The PSTR/SNS Scheme for Real-Time Fault Tolerance via Active Object Replication and Network Surveillance

ÐThe time-triggered message-triggered object (TMO) scheme was formulated a few years ago as a major extension of the conventional object structuring schemes with the idealistic goal of facilitating general-form design and timeliness-guaranteed design of complex real-time application systems. Recently, as a new scheme for realizing TMO-structured distributed and parallel computer systems capable of both hardware and software fault tolerance, we have formulated and demonstrated the primary-shadow TMO replication (PSTR) scheme. An important new extension of the PSTR scheme discussed in this paper is an integration of the PSTR scheme and a network surveillance (NS) scheme. This extension results in a significant improvement in the fault coverage and recovery time bound achieved. The NS scheme adopted is a recently developed scheme effective in a wide range of point-to-point networks and it is called the supervisor-based NS (SNS) scheme. The integration of the PSTR scheme and the SNS scheme is called the PSTR/SNS scheme. The recovery time bound of the PSTR/SNS scheme is analyzed on the basis of an implementation model that can be easily adapted to various commercial operating system kernels. Index TermsÐTime-triggered message-triggered object, TMO, primary-shadow TMO replication, PSTR, network surveillance, NS, SNS, point-to-point networks, real-time systems, recovery time bound.