Architectures and disaster recovery strategies for survivable telecommunications services

The events of September 11, 2001, not only changed the public worldview of security and trust but also the telecommunications industry's view of how it must address Homeland Security requirements for service survivability and recovery. Historically, public telecommunications service has evolved to be highly reliable through hardware and software redundancy, fault recognition, and containment; it now needs to be highly survivable to limit the extent of service loss after a catastrophic loss of infrastructure. This paper defines service survivability and reliability and highlights the similarities and differences in procedures and mechanisms that are required for each. The topic is discussed from two perspectives: (1) architectural principles that support the minimization of service loss and (2) disaster recovery plans and procedures that support rapid, predictable restoration of service after a loss. Alternative architectures with improved survivability are examined within the context of the current circuit-based public switched telephone network (PSTN) and other technologies, such as wireless and voice over Internet protocol (VoIP).