BFD is a simple protocol for detecting failures in a network. BFD uses a ‟hello” mechanism that sends control messages periodically to the far end and receives periodic control messages from the far end. BFD is implemented in asynchronous mode only, meaning that neither end responds to control messages; rather, the messages are sent in the time period configured at each end.
A T-LDP session is a session between either directly or non-directly connected peers and requires that adjacencies be created between two peers. BFD for T-LDP sessions allows support for tracking of failures of nodes that are not directly connected. BFD timers must be configured under the system router interface context before being enabled under T-LDP.
BFD tracking of an LDP session associated with a T-LDP adjacency allows for faster detection of the status of the session by registering the loopback address of the peer as the transport address.