Abstract: A fault-tolerant call-processing adjunct processor comprises a redundant, duplicated, service unit provisioning and maintenance processor), a duplicated LAN connected to both service units, and plurality of served units (voice-processing processors) each connected to both LANs. Each service unit and each served unit has a duplicate copy of mission-critical information (customer records and commands). Both service units are continuously exercised by operating in an active-active configuration. The service units alternate the use of the LANs, thereby continuously exercising both LANs and providing independent duplicate sources of the mission-critical information to the served units. All sending units rely on having their mission-critical communications timely acknowledged by all receiving units. Served units retry with the other service unit those communications that failed with a preferred service unit. All units store failed communications for subsequent retry.