This document defines extensions to the failure-detection protocol
for Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs)
known as "LSP Ping" that allow selection of the LSP to use for the
echo reply return path. Enforcing a specific return path can be used
to verify bidirectional connectivity and also increase LSP ping
robustness. It may also be used by Bidirectional Forwarding
Detection (BFD) for MPLS bootstrap signaling thereby making BFD for
MPLS more robust.