"A set of prior RFCs specify procedures for supporting multicast in BGP/MPLS IP VPNs. These procedures allow customer multicast data to travel across a service provider's backbone network through a set of multicast tunnels. The tunnels are advertised in certain BGP multicast auto-discovery routes@ by means of a BGP attribute known as the ""Provider Multicast Service Interface (PMSI) Tunnel"" attribute. Encodings have been defined that allow the PMSI Tunnel attribute to identify bidirectional (multipoint-to-multipoint) multicast distribution trees. However@ the prior RFCs do not provide all the necessary procedures for using bidirectional tunnels to support multicast VPNs. This document updates RFCs 6513@ 6514@ and 6625 by specifying those procedures. In particular@ it specifies the procedures for assigning customer multicast flows (unidirectional or bidirectional) to specific bidirectional tunnels in the provider backbone@ for advertising such assignments@ and for determining which flows have been assigned to which tunnels."