Which two statements describe the purpose of a BGP notification message?

A BGP NOTIFICATION message is one of the four core message types defined in RFC 4271, alongside OPEN, UPDATE, and KEEPALIVE, and it serves a very specific and narrow purpose within the protocol: whenever a BGP speaker detects an unrecoverable, fatal condition in the session — such as a malformed OPEN message, an unsupported capability, a hold-timer expiration, a finite-state-machine error, or an administratively initiated reset — it transmits a NOTIFICATION message to its peer immediately before closing the underlying TCP connection and tearing down the session entirely. This confirms that a NOTIFICATION always signals the termination of the session upon a fatal error, never a routine, in-session update. Structurally, every NOTIFICATION message carries a defined error code and error subcode field, which together precisely classify the category and specific nature of the fault that triggered the termination (for example, 'Cease' with a subcode indicating administrative shutdown, or 'Update Message Error' with a subcode indicating a malformed attribute), giving the receiving peer's administrator concrete diagnostic information about exactly why the session was torn down. Updating route attributes while keeping a session alive is the role of the UPDATE message, not NOTIFICATION, and refreshing a neighbor's table without resetting the session describes the optional Route Refresh capability (a separate, distinct BGP mechanism), neither of which describes NOTIFICATION's function. Reference topics: Junos Enterprise Routing – BGP, BGP Message Types and the NOTIFICATION Message.