Evaluating a Dependable Distributed System with Multiple Critical Tasks

Yinong Chen    and    Zhongshi He
Highly Dependable Systems Research Programme
University of the Witwatersrand , Johannesburg, South Africa
{yinong, zhe}@cs.wits.ac.za
http://www.cs.wits.ac.za/research/programme.html

 Full Paper in Postscript File


Abstract

The aim of our research is to develop a distributed system that 
support a variety of tasks. Currently, we are implementing Internet 
applications on the system, including firewall, web and mail 
applications. These applications have different levels of 
dependability requirements. Depending on their criticality, a 
single task may execute on one, two or more computer nodes. 
Fault tolerant protocols are used to detect the disagreement 
among replicas. A reconfiguration protocol is used to identify 
the faulty nodes according to the fault reports from the fault 
tolerant protocols. It then isolates the faulty nodes from the 
system and reallocates their tasks to other working nodes. As 
a part of the project, this work focuses on the dependability 
analysis. The dependability attributes under modelling are the 
reliability of the system and the risk that an unacceptable 
packet is accepted in the firewall application.

Keywords: reliability, risk, modelling, fault tolerance.