BFD tracking of an LDP session associated with a T-LDP adjacency allows for faster detection of the liveliness of the session by registering the peer transport address of a LDP session with a BFD session. The source or destination address of the BFD session is the local or remote transport address of the targeted or link (if peers are directly connected) Hello adjacency which triggered the LDP session.
By enabling BFD for a selected targeted session, the state of that session is tied to the state of the underneath BFD session between the two nodes. The parameters used for the BFD are set with the BFD command under the IP interface which has the source address of the TCP connection.