When initiating an LDP session to a non-directly connected MPLS router, which LDP message type does the target send back over UDP?

When an LDP router wants to establish a session with a non-directly connected peer, it uses an extended discovery mechanism. This involves sending an LDP Discovery Hello message to the targeted router's specific IP address. The target router then responds with an extended discovery message (also a Hello message) over UDP, confirming its LDP capabilities and parameters. This exchange allows LDP to discover potential peers beyond directly connected links. Notification messages are used for error reporting or session termination. Session messages are used for managing the LDP session itself, after discovery. Advertisement messages are used to exchange label mappings for prefixes.