Cluster communications ensure that VCS is continuously aware of the status of each system's service groups and resources. They also enable VCS to recognize which systems are active members of the cluster, which have joined or left the cluster, and which have failed.
See About the high availability daemon (HAD).
See About the HostMonitor daemon.
See About Group Membership Services and Atomic Broadcast (GAB).
See About Low Latency Transport (LLT).
See About the I/O fencing module.