Fault-Tolerant Two-Stage Open Queuing Systems With Server Failures at Both Stages

Two-stage open queuing systems are used to model and evaluate interaction between two systems in computer and communication networks. Application areas include two-stage internetworking mechanisms, memory servers, and interaction of wireless communication systems. Realistic features, such as finite capacities, feedback from one stage to another, and failures of servers usually complicate analytic solutions. This study presents a new analytical model and solution approach for two-stage open queuing systems with feedback, blocking, and multiple servers, as well as failures at both stages. Unlike the existing studies, systems considered in both stages can be fault tolerant. Numerical results presented comparatively with simulation show that the new approach performs well, in terms of accuracy and computation time.