A method comprising: maintaining, by a network device , a keep-alive transmit timer and a keep-alive detection timer associated with a communication session with a peer network device within a network , wherein the keep-alive transmit timer defines a transmit time interval for transmitting keep-alive probe packets for the communication session and the keep-alive detection timer defines a current detection interval within which a keep-alive response packet from the peer network device must be received to avoid a failure event for the communication session ; responsive to expiration of the keep-alive transmit timer during the current detection interval, outputting, by the network device , a first keep-alive probe packet associated with the communication session with the peer network device , wherein the keep-alive probe packet includes quality of service, QoS, settings that control forwarding priority of the keep-alive probe packet by packet-switching devices within the network , and wherein the QoS settings have a value indicating a first priority level; and responsive to a second expiration of the keep-alive transmit timer associated with the current detection interval, determining, by the network device , whether a keep-alive response packet has been received from the peer network device since output of the first keep-alive probe packet and, when the keep-alive response packet has not been received, outputting a second keep-alive probe packet associated with the communication session , wherein the second keep-alive probe packet includes QoS settings having a value indicating a second priority level increased from the first priority level. maintaining, by a network device , a keep-alive transmit timer and a keep-alive detection timer associated with a communication session with a peer network device within a network , wherein the keep-alive transmit timer defines a transmit time interval for transmitting keep-alive probe packets for the communication session and the keep-alive detection timer defines a current detection interval within which a keep-alive response packet from the peer network device must be received to avoid a failure event for the communication session ; responsive to expiration of the keep-alive transmit timer during the current detection interval, outputting, by the network device , a first keep-alive probe packet associated with the communication session with the peer network device , wherein the keep-alive probe packet includes quality of service, QoS, settings that control forwarding priority of the keep-alive probe packet by packet-switching devices within the network , and wherein the QoS settings have a value indicating a first priority level; and responsive to a second expiration of the keep-alive transmit timer associated with the current detection interval, determining, by the network device , whether a keep-alive response packet has been received from the peer network device since output of the first keep-alive probe packet and, when the keep-alive response packet has not been received, outputting a second keep-alive probe packet associated with the communication session , wherein the second keep-alive probe packet includes QoS settings having a value indicating a second priority level increased from the first priority level. <EOS>