PhD Forum: Challenges of Availability and Cost Assessments for Network-Attack-Resilient Byzantine Systems

Byzantine Fault Tolerant (BFT) system designs are developing to counter more sophisticated compromise and attack scenarios. Network-attack-resilient-BFT systems have developed frameworks for distributing replicas among multiple sites. Network-attack-resilient BFT systems are also resilient against sites' failures. These kinds of BFT systems are characterized by having a large number of servers, thus, some designs use a combination of data center and on-premises replicas to lower the overall costs. Availability analyses are inexpensive analytical methods that can be applied in the first stages of choosing the system design to measure the overall availability. The objective is to evaluate the availability of these new emerging BFT systems. The findings from this analysis could used as a guide in developing new system designs, or to establish a framework for selecting an existing BFT system. Two availability modelling techniques can be used to measure and understand the accessibility of the BFT systems: non-state space availability models and state space availability models. This paper highlights some of the challenges in developing such availability models. Conducting a cost analysis, combined with availability analysis, provides a clear understanding of the cost-benefit trade-off involved in investing in such systems.