The SIP server can be comprised of an engine tier and a state tier
distributed on a cluster network. Engine nodes in the engine tier can
process SIP messages and can read/write state information from/to the
state tier. State tier can maintain state information in a set of
partitions of one or more replicas which contain duplicate information.
The engine nodes can be adapted to detect and report replica failures and
the replicas can in turn be adapted to detect and report engine node
failures. Replicas can detect faults with an engine node if the engine
node fails to poll the replica for a specified period of time and can
then report the failure. The engine node can detect failures of a replica
when reading or writing state information and can report the failure to
another replica, which can be responsible for updating the partition view
to exclude dead replicas.