Graceful Degradation in TSS-BQS Systems
Wen Wang · Chinese Journal of Computers · 2012
By integrating threshold signature schemes with different types of Byzantine quorum systems(i.e.,masking BQS and dissemination BQS in this paper),we can build two TSS-BQS systems,called the TSS-mBQS system and the TSS-dBQS system.The TSS-mBQS system produces better performance than the TSS-dBQS one.Based on this observation,we design graceful degradation in TSS-BQS systems: In the beginning,the system consisting of n=3fd+1 servers,runs in the TSS-mBQS state and tolerates up to fm= ■fd/2」 Byzantine faulty servers;with the increasing number of servers which might be faulty,the system switches to the TSS-dBQS state,and tolerates up to fd Byzantine faulty servers at the cost of performance degradation.Without harming the system's fault-tolerance,the graceful degradation improves its performance on average.Moreover,this graceful degradation doesn't interrupt the storage services of the system,and is transparent to clients who don't need to know the system state(i.e.,the TSS-mBQS or the TSS-dBQS state).