Quick Answer

The correct match is Notification for reporting errors or advisory information. This is because LDP message types are strictly categorized by their function within the MPLS control plane: Discovery relies on Hello messages to find neighbors, Session management uses Initialization and Keepalive messages to establish and maintain the TCP session, and Advertisement uses Label Mapping messages to distribute label bindings. On the ENCOR 350-401 exam, this drag-and-drop task tests your ability to distinguish these four core LDP message categories without confusing their roles—a common trap is mixing up the Notification function with Keepalive, but remember that Keepalive only verifies session liveness, while Notification signals actual errors or shutdowns. To lock this in, use the mnemonic “D-S-A-N” for Discovery, Session, Advertisement, Notification—each maps to Hello, Init/Keepalive, Label Mapping, and Error reporting respectively.