What condition must be met for the BGP to move from OpenSent to OpenConfirm state?

For BGP (Border Gateway Protocol) to transition from the OpenSent state to the OpenConfirm state, it is essential for the BGP speaker to receive a valid OPEN message from its peer. The OpenSent state occurs when a BGP speaker has sent an OPEN message to its peer but has not yet received any response. The reception of this OPEN message is a critical step because it confirms that the neighboring BGP peer is operational and is willing to participate in the BGP session.

Once the OPEN message is received and validated, the local BGP speaker can proceed to send a KEEPALIVE message to the peer and transition to the OpenConfirm state. This state indicates that both peers have exchanged OPEN messages and are now moving towards establishing a fully operational BGP session.

In contrast, the other options do not facilitate this state transition. A TCP connection failure or a timeout would disrupt the BGP session entirely, preventing a transition. The 3-way handshake (3WHS) is part of the TCP connection establishment process, which, while necessary for the initial connection, is not what specifically drives the state change from OpenSent to OpenConfirm in BGP.