BIER (Bit Indexed Explicit Replication) introduces a method for multicast flow forwarding, without storing states in every node along the multicast path. BIER provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to maintain any multicast related per-flow state. That really simplifies configuration and states of intermediate routers.
SDN controller is supposed to support BIER future, to make devices support BIER more easily and BIER network configuration more simply.
