Support For Optimistic Synchronization
- state saving and restoration implemented locally within each federate
- cancel erroneous messages via Retract mechanism
- RTI deletes canceled message if not yet delivered to federate
- RTI forwards Retract operation to federate if it already delivered message (could cause secondary rollback, additional anti-messages)
- also used by conservative federates (e.g., to model preemption)
Global Virtual Time (GVT):
- LBTS provides lower bound on time stamp of future messages
- rollback caused by receiving/canceling messages “in the past”
- GVT =min(LBTS, time stamp of local events+lookahead); compute locally
synchronization transparency
- committed events: events in RTIi with time stamp < LBTSi; will not be later canceled
- RTI only passes committed events to conservative federates
- optimistic federates can request delivery of uncommitted events (FlushQueue)