US Patent 10411948 Cooperative active-standby failover between network systems

A method of determining the state of each peer node in a pair of first and second peer nodes is provided. The first node is configured as a confirmed active node and the second node is configured as a standby node. The second node transitions into a tentative active mode when a predetermined number of heartbeat messages are lost between the pair nodes while the first and second nodes remain functional. The second node receives a first message from the first node after the heartbeat messages are established between the peer nodes. The first message indicates that the first node is in the confirmed active mode. In response to the first message, the second node transitions from the tentative active mode into the standby mode and sends a second message from the second node to the first node indicating that the second node is in the standby mode.