This document defines an enhancement to Bi-directional Forwarding Detection (BFD) for MPLS LSPs [MPLS-BFD] that can be used to specify the return path of BFD control packets for a specific BFD session. Specifying co-routed or protected return path increases robustness of BFD failure detection and reduces false positives. This document also defines a way to avoid duplicate BFD sessions currently encountered with Co-routed Bidirectional LSP and Associated Bidirectional LSP. The enhancement halves the BFD sessions over those LSPs, and allows a Co-routed Bidirectional LSPs or Associated Bidirectional LSPs to be protected and switched as a single entity.