A forwarding equivalence class (FEC) entry is the data structure that holds all reachable vias where the packets should be sent to, for certain routes. Before this feature, a FEC could not contain both IPv4 next hop vias and IPv6 next hop vias. This feature starts supporting FECs that have both IPv4 next hop vias and IPv6 next hop vias. In an Equal Cost Multi-Path (ECMP) FEC, some of the vias may have IPv4 next hop and others may have IPv6 next hop. 

This feature provides the capability to specify the label stack of the return path from the S-BFD reflector to the S-BFD initiator on the S-BFD initiator, which can be a different path from the shortest/best IGP path from the S-BFD reflector back to the S-BFD initiator, in order that the forwarding of the S-BFD packets would not be impacted by IP routing convergence, i.e., the stability of S-BFD session is not impacted by the IP routing convergence time. 

This feature monitors the BGP session status. When a BGP session goes down, traffic originally forwarded to the next hops learned from the downed BGP peer is quickly diverted to a backup path if any, or in the case of ECMP, remaining ECMP members.