Hi
Please read below quote, I hope this will answer your question
MPLS LDP Session Protection uses LDP Targeted Hellos to protect LDP sessions. Take, for example, two directly connected routers that have LDP enabled and can reach each other through alternate IP routes in the network. An LDP session that exists between two routers is called an LDP Link Hello Adjacency. When MPLS LDP Session Protection is enabled, an LDP Targeted Hello Adjacency is also established for the LDP session. If the link between the two routers fails, the LDP Link Adjacency also fails. However, if the LDP peer is still reachable through IP, the LDP session stays up, because the LDP Targeted Hello Adjacency still exists between the routers. When the directly connected link recovers, the session does not need to be reestablished, and LDP bindings for prefixes do not need to be relearned.
http://www.cisco.com/c/en/us/td/docs/ios/mpls/configuration/guide/12_2sy/mp_12_2sy_book/mp_ldp_sessn_prot.html
Let me know if you have further query
Regards,
Sandip