In one example, a network device includes a plurality of interface cards to send and receive packets over a network, a primary control unit of the network device, and a secondary control unit of the network device configured to detect a failover event that causes the network device to failover from the primary control unit to the secondary control unit. An operating system of the secondary control unit may be configured to send, in response to detecting the failover event, a session maintenance message on each of a plurality of application-level communication sessions in accordance with a prioritized data structure having a plurality of hierarchically arranged nodes, each of the nodes associated with a different subset of the communication sessions having a common session timeout value.