Managing HP Serviceguard for Linux, Eighth Edition, March 2008

Understanding Serviceguard Software Components
Responses to Failures
Chapter 392
Network Communication Failure
An important element in the cluster is the health of the network itself.
As it continuously monitors the cluster, each node listens for heartbeat
messages from the other nodes confirming that all nodes are able to
communicate with each other. If a node does not hear these messages
within the configured amount of time, a node timeout occurs, resulting in
a cluster re-formation and later, if there are still no heartbeat messages
received, a reboot. See “What Happens when a Node Times Out” on
page 88.