SAMPAIO, L. M. R.; http://lattes.cnpq.br/4584896935221260; SAMPAIO, Lívia Maria Rodrigues.
Resumen:
Providing fault tolerance mechanisms through services can decrease the complexity in
developing dependable distributed applications. This is because the application programmer
will be able to use the services without needing to know how these services were implemented
. In this work we propose hardware and software fault-tolerant processing services
for off-the-shelf distributed systems. In these systems there no upper bound for the message
passing and communication delays, so, they are asynchronous systems. Further, we study
the dependability degree that can be achieved using these services and present some implementation
strategies. Finally, we defined a protocol for message ordering which is required
for managing redundancy into the group of replicated processors over which the processing
services are built.
Dependable applications are, in a lesser or greater extent, critical. This fact yields the
necessity of validating the implementation of all the services being used by these applications.
In order to facilitate this task, a number of system models has been proposed in the
literature, each one having its own advantages and disadvantages. In the case of the processing
services being proposed in this work, we followed a hybrid approach that gathers
the facilities of well know system models, the asynchronous system model with unreliable
failure detectors and the timed asynchronous system model, eliminating their respective inconveniences.
The objective is to obtain an extended timed asynchronous system model that
allows the specification of simple and practical solutions. Such a model incorporates two
extra services: an unreliable failure detection service and a reliable broadcast service. The
protocols that implement these services are defined and validated, assuring the characteristics
of the referred extended model.