 7024: Virtual Hub-and-Spoke in BGP/MPLS VPNs, H. Jeng, J. Uttaro, L. Jalil, B. Decraene, Y. Rekhter, R. Aggarwal2013-10-01T23:00:00-00:00Furthermore, when PE routers use ingress replication to carry the multicast traffic of VPN customers, the approach described in this document may, under certain circumstances, reduce bandwidth inefficiency associated with ingress replication and redistribute the replication load among PE routers.