Keepalive messages are used to help maintain the integrity of the LDP session.

After an LDP session is established, an LSR maintains the integrity of the session by sending Keepalive messages. The Keepalive timer for each peer session resets whenever it receives any LDP protocol message or a Keepalive message on that session. When the Keepalive timer expires, LDP concludes that the TCP connection is bad or the peer is dead and terminates the session.