A control connection SHOULD be closed by closing the underlying TCP connection under the following circumstances:
1. If a control connection is not in the established state (i.e., Start-Control-Connection-Request and Start-Control-Connection-Reply have not been exchanged), a control connection SHOULD be closed after 60 seconds by a peer waiting for a Start-Control-Connection-Request or Start-Control-Connection-Reply message.
2. If a peer's control connection is in the established state and has not received a control message for 60 seconds, it SHOULD send a Echo-Request message. If an Echo-Reply is not received 60 seconds after the Echo-Request message transmission, the control connection SHOULD be closed.