What occurs in the Established state of BGP?

In the Established state of BGP (Border Gateway Protocol), peers actively engage in exchanging UPDATE messages, which contain information about available routes and their attributes. This state is crucial for BGP operations, as it signifies that the peers have successfully completed the initial handshake process, including the exchange of OPEN and KEEPALIVE messages.

When in the Established state, any routing updates, withdrawals, or error notifications are communicated. Specifically, UPDATE messages are sent to share routing information, and if an error is detected at any point, NOTIFICATION messages are used to inform the peer of the issue encountered. This communication ensures that both BGP peers maintain an accurate and up-to-date view of the network topology, which is essential for the efficient functioning of the BGP routing protocol.

Thus, the ability to exchange UPDATE messages and the provision for NOTIFICATION messages upon errors are defining characteristics of the BGP Established state, making this the correct choice.